Methods for the Determination of Metals in Environmental Samples

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METHODS FOR THE DETERMINATION OF METALS AND INORGANIC CHEMICALS IN ENVIRONMENTAL SAMPLES

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METHODS FOR THE

DETERMINATION OF METALS AND INORGANIC CHEMICALS IN ENVIRONMENTAL SAMPLES

Environmental Monitoring Systems Laboratory Environmental Protection Agency Cincinnati, Ohio

NOY ES PUBLICATIONS Westwood, New Jersey, U.S.A.

Copyright 0 1996 by Noyes Publications No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system without permission in writing from the Publisher. Library of Congress Catalog Card Number: 96-12588 ISBN. 0-8155-1398-4 Printed in the United States Published in the United States of America by Noyes Publications 369 Faimiew Avenue Westwood, New Jersey 07675 10 9 8 7 6 5 4 3 2 1

Library of Congress Cataloging-in-Publication Data Methods for the determination of metals and inorganics in environmental samples / by Environmental Monitoring Systems Laboratory. p. cm. ISBN 0-8155-1398-4 1. Metals--Analysis--Laboratory manuals. 2. Inorganic compounds-Analysis--Labratory manuals. 3. Water--Analysis--Labratory manuals. 4. Sewage--Analysis--Laboratory manuals. I. Environmental Monitoring Systems Laboratory (Cincinnati, Ohio) TD196.M4M4897 1996 96-12588 628.1'61--dc20

CIP

FOREWORD Environmental measurements are required Po determine the quality of ambient waters and the character of waste effluents. The Environmental Monitoring Systems Laboratory-Cincinnati (EMSL-Cincinnati) conducts research to: Develop and evaluate analytical methods to identify and measure the concentration of chemical pollutants in marine and estuarine waters, drinking waters, surface waters, groundwaters, wastewaters, sediments, sludges, and so1id wastes . Investigate methods for the identification and measurement of viruses, bacteria and other microbiological organisms in aqueous samples and to determine the responses of aquatic organisms to water quality. Develop and operate a quality assurance program to support the achievement of data quality objectives in measurements of pollutants in marine and estuarine waters, drinking water, surface water, groundwater, wastewater, sediment and solid waste. Develop methods and models to detect and quantify responses in aquatic and terrestrial organisms exposed to environmental stressors and to correlate the exposure with effects on chemical and biological indicators. This supplement to the EMSL-Cincinnati publication, "Methods for the Determination of Metals in Environmental Samples" was prepared to revise and place in the Environmental Monitoring Management Council (EMMC) format certain spectrochemical methods used for metals analyses in regulatory compliance monitoring programs. Also, included in this supplement is a new method, Method 200.15 Determination of Metals and Trace Elements in Water by Ultrasonic Nebulization Inductively Coupled Plasma-Atomic Emission Spectrometry. This method is intended for analysis of ambient waters with possible limited use in regulatory compliance monitoring. We are pleased to provide this updated supplement to the manual and believe that it will be of considerable value to many public and private laboratories that wish to determine metals in environmental media for regulatory or other reasons. This EMSL-Cincinnati publication, "Methods for the Deterniination of Inorganic Substances in Environmental Samples," was prepared as the continuation of an initiative to gather together a compendium of standardized laboratory analytical methods for the determination V

vi

Foreword

of inorganic substances in water and wastewater. We are pleased to provide this manual and believe that it will be of considerable value to many public and private laboratories involved in inorganic analyses for regulatory or other reasons. Thomas A. Clark, Director

INTRODUCTION METHODS FOR THE DETERMINATION OF METALS IN ENVIRONMENTAL SAMPLES Six of the seven methods appearing in this supplement were included in the first publication of the manual "Determination of Metals in Environmental Samples," EPA 600 4-91/010, June, 1991. The one new method appearing in this supplement is Method 200.15, Determination of Metals and Trace Elements in Water by Ultrasonic Nebulization Inductively Coupled PlasmaAtomic Emission Spectrometry. Method 200.15 was developed to extend the analytical range of the ICP-AES technique to lower concentrations. Its usefulness for the analysis of drinking water is evident by the performance data included in the method. Unlike the 1991 manual (EPA 600 4-91/010) which contains 13 methods for a variety of sample matrices, this supplement is focused more on the analysis of water and wastes. Its purpose is for use in compliance monitoring of National Pollution Discharge Elinlination System (NPDES) effluents as required under the Clean Water Act and compliance monitoring of drinking water as required under the Safe Drinking Water Act. These methods are also useful for the analysis of ambient waters with the exclusion of marine water. The methods included in this supplement have been prepared in the format adopted by the Eiivironmental Monitoring Management Council (EMMC). In this format method sections are ordered in a specific manner and purpose with the addition of two new sections on pollution prevention and waste management. All methods have the same approach to analytical quality control in that initial demonstration of performance is required prior to method use, and assessing ongoing laboratory performance is mandatory. However, the required frequency of demonstration has been lessened and the acceptance control limits have been widened. Also, the required limits used in assessing recovery data from fortified matrices have been widened. Where available multi-laboratory data and regression equations Rave been included in the methods.

The multi-analyte methods (200.7, 200.8, 200.9, and 200.15) all utilize the same total recoverable sample digestion procedure that is described in Method 200.2 as a stand-alone procedure. This procedure also is applicable to flame atomic absorption determinations. Using a common sample preparation for all spectrochemical techniques is convenient and can reduce cost of analyses. vii

...

Introduction

VIII

Changes to previous versions of specific methods are as follows: 0

Cerium has been added to Method 200.7 for correction of potential spectral interferences

0

Titanium has been added as an analyte to Method 200.7 Mercury has been added to Method 200.8 for the analysis of drinking water with turbidity of (1 NTU

o

Zinc has been deleted from Method 200.9 because its determination by the graphite furnace techniques is impractical

0

Digestion of Method 245.1 mercury calibration standards is no longer required.

METHODS FOR THE DETERMINATION OF INORGANIC SUBSTANCES IN ENVIRONMENTAL SAMPLES The original version of this manual was issued in November 1969 by the Federal Water Pollution Control Administration as "FWPCA Methods for Chemical Analysis of Water and Wastes." With the creation of the United States Environmental Protection Agency (USEPA) came "Methods for Chemical Analysis of Water and Wastes 1971" Publication No. 160207/71. The second edition was issued in 1974 as EPA 625/6-74-003, and the third edition in 1979 as EPA 600/4/79-020. The current version, an updated second printing of the third edition, was revised and issued in March 1983. The methods contained in the I983 manual form the basis for most of the methodology approved for compliance monitoring of inorganic parameters specified under the Clean Water Act (NPDES) and contaminants regulated under the Safe Drinking Water Act. In 1991, a number of new and revised metals methods were incorporated into a new publication entitled, "Methods for the Determination of Metals in Environmental Samples." Concurrently, the decision was made to revise and update selected non-metal methods to be issued under the name "Methods for the Determination of Inorganic Substances in Environmental Samples." For both the metals and non-metals manuals, several important features were adopted: o

Consistent use of terminology, a feature especially helpful in the quality control sections where standardized terminology is not yet available. The terms were carefully selected to be meaningful without extensive definition, and therefore should be easy to understand and use. New sections are included with expanded useful coverage of safety, quality control, pollution prevention and waste management. All methods are presented in the new EPA standard Environmental Monitoring Management Council (EMMC) format.

Although a number of other methods included the 1983 edition of USEPA "Methods for Chemical Analysis of Water and Wastes," Standard Methods for the Examination of Water

Introduction

ix

and Wastewater, and American Society for Testing and Materials Annual Book of Standards (ASTM) are acceptable for compliance monitoring, the revised methods contained in this publication are considered to be the most useful in terms of future regulatory requirements. They represent a selection of air segmented automated, semi-automated, or amenable to automation methodology that provides the following advantages over their manual counterparts. 0

Higher sample throughput for faster analysis and improved precision.

0

Faster analysis allows more time to perform the updated quality control required to insure valid results.

0

Lower per analysis reagent consumption to reduce waste production and minimize disposal costs. The inclusion of multi-laboratory data generated from USEPA performance evaluation studies.

The following methods are included with specific features and improvements: 0

A revised version of TPA turbidity Method 180.1 that minimizes the direct use of hydrazine sulfate.

o

An updated version of EPA Method 300.0 for anions by ion chromatography.

0

A new stand alone semi-automated revision of EPA cyanide Method 335.2 that specifies the use of the downsized midi-distillation procedure.

0

A new semi-automated version of the EPA phenolics Method 420.2. The optional use of a non-mercury catalyst in EPA TKN Method 351.2.

0

All methods allow the optional use of reduced reagent and distillationdigestion volumes.

Most of the methods include the option of limited performance-based modifications or improvements. James W. O'Dell, John D. Pfaff, William L. Budde Chemistry Research Division

NOTICE To the best of our knowledge the information in this publication is accurate; however, the Publisher does not assume any responsibility or liability for the accuracy or completeness of, or consequences arising from, such information. This book is intended for informational purposes only. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the Publisher. Final determination of the suitability of any information or product fox use contemplated by any user, and the manner of that use, is the sole responsibility of the user. We recommend that anyone intending to rely on any recommendation of materials or procedures mentioned in this publication should satisfy himself as to such suitability, and that he can meet all applicable safety and health standards. X

CONTENTS AND SUBJECT INDEX PART I METHODS FOR THE DETERMINATION OF METALS IN ENVIRONMENTAL SAMPLES Determination of Acid-Soluble Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Sample Preparation Procedure for Spectrochemical Determination of . . . I2 Total Recoverable Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200.3 Sample Preparation Procedure for Spectrochemical Determination of Total Recoverable Elements in Biological Tissues . . . . . . . . . . . . . . . . 24 200.7 Determination of Metals and Trace Elements in Water and Wastes by Inductively Coupled Plasma-Atomic Emission Spectrometry . . . . . . . . . 31 200.8 Determination of Trace Elements in Waters and Wastes by Inductively Coupled Plasma-Mass Spectrometry . . . . . . . . . . . . . . . . . 88 200.9 Deterniination of Trace Elements by Stabilized Temperature Graphite . . 146 Furnace Atomic Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200.10 Determination of Trace Elements in Marine Waters by On-Line Chelation Preconcentration and Inductively Coupled Plasma. . 187 Mass Spectrometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200.11 Determination of Metals in Fish Tissue by Inductively Coupled Plasma-Atomic Emission Spectrometry . . . . . . . . . . . . . . . . . . . . . . 210 200.15 Determination of Metals and Trace Elements in Water by Ultrasonic Nebulization Inductively Coupled Plasma-Atomic Emission . . 243 Spectrometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218.6 Determination of Dissolved Hexavalent Chromium in Drinking Water, Groundwater, and Industrial Wastewater Effluents by Ion . . 290 Chromatography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245.1 Determination of Mercury in Water by Cold Vapor Atomic Absorption . . 305 Spectrometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245.3 Determination of Inorganic Mercury (11) and Selected Organomercurials in Drinking and Groundwater by High Performance Liquid Chromolography (HPLC) with Electrochemical Detection (ECD) . . . . . . . . . . 323 245.5 Detemiination of Mercury in Sediments by Cold Vapor Atomic . . 349 Absorption Spectrometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245.6 Deterniination of Mercury in Tissues by Cold Vapor Atomic Absorption . . 363 Spectrometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

200.1 200.2

Xi

xii

Contents and Subject Index

PART I1 METHODS FOR THE DETERMINATION OF INORGANIC SUBSTANCES IN ENVIRONMENTAL SAMPLES 180.1 300.0 335.4 350.1 351.2 353.2

Determination of Turbidity by Nephelometry . . . . . . . . . . . . . . . . . . . . . . Determination of Inorganic Anions by Ion Chromatography . . . . . . . . . . . Determination of Total Cyanide by Semi-Automated Colorimetry . . . . . . . . Determination of Ammonia Nitrogen by Semi-Automated Colorimetry . . . . . , . . . . . . . . . . . . . . . . . . . . . * . . . . ~. . , . . . . . . Determination of Total Kjeldahl Nitrogen by Semi-Automated Colorimetry . . . . . . . . . . . . . . . . . . . . ~.. . . . . . . . . . . ~. . . . . . . . Determination of Nitrate-Nitrite Nitrogen by Automated Colorimetry . . . . . . ~. . ~. . . . . . . . ~. . . . . . . . . . . . . , * . . . . . . Determination of Phosphorous by Semi-Automated Colorimetry . . . . . . . . . Determination of Sulfate by Automated Colorimetry . . . . . . . . . . . . . . . . . The Determination of Chemical Oxygen Demand by Semi-Automated Colorimetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Deterniination of Total Recoverable Phenolics by Semi-Automated Colorimetry . . . . . . . . . . ~. . . . . . . . . . . . . . . . . . . . . . . . . . . . ~

~

365.1 375.2 410.4 420.4

D

.

.

I

378 388 418 434 449

464 479 496

509 522

PART I METHODS FOR THE DETERMINATION OF METALS IN ENVIRONMENTAL SAMPLES

1

2

Methods for the Determination

METHOD 200.1 DETERMINATION OF ACID-SOLUBLE METALS

Theodore D. Martin and James W . O'Dell Inorganic Chemistry Branch Chemistry Research Division and Gerald D . McKee Office o f the Director

Revision 2.0 April 1991

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

Metals

3

METHOD 200.1 DETERMINATION OF ACID-SOLUBLE METALS 1.

SCOPE AND APPLICATION

1.1

This method can be used to determine acid-soluble metals’ in ambient waters and aqueous wastes. Results from this method may be used to calculate or estimate the potential impact on aquatic life and water quality. It is applicable to the analysis of arsenic ( A s ) , cadmium (Cd), chromium (Cr), copper (Cu) , and lead (Pb) .

1.2 This method provides instructions for sample handling, preservation, and preparation prior to analysis using spectrochemical methods given in this manual. Specific references are listed in Sect. 1 1 . 3 of this method. 1 . 3 This method is designed to be a supplement to approved EPA

spectrophotometric and spectrochemical methods, however, it does not provide for oxidation state or organometallic speciation. For a summary and description of the analytical techniques employed, their estimated instrumental detection limits, definition of terms specific to each technique, types of interferences encountered, instrumental requirements, reagents and standards required for analysis, calibration, general instrumental operating procedures, instrumental qua1 ity control, data calculation and reporting, see appropriate parts of the methods referenced in Sect. 1 1 . 3 of this method. 2.

SUMMARY OF METHOD

2.1 This method describes procedural instruction for treating an aqueous sample for determination of acid-soluble metals prior to either atomic absorption or atomic emission spectrochemical analysis. The aqueous sample is acidified to a pH of 1.,75 f 0 . 1 and held for a period of at least 16 h before being filtered through a 0.45-1m membrane filter and appropriately processed for analysis. 3.

DEFINITIONS

3.1

4.

Acid-Soluble Metal: That portion of the metal concentration that will pass through a 0.45-pm membrane filter after the solution to be filtered has been adjusted to within a DH 1.75 f 0.1 and held for a period of 16 h .

INTERFERENCES

4.1

Contamination is of primary concern in determining acid-solub e metals. All sample containers, labware, filtering and sample processing apparatus should be washed as described in Sect. 8

4

5.

Methods for the Determination SAFETY 5.1

6.

7.

Ammonium h y d r o x i d e and n i t r i c a c i d a r e m o d e r a t e l y t o x i c and i r r i t a t i n g t o s k i n and mucus membranes. Use c o n c e n t r a t e d r e a g e n t s i n a hood and i f eye o r s k i n c o n t a c t occurs, f l u s h w i t h l a r g e volumes o f w a t e r . Always wear s a f e t y g l a s s e s o r a s h i e l d f o r eye p r o t e c t i o n when w o r k i n g w i t h t h e s e r e a g e n t s .

APPARATUS 6.1

pH M e t e r - l a b o r a t o r y o r f i e l d model: A wide v a r i e t y o f i n s t r u m e n t s a r e c o m m e r c i a l l y a v a i l a b l e w i t h v a r i o u s s p e c i f i c a t i o n s and o p t i o n a l equipment. The i n s t r u m e n t must be capable o f measuring pH t o 0 . 1 u n i t s and s h o u l d be a m e t e r equipped w i t h a c o m b i n a t i o n e l e c t r o d e .

6.2

F i l t e r f u n n e l and s u p p o r t : O n l y g l a s s o r p l a s t i c f i l t e r i n g apparatus s h o u l d be used. The s u p p o r t s h o u l d be c a p a b l e o f a c c e p t i n g b o t h t h e p r e f i l t e r and f i n e f i l t e r w h i l e m a i n t a i n i n g a no-leak s e a l between t h e f u n n e l and s u p p o r t . The Gelman model 4201 o r equivalent i s acceptable.

6.3

S u c t i o n f l a s k , 500-mL c a p a c i t y .

6.4

Membrane f i l t e r d i s c s : Because t h e sample s o l u t i o n t o be f i l t e r e d w i l l be o f l o w pH (1.75 k O . l ) , t h e f i l t e r media may be e i t h e r a p o l y v i n y l c h l o r i d e a c r y l i c copolymer o r mixed e s t e r s o f c e l l u l o s e m a t e r i a l . The f o l l o w i n g 47-mm membrane f i l t e r s o r e q u i v a l e n t a r e acceptable. 6.4.1

Fine p r e f i l t e r :

DM-800, 0.8-pm (Gelman No.64502)

6.4.2

Fine f i l t e r : DM-450, 0.45-pm (Gelman No. 64515) o r HAWP-047, 0.45 pm ( M i l l i p o r e No. HAWP 047 00)

6.5

Sample c o l l e c t i o n c o n t a i n e r s : C u b i t a i n e r , p o l y e t h y l e n e , 1 q u a r t (0.95L) c a p a c i t y o r e q u i v a l e n t .

6.6

Sample s t o r a g e b o t t l e s : Wide-mouth h i g h - d e n s i t y p o l y e t h y l e n e w i t h p o l y p r o p y l e n e screw cap c l o s u r e , 500-mL c a p a c i t y .

6.7

Glassware:

6.8

For t h e apparatus and equipment needed f o r t h e a n a l y t i c a l t e c h n i q u e employed, see t h e s p e c i f i c r e f e r e n c e s .

C l a s s A v o l u m e t r i c f l a s k s and p i p e t s o f v a r i o u s volumes.

REAGENTS AND STANDARDS 7.1

Deionized, d i s t i l l e d w a t e r : Prepare by p a s s i n g d i s t i l l e d w a t e r t h r o u g h a mixed bed o f c a t i o n and a n i o n exchange r e s i n s . Use d e i o n i z e d , d i s t i l l e d w a t e r f o r t h e p r e p a r a t i o n o f a l l r e a g e n t s and as d i l u t i o n o r r i n s e w a t e r . The p u r i t y o f t h i s w a t e r must be e q u i v a l e n t t o ASTM Type 11 r e a g e n t w a t e r o f S p e c i f i c a t i o n D 11933.

Metals 7.2

Nitric acid, conc. (sp.gr. 1 . 4 1 ) , ultra-high purity grade or equivalent. Redistilled acid is acceptable. 7.2.1

7.3

Nitric acid, ( l t l ) : Add 500 mL conc. HNO (Sect. 7 . 2 ) to 400 mL deionized, distilled water (Sect. j . 1 ) and dilute to 1 L.

Hydrochloric acid, conc. (sp. gr. 1 . 1 9 ) . 7.3.1

8.

5

Hydrochloric acid, ( l t l ) : Add 500 mL conc. HC1 (Sect. 7 . 3 ) to 400 mL deionized, distilled water (Sect. 7 . 1 ) and dilute to 1 L .

7.4

Ammonium Hydroxide, ( 1 t 9 ) : Dilute 10 mL conc. ammonium hydroxide, NH,OH (analytical reagent grade), to 100 mL with deionized, distilled water (Sect. 7 . 1 ) .

7.5

Buffer solutions: Two buffer solutions are required, one in the range of pH 2 and the other at pH 7 . These may be prepared or purchased as commercially available certified solutions. The use of purchased buffer solutions certified at a pH of 2 and 7 is recommended.

SAMPLE COLLECTION, PRESERVATION AND STORAGE

8.1

For the determination of acid-soluble metals, contamination and loss are of prime concern. Dust in the laboratory environment, impurities in reagents and improperly cleaned laboratory apparatus which the sample contacts are all potential sources of contamination. Sample containers can introduce either positive or negative errors in the measurement of metals by (a) contributing contaminants through leaching or surface desorption and/or (b) by depleting concentration through adsorption. Laboratory glassware, including the sample collection cubitainer and the polyethylene samp7e storage bottle, as well as the filtering apparatus should be thoroughly washed with detergent and tap water; thoroughly rinsed with ( l f l ) nitric acid, tap water, ( l t l ) hydrochloric acid, tap water and finally deionized distilled water in that order (See Notes 1 and 2 ) . To remove difficult organic deposits from glassware, a commercial product, NOCHROMIX, available from Godax Laboratories, 480 Canal Street, New York, New York 10013 may be used. This product should not be used on plastic containers or filtering apparatus.

NOTE 1:

If it can be documented through an active analytical quality control program using spiked samples, laboratory control standards and reagent blanks that certain steps in the cleaning procedure are not required, those steps may be eliminated from the procedure.

NOTE 2 :

6

Methods for the Determination

8.2 At the time o f sample collection, the sample cubitainer is rinsed

with the sample solution and the rinse portion discarded. The cubitainer is then filled with approximately 800 mL o f sample, acidified with 2 mL of (ltl) nitric acid and mixed. For most ambient waters the acid addition will lower the pH to near 2, but not lower than 1.75. The cubitainer is sealed, placed in an ice chest at 4 " C , and returned to the laboratory. Note the date and time of preservation on the sample tag. 8.3 The sample should not be held more than 3 days at 4°C from the day of collection before processing is started. The filtrate is estimated to be stable for 30 days. 9.

CALIBRATION AND STANDARDIZATION

9.1 Calibration of pH meter - Because of the wide variety of pH meters and accessories, detailed operating procedures cannot be incorporated into this method. Each analyst must be acquainted with the operation of the system being used and familiar with all instrument functions. Special attention to care of the combination electrode is recommendedi See Method 150.1 given in EPA 600/4-79-020, March 1983 . 9.2 Each instrument/electrode system must be calibrated at a minimum of two points, one at or near pH 2, the other at pH 7. Calibrate according to manufacturer's instructions and measure the pH of each sample. Using deionized distilled water (Sect. 7.1), rinse the electrode system after each pH measurement. 10.

QUALITY CONTROL

10.1 The following quality assurance procedures represent 5% of the analyzed sample load for 20 samples. 10.2 To measure recovery and cross contamination between samples that may occur, 300 mL o f a laboratory control standard containing all six metals, each at a concentration above 1OX its determined method detection limit (MDL), is transferred to a cleaned cubitainer, adjusted to a pH range of 1.75 ? 0.1 and allowed to stand for a minimum of 16 h. At a selected point midway through the group of samples to be analyzed, the control standard is filtered. The analyzed values should be within the warning limits of f2 standard deviations of an established mean value as determined from seven prior replicate analyses. If an analyzed value was greater than +3 standard deviations from the mean, the analysis was out of control. 10.3 To determine the MDL of each metal, prepare seven aliquots of the sample matrix of concern, spike the aliquots with each metal to a concentration o f 3 to 5 times its estimated detection limit and follow the procedure - "Definition and Procegure for the Determination o f the Method Detection Limit.

Metals

11.

7

PROCEDURE

11.1 SAMPLE pH ADJUSTMLNT For the determination of acid-soluble metals, the pH o f the sample must be 1.75 f 0.1. Upon receiving the sample in the laboratory, check the sample tag for proper preservation and to see that the holding time has not been exceeded. Allow the sample to come to room temperature, calibrate the pH meter and measure the pH of the sample in the cubitainer. Using deionized distilled water (Sect. 7.1), rinse the electrode system after each pH measurement. Do not wipe the electrode. ~

11.1.1

If the sample pH is between 1.65 and 1.85, mix the sample and allow to stand at room temperature for a minimum of 16 h f o r required dissolution. At the end of the extraction period, measure the pH again to verify that the proper pH was maintained, and if so, filter according to paragraph If pH was not maintained, a new sample should be 11.2. requested and more care and time taken in the initial pH adjustment.

11.1.2

If the sample pH is above 1.85, add (ltl) nitric acid in a dropwise manner, mix the sample in the cubitainer by inverting and shaking and redetermine the pH. Continue adding small increments of the (1t1) nitric acid and mix until the sample is within the desired pH range. If the pH should go below 1.65, add (1t9) ammonium hydroxide (Sect. 7.3) in a dropwise manner until the sample is within the pHrange of 1.65 to 1.85. Once the pH of the sample is properly adjusted and thoroughly mixed, set the sample aside for a minimum of 16 h for the required dissolution to occur. At the end of the extraction period, measure the pH again to verify the proper pH was maintained, and if so, filter according to paragraph 11.2. If pH was not maintained, a new sample should be requested and more care and time taken in the initial pH adjustment .

11.1.3

If upon receipt the sample has a pH below 1.65, the sample should be discarded and the collection of a new sample requested. The sample collection team should be informed of the reason why the previous sample was rejected.

11.2 SAMPLE FILTRATION - For determination of acid-soluble metals, the pH-adjusted sample is filtered through a 0.45-pm membrane filter. To prevent clogging of the filter, the sample is first passed through a fine prefilter. 11.2.1

Before filtering any sample make certain that the filtering apparatus (Sects. 6.2 and 6.3), polyethylene storage bottles (Sect. 6.7) and other necessary glassware have been cleaned by the procedure described in Sect. 8.1

8

Methods for the Determination 11.2.2

I n s e r t t h e l - i l t e r s u p p o r t o f t h e f i l t e r i n g apparatus t h r o u g h t h e p r o p e r s i z e r u b b e r s t o p p e r and w r a p t h e s t o p p e r w i t h 1 i n . PTFE l a b o r a t o r y t a p e t o p r e v e n t c o n t a m i n a t i o n . Secure t h e f l a s k i n an u p r i g h t p o s i t i o n and p l a c e t h e s u p p o r t i n t h e neck of t h e s u c t i o n f l a s k . Connect t h e s u c t i o n f l a s k t o t h e vacuum 1 i n e .

11.2.3

P l a c e t h e membrane f i l t e r s ( S e c t . 6 . 4 ) on t h e f i l t e r s u p p o r t i n t h e f o l l o w i n g o r d e r : f i r s t t h e 0.45-pm f i n e f i l t e r and t h e n t h e 0.8-pm p r e f i l t e r . Assemble t h e f i l t e r f u n n e l t o t h e s u p p o r t as recommended by t h e m a n u f a c t u r e r .

11.2.4

Do n o t m i x t h e sample, b u t c a r e f u l l y d e c a n t a p p r o x i m a t e l y 50 mL o f sample f r o m t h e c u b i t a i n e r i n t o t h e f i l t e r i n g f u n n e l and a p p l y t h e vacuum. A f t e r f i l t r a t i o n , b r e a k t h e vacuum, remove t h e f i l t e r i n g apparatus, r i n s e t h e s u c t i o n f l a s k w i t h t h e f i l t r a t e and d i s c a r d .

11.2.5

Reassemble t h e f i l t e r i n g a p p a r a t u s and s u c t i o n f l a s k , r e a p p l y t h e vacuum and c a r e f u l l y decant a p p r o x i m a t e l y 250 o f a d d i t i o n a l sample i n t o t h e f i l t e r i n g apparatus.

mL

11.2.6

When f i l t r a t i o n i s complete, b r e a k t h e vacuum, t r a n s f e r t h e f i l t r a t e t o a l a b e l e d , cleaned, p o l y e t h y l e n e s t o r a g e b o t t l e ( S e c t . 6.7) and s t o r e u n t i l a l l analyses have been completed, n o t t o exceed 30 days. The r e m a i n i n g u n f i l t e r e d p o r t i o n o f t h e sample may be d i s c a r d e d .

11.2.7

B e f o r e f i l t e r i n g a d d i t i o n a l samples, d i s c a r d t h e f i l t e r s , r i n s e t h e s u c t i o n f l a s k and f i l t e r i n g apparatus w i t h c o p i o u s amounts o f d e i o n i z e d d i s t i l l e d w a t e r ( S e c t . 7.1), d i s c a r d t h e r i n s e w a t e r and d r a i n away any excess w a t e r .

11.2.8

Repeat t h e above p r o c e d u r e u n t i l a l l samples and q u a l i t y c o n t r o l a1 i q u o t s have been f i l t e r e d .

11.3 SAMPLE ANALYSES - The l e v e l o f m e t a l c o n c e n t r a t i o n w i l l d e t e r m i n e t h e a n a l y t i c a l method s e l e c t e d t o complete t h e a n a l y s i s . 11.3.1

I n d u c t i v e l y c o u p l e d plasma-atomic e m i s s i o n (ICP) s p e c t r o m e t r i c analyses - The a c i d - s o l u b l e m e t a l s As, Cd, C r , Cu and Pb can be analyzed by d i r e c t a s p i r a t i o n ICP s p e c t r o m e t r y u s i n g t h e p r o c e d u r e d e s c r i b e d i n Method 200.7 o f t h i s manual. To p r e p a r e t h e sample f o r analyses, p i p e t 2 mL ( l t l ) h y d r o c h l o r i c a c i d i n t o a 50-mL v o l u m e t r i c f l a s k and d i l u t e t o t h e mark w i t h sample f i l t r a t e . T h i s d i l u t i o n r e q u i r e s an a p p r o p r i a t e f a c t o r be a p p l i e d t o t h e f i n a l c a l c u l a t i o n s . I n t h e absence o f an e s t a b l i s h e d MDL (Sect. l O . Z . l ) , the f o l l o w i n g estimated instrumental d e t e c t i o n l i m i t f o r each element s h o u l d be c o n s i d e r e d t h e l i m i t o f analysis.

Metals

Element

Estimated D e t e c t i o n L i m i t mq/L

0.03 0.02 0.007 0.003 0.03

As Cd Cr cu Pb 11.3.2

9

D i r e c t a s p i r a t i o n flame atomic a b s o r p t i o n (FLAA) analyses - The a c i d - s o l u b l e metals Cd, C r , Cu and Pb can be analyzed by procedures g i v e n i n approved FLAA methods w i t h o u t r e q u i r i n g a d d i t i o n a l processing o f t h e f i l t r a t e b e fo re a n a l y s i s . L i s t e d below are t h e method numbers and estimated i n s tru m e n ta l d e t e c t i o n l i m i t s , which i n t h e absence o f an e s t a b l i s h e d MDL (Sect. 10.2.1), should be considered t h e FLAA l i m i t o f a n a l y s i s f o r d i r e c t a s p i r a t i o n . I n a d d i t i o n t o t h e i n d i v i d u a l methods, f o r t h e proper a n a l y s i s procedure, see p a r t s 9 . 1 o f Section 200.0: Atomic Absorption Methods g i v e n i n EPA 600/4-79-020, March 19832

.

Element Cd Cr

cu Pb

11.3.3

Method Number

Estimated D e t e c t i o n L i m i t , mq/L

213.1 218.1 220.1 239.1

0.005 0.05 0.02 0.1

S t a b i l i z e d Temperature Graphite Furnace Atomic Absorption (STGFAA) ANALYSES - For STGFAA a n a l y s i s o f t h e a c i d - s o l u b l e metals As, Cd, C r , Cu and Pb, an a l i q u o t o f t h e f i l t r a t e must be t r e a t e d w i t h t h e a p p r o p r i a t e m a t r i x m o d i f i e r s b e fo re a n a l y s i s . For proper i n s t r u m e n t a l STGFAA c a l i b r a t i o n and suggested o p e ra ti n g c o n d i t i o n s see Method 200.9 o f t h i s manual. I n t h e absence o f an e s t a b l i s h e d MDL (Sect. lO.Z.l), t h e f o l l o w i n g estimated STGFAA i n s t r u m e n t a l d e t e c t i o n 1 i m i t f o r each element should be considered t h e l i m i t o f anaysis. Element As Cd Cr cu

Estimated D e t e c t i o n L i m i t UQ/L

0.9 0.05 0.2 1.0

10

Methods for the Determination

12

CALCULATIONS 12.1 See the appropriate section o f the recornmended methods o f analysis. 12.2 Final results o f these calculations should be reported as mg/L acid-

soluble metal. 13

PRECISION AND RECOVERY 13.1 Precision and recovery data for Cd, Cr, Cu, and Pb by this method u s i n g inductively coupled plasma-atomic emission spectrometric analyses are given in Table 1. The data are for three levels of concentration using varying amounts o f the same sludge material

spiked into river water. Seven replicate samples were prepared for each level o f concentration. River water controls were subtracted from each level of spike. The percent recovery calculation i s based on "total-recoverable" analysis o f the same samples. Accuracy data on actual samples cannot be obtained.

13.2 Precision data on the determination of acid-soluble metals by this method using atomic absorption spectrophotometric analyses are estimated to be similar to the data in the methods referenced. 14.

REFERENCES 1.

Water Quality Criteria; Availability o f Documents, Federal Register, Vol. 50, NO. 145, July 29, 1985, pp. 30784-30796.

2.

Chemical Analysis o f Water and Wastes, EPA 600/4-79-020, (Revised, March 1983), U . S . Environmental Protection Agency, Office of Research and Development, Environmental Monitoring and Support Laboratory, Cincinnati, Ohio.

3.

Annual Book o f ASTM Standards, Part 31, American Society for Testing and Materials, 1916 Race St., Philadelphia, PA, 19103.

4.

Code of Federal Regulations 40, Ch. 1, Pt. 136 Appendix B.

TABLE 1.

2.5 g

PERCENT RECOVERY(') OF ACID SOLUBLE METALS") FROM SLUDGE MATERIAL SPIKED I N R I V E R WATER

Sludge/L

1 .O g S1 udge/L

Acid S o l u b l e Total Recoverable Mean mq/L Metal ms/L

1. 2.

Std.

Dev.

0.25 g Sludge/L

Acid S o l u b l e

Total Percent Recoverable Recovery mq/L

Mean

Acid S o l u b l e

mq/L

Std. Dev.

Percent Recovery

Total Recoverable ms/L

Mean

Std.

mq!L

Dev.

Percent Recovery

Cd

0.085

0.074

f0.002

87%

0.036

0.030

f0.002

83%

0.010

0.009 fO.OO1

90%

Cr

7.48

3.18

f0.085

43%

3.28

1.21

f0.070

37%

0.669

0.326 f0.032

49%

cu

1.17

1.11

f0.025

95%

0.502

0.442

f0.019

88%

0.130

0.115 f0.006

88%

Pb

0.601

0.311

fO.O1O

52%

0.268

0.137

f0.008

51%

0.067

0.042 i0.007

63%

P e r c e n t r e c o v e r y i s based on the " t o t a l r e c o v e r a b l e " v a l u e All d a t a o b t a i n e d from I C P a n a l y s e s .

12

Methods for the Determination

METHOD 200.2 SAMPLE PREPARATION PROCEDURE FOR SPECTROCHEMICAL DETERMINATION OF TOTAL RECOVERABLE ELEMENTS

Revision 2.8 EMMC Version

T.D. Martin, E.R. Martin, and S . E . Long (Technology Applications, Inc.) Method 200.2, Revision 1.1 (1989)

T.D. Martin, S.E. Long (Technology Applications Inc.), and J.T. Creed Method 200.2, Revision 2.3 (1991) T.D. Martin, J.T. Creed, and C.A. Brockhoff (1994)

-

Method 200.2, Revision 2.8

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U. S. ENVIRONMENTAL PROTECTION AGENCY C I N C I N N A T I , OHIO 45268

-

Metals

13

METHOD 200.2 SAMPLE PREPARATION PROCEDURE FOR SPECTROCHEMICAL DETERMINATION OF TOTAL RECOVERABLE ELEMENTS

1.0 SCOPE AND APPLICATION 1.1 T h i s method p r o v i d e s sample p r e p a r a t i o n p r o c e d u r e s f o r t h e d e t e r m i n a t i o n o f t o t a l recoverable analytes i n groundwaters, surface w a t e r s , d r i n k i n g w a t e r s , w a s t e w a t e r s , and, w i t h t h e e x c e p t i o n o f s i l i c a , i n s o l i d t y p e samples such as s e d i m e n t s , s l u d g e s and s o i l s . Aqueous samples c o n t a i n i n g suspended o r p a r t i c u l a t e m a t e r i a l 2 1% ( W / V ) s h o u l d b e e x t r a c t e d as a s o l i d t y p e sample. T h i s method i s a p p l i c a b l e t o the following analytes: Chemical A b s t r a c t S e r v i c e s R e g i s t r y Numbers (CASRN)

Analyte

7429-90-5 7440-36-0 7440-38-2 7440-42-8 7440-39-3 7440-41-7 7440-43-9 7440-70-2 7440-47-3 7440-48-4 7440-50-8 7439-89-6 7439-92-1 7439-93-2 7439-95-4 7439-96-5 7439-97-6 7439-98-7 7440-02-0 7723-14-0 7440-09-7 7782-49-2 7631-86-9 7440-22-4 7440-23-5 7440-24-6

A1 umi num A n t i mony Arsenic Boron B a r i um B e r y l 1 ium Cadmi um Calcium Chromi um Cobalt Copper

Iron Lead Lithium Magnesi urn Manganese Mercury Molybdenum Nickel Phosphorus P o t ass ium S e l e n i urn S i l icaa S i 1v e r Sod iurn S t r o n t ium ( c o n t i n u e s on n e x t page) ~

a

T h i s method i s

~~~

not s u i t a b l e

~

f o r the determination o f s i l i c a i n solids.

R e v i s i o n 2.8 Hay 1994

14

Methods for the Determination

C hem ic a 1 Ab s t r a c t Se r v ic e s

Anal y t e

R e g i s t r y Numbers (CASRN)

7440-28-0 7440-29-1 7440-3 1-5 7440-61-1 7440-62-2 7440-66-6

1.2

F o r r e f e r e n c e where t h i s method i s a p p r o v e d f o r use i n c o m p l i a n c e m o n i t o r i n g programs [ e . g . , C l e a n Water A c t (NPDES) o r S a f e D r i n k i n g Water A c t (SDWA)] c o n s u l t b o t h t h e a p p r o p r i a t e s e c t i o n s o f t h e Code o f f e d e r a l R e g u l a t i o n (40 CFR P a r t 136 T a b l e 1B f o r NPDES, and P a r t 141 § 141.23 f o r d r i n k i n g w a t e r ) , and t h e l a t e s t F e d e r a l R e g i s t e r announcements.

1.3

Samples p r e p a r e d b y t h i s method c a n be a n a l y z e d b y t h e f o l l o w i n g methods g i v e n i n t h i s s u p p l e m e n t : Method 200.7, D e t e r m i n a t i o n o f M e t a l s and T r a c e E l e m e n t s b y I n d u c t i v e l y Coup ed 'Plasma-Atomic E m i s s i o n S p e c t r o m e t r y ; Method 200.8, D e t e r m i n a t i o n o f T r a c e Elements By I n d u c t i v e l y Coupled Plasma-Mass S p e c t r o m e t r y ; ind Method 200.9, D e t e r n i i n a t i o n o f T r a c e Elements by S t a b i l i z e d T e m p e r a t u r e G r a p h i t e F u r n a c e A t o m i c A b s o r p t i o n S p e c t r o m e t r y . A l s o , t h i s method can be used p r i o r t o a n a l y s i s by d i r e c t a s p i r a t i o n f l a m e a t o m i c a b s o r p t i o n f o r t h e above l i s t o f a n a l y t e s w i t h t h e e x c e p t i o n o f t h e f o l l o w i n g : As, B, Hg, P, Se, SiO,, Th, and U.

1.4

The p r e p a r a t i o n p r o c e d u r e s d e s c r i b e d i n t h i s method a r e not recommended p r i o r t o a n a l y s i s by t h e c o n v e n t i o n a l g r a p h i t e f u r n a c e t e c h n i q u e , commonly r e f e r e d t o as " o f f - t h e - w a l l " , n o n - p l a t f o r m o r non-delayed a t o m i z a t i o n . I t i s b e l i e v e d t h a t t h e r e s u l t i n g c h l o r i d e c o n c e n t r a t i o n i n t h e p r e p a r e d s o l u t i o n s c a n cause e i t h e r a n a l y t e v o l a t i l i z a t i o n l o s s p r i o r t o a t o m i z a t i o n o r an u n r e m e d i a b l e c h e m i c a l v a p o r s t a t e i n t e r f e r e n c e f o r some a n a l y t e s when a n a l y z e d u s i n g t h e conventional graphite furnace technique.

1.5

T h i s method i s s u i t a b l e f o r p r e p a r a t i o n o f aqueous samples c o n t a i n i n g s i l v e r c o n c e n t r a t i o n s up t o 0 . 1 mg/L. f o r t h e a n a l y s i s o f w a s t e w a t e r samples c o n t a i n i n g h i g h e r c o n c e n t r a t i o n s o f s i l v e r , s u c c e e d i n g s m a l l e r volume, w e l l m i x e d a l i q u o t s must be p r e p a r e d u n t i l t h e a n a l y s i s s o l u t i o n c o n t a i n s < 0 . 1 mg/L s i l v e r . The e x t r a c t i o n o f s o l i d samples c o n t a i n i n g c o n c e n t r a t i o n s o f s i l v e r > 50 mg/kg s h o u l d be t r e a t e d i n a s i m i l a r manner. A l s o , t h e e x t r a c t i o n o f t i n f r o m s o l i d samples s h o u l d be p r e p a r e d a g a i n u s i n g a l i q u o t s < 1 g when d e t e r m i n e d sample c o n c e n t r a t i o n s exceed 1%.

1.6

When u s i n g t h i s method f o r d e t e r m i n a t i o n o f b o r o n and s i l i c a i n aqueous samples, o n l y p l a s t i c o r q u a r t z l a b w a r e s h o u l d be used f r o m R e v i s i o n 2 . 8 May1994

Metals

15

t h e t i m e o f sample c o l l e c t i o n t o t h e c o m p l e t i o n o f t h e a n a l y s i s . F o r a c c u r a t e d e t e r m i n a t i o n s o f b o r o n i n s o l i d samples o n l y q u a r t z o r PTFE b e a k e r s s h o u l d be used d u r i n g a c i d e x t r a c t i o n w i t h immediate t r a n s f e r o f an e x t r a c t a l i q u o t t o a p l a s t i c c e n t r i f u g e t u b e f o l l o w i n g d i l u t i o n o f t h e e x t r a c t t o volume. When p o s s i b l e , b o r o s i l i c a t e g l a s s s h o u l d be avoided t o prevent contamination o f these a n a l y t e s .

2.0

1.7

T h i s method w concentrations analysis o f concentrations possible a f t e r

i l l s o l u b i l i z e and h o l d i n s o l u t i o n o n l y o f barium i n t h e presence o f f r e e s u l f a t e . b a r i u m i n samples h a v i n g v a r y i n g and o f s u l f a t e , a n a l y s i s s h o u l d be c o m p l e t e d as sample p r e p a r a t i o n .

1.8

T h i s method i s n o t s u i t a b l e f o r t h e d e t e r m i n a t i o n o f v o l a t i l e l o w b o i l i n g p o i n t o r g a n o - m e r c u r y compounds.

minimal For the unknown soon as

SUMMARY OF METHOD 2.1

S o l i d and aqueous samples a r e p r e p a r e d i n a s i m i l a r manner f o r a n a l y s i s . N i t r i c and h y d o c h l o r i c a c i d s a r e d i s p e n s e d i n t o a b e a k e r c o n t a i n i n g an a c c u r a t e l y weighed o r measured, w e l l mixed, homogeneous aqueous o r s o l i d sample. Aqueous samples a r e f i r s t r e d u c e d i n volume b y g e n t l e h e a t i n g . Then, m e t a l s and t o x i c e l e m e n t s a r e e x t r a c t e d f r o m e i t h e r s o l i d samples o r t h e u n d i s s o l v e d p o r t i o n o f aqueous samples b y c o v e r i n g t h e b e a k e r w i t h a w a t c h g l a s s and r e f l u x i n g t h e sample i n t h e A f t e r extraction, the solubilzed d i l u t e a c i d m i x t u r e f o r 30 m i n . a n a l y t e s a r e d i l u t e d t o s p e c i f i e d volumes w i t h ASTM t y p e I w a t e r , m i x e d and e i t h e r c e n t r i f u g e d o r a l l o w e d t o s e t t l e o v e r n i g h t b e f o r e a n a l y s i s . D i l u t e d samples a r e t o be a n a l y z e d b y t h e a p p r o p r i a t e mass a n d / o r a t o m i c s p e c t r o m e t r y methods as soon as p o s s i b l e a f t e r preparation.

3.0 DEFINITIONS 3.1

F i e l d Reagent B l a n k (FRB) - An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i x t h a t i s p l a c e d i n a sample c o n t a i n e r i n t h e l a b o r a t o r y and t r e a t e d a s a sample i n a l l r e s p e c t s , i n c l u d i n g s h i p m e n t t o t h e sampling s i t e , exposure t o t h e sampling s i t e c o n d i t i o n s , storage, p r e s e r v a t i o n , and a l l a n a l y t i c a l p r o c e d u r e s . The p u r p o s e o f t h e FRB i s t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e f i e l d environment (Sect 8.3).

3.2

S o l i d Sample - F o r t h e p u r p o s e o f t h i s method, a sample t a k e n f r o m m a t e r i a l c l a s s i f i e d as e i t h e r s o i l , s e d i m e n t o r s l u d g e .

3.3

T o t a l R e c o v e r a b l e A n a l y t e - The c o n c e n t r a t i o n o f a n a l y t e d e t e r m i n e d t o be i n e i t h e r a s o l i d sample o r an u n f i l t e r e d aqueous sample f o l l o w i n g t r e a t m e n t by r e f l u x i n g w i t h h o t d i l u t e m i n e r a l a c i d .

3.4

W a t e r Sample - F o r t h e p u r p o s e o f t h i s method, a sample t a k e n f r o m one o f t h e f o l l o w i n g sources: d r i n k i n g , s u r f a c e , ground, storm r u n o f f , i n d u s t r i a l o r domestic wastewater.

R e v i s i o n 2.8 Hay 1994

16 4.0

Methods for the Determination INTERFERENCES

4.1

In sample preparation, contamination i s of pt I I I W (ori(ern. The hork area, including bench top and fume hood, should be periodically cleaned in order to eliminate environmental cont
4.2 Chemical interfrrrinccs dre matrix dependerii n i ~ d[ annot be documented previous to analy5is. 4.3 Boron and silica from the glassware will grow i1it.o the sample solution during and following sample processing. For critical determinations of boron and silica, only quartz and/or P T F E plastic labware should be used. When quartz beakers are not available for extraction of solid samples, to reduce boron contamination, iniiriediately transfer an aliquot of the diluted extract to a plastic centrifuge tube for storage until time o f analysis. A series of laboratory reagent blanks can be used to monitor and indicate the contamination effect. 5.0

SAFETY

5.1 All personnel handling environmental samples known to contain or t o have been in contact with human waste should be immunized against known disease causative agents. 5.2 The acidification of samples containing reactive materials may result in the release of toxic gases, such as cyanides or sulfides. Acidification of samples should be done in a fume hood. 5.3 Material safety data sheets for all chemical reagents should be available to and understood by all personnel using this method. Specifically, concentrated hydrochloric acid and concentrated nitric acid are moderately toxic and extremely irritating to skin and mucus membranes. Use these reagents in a hood whenever possible and if eye or skin contact occurs, flush with large volumes of water. Always wear safety glasses or a shield for eye protection when working with these reagents . 2 8 3 , 4 6.0

EQUIPMENT AND SUPPLIES

6.1 Analytical balance, with capability to measure to 0.1 mg, for use in weighing solids, and for determining dissolved solids in extracts. 6.2 Single pan balance, with capability of weighing to 0.01 g , for use in rapid weighing solids and liquids or samples in excess of 10 g. 6.3 A temperature adjustable temperature of 95OC. 6.4

hot

plate capable o f

maintaining

a

(optional) A temperature adjustable block digester capable of maintaining a temperature of 95OC and equipped with 250-mL constricted digestion tubes.

Revision 2.8 May 1994

Metals

17

6.5

( o p t i o n a l ) A s t e e l c a b i n e t c e n t r i f u g e w i t h g u a r d bowl, e l e c t r i c t i m e r and b r a k e .

6.6

A g r a v i t y convection d r y i n g oven w i t h t h e r i i i o s t a t i c c o n t r o l c a p a b l e of m a i n t a i n i n g 180°C f 5°C.

6.7

( o p t i o n a l ) An a i r displacement p i p e t t e r c a p a b l e of d e l i v e r i n g volumes ranging from 0 . 1 t o 2500 pL with a n a s s o r t m e n t of high q u a l i t y disposable pipet t i p s .

6.8

Mortar and p e s t l e , ceramic o r n o n m e t a l l i c m a t e r i a l .

6.9

Polypropylene s i e v e , 5-mesh ( 4 mm o p e n i n g ) .

6.10 LABWARE - For d e t e r m i n a t i o n o f t r a c e l e v e l s of e l e m e n t s , contamination and l o s s a r e of prime c o n s i d e r a t i o n . P o t e n t i a l contamination s o u r c e s i n c l u d e improperly c l e a n e d l a b o r a t o r y a p p a r a t u s and g e n e r a l contamination w i t h i n t h e l a b o r a t o r y environment from dust, e t c . A c l e a n 1 a b o r a t o r y work a r e a d e s i g n a t e d f o r t r a c e element sample handling must be used. Sample c o n t a i n e r s can i n t r o d u c e p o s i t i v e and n e g a t i v e e r r o r s i n t h e d e t e r m i n a t i o n of t r a c e elements by ( 1 ) c o n t r i b u t i n g contaminants through s u r f a c e d e s o r p t i o n o r l e a c h i n g , ( 2 ) d e p l e t i n g element c o n c e n t r a t i o n s through a d s o r p t i o n p r o c e s s e s . All r e u s a b l e labware ( g l a s s , q u a r t z , p o l y e t h y l e n e , PTFE, FEP, e t c . ) should be s u f f i c i e n t l y c l e a n f o r t h e t p s k o b j e c t i v e s . Several procedures found t o p r o v i d e c l e a n labware i n c l u d e soaking o v e r n i g h t and thoroughly washing w i t h l a b o r a t o r y - g r a d e d e t e r g e n t and w a t e r , r i n s i n g with t a p w a t e r , and soaking f o r f o u r hours o r more i n 20% ( V / V ) n i t r i c a c i d o r a m i x t u r e of d i l u t e n i t r i c and h y d r o c h l o r i c a c i d ( 1 + 2 + 9 ) , followed by r i n s i n g w i t h ASTM Type I g r a d e w a t e r and s t o r i n g c l e a n . NOTE:

Chromic a c i d must not be used f o r c l e a n i n g g l a s s w a r e .

6.10.1

Glassware - Volumetric f l a s k s , g r a d u a t e d c y l i n d e r s , funne and c e n t r i f u g e tubes ( g l a s s a n d / o r metal f r e e p l a s t i c ) .

6.10.2

Assorted c a l i b r a t e d p i p e t t e s .

6.10.3

Conical P h i l l i p s beakers (Corning 1080-250 o r e q u i v a l e n t 250-mL w i t h 50-mm watch g l a s s e s .

6.10.4

G r i f f i n b e a k e r s , 250-mL w i t h 75-mm ( o p t i o n a l ) 75-mm r i b b e d watch g l a s s e s .

6.10.5

(optional) covers.

6.10.6

Evaporating d i s h e s or high-form c r u c i b l e s , p o r c e l a i n , 100 rnL capacity.

6.10.7

Wash b o t t l e - One p i e c e stem, Teflon F E P b o t t l e with Tefzel ETFE screw c l o s u r e , 125-mL c a p a c i t y .

PTFE and/or q u a r t z b e a k e r s ,

watch

glasses

and

250-mL with PTFE

Revision 2.8 Hay 1994

18

Methods for the Determination

7.0

REAGENTS AND STANDARDS 7.1

Reagents may contain elemental inipur i t I P X which might affect analytical data High-purity reaqcnts 5hould be used whenever possible. All acids used for this method m u s t be of ultra high-purity grade. 7.1.1

Nitric acid, concentrated (sp.gr. 1.41).

7.1.2

Nitric acid ( l t l ) - Add 500 mL conc. nitric acid to 400 mL of ASTM type I water and dilute to 1 L .

7.1.3

Hydrochloric acid, concentrated (sp.gr. 1.19).

7.1.4

Hydrochloric acid ( l t l ) - Add 500 mL conc. hydrochloric acid to 400 mL of ASTM type I water and dilute to 1 L .

7.1.5

Hydrochloric acid (1t4) - Add 200 ml conc. hydrochloric acid to 400 mL of ASTM type I water and dilute to 1 L.

7.2 Reagent water - For all sample preparation and dilutions, ASTM type I water (ASTM D 1 1 9 3 ) 5 is required. Suitable water may be prepared by passing distilled water through a mixed bed of anion and cation exchange resins. 7.3

8.0

Refer to the appropriate analytical method for the preparation of standard stock solutions, calibration standards, and quality control solutions.

SAMPLE COLLECTION, PRESERVATION, AND STORAGE

8.1

For determination of total recoverable elements in aqueous samples, the samples must be acid preserved prior to aliquoting for either sample processing or determination by direct spectrochemical analysis. For proper preservation samples are n o t filtered, but acidified with ( l t l ) nitric acid to pH < 2. Preservation may be done at the time of sample collection, however, to avoid the hazards of strong acids in the field, transport restrictions, and possible contamination it is recommended that the samples be returned to the laboratory within two weeks of collection and acid preserved upon receipt in the laboratory. Following acidification, the sample should be mixed and held for sixteen hours. (Normally, 3 mL of ( l t l ) nitric acid per liter o f sample i s sufficient for most ambient and drinking water samples). The pH of all aqueous samples must be tested immediately prior to withdrawing an aliquot for processing to ensure the sample has been properly preserved. If for some reason such as high alkalinity the sample pH is verified to be > 2 , more acid must be added and the sample held for sixteen hours until verified to be pH < 2. If properly acid preserved, the sample can be held up to 6 months before anal ys i s . NOTE:

When the nature of the sample is either unknown or is known to be hazardous, acidification should be done in a fume hood. See Section 5.2. Revision2.8 May1994

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8.2 Solid samples require no preservation prior to analysis other than storage at 4 ° C . There is no established holding time limitation for solid samples. 8.3 For aqueous samples, a field blank should be prepared and analyzed as required by the data user. Use the same container and acid as used in sample col lect ion. 9.0 OUALITY CONTROL

9.1 Each laboratory determining total recoverable elements is required to operate a formal quality control ( Q C ) program. The minimum requirements of a Q C program consist of an initial demonstration of laboratory capability, and the analysis of laboratory reagent blanks, fortified blanks and quality control samples as a continuing check on performance. The laboratory is required to maintain performance records that define the quality of data generated. 9.2 Specific instructions on accomplishing the described aspects of the QC program are discussed in the analytical methods (Sect. 1.3). 10.

CALIBRATION AND STANDARDIZATION 10.1 Not applicable. selected.

Follow instructions given in the analytical method

11.0 PROCEDURE

11.1 Aqueous Sample Preparation - Total Recoverable Analytes 11.1.1

For the determination of total recoverable analytes in aqueous samples, transfer a 100 mL (k 1 mL) aliquot from a well mixed, acid preserved sample to a 250-mL Griffin beaker (Sects. 1.2, 1.5, 1.6, 1.7, & 1.8). (When necessary, smaller sample aliquot volumes may be used.) NOTE:

If the sample contains undissolved solids > 1%, a well mixed, acid preserved aliquot containing no more than 1 g particulate material should be cautiously evaporated to near 10 mL and extracted using the acidmixture procedure described in Sections 11.2.3 thru 11.2.8.

11.1.2 Add 2 mL (ltl) nitric acid and 1.0 mL of (ltl) hydrochloric acid to the beaker containing the measured volume of sample. Place the beaker on the hot plate for solution evaporation. The hot plate should be located in a fume hood and previously adjusted to provide evaporation at a temperature of approximately but no higher than 8 5 ° C . (See the following note.) The beaker should be covered with an elevated watch glass or other necessary steps should be taken to prevent sample contamination from the fume hood environment.

Revision2.8 May1994

20

Methods for the Determination NOTE:

For p r o p e r h e a t i n g a d j u s t t h e temperature c o n t r o l o f t h e h o t p l a t e such t h a t an uncovered G r i f f i n beaker c o n t a i n i n g 50 mL o f w a t e r p l a c e d i n t h e c e n t e r o f t h e h o t p l a t e can be m a i n t a i n e d a t a temperature a p p r o x i m a t e l y b u t no h i g h e r t h a n 85°C. (Once t h e beaker i s covered w i t h a watch g l a s s t h e temperature o f t h e w a t e r w i l l r i s e t o a p p r o x i m a t e l y 95°C.)

11.1.3

Reduce t h e volume o f t h e sample a l i q u o t t o about 20 mL by g e n t l e h e a t i n g a t 85°C. DO NOT B O I L . T h i s s t e p t a k e s about 2 h f o r a 100 mL a l i q u o t w i t h t h e r a t e o f e v a p o r a t i o n r a p i d l y i n c r e a s i n g as t h e sample volume approaches 20 mL. (A spare beaker c o n t a i n i n g 20 mL o f w a t e r can be used as a gauge.)

11.1.4

Cover t h e l i p o f t h e beaker w i t h a watch g l a s s t o reduce a d d i t i o n a l e v a p o r a t i o n and g e n t l y r e f l u x t h e sample f o r 30 m i n u t e s . ( S l i g h t b o i l i n g may occur, b u t v i g o r o u s b o i l i n g must be avoided t o p r e v e n t l o s s o f t h e HC1-H,O azeotrope.)

11.1.5

A l l o w t h e beaker t o c o o l . Q u a n t i t a t i v e l y t r a n s f e r t h e sample s o l u t i o n t o a 50-mL v o l u m e t r i c f l a s k , make t o volume w i t h r e a g e n t w a t e r , s t o p p e r and m i x .

11.1.6

A l l o w any u n d i s s o l v e d m a t e r i a l t o s e t t l e o v e r n i g h t , o r c e n t r i f u g e a p o r t i o n o f t h e p r e p a r e d sample u n t i l c l e a r . ( I f a f t e r c e n t r i f u g i n g o r s t a n d i n g o v e r n i g h t t h e sample c o n t a i n s suspended s o l i d s t h a t would c l o g t h e n e b u l i z e r , a p o r t i o n o f t h e sample may be f i l t e r e d f o r t h e i r removal p r i o r t o analysis. However, c a r e should be e x e r c i s e d t o a v o i d p o t e n t i a l c o n t a m i n a t i o n f r o m f i l t r a t i o n . ) The sample i s now r e a d y f o r a n a l y s i s by e i t h e r i n d u c t i v e l y coupled plasma-atomic e m i s s i o n s p e c t r o m e t r y o r d i r e c t a s p i r a t i o n f l a m e and s t a b i l i z e d t e m p e r a t u r e g r a p h i t e f u r n a c e atomic a b s o r p t i o n spectroscopy ( S e c t s . 1.3 & 1 . 4 ) .

11.1.7

To r e a d y t h e sample f o r analyses by i n d u c t i v e l y coupled plasma-mass s p e c t r o m e t r y ( S e c t . 1 . 3 ) , a d j u s t t h e c h l o r i d e c o n c e n t r a t i o n by p i p e t t i n g 20 mL o f t h e p r e p a r e d s o l u t i o n i n t o a 50-mL v o l u m e t r i c f l a s k , d i l u t e t o volume w i t h r e a g e n t w a t e r and m i x . ( I f the dissolved s o l i d s i n t h i s s o l u t i o n are > 0.2%, a d d i t i o n a l d i l u t i o n may be r e q u i r e d t o p r e v e n t c l o g g i n g o f t h e e x t r a c t i o n and/or skimmer cones. I n t e r n a l standards a r e added a t t h e t i m e o f a n a l y s i s . )

11.1.8

Because t h e e f f e c t s o f v a r i o u s m a t r i c e s on t h e s t a b i l i t y o f d i l u t e d samples cannot be c h a r a c t e r i z e d , a l l analyses s h o u l d be performed as soon as p o s s i b l e a f t e r t h e completed preparation.

11.2 S o l i d Sample P r e p a r a t i o n - T o t a l Recoverable A n a l y t e s 11.2.1

For t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e a n a l y t e s i n s o l i d samples, m i x t h e sample t h o r o u g h l y and t r a n s f e r a p o r t i o n R e v i s i o n 2.8 May 1994

Metals

21

( > 20 g ) t o t a r e d w e i g h i n g d i s h , weigh t h e sample and r e c o r d ( f o r samples w i t h < 35% m o i s t u r e a 20 g the w e t weight. portion i s sufficient. For samples w i t h m o i s t u r e > 35% a l a r g e r a l i q u o t 5 0 - 1 0 0 g i s r e q u i r e d . ) Dry t h e sample t o a c o n s t a n t w e i g h t a t 60°C and r e c o r d t h e d r y w e i g h t f o r c a l c u l a t i o n o f percent s o l i d s (Sect. 1 2 . 1 ) . (The sample i s d r i e d a t 60°C t o p r e v e n t t h e l o s s o f mercury and o t h e r p o s s i b l e v o l a t i l e m e t a l l i c compounds, t o f a c i l i t a t e s i e v i n g , and t o ready t h e sample f o r g r i n d i n g . )

11.2.2

To achieve homogeneity, s i e v e t h e d r i e d sample u s i n g a 5-mesh p o l y p r o p y l e n e s i e v e and g r i n d i n a m o r t a r and p e s t l e . (The s i e v e , m o r t a r and p e s t l e s h o u l d be cleaned between samples.) From t h e d r i e d , ground m a t e r i a l weigh a c c u r a t e l y a r e p r e s e n t a t i v e 1.0 f 0.01 g a l i q u o t ( W ) o f t h e sample and t r a n s f e r t o a 250-mL P h i l l i p s beaker f o r a c i d e x t r a c t i o n (Sects. 1.5, 1.6, 1.7, & 1 . 8 ) .

11.2.3

To t h e beaker add 4 mL o f (ltl) HNO, and 10 mL o f ( 1 t 4 ) HC1. Cover t h e l i p o f t h e beaker w i t h a watch g l a s s . Place t h e beaker on a h o t p l a t e f o r r e f l u x e x t r a c t i o n o f t h e a n a l y t e s . The h o t p l a t e s h o u l d be l o c a t e d i n a fume hood and p r e v i o u s l y adjusted t o provide a r e f l u x temperature o f approximately 95OC. (See t h e f o l l o w i n g n o t e . )

NOTE:

For proper heating i d j u s t the temperature c o n t r o l o f t h e h o t p l a t e such t h a t an uncovered G r i f f i n beaker c o n t a i n i n g 50 mL o f w a t e r p l a c e d i n t h e c e n t e r o f t h e h o t p l a t e can be m a i n t a i n e d a t a t e m p e r a t u r e a p p r o x i m a t e l y b u t no h i g h e r t h a n 85OC. (Once t h e beaker i s covered w i t h a watch g l a s s t h e t e m p e r a t u r e o f t h e w a t e r w i l l r i s e t o a p p r o x i m a t e l y 95OC.) A l s o , a b l o c k d i g e s t e r c a p a b l e o f m a i n t a i n i n g a t e m p e r a t u r e o f 95OC and equipped w i t h 250-mL c o n s t r i c t e d v o l u m e t r i c d i g e s t i o n tubes may be s u b s t i t u t e d f o r t h e h o t p l a t e and c o n i c a l beakers i n t h e e x t r a c t i o n s t e p .

11.2.4

Heat t h e sample and g e n t l y r e f l u x f o r 30 min. Very s l i g h t b o i l i n g may o c c u r , however v i g o r o u s b o i l i n g must be avoided t o p r e v e n t l o s s o f t h e HC1-H,O azeotrope. Some s o l u t i o n e v a p o r a t i o n w i l l o c c u r ( 3 t o 4 mL).

11.2.5

A l l o w t h e sample t o c o o l and q u a n t i t a t i v e l y t r a n s f e r t h e e x t r a c t t o a 100-mL v o l u m e t r i c f l a s k . D i l u t e t o volume w i t h r e a g e n t w a t e r , s t o p p e r and m i x .

11.2.6

A l l o w t h e sample e x t r a c t s o l u t i o n t o s t a n d o v e r n i g h t t o separate i n s o l u b l e m a t e r i a l o r centrifuge a p o r t i o n o f t h e sample s o l u t i o n u n t i l c l e a r . ( I f after centrifuging or s t a n d i n g o v e r n i g h t t h e e x t r a c t s o l u t i o n c o n t a i n s suspended s o l i d s t h a t would c l o g t h e n e b u l i z e r , a p o r t i o n o f t h e e x t r a c t s o l u t i o n may be f i l t e r e d f o r t h e i r removal p r i o r t o a n a l y s i s . However, c a r e s h o u l d be e x e r c i s e d t o a v o i d p o t e n t i a l c o n t a m i n a t i o n from f i l t r a t i o n . ) The sample i s now ready f o r R e v i s i o n 2 . 8 May1994

22

Methods for the Determination a n a l y s i s by e i t h e r i n d u c t i v e l y coupled plasma-atomic e m i s s i o n s p e c t r o m e t r y o r d i r e c t a s p i r a t i o n flame and s t a b i l i z e d t e m p e r a t u r e g r a p h i t e f u r n a c e atomic a b s o r p t i o n spectroscopy (Sects. 1 . 3 & 1.4). 11.2.7

To ready t h e sample f o r analyses by i n d u c t i v e l y c o u p l e d plasma-mass s p e c t r o m e t r y ( S e c t . 1 . 3 ) , a d j u s t t h e c h l o r i d e c o n c e n t r a t i o n by p i p e t t i n g 10 mL o f t h e prepared s o l u t i o n i n t o a 50-mL v o l u m e t r i c f l a s k , d i l u t e t o volume w i t h r e a g e n t w a t e r and m i x . ( I f the dissolved s o l i d s i n t h i s s o l u t i o n are > 0.2%, a d d i t i o n a l d i l u t i o n may be r e q u i r e d t o p r e v e n t c l o g g i n g o f t h e e x t r a c t i o n and/or skimmer cones. I n t e r n a l standards a r e added a t t h e t i m e o f a n a l y s i s . )

11.2.8

Because t h e e f f e c t s o f v a r i o u s m a t r i c e s on t h e s t a b i l i t y o f d i l u t e d samples cannot be c h a r a c t e r i z e d , a l l analyses s h o u l d be performed as soon as p o s s i b l e a f t e r t h e completed preparation,

11.3 Sample A n a l y s i s - Use an a n a l y t i c a l method l i s t e d i n S e c t . 1.3.

12.0 DATA ANALYSIS AND CALCULATIONS 12.1 To r e p o r t p e r c e n t s o l i d s i n s o l i d samples ( S e c t . 11.2) c a l c u l a t e as f o l 1ows : % s o l i d s (S)

=

DW - x 100

ww

where:

DW WW

NOTE:

If t h e d a t a u s e r , program o r l a b o r a t o r y r e q u i r e s t h a t t h e r e p o r t e d p e r c e n t s o l i d s be determined by d r y i n g a t 105"C, r e p e a t t h e p r o c e d u r e g i v e n i n S e c t i o n 11.2.1 u s i n g a s e p a r a t e p o r t i o n ( > 20 g ) o f t h e sample and d r y t o c o n s t a n t w e i g h t a t 103-105°C.

= Sample w e i g h t ( 9 ) d r i e d a t 6OoC = Sample w e i g h t (9) b e f o r e d r y i n g

12.2 C a l c u l a t i o n and t r e a t m e n t o f d e t e r m i n e d a n a l y t e d a t a a r e d i s c u s s e d i n a n a l y t i c a l methods l i s t e d i n S e c t . 1.3.

13.0 METHOD PERFORMANCE 13.1 Not a p p l i c a b l e . i n S e c t . 1.3.

A v a i l a b l e d a t a i n c l u d e d i n a n a l y t i c a l methods l i s t e d

14.0 POLLUTION PREVENTION

14.1 P o l l u t i o n p r e v e n t i o n encompasses any t e c h n i q u e t h a t reduces o r e l i m i n a t e s t h e q u a n t i t y o r t o x i c i t y o f waste a t t h e p o i n t o f g e n e r a t i o n . Numerous o p p o r t u n i t i e s f o r p o l l u t i o n p r e v e n t i o n e x i s t i n l a b o r a t o r y o p e r a t i o n . The EPA has e s t a b l i s h e d a p r e f e r r e d h i e r a r c h y o f e n v i r o n m e n t a l management t e c h n i q u e s t h a t p l a c e s p o l l u t i o n R e v i s i o n 2.8 Hay 1994

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prevention as the management option of first choice. Whenever feasible, laboratory personnel should use pollution prevention techniques to address their waste generation. When wastes cannot be feasibly reduced at the source, the Agency recommends recycling as the next best option. 14.2 For information about pollution prevention that may be applicable to laboratories and research institutions, consult less i s Better: Laboratory Chemical Management for Waste Reduction, available from the American Chemical Society's Department of Government Relations and Science Policy, 1155 16th Street N . W . , Washington D.C. 20036, (202)872-4477. 15.0 YASTE MANAGEMENT 1 5 . 1 The Environmental Protection Agency requires that laboratory waste

management practices be conducted consistent with all applicable rules and regulations. The Agency urges laboratories to protect the air, water, and land by minimizing and controlling all releases from hoods and bench operations, complying with the letter and spirit of any sewer discharge permits and regulations, and by complying with all solid and hazardous waste regulations, particularly the hazardous waste identification rules and land disposal restrictions. For further information on waste management consult The Waste Management Manual for Laboratory Personnel, ayailable from the American Chemical Society at the address listed in the Section 14.2. 16.0 REFERENCES

1.

Martin, T.D. and E.R. Martin, "Evaluation o f Method 200.2 Sample Preparation Procedure for Spectrochemical Analyses o f Total Recoverable Elements," December 1989, U.S. Environmental Protection Agency, Office of Research and Development, Environmental Monitoring Systems Laboratory, Cincinnati, Ohio 45268.

2.

"OSHA Safety and Health Standards, General Industry," (29 CFR 1910), Occupational Safety and Health Administration, OSHA 2206, revised January 1976.

3.

"Safety in Academic Chemistry Laboratories," American Chemical Society Publication, Committee on Chemical Safety, 3rd Edition, 1979.

4.

"Proposed OSHA Safety and Health Standards, Laboratories," Occupational Safety and Health Administration, Federal Register, July 24, 1986.

5.

Annual Book of ASTM Standards, Volume 11.01

Revision 2.8 May 1994

24

Methods for the Determination METHOD 200.3 SAMPLE PREPARATION PROCEDURE FOR SPECTROCHEMICAL DETERMINATION OF TOTAL RECOVERABLE ELEMENTS I N BIOLOGICAL TISSUES

W i 11 iam McDaniel

U.

Environmental Services D i v i s i o n Region I V S . Environmental P r o t e c t i o n Agency

Revision 1.0 A p r i l 1991

Adapted by:

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U. S . ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

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METHOD 200.3 SAMPLE PREPARATION PROCEDURE FOR SPECTROCHEMICAL DETERMINATION OF TOTAL RECOVERABLE ELEMENTS I N BIOLOGICAL TISSUES 1.

SCOPE AND APPLICATION 1.1 This method provides sample preparation procedures for the

determination o f total recoverable elements in biological tissue samples. 1.2

This method is applicable to the following elements: Analvte A1 umi num Antimony Arsenic Bar i um Beryl 1 i um Cadmi um Calcium Chromium Cobalt Copper Iron Lead Lithium Magnesium Manganese Mercury Molybdenum Nickel Phosphorus Potass i um Selenium S i 1 ver Sod i um Stront i um Thallium Thori um Uranium Vanadium Zinc

1.3

Chemical Abstract Services Reaistry Numbers (CASRNI 7429-90-5 7440-36-0 7440-38-2 7440-39-3 7440-41-7 7440-43-9 7440-70-2 2440-47-3 7440-48-4 7440-50-8 7439-89-6 7439-92-1 7439-93-2 7439-95-4 7439-96-5 7439-97-6 7439-98- 7 7440-02-0 7723-14-0 7440-09-7 7782-49-2 7440-22-4 7440-23-5 7440-24-6 7440-28-0 7440-29-1 7440-61- 1 7440-62-2 7440-66-6

Samples prepared by this method can be analyzed by inductively coupled plasma-atomic emission spectrometry (ICP-AES) Method 2 0 0 . 7 , "Determination of Metals and Trace Elements by Inductively Coupled Plasma-Atomic Emission Spectrometry," inductively coupled plasmamass spectrometry (ICP-MS) Method 200.8, "Determination of Metals

Methods for the Determination and Trace Elements by I n d u c t i v e l y Coupled Plasma-Mass S p e c t r o m e t r y , " and s t a b i l i z e d t e m p e r a t u r e p l a t f o r m g r a p h i t e f u r n a c e a t o m i c a b s o r p t i o n (STGFAA), Method 200.9, " D e t e r m i n a t i o n o f Trace Elements by S t a b i l i z e d Temperature G r a p h i t e Furnace Atomic A b s o r p t i o n S p e c t r o m e t r y " . See a n a l y t i c a l methods mentioned f o r s e l e c t i o n o f t h e a p p r o p r i a t e method f o r d e t e r m i n a t i o n o f a s p e c i f i c a n a l y t e . SUMMARY OF METHOD

2.1

Up t o 5 g o f a f r o z e n t i s s u e sample i s t r a n s f e r r e d t o a 125 mL f l a s k . The t i s s u e i s d i g e s t e d w i t h n i t r i c a c i d , hydrogen p e r o x i d e and h e a t . T h i s d i g e s t i o n r e s u l t s i n a c l e a r s o l u t i o n t h a t i s t h e n analyzed by mass o r a t o m i c s p e c t r o m e t r y methods. The d e t e r m i n e d metal c o n c e n t r a t i o n i s r e p o r t e d i n microgram/gram ( p g / g ) wet t i s s u e weight.

DEFINITIONS

3.1

TOTAL RECOVERABLE - The c o n c e n t r a t i o n o f a n a l y t e d e t e r m i n e d t o be i n e i t h e r a s o l i d sample o r an u n f i l t e r e d aqueous sample f o l l o w i n g t r e a t m e n t by r e f l u x i n g w i t h h o t d i l u t e m i n e r a l a c i d .

3.2

LABORATORY REAGENT BLANK (LRB) - A s o l u t i o n o f r e a g e n t s t h a t i s t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a l l g l a s s w a r e and equipment t h a t a r e used w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e l a b o r a t o r y environment, r e a g e n t s , o r apparatus.

INTERFERENCES

4.1

Chromium c o n t a m i n a t i o n o f b i o l o g i c t l samples f r o m t h e use o f s t a i n l e s s s t e e l has been r e p o r t e d . Use o f s p e c i a l c u t t i n g implements and d i s s e c t i n g board made f r o m m a t e r i a l s t h a t a r e n o t o f i n t e r e s t i s recommended. K n i f e b l a d e s made o f t i t a n i u m w i t h T e f l o n handles have been s u c c e s s f u l l y used.

4.2

I n sample p r e p a r a t i o n , c o n t a m i n a t i o n i s o f p r i m e concern. The work area, i n c l u d i n g bench t o p and fume hood, s h o u l d be p e r i o d i c a l l y cleaned i n o r d e r t o e l i m i n a t e e n v i r o n m e n t a l c o n t a m i n a t i o n .

4.3

Chemical i n t e r f e r e n c e s a r e m a t r i x dependent and cannot be p r e d i c t e d .

5.1

A l l personnel h a n d l i n g e n v i r o n m e n t a l samples known t o c o n t a i n o r t o have been i n c o n t a c t w i t h human waste s h o u l d be immunized a g a i n s t known d i s e a s e c a u s a t i v e agents.

5.2

M a t e r i a l s a f e t y d a t a sheets f o r a l l chemical r e a g e n t s s h o u l d be a v a i l a b l e t o and understood by a l l personnel u s i n g t h i s method. Concentrated n i t r i c and h y d r o c h l o r i c a c i d s a r e m o d e r a t e l y t o x i c and e x t r e m e l y i r r i t a t i n g t o s k i n and mucus membranes. Hydrogen p e r o x i d e

Metals

27

is a strong oxidizing reagent. Use these reagents in a hood whenever possible and if eye or skin contact occurs, flush with large volumes of water. Always wear safety glasses or a shield for eye protection when working with these reagents. 6.

APPARATUS AND EQUIPMENT

6.1 LABWARE - For determination of trace levels o f elements, contamination and loss are o f prime consideration. Potential contamination sources include improperly cleaned laboratory apparatus and general contamination within the laboratory environment from dust, etc. A clean laboratory work area designated for trace element sample handling must be used. Sample containers can introduce positive and negative errors in the determination of trace elements by contributing contaminants through surface desorption/leaching, or depleting element concentrations through adsorption processes. All reusable labware (glass, quartz, polyethylene, Teflon, etc.), including the sample container, should be cleaned prior to use or shown to be contaminant free. Labware should be soaked overnight and thoroughly washed with laboratorygrade detergent and water, rinsed with water, and soaked for four hours in a mixture of dilute nitric and hydrochloric acid (1+2+9), followed by rinsing with water, ASTM type I water and oven drying. NOTE:

Chromic acid must not be used for cleaning glassware.

6.1.1 Glassware - Volumetric flasks, graduated cylinders and 125-mL Erlenmeyer fl asks,

6.1.2 Assorted calibrated pipettes. 6.1.3 Wash bottle - One piece stem, Teflon FEP bottle with Tefzel ETFE screw closure, 125-mL capacity.

6.2 SAMPLE PROCESSING EQUIPMEN1 6.2.1 Balance 0.1 mg.

-

Analytical, capable o f accurately weighing to

6.2.2 Hot Plate - (Corning PClOO or equivalent). hot plate will aid in sample digestion.

An oscillating

6.3 TISSUE DISSECTING EQUIPMENT 6.3.1. Dissecting Board: Polyethylene or other inert, nonmetallic material, any non-wetting, easy-to-clean or disposable surface is suitable. Adhesive backed Teflon or plastic film may be convenient to use.

6.3.2 forceps: Plastic, Teflon or Teflon coated.

28

Methods for the Determination

6.3.3 S u r g i c a l Blades: D i s p o s a b l e s t a i n l e s s s t e e l w i t h s t a i n l e s s s t e e l o r p l a s t i c h a n d l e ( S e c t . 4.1). 6.3.4 S c i s s o r s :

Stainless steel

6.3.5 P l a s t i c bags w i t h w a t e r t i g h t s e a l , m e t a l f r e e . 6.3.6 Label tape:

Self-adhesive, v i n y l coated marking tape, s o l v e n t r e s i s t a n t , u s a b l e f o r temperatures f r o m t121OC t o -23OC.

6.3.7 P o l y v i n y l c h l o r i d e o r r u b b e r g l o v e s , t a l c - f r e e . 7.

REAGENTS AND CONSUMABLE HATERIALS

7.1

Reagents may c o n t a i n e l e m e n t a l i m p u r i t i e s w h i c h m i g h t a f f e c t a n a l y t i c a l d a t a . H i g h - p u r i t y r e a g e n t s s h o u l d be used whenever p o s s i b l e . A l l a c i d s used f o r t h i s method must be o f u l t r a h i g h p u r i t y grade.

7.1.1

N i t r i c acid, concentrated (sp.gr.

7.1.2

Hydrochloric acid, concentrated (sp.gr.

7.1.3

Hydrogen p e r o x i d e (30%)

1.41). 1.19).

7.2 WATER - F o r a l l sample p r e p a r a t i o n and d i l u t i o n s , ASTM t y p e I w a t e r (ASTM D1193) i s r e q u i r e d . S u i t a b l e w a t e r may be p r e p a r e d b y p a s s i n g d i s t i l l e d w a t e r t h r o u g h a mixed bed o f a n i o n and c a t i o n exchange resins. 8.

SAMPLE COLLECTION, PRESERVATION AND STORAGE

8.1

A p p r o p r i a t e i n d i v i d u a l t i s s u e samples s h o u l d bf t a k e n soon a f t e r If dissection o f c o l l e c t i o n and must be t a k e n p r i o r t o f r e e z i n g t h e t i s s u e cannot be performed i m m e d i a t e l y a f t e r c o l l e c t i o n , i t s h o u l d be p l a c e d i n a p l a s t i c bag (Sect. 6.3.5), s e a l e d and p l a c e d on i c e o r r e f r i g e r a t e d a t a p p r o x i m a t e l y 4 ° C .

8.2

P r i o r t o d i s s e c t i o n , t h e t i s s u e s h o u l d be r i n s e d w i t h m e t a l - f r e e w a t e r and b l o t t e d d r y . D i s s e c t i o n s h o u l d be p e r f o r m e d w i t h i n 24 hours o f c o l l e c t i o n . Each i n d i v i d u a l t i s s u e sample s h o u l d a l s o be r i n s e d w i t h m e t a l - f r e e w a t e r , b l o t t e d dry, and f r o z e n a t <-2O0C (dry ice).

8.3

T i s s u e samples o f up t o 5 g s h o u l d be t a k e n u s i n g a s p e c i a l implement ( S e c t . 4.1) and handled w i t h p l a s t i c f o r c e p s (Sect. 6 . 3 . 2 p .

.

8.4 A maximum h o l d i n g t i m e f o r f r o z e n samples has n o t been determined.

Metals 9.

29

CALIBRATION AND STANDARDIZATION

9.1

Not a p p l i c a b l e . selected.

F o l l o w i n s t r u c t i o n s g i v e n i n t h e a n a l y t i c a l method

10. 10.1 Each l a b o r a t o r y d e t e r m i n i n g t o t a l r e c o v e r a b l e elements i s r e q u i r e d t o o p e r a t e a f o r m a l q u a l i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f a QC program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y and a n a l y s i s o f l a b o r a t o r y r e a g e n t b l a n k s and f o r t i f i e d b l a n k s and samples as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n performance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f data generated. 10.2 S p e c i f i c i n s t r u c t i o n s on a c c o m p l i s h i n g t h e d e s c r i b e d a s p e c t s o f t h e QC program a r e d i s c u s s e d i n t h e a n a l y t i c a l methods. 11.

PROCEDURE

1 1 . 1 Sample P r e p a r a t i o n - P l a c e up t o a 5 g subsample o f f r o z e n t i s s u e i n t o a 125-mL e r l e n m e y e r f l a s k . Any sample s p i k i n g s o l u t i o n s s h o u l d be added a t t h i s t i m e and a l l o w e d t o be i n c o n t a c t w i t h t h e sample p r i o r t o addition o f acid. 11.2 Add 10 mL o f c o n c e n t r a t e d n i t r i c a c i d and warm on a h o t p l a t e u n t i l t h e t i s s u e i s s o l u b i l i z e d . G e n t l e s w i r l i n g t h e samples o r use o f an o s c i l l a t i n g h o t p l a t e w i l l a i d i n t h i s process. 11.3 I n c r e a s e t e m p e r a t u r e t o n e a r b o i l i n g u n t i l t h e s o l u t i o n b e g i n s t o t u r n brown. Cool sample, add an a d d i t i o n a l 5 mL o f c o n c e n t r a t e d n i t r i c a c i d and r e t u r n t o t h e h o t p l a t e u n t i l t h e s o l u t i o n once a g a i n b e g i n s t o t u r n brown. 11.4 Cool sample, add an a d d i t i o n a l 2 mL o f c o n c e n t r a t e d n i t r i c a c i d , r e t u r n t o t h e h o t p l a t e and r e d u c e t h e volume t o 5-10 mL. Cool sample, add 2 mL o f 30% hydrogen p e r o x i d e , r e t u r n sample t o t h e h o t p l a t e and reduce t h e volume t o 5-10 mL. 11.5 Repeat Sect. 11.4 u n t i l t h e s o l u t i o n i s c l e a r o r u n t i l a t o t a l o f 10 mL o f p e r o x i d e has been added. NOTE: A l a b o r a t o r y r e a g e n t b l a n k i s e s p e c i a l l y c r i t i c a l i n t h i s p r o c e d u r e because t h e p r o c e d u r e c o n c e n t r a t e s any r e a g e n t c o n t a m i n a n t s . 11.6 Cool t h e sample, add 2 mL o f c o n c e n t r a t e d h y d r o c h l o r i c a c i d , r e t u r n t o t h e h o t p l a t e and reduce t h e volume t o 5 mL. 11.7 A l l o w t h e sample t o c o o l and q u a n t i t a t i v e l y t r a n s f e r t o a 100-mL v o l u m e t r i c f l a s k . D i l u t e t o volume w i t h ASTM t y p e I w a t e r , mix, and a l l o w any i n s o l u b l e m a t e r i a l t o s e p a r a t e . . The sample i s now r e a d y f o r a n a l y s i s by e i t h e r ICP-AES o r STGFAA. F o r a n a l y s i s by ICP-MS an additional d i l u t i o n (1t4) i s required.

30

Methods for the Determination 11.8 Sample A n a l y s i s - Use one o f t h e a n a l y t i c a l methods l i s t e d i n Sect. 1.3.

12.

CALCULATIONS 12.1 Not a p p l i c a b l e . 1.3.

13.

Discussed i n a n a l y t i c a l methods l i s t e d i n S e c t .

PRECISION AND ACCURACY 13.1 Not a p p l i c a b l e . A v a i l a b l e d a t a i n c l u d e d i n a n a l y t i c a l methods l i s t e d i n Sect. 1 . 3 .

14.

REFERENCES 1.

V e r s i e c k , J., and F . B a r b i e r , "Sample C o n t a m i n a t i o n as A Source o f E r r o r i n Trace-Element A n a l y s i s o f B i o l o g i c a l Samples," T a l a n t a , V O I . 29, pp. 973-984, 1982.

2.

Ney, J . J . , and M. G. M a r t i n , " I n f l u e n c e s o f P r e f r e e z i n g on Heavy M e t a l C o n c e n t r a t i o n s i n B l u e g i l l S u n f i s h , " Water Res., V o l . 19, NO. 7 , pp. 905-907, 1985.

3.

"The P i l o t N a t i o n a l Environmental Specimen Bank," NBS S p e c i a l P u b l i c a t i o n 656, U. S . Department o f Commerce, August; 1983.

4.

K o i r t y o h a n n , S . R., and H. C. Hopps, "Sample S e l e c t i o n , C o l l e c t i o n , P r e s e r v a t i o n and S t o r a g e f o r Data Bank on Trace Elements i n Human Tissue," F e d e r a t i o n Proceedings, V o l . 40, No. 8, June, 1981.

Metals

31

METHOD 200.7 DETERMINATION OF METALS AND TRACE ELEMENTS I N WATER AND WASTES BY INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY

Revision 4.4 EMMC V e r s i o n

USEPA-ICP Users Group ( E d i t e d by T.D. M a r t i n and J.F. Kopp) - Method 200.7, R e v i s i o n 1.0, ( P r i n t e d 1979, P u b l i s h e d 1982) T.D. M a r t i n and E.R. M a r t i n - Method 200.7,

R e v i s i o n 3.0 (1990)

T.D. M a r t i n , C.A. B r o c k h o f f , J.T. Creed, and S.E. Long (Technology A p p l i c a t i o n s I n c . ) - Method 200.7, R e v i s i o n 3.3 (1991) T.D. M a r t i n , C.A. B r o c k h o f f , J.T. Creed, and EMMC Methods Work Group 200.7, R e v i s i o n 4.4 (1994)

ENVIRONMENTAL HONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U. S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

-

Method

32

Methods for the Determination METHOD 200.7

DETERMINATION OF METALS AND TRACE ELEMENTS I N WATER AND WASTES BY INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY

1.0 SCOPE AND APPLICATION

1.1 Inductively coupled plasma-atomic emission spectrometry (ICP-AES) is used to determine metals and some nonmetals in solution. This method is a conso1icla;ion o f existing methods for water, wastewater, and sol id wastes. (For analysis of petroleum products see references 5 and 6 Sect. 16.0) This method is applicable to the following analytes:

Analyte A1 umi num Anti mony Arsenic Barium Beryl 1 i um Boron Cadmi um Calcium Ceriuma Chromi um Cobalt Copper Iron Lead Lithium Magnesium Manganese Mercury Molybdenum Nickel Phosphorus Potass i urn Selenium Silicab

Chemical Abstract Services Registry Numbers (CASRN) 7429-90-5 7440-36-0 7440- 38-2 7440-39-3 7440-41-7 7440-42-8 7440-43-9 7440-70-2 7440-45-1 7440-47-3 7440-48-4 7440-50-8 7439-89-6 7439-92-1 7439-93-2 7439-95-4 7439-96-5 7439-97-6 7439-98-7 7440-02-0 7723-14-0 7440-09-7 7782-49-2 7631-86-9

(continues on next page) Cerium has been included as method analyte for correction of potential interelement spectral interference.

a

This method is not suitable for the determination of silica in solids. Revision 4 . 4

May

1994

Metals

An a 1y t e Silver Sod iurn S t r o n t ium Thal 1 i urn Tin T i t a n i urn Vanad ium Zinc

33

Chemical A b s t r a c t S e r v i c e s R e g i s t r y Numbers (CASRN) 7440-22-4 7440-23-5 7440-24-6 7440-28-0

7440-31-5 7440-32-6 7440-62-2 7440-66-6

1.2

For r e f e r e n c e where t h i s method i s approved f o r use i n compliance m o n i t o r i n g programs [e.g., Clean Water A c t (NPDES) o r Safe D r i n k i n g Water A c t (SDWA)] c o n s u l t b o t h t h e a p p r o p r i a t e s e c t i o n s o f t h e Code o f Federal R e g u l a t i o n (40 CFR P a r t 136 Table 1B f o r NPDES, and P a r t 141 9 141.23 f o r d r i n k i n g w a t e r ) , and t h e l a t e s t Federal R e g i s t e r announcements.

1.3

ICP-AES can be used t o d e t e r m i n e d i x s o l v e d a n a l y t e s i n aqueous samples a f t e r s u i t a b l e f i l t r a t i o n and a c i d p r e s e r v a t i o n . To reduce p o t e n t i a l i n t e r f e r e n c e s , d i s s o l v e d s o l i d s s h o u l d be < 0.2% (w/v) (Sect. 4 . 2 ) .

1.4

W i t h t h e e x c e p t i o n o f s i l v e r , where t h i s method i s approved f o r t h e d e t e r m i n a t i o n o f c e r t a i n m e t a l and m e t a l l o i d contaminants i n d r i n k i n g w a t e r , samples may be analyzed d i r e c t l y by pneumatic n e b u l i z a t i o n w i t h o u t a c i d d i g e s t i o n i f t h e sample has been p r o p e r l y p r e s e r v e d w i t h a c i d and has t u r b i d i t y o f < 1 NTU a t t h e t i m e o f a n a l y s i s . T h i s t o t a l r e c o v e r a b l e d e t e r m i n a t i o n p r o c e d u r e i s r e f e r r e d t o as " d i r e c t analysis". However, i n t h e d e t e r m i n a t i o n o f some p r i m a r y d r i n k i n g w a t e r m e t a l contaminants, p r e c o n c e n t r a t i o n of t h e sample may be r e q u i r e d p r i o r t o a n a l y s i s i n o r d e r t o meet d r i n k i n g w a t e r acceptance performance c r i t e r i a ( S e c t s . 11.2.2 t h r u 11.2.7).

1.5

F o r t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e a n a l y t e s i n aqueous and s o l i d samples a d i g e s t i o n / e x t r a c t i o n i s r e q u i r e d p r i o r t o a n a l y s i s when t h e elements a r e n o t i n s o l u t i o n (e.g., s o i l s , sludges, sediments and aqueous samples t h a t may c o n t a i n p a r t i c u l a t e and suspended s o l i d s ) . Aqueous samples c o n t a i n i n g suspended o r p a r t i c u l a t e m a t e r i a l 2 1% (w/v) s h o u l d be e x t r a c t e d as a s o l i d t y p e sample.

1.6

When d e t e r m i n i n g boron and s i l i c a i n aqueous samples, o n l y p l a s t i c , PTFE o r q u a r t z labware s h o u l d be used from t i m e of sample c o l l e c t i o n t o completion o f analysis. F o r a c c u r a t e d e t e r m i n a t i o n o f boron i n s o l i d samples o n l y q u a r t z o r PTFE beakers s h o u l d be used d u r i n g a c i d e x t r a c t i o n w i t h immediate t r a n s f e r o f an e x t r a c t a l i q u o t t o a p l a s t i c c e n t r i f u g e t u b e f o l l o w i n g d i l u t i o n o f t h e e x t r a c t t o volume. When possible, b o r o s i l i c a t e g l a s s s h o u l d be avoided t o p r e v e n t contamination o f these analytes. R e v i s i o n 4.4 May 1994

34

Methods for the Determination

1.7 Silver is only slightly soluble in the presence o f chloride unless there is a sufficient chloride concentration to form the soluble chloride complex. Therefore, low recoveries of silver may occur in samples, fortified sample matrices and even fortified hldnks if determined as a dissolved analyte or by "direct analysis" where the sample has not been processed using the total recoverable mixed acid digestion. For this reason it is recommended that samples be digested prior to the determination of silver. The total recoverable sample digestion procedure given in this method is suitable for the determination of silver in aqueous samples containing concentrations up to 0.1 mg/L. For the analysis of wastewater samples containing higher concentrations o f silver, succeeding smaller volume, well mixed aliquots should be prepared until the analysis solution contains < 0.1 mg/L silver. The extraction of solid samples containing concentrations of silver > 50 mg/kg should be treated in a similar manner. Also, the extraction of tin from solid samples should be prepared again using aliquots < 1 g when determined sample concentrations exceed 1%. 1.8

The total recoverable sample digestion procedure given in this method will solubilize and hold in solution only minimal concentrations o f barium in the presence of free sulfate. For the analysis of barium in samples having varying and unknown concentrations of sulfate, analysis should be completed as soon as possible after sample preparation.

1.9

The total recoverable sample digestion procedure given in this method is not suitable for the determination of volatile organo-mercury compounds. However, if digestion is not required (turbidity < 1 NTU), the combined concentrations of inorganic and organo-mercury in solution can be determined by "direct analysis" pneumatic nebulization provided the sample solution is adjusted to contain the same mixed acid (HNO, t HC1) matrix as the total recoverable calibration standards and blank solutions.

1.10 Detection limits and linear ranges for the elements will vary with the wavelength selected, the spectrometer, and the matrices. Table 1 provides estimated instrument detection limits for the listed wavelengths.' However, actual method detection 1 imits and 1 inear working ranges will be dependent on the sample matrix, instrumentation, and selected operating conditions. 1.11 Users of the method data should state the data-quality ohjectives

prior to analysis. Users of the method must document and have on file the required initial demonstration performance data described in Section 9.2 prior to using the method for analysis. 2.0

SUMMARY OF METHOD 2.1

An aliquot of a well mixed, homogeneous aqueous or solid sample is accurately weighed or measured for sample processing. For total recoverable analysis of a solid or an aqueous sample containing undissolved material, analytes are first solubilized by gentle refluxing with nitric and hydrochloric acids. Aft,er cooling, the sample is made up to volume, is mixed and centrifuged or allowed to Revision 4.4 Hay 1994

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settle overnight prior to analysis. For the determination of dissolved analytes in a filtered aqueous sample aliquot, or for the "direct analysis" total recoverable determination of analytes in drinking water where sample turbidity is < 1 NTU, the sample is made ready for analysis by the appropriate addition of nitric acid, and then diluted to a predetermined volume and mixed before analysis. 2.2 The analysis described in this method involves multielemental determinations by ICP-AES using sequential or simultaneous instruments. The instruments measure characteristic atomic-line emission spectra by optical spectrometry. Samples are nebulized and the resulting aerosol is transported to the plasma torch. Element specific emission spectra are produced by a radio-frequency inductively coupled plasma. The spectra are dispersed by a grating spectrometer, and the intensities of the line spectra are monitored at specific wavelengths by a photosensitive device. Photocurrents from the photosensitive device are processed and controlled by a computer system. A background correction technique is required to compensate for variable background contribution to the determination o f the analytes. Background must be measured adjacent to the analyte wavelength during analysis. Various interferences must be considered and addressed appropriately as discussed in Sections 4, 7, 9, 10, and 11. 3.0

DEFINITIONS 3.1

Calibration Blank - A volume of reagent water acidified with the same acid matrix as in the calibration standards. The calibration blank is a zero standard and i s used to calibrate the ICP instrument (Sect. 7.10.1).

3.2 Calibration Standard (CAL) - A solution prepared from the dilution o f stock standard solutions. The CAL solutions are used to calibrate the instrument response with respect to analyte concentration (Sect. 7 . 9 ) . 3.3

Dissolved Analyte - The concentration of analyte in an aqueous sample that will pass through a 0.45-pm membrane filter assembly prior to sample acidification (Sect. 11.1).

3.4

Field Reagent Blank (FRB) - An aliquot of reagent water or other blank matrix that is placed in a sample container in the laboratory and treated as a sample in all respects, including shipment to the sampling site, exposure to the sampling site conditions, storage, preservation, and all analytical procedures. The purpose of the FRB is to determine if method analytes or other interferences are present in the field environment (Sect 8.5).

3.5 Instrument Detection Limit ( I D L ) - The concentration equivalent to the analyte signal which is equal to three times the standard deviation of a series of ten replicate measurements of the calibration blank signal at the same wavelength (Table 1.). 3.6

Instrument Performance Check (IPC) Solution - A solution of method analytes, used to evaluate the performance of the instrument system Revision 4.4 Hay 1994

36

Methods for the Determination w i t h r e s p e c t t o a d e f i n e d set. o f method c r i t e r i a ( S e c t s . 9.3.4).

7.11 &

3.7

I n t e r n a l Standard - Pure a n a l y t e ( s ) added t o a sample, e x t r a c t , o r s t a n d a r d s o l u t i o n i n known amount(s) and used t o measure t h e r e l a t i v e responses o f o t h e r method a n a l y t e s t h a t a r e components o f t h e same sample o r s o l u t i o n . The i n t e r n a l s t a n d a r d must be an a n a l y t e t h a t i s n o t a sample component ( S e c t . 1 1 . 5 ) .

3.8

L a b o r a t o r y D u p l i c a t e s (LD1 and LD2) - Two a l i q u o t s o f t h e same sample t a k e n i n t h e l a b o r a t o r y and analyzed s e p a r a t e l y w i t h i d e n t i c a l procedures. Analyses o f LD1 and LO2 i n d i c a t e s p r e c i s i o n a s s o c i a t e d w i t h l a b o r a t o r y procedures, b u t n o t w i t h sample c o l l e c t i o n , p r e s e r v a t i o n , o r s t o r a g e procedures.

3.9

L a b o r a t o r y F o r t i f i e d B l a n k (LFB) - An a l i q u o t o f LRB t o which known q u a n t i t i e s of t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e methodology i s i n c o n t r o l and whether t h e l a b o r a t o r y i s capable o f making a c c u r a t e and p r e c i s e measurements ( S e c t s . 7 . 1 0 . 3 & 9.3.2).

3 . 1 0 L a b o r a t o r y F o r t i f i e d Sample M a t r i x (LFM) - An a l i q u o t o f an environmental sample t o which known q u a n t i t i e s o f t h e method a n a l y t e s The LFM i s a n a l y z e d e x a c t l y l i k e a a r e added i n t h e l a b o r a t o r y . sample, and i t s purpose i s t o d e t e r m i n e whether t h e sample m a t r i x contributes bias t o the analytical results. The background c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be determined i n a separate a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s ( S e c t . 9 . 4 ) .

3.11 L a b o r a t o r y Reagent B l a n k (LRB) - An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a17 glassware, equipment, s o l v e n t s , r e a g e n t s , and i n t e r n a l standards t h a t a r e used w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e l a b o r a t o r y environment, r e a g e n t s , o r apparatus ( S e c t s . 7 . 1 0 . 2 & 9.3.1).

3.12 L i n e a r Dynamic Range (LDR) - The c o n c e n t r a t i o n range o v e r which t h e i n s t r u m e n t response t o an a n a l y t e i s l i n e a r ( S e c t . 9 . 2 . 2 ) .

3.13 Method D e t e c t i o n L i m i t (MDL) - The minimum c o n c e n t r a t i o n o f an a n a l y t e t h a t can be i d e n t i f i e d , measured, and r e p o r t e d w i t h 99% c o n f i d e n c e t h a t t h e a n a l y t e c o n c e n t r a t i o n i s g r e a t e r t h a n z e r o ( S e c t . 9.2.4 and Table 4.).

3 . 1 4 Plasma S o l u t i o n - A s o l u t i o n t h a t i s used t o d e t e r m i n e t h e oDtimum h e i g h t above t h e work c o i l f o r v i e w i n g t h e plasma ( S e c t s . 7.15 & 10.2.3). 3 . 1 5 Q u a l i t y C o n t r o l Sample (QCS) - A s o l u t i o n o f method a n a l y t e s o f known c o n c e n t r a t i o n s which i s used t o f o r t i f y an a l i q u o t o f L R B o r sample m a t r i x . The QCS i s o b t a i n e d f r o m a source e x t e r n a l t o t h e l a b o r a t o r y R e v i s i o n 4.4 May 1994

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and d i f f e r e n t f r o m t h e source o f c a l i b r a t i o n s t a n d a r d s . I t i s used t o check e i t h e r l a b o r a t o r y o r i n s t r u m e n t performance ( S e c t s . 7.12 & 9.2.3). 3.16 S o l i d Sample - F o r t h e purpose o f t h i s method, a sample t a k e n from m a t e r i a l c l a s s i f i e d as e i t h e r s o i l , sediment o r s l u d g e . 3.17 S p e c t r a l I n t e r f e r e n c e Check (SIC) S o l u t i o n - A s o l u t i o n o f s e l e c t e d method a n a l y t e s of h i g h e r c o n c e n t r a t i o n s which i s used t o e v a l u a t e t h e p r o c e d u r a l r o u t i n e f o r c o r r e c t i n g known i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e s w i t h r e s p e c t t o a d e f i n e d s e t o f method c r i t e r i a ( S e c t s . 7.13, 7.14 & 9 . 3 . 5 ) . 3.18 Standard A d d i t i o n - The a d d i t i o n o f a known amount o f a n a l y t e t o t h e sample i n o r d e r t o d e t e r m i n e t h e r e l a t i v e response o f t h e d e t e c t o r t o an a n a l y t e w i t h i n t h e sample m a t r i x . The r e l a t i v e response i s t h e n used t o assess e i t h e r an o p e r a t i v e m a t r i x e f f e c t o r t h e sample a n a l y t e c o n c e n t r a t i o n ( S e c t s . 9.5.1 & 1 1 . 5 ) . 3.19 S t o c k Standard S o l u t i o n - A c o n c e n t r a t e d s o l u t i o n c o n t a i n i n g one o r more method a n a l y t e s p r e p a r e d i n t h e l a b o r a t o r y u s i n g assayed r e f e r e n c e m a t e r i a l s o r purchased f r o m a r e p u t a b l e commercial source (Sect. 7.8). 3.20 T o t a l Recoverable A n a l y t e - The c a n c e n t r a t i o n o f a n a l y t e determined e i t h e r by “ d i r e c t a n a l y s i s ” o f an u n f i l t e r e d a c i d p r e s e r v e d d r i n k i n g w a t e r sample w i t h t u r b i d i t y o f < 1 NTU ( S e c t . 11.2.1), o r by a n a l y s i s o f t h e s o l u t i o n e x t r a c t o f a s o l i d sample o r an u n f i l t e r e d aqueous sample f o l l o w i n g d i g e s t i o n by r e f l u x i n g w i t h h o t d i l u t e m i n e r a l a c i d ( s ) as s p e c i f i e d i n t h e method ( S e c t s . 11.2 & 1 1 . 3 ) . 3.21 Water Sample - F o r t h e purpose o f t h i s method, a sample t a k e n f r o m one o f t h e f o l l o w i n g sources: d r i n k i n g , s u r f a c e , ground, storm r u n o f f , i n d u s t r i a l o r domestic wastewater.

4.0

INTERFERENCES 4.1

S p e c t r a l i n t e r f e r e n c e s a r e caused by background e m i s s i o n from c o n t i n u o u s o r r e c o m b i n a t i o n phenomena, s t r a y l i g h t f r o m t h e l i n e e m i s s i o n o f h i g h c o n c e n t r a t i o n elements, o v e r l a p o f a s p e c t r a l l i n e f r o m a n o t h e r element, o r u n r e s o l v e d over1 ap o f m o l e c u l a r band s p e c t r a . 4.1.1

Background e m i s s i o n and s t r a y l i g h t can u s u a l l y be compensated f o r by s u b t r a c t i n g t h e background e m i s s i o n determined by measurement(s) a d j a c e n t t o t h e a n a l y t e wavelength peak. S p e c t r a l scans o f samples o r s i n g l e element s o l u t i o n s i n t h e a n a l y t e r e g i o n s may i n d i c a t e n o t o n l y when a l t e r n a t e wavelengths a r e d e s i r a b l e because o f severe s p e c t r a l i n t e r f e r e n c e , b u t a l s o w i l l show whether t h e most a p p r o p r i a t e e s t i m a t e o f t h e background e m i s s i o n i s p r o v i d e d by an i n t e r p o l a t i o n f r o m measurements on b o t h s i d e s o f t h e wavelength peak o r by t h e measured e m i s s i o n on one s i d e o r t h e other. The l o c a t i o n ( s ) s e l e c t e d f o r t h e measurement o f background i n t e n s i t y w i l l be determined by t h e c o m p l e x i t y o f R e v i s i o n 4 . 4 May1994

38

Methods for the Determination

the spectrum adjacent to the wavelength peak. The location(s) used for routine measurement must be free of off-line spectral interference (interelement or molecular) or adequately corrected to reflect the same change in background intensity as occurs at the wavelength peak. 4.1.2

Spectral overlaps may be avoided by using an alternate wavelength or can be compensated for by equations that correct for interelement contributions, which involves measuring the interfering elements. Some potential on-line spectral interferences observed for the recommended wavelengths are given in Table 2. When operative and uncorrected, these interferences will produce false-positive determinations and be reported as analyte concentrations. The interferences listed are only those that occur between method analytes. Only interferences of a direct overlap nature that were observed with a single instrument having a working resolution o f 0.035 nm are listed. More extensive information on interferant effects at variou: wavelengths and resolutions is available in Boumans’ Tables. Users may apply interelement correction factors determined on their instruments within tested concentration ranges to compensate (off-line or online) for the effects of interfering elements.

4.1.3

When interelement corrections are applied, there is a need to verify their accuracy by analyzing spectral interference check solutions as described in Section 7 . 1 3 . Interelement corrections will vary for the same emission line among instruments because of differences in resolution, as determined by the grating plus the entrance and exit slit widths, and by the order of dispersion. Interelement corrections will also vary depending upon the choice of background correction points. Selecting a background correction point where an interfering emission line may appear should be avoided when practical. Interelement corrections that constitute a major portion of an emission signal may not yield accurate data. Users should not forget that some samples may contain uncommon elements that could contribute spectral interferences .7*8

4.1.4

The interference effects must be evaluated for each individual instrument whether configured as a sequential or simultaneous instrument. For each instrument, intensities will vary not only with optical resolution but also with operating conditions (such as power, viewing height and argon flow rate). When using the recommended wavelengths given in Table 1 , the analyst is required t o determine and document for each wavelength the effect from the known interferences given in Table 2 , and to utilize a computer routine for their automatic correction on all analyses. To determine the appropriate location for off-1 ine background correction, the user must scan the area on either side adjacent to the wavelength and record the apparent emission intensity from all other method analytes. This spectral information must be documented and Revision 4.4 Hay 1994

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kept on file. Ihe location selected for background correction must be either free of off-line interelement spectral int.erfrrc!ncc> or a computer routine must be used for their aut.omat.ic corri?(.t.ion on all determinations. I f a wavelength other than t ti(! recoinmended wavelength is used, the user must det.ermirre and document both the on-1 ine and off-1 ine spectral int.erferen(-r Pffect from all method analytes and provide for their dutoinnt.ic correction on all analyses. Tests to determine t h e spectral interference must be done using analyte concentrations that will adequately describe the interference. Normally, 100 mg/L single element solutions are sufficient, however, for analytes such as iron that may be found at high concentration a more appropriate test would be to use a concentration near the upper LDR limit. See Section 10.4 for required spectral interference test criteria. 4.1.5

4.2

When interelement corrections are not used, either on-going S I C solutions (Sect. 7.14) must be analyzed to verify the absence o f interel ement spectral interference or a computer software routine must be employed for comparing the determinative data to limits files for notifying the analyst when an interfering element is detected in the sample at a concentration that will produce either an apparent false positive concentration, > the analyte I D L , or false negative analyte concentration, < the 99% lower control limit of the calibration blank. When the interference accounts for 10% or more o f the analyte concentration, either an alternate wavelength free of interference or another approved test procedure must be used to complete the analysis. For example, the copper peak at 213.853 nm could be mistaken for the zinc peak at 213.856 nm in solutions with high copper and low zinc concentrations. For this example, a spectral scan in the 213.8-nm region would not reveal the misidentification because a single peak near the zinc location would be observed. The possibility of this misidentification of copper for the zinc peak at 213.856 nm can be identified by measuring the copper at another emission line, e.g. 324.754 nm. Users should be aware that, depending upon the instrumental resolution, a1 ternate wavelengths with adequate sensitivity and freedom from interference may not be available for all matrices. In these circumstances the analyte must be determined using another approved test procedure.

Physical interferences are effects associated with the sample nebulization and transport processes. Changes in viscosity and surface tension can cause significant inaccuracies, especially in samples containing high dissolved solids or high acid concentrations. If physical interferences are present, they must be reduced by such means as a high-solids nebulizer, diluting the sample, using a peristaltic pump, or using an appropriate internal standard element. Another problem that can occur with high dissolved solids is salt buildup at the tip of the nebulizer, which affects aerosol flow rate and causes instrumental drift. This problem can be controlled by a high-solids nebulizer, wetting the argon prior to nebulization, using Revision 4 . 4 Hay 1994

40

Methods for the Determination a tip washer, or diluting the sample. Also, it has been reported that better control of the argon flow rates, especially for the nebulizer, improves instrument stab'rlityand precision; this is accomplished with the use of mass flow controllers.

5.0

4.3

Chemical interferences include molecular-compound formation, ionization effects, and solute-vaporization effects. Normally, these effects are not significant with the ICP-AES technique. If observed, they can be minimized by careful selection of operating conditions (such as incident power and observation height), by buffering of the sample, by matrix matching, and by standard-addition procedures. Chemical interferences are highly dependent on matrix type and the specific analyte element.

4.4

Memory interferences result when analytes in a previous sample contribute to the signals measured in a new sample. Memory effects can result from sample deposition on the uptake tubing to the nebulizer, and from the buildup of sample material in the plasma torch and spray chamber. The site where these effects occur is dependent on the element and can be minimized by flushing the system with a rinse blank between samples (Sect. 7 . 1 0 . 4 ) . The possibility of memory interferences should be recognized within an analytical run and suitable rinse times should be used to reduce them. The rinse times necessary for a particular element must be estimated prior to analysis. This may be achieved by aspirating a standard containing elements corresponding to either their LDR or a concentration ten times those usually encountered. The aspiration time should be the same as a normal sample analysis period, followed by analysis of the rinse blank at designated intervals. The length of time required to reduce analyte signals to within a factor of two of the method detection limit, should be noted. Until the required rinse time is established, this method requires a rinse period of at least 60 sec between samples and standards. If a memory interference is suspected, the sample must be re-analyzed after a long rinse period.

SAFETY

5.1

The toxicity or carcinogenicity of each reagent used in this method have not been fully established. Each chemical should be regarded as a potential health hazard and exposure to these compounds should be as low as reasonably achievable. Each laboratory is responsible for maintaining a current awareness file of OSHA regulations regard?-y9 the safe handling of the chemicals specified in this method. A reference file of material data handling sheets should also be made available to all personnel involved in the chemical analysis. Specifically, concentrated nitric and hydrochloric acids present various hazards and are moderately toxic and extremely irritating to skin and mucus membranes. Use these reagents in a fume hood whenever possible and if eye or skin contact occurs, flush with large volumes of water. Always wear safety glasses or a shield for eye protection, protective clothing and observe proper mixing when working with these reagents.

Revision 4 . 4 May 1994

Metals

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5.2

The a c i d i f i c a t i o n o f samples c o n t a i n i n g r e a c t i v e m a t e r i a l s may r e s u l t i n t h e r e l e a s e o f t o x i c gases, such as cyanides o r s u l f i d e s . A c i d i f i c a t i o n o f samples s h o u l d be done i n a fume hood.

5.3

A l l personnel h a n d l i n g e n v i r o n m e n t a l samples known t o c o n t a i n o r t o have been i n c o n t a c t w i t h human waste s h o u l d be immunized a g a i n s t known d i s e a s e c a u s a t i v e agents.

5.4

The i n d u c t i v e l y c o u p l e d plasma s h o u l d o n l y be viewed w i t h p r o p e r eye p r o t e c t i o n from the u l t r a v i o l e t emissions.

5.5

I t i s t h e r e s p o n s i b i l i t y o f t h e u s e r o f t h i s method t o comply w i t h r e l e v a n t d i s p o s a l and waste r e g u l a t i o n s . F o r guidance see S e c t i o n s 14.0 and 15.0.

EQUIPMENT AND 6.1

SUPPLIES

I n d u c t i v e l y c o u p l e d plasma e m i s s i o n s p e c t r o m e t e r : 6.1.1

C o m p u t e r - c o n t r o l l e d e m i s s i o n spectrometer w i t h backgroundc o r r e c t i o n c a p a b i l i t y . The spectrometer must be capable o f meeting and complying w i t h t h e r e q u i r e m e n t s d e s c r i b e d and r e f e r e n c e d i n S e c t i o n 2.2.

6.1.2

Radio-frequency g e n e r a t o r c o m p l i a n t w i t h FCC r e g u l a t i o n s .

6.1.3

Argon gas s u p p l y - H i g h p u r i t y grade (99.99%). When analyses a r e conducted f r e q u e n t l y , l i q u i d argon i s more economical and r e q u i r e s l e s s f r e q u e n t replacement o f t a n k s t h a n compressed argon i n c o n v e n t i o n a l c y l i n d e r s .

6.1.4

A v a r i a b l e speed p e r i s t a l t i c pump i s r e q u i r e d t o d e l i v e r b o t h s t a n d a r d and sample s o l u t i o n s t o t h e n e b u l i z e r .

6.1.5

( o p t i o n a l ) Mass f l o w c o n t r o l l e r s t o r e g u l a t e t h e argon f l o w r a t e s , e s p e c i a l l y t h e a e r o s o l t r a n s p o r t gas, a r e h i g h l y recommended. T h e i r use w i l l p r o v i d e more e x a c t i n g c o n t r o l o f r e p r o d u c i b l e p l asma c o n d i t i o n s .

6.2

A n a l y t i c a l balance, w i t h c a p a b i l i t y t o measure t o 0.1 mg, f o r use i n w e i g h i n g s o l i d s , f o r p r e p a r i n g standards, and f o r d e t e r m i n i n g dissolved solids i n digests o r extracts.

6.3

A temperature adjustable t e m p e r a t u r e o f 95OC.

6.4

A t e m p e r a t u r e a d j u s t a b l e b l o c k d i g e s t e r capable o f (optional) m a i n t a i n i n g a t e m p e r a t u r e o f 95OC and equipped w i t h 250-mL c o n s t r i c t e d d i g e s t i o n tubes.

6.5

( o p t i o n a l ) A s t e e l c a b i n e t c e n t r i f u g e w i t h g u a r d bowl, e l e c t r i c t i m e r and b r a k e .

hot

plate

capable

of

maintaining

a

R e v i s i o n 4 . 4 May 1994

42

Methods for the Determination

6.6 A gravity convection drying oven with thermostatic control capable o f maintaining 180°C f 5OC.

6.7 (optional) An air displacement pipetter capable of delivering volumes ranging from 0.1 to 2500 pL with an assortment o f high quality disposable pipet tips. 6.8 Mortar and pestle, ceramic or nonmetallic material.

6.9 Polypropylene sieve, 5-mesh ( 4 mm opening). 6.10 Labware - For determination of trace levels of elements, contamination and loss are of prime consideration. Potential contamination sources include improperly cleaned 1 aboratory apparatus and general contamination within the laboratory environment from dust, etc. A clean 1 aboratory work area designated for trace element sample handling must be used. Sample containers can introduce positive and negative errors in the determination of trace elements by (1) contributing contaminants through surface desorption or leaching, (2) depleting element concentrations through adsorption processes. All reusable labware (glass, quartz, polyethylene, PTFE, FEP, etc.) should be sufficiently clean for the task objectives. Several procedures found to provide clean labware include washing with a detergent solution, rinsing with tap water, soaking for 4 h or more in 20% (v/v) nitric acid or a mixture of HNO, and HC1 (1+2+9), rinsing with reagent water and storing clean.*13 Chromic acid cleaning solutions must be avoided because chromium is an analyte. 6.10.1 Glassware - Volumetric flasks, graduated cylinders, funnels and centrifuge tubes (glass and/or metal-free plastic). 6.10.2 Assorted calibrated pipettes.

6.10.3 Conical Phillips beakers (Corning 1080-250 or equivalent), 250-mL with 50-mm watch glasses. 6.10.4 Griffin beakers, 250-mL with 75-mm watch (optional) 75-mm ribbed watch glasses.

glasses

and

6.10.5 (optional) PTFE and/or quartz Griffin beakers, 250-mL with PTFE covers.

6.10.6 Evaporating dishes or high-form crucibles, porcelain, 100 mL capaci ty . 6.10.7 Narrow-mouth storage bottles, FEP (fluorinated ethylene propylene) with screw closure, 125-mL to l-L capacities. 6.10.8 One-piece stem FEP wash bottle with screw closure, 125-mL capacity.

Revision 4.4 Hay 1994

Metals 7.0

43

REAGENTS AND STANDARDS

7.1 Reagents may contain elemental

impurities which might affect analytical data. Only high-purity reagents that conform to the American Chemical Society specifications should be used whenever possible. If the purity of a reagent is in question, analyze for contamination. All acids used for this method must be o f ultra highpurity grade or equivalent. Suitable acids are available from a number o f manufacturers. Redistilled acids prepared by sub-boil ing di st i 1 1 at ion are acceptable.

7.2 Hydrochloric acid, concentrated (sp.gr. 1.19) - HC1. 7.2.1

Hydrochloric acid (ltl) - Add 500 mL concentrated HC1 to 400 mL reagent water and dilute to 1 L.

7.2.2

Hydrochloric acid (lt4) - Add 200 m L concentrated HC1 to 400 mL reagent water and dilute to 1 L.

7.2.3

Hydrochloric acid (1t20) mL reagent water.

-

Add 10 mL concentrated HC1 to 200

7.3 Nitric acid, concentrated (sp.gr. 1.41)

-

HNO,.

7.3.1

Nitric acid (1t1) - Add 500 mL concentrated HNO, to 400 mL reagent water and dilute to 1 L .

7.3.2

Nitric acid (1t2) reagent water.

7.3.3

Nitric acid (1t5) - Add 50 mL concentrated HNO, to 250 mL reagent water.

7.3.4

Nitric acid (1t9)

-

-

Add 100 mL concentrated HNO, to 200 mL

Add 10 mL concentrated HNO, to 90 mL

reagent water.

7.4 Reagent water. A11,references to water in this method refer to ASTM Type I grade water.

7.5 Ammonium hydroxide, concentrated (sp. gr. 0.902). 7.6 Tartaric acid, ACS reagent grade.

7.7 Hydrogen peroxide, 50%, stabilized certified reagent grade. 7.8 Standard Stock Solutions - Stock standards may be purchased or prepared from ultra-high purity grade chemicals (99.99 to 99.999% All compounds must be dried for 1 h at 105"C, unless pure). otherwise specified. It is recommended that stock solutions be stored in FEP bottles. Replace stock standards when succeeding dilutions for preparation of calibration standards cannot be verified. CAUTION:

Many of these chemicals are extremely toxic if inhaled or swallowed (Sect. 5.1). Wash hands thoroughly after handling. Revision 4.4 Hay 1994

44

Methods for the Determination T y p i c a l s t o c k s o l u t i o n p r e p a r a t i o n procedures f o l l o w f o r l - L q u a n t i t i e s , b u t f o r t h e purpose o f p o l l u t i o n p r e v e n t i o n , t h e a n a l y s t i s encouraged t o p r e p a r e s m a l l e r q u a n t i t i e s when p o s s i b l e . C o n c e n t r a t i o n s a r e c a l c u l a t e d based upon t h e w e i g h t o f t h e p u r e element o r upon t h e w e i g h t o f t h e compound m u l t i p l i e d b y t h e f r a c t i o n o f t h e a n a l y t e i n t h e compound. From p u r e element , w e i g h t (mg ) Concentration = volume (L) From p u r e compound, w e i g h t (mg) x g r a v i m e t r i c f a c t o r Concentration = volume ( L ) where : g r a v i m e t r i c f a c t o r = the weight f r a c t i o n o f t h e gnalyte i n the compound. 7.8.1

Aluminum s o l u t i o n , s t o c k , 1 mL = 1000 p g A l : D i s s o l v e 1.000 g o f aluminum m e t a l , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n an a c i d m i x t u r e o f 4.0 mL o f ( l t l ) HC1 and 1.0 mL o f c o n c e n t r a t e d HNO, i n a beaker. Warm beaker slowly t o e f f e c t solution. When d i s s o l u t i o n i s complete, t r a n s f e r s o l u t i o n q u a n t i t a t i v e l y t o a l - L f l a s k , add an a d d i t i o n a l 10.0 mL o f ( l t l ) HC1 and d i l u t e t o volume w i t h reagent water.

7.8.2

Antimony s o l u t i o n , s t o c k , 1 mL = 1000 p g Sb: D i s s o l v e 1.000 g o f antimony powder, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 20.0 rnL ( l t l ) HNO, and 10.0 mL c o n c e n t r a t e d HC1. Add 100 mL r e a g e n t w a t e r and 1.50 g t a r t a r i c acid. Warm s o l u t i o n s l i g h t l y t o e f f e c t complete d i s s o l u t i o n . Cool s o l u t i o n and add r e a g e n t w a t e r t o volume i n a l - L volumetric flask.

7.8.3

A r s e n i c s o l u t i o n , s t o c k , 1 mL = 1000 p g As: D i s s o l v e 1.320 g o f As,O, ( A s f r a c t i o n = 0.7574), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 100 mL o f r e a g e n t w a t e r c o n t a i n i n g 10.0 mL c o n c e n t r a t e d NH OH. Warm t h e s o l u t i o n g e n t l y t o e f f e c t d i s s o l u t i o n . A c i d i t y t h e s o l u t i o n w i t h 20.0 mL c o n c e n t r a t e d HNO, and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h reagent water.

7.8.4

Barium s o l u t i o n , s t o c k , 1 mL = 1000 pg Ba: D i s s o l v e 1.437 g BaCO, (Ba f r a c t i o n = 0.6960), weighed a c c u r a t e l y t o a t l e a s t R e v i s i o n 4.4 May 1994

Metals

45

f o u r s i g n i f i c a n t f i g u r e s , i n 150 mL ( 1 t 2 ) HNO, w i t h h e a t i n g and s t i r r i n g t o degas and d i s s o l v e compound. L e t solution c o o l and d i l u t e w i t h r e a g e n t w a t e r i n 1-L v o l u m e t r i c f l a s k . 7.8.5

B e r y l l i u m s o l u t i o n , s t o c k , 1 mL = 1000 pg Be: DO NOT DRY. D i s s o l v e 19.66 g BeS04*4H,0 (Be f r a c t i o n = 0.0509), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n reagent water, add 10.0 mL Concentrated HNO,, and d i l u t e t o volume i n a 1-L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r .

7.8.6

Boron s o l u t i o n , s t o c k , 1 mL = 1000 p g B: DO NOT DRY. D i s s o l v e 5.716 g anhydrous H BO ( B f r a c t i o n = 0.1749), weighed a c c u r a t e l y t o a t l e a s € Sour s i g n i f i c a n t f i g u r e s , i n reagent w a t e r and d i l u t e i n a 1-L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r . T r a n s f e r i m m e d i a t e l y a f t e r m i x i n g t o a c l e a n FEP b o t t l e t o m i n i m i z e any l e a c h i n g o f boron f r o m t h e g l a s s v o l u m e t r i c c o n t a i n e r . Use o f a nonglass v o l u m e t r i c f l a s k i s recommended t o a v o i d boron c o n t a m i n a t i o n f r o m glassware.

7.8.7

Cadmium s o l u t i o n , s t o c k , 1 mL = 1000 p g Cd: D i s s o l v e 1.000 g Cd m e t a l , a c i d cleaned w i t h ( 1 t 9 ) HNO,, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 50 mL ( l t l ) HNO w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e w i t h r e a g e n t w a t e r i n a 1-L v o l u m e t r i c f l a s k .

7.8.8

Calcium s o l u t i o n , s t o c k , 1 mL = 1000 p g Ca: Suspend 2.498 g CaCO (Ca f r a c t i o n = 0.4005), d r i e d a t 180°C f o r 1 h b e f o r e weighing, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n r e a g e n t w a t e r and d i s s o l v e c a u t i o u s l y w i t h a minimum amount o f ( l t l ) HNO,. Add 10.0 mL c o n c e n t r a t e d HNO, and d i l u t e t o volume i n a 1-L v o l u m e t r i c f l a s k w i t h reagent water.

7.8.9

Cerium s o l u t i o n , s t o c k , 1 mL = 1000 pg Ce: S l u r r y 1.228 g CeO, (Ce f r a c t i o n = 0.8141), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 100 mL c o n c e n t r a t e d HNO, and evaporate t o dryness. S l u r r y t h e r e s i d u e i n 20 mL H20, add 50 mL c o n c e n t r a t e d HNO,, w i t h h e a t and s t i r r i n g add 60 mL 50% HzOz d r o p w i s e i n 1 mL increments a l l o w i n g p e r i o d s o f s t i r r i n g B o i l o f f excess H202 b e f o r e between t h e 1 mL a d d i t i o n s . d i l u t i n g t o volume i n a I - L v o l u m e t r i c f l a s k w i t h r e a g e n t water.

7.8.10

Chromium s o l u t i o n , s t o c k , 1 mL = 1000 p g C r : D i s s o l v e 1.923 g CrO, ( C r f r a c t i o n = 0.5200), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 120 mL ( 1 t 5 ) HNO,. When s o l u t i o n i s complete, d i l u t e t o volume i n a 1-L v o l u m e t r i c f l a s k w i t h reagent water.

7.8.11

C o b a l t s o l u t i o n , s t o c k , 1 mL = 1000 pg Co: D i s s o l v e 1.000 g Co m e t a l , a c i d cleaned w i t h ( 1 t 9 ) HNO,, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 50.0 mL ( l t l ) HNO,. Let s o l u t i o n c o o l and d i l u t e t o volume i n a 1-L v o l u m e t r i c f l a s k w i t h reagent water. R e v i s i o n 4 . 4 May1994

46

Methods for the Determination 7.8.12

Copper s o l u t i o n , s t o c k , 1 mL = 1000 p g Cu: D i s s o l v e 1.000 g Cu m e t a l , a c i d cleaned w i t h ( 1 t 9 ) HN03, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , I n 50.0 mL ( l t l ) HNO, w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e i n a 1-L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r .

7.8.13

I r o n s o l u t i o n , s t o c k , 1 mL = 1000 p g Fe: D i s s o l v e 1.000 g Fe m e t a l , a c i d cleaned w i t h ( l t l ) HC1, weighed a c c u r a t e l y t o f o u r s i g n i f i c a n t f i g u r e s , i n 100 mL ( l t l ) HC1 w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e w i t h r e a g e n t w a t e r i n a 1-L v o l u m e t r i c f l a s k .

7.8.14

Lead s o l u t i o n , s t o c k , 1 mL = 1000 p g Pb: D i s s o l v e 1.599 g Pb(N0,) (Pb f r a c t i o n = 0.6256), weighed a c c u r a t e l y t o a t l e a s t t o u r s i g n i f i c a n t f i g u r e s , i n a minimum amount o f ( 1 t 1 ) Add 20.0 mL ( l t l ) HNO, and d i l u t e t o volume i n a l - L HNO,. volumetric f l a s k w i t h reagent water.

7.8.15

L i t h i u m s o l u t i o n , s t o c k , 1 mL = 1000 p g L i : D i s s o l v e 5.324 g Li,CO, ( L i f r a c t i o n = 0.1878), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n a minimum amount o f ( l t l ) HC1 and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r .

7.8.16

Magnesium s o l u t i o n , s t o c k , 1 mL = 1000 p g Mg: D i s s o l v e 1.000 g c l e a n l y p o l i s h e d Mg r i b b o n , a c c u r a t e l y weighed t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n s l o w l y added 5.0 mL ( l t l ) HC1 (CAUTION: r e a c t i o n i s v i g o r o u s ) . Add 20.0 mL ( l t l ) HNO, and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r .

7.8.17

Manganese s o l u t i o n , s t o c k , 1 mL = 1000 p g Mn: D i s s o l v e 1.000 g o f manganese m e t a l , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 50 mL ( l t l ) HNO, and d i l u t e t o volume i n a l - L volumetric f l a s k w i t h reagent water.

7.8.18

Mercury s o l u t i o n , s t o c k , 1 mL = 1000 p g Hg: DO NOT DRY. CAUTION: h i g h l y t o x i c element. D i s s o l v e 1.354 g HgC1, (Hg f r a c t i o n = 0.7388) i n r e a g e n t w a t e r . Add 50.0 mL c o n c e n t r a t e d HNO, and d i l u t e t o volume i n 1-L v o l u m e t r i c f l a s k w i t h r e a g e n t water.

7.8.19

Molybdenum s o l u t i o n , s t o c k , 1 mL = 1000 p g Mo: D i s s o l v e 1.500 g MOO, (Mo f r a c t i o n = 0.6666), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n a m i x t u r e o f 100 mL r e a g e n t w a t e r and 10.0 mL c o n c e n t r a t e d NH,OH, h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e w i t h r e a g e n t w a t e r i n a l - L volumetric flask.

7.8.20

N i c k e l s o l u t i o n , s t o c k , 1 mL = 1000 p g N i : D i s s o l v e 1.000 g of n i c k e l m e t a l , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 20.0 mL h o t c o n c e n t r a t e d HNO,, c o o l , and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h r e a g e n t water.

R e v i s i o n 4.4 May 1994

Metals

47

7.8.21

Phosphorus s o l u t i o n , s t o c k , 1 mL = 1000 pg P : D i s s o l v e 3.745 g NH,H PO, ( P f r a c t i o n = 0 . 2 6 9 6 ) , weighed a c c u r a t e l y t o a t l e a s t t o u r s i g n i f i c a n t f i g u r e s , i n 200 mL r e a g e n t water and d i l u t e t o volume in a 1 - L v o l u m e t r i c f l a s k with r e a g e n t w a t e r .

7.8.22

Potassium s o l u t i o n , s t o c k , 1 rnL = 1000 pg K : D i s s o l v e 1.907 g KC1 ( K f r a c t i o n = 0.5244) d r i e d a t l l O " C , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , in r e a g e n t w a t e r , add 20 mL ( 1 t 1 ) HC1 and d i l u t e t o volume i n a l-L volumetric f l a s k with reagent water.

7.8.23

Selenium s o l u t i o n , s t o c k , 1 mL = 1000 pg Se: D i s s o l v e 1.405 g SeO, (Se f r a c t i o n = 0 . 7 1 1 6 ) , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 200 mL r e a g e n t water and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k with r e a g e n t w a t e r .

7.8.24

S i l i c a s o l u t i o n , s t o c k , 1 mL = 1000 pg SiO : DO NOT DRY. D i s s o l v e 2.964 g (NH,),SiF6, weighed a c c u r a t e 5 y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 200 mL ( 1 t 2 0 ) HC1 with h e a t i n g a t 85°C t o e f f e c t d i s s o l u t i o n . Let s o l u t i o n cool and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k with r e a g e n t w a t e r .

7.8.25

S i l v e r s o l u t i o n , s t o c k , 1 mL = 1000 pg Ag: D i s s o l v e 1.000 g Ag m e t a l , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 80 mL ( 1 t 1 ) HNO, with h e a t i n g t o e f f e c t d i s s o l u t i o n . Let s o l u t i o n cool and d i l u t e with r e a g e n t water i n a l-L v o l u m e t r i c f l a s k . S t o r e s o l u t i o n i n amber b o t t l e o r wrap b o t t l e completely w i t h aluminum f o i l t o p r o t e c t s o l u t i o n from l i g h t .

7.8.26

Sodium s o l u t i o n , s t o c k , 1 mL = 1000 pg Na: D i s s o l v e 2.542 g NaCl (Na f r a c t i o n = 0.3934), weighed a c c u r a t e l y t o a t l e a s t four s i g n i f i c a n t figures, in reagent water. Add 10.0 mL c o n c e n t r a t e d HNO, and d i l u t e t o volume i n a l-L volumetric f l a s k with reagent water.

7.8.27

S t r o n t i u m s o l u t i o n , s t o c k , 1 mL = 1000 fig S r : D i s s o l v e 1.685 g SrCO, ( S r f r a c t i o n = 0.5935), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 200 mL r e a g e n t w a t e r with dropwise a d d i t i o n o f 100 mL ( l t l ) HC1. D i l u t e t o volume i n a l - L volumetric f l a s k with reagent water.

7.8.28

Thallium s o l u t i o n , s t o c k , 1 mL = 1000 pg T1: D i s s o l v e 1.303 g TlNO, (T1 f r a c t i o n = 0 . 7 6 7 2 ) , weighed a c c u r a t e l y t o a t l e a s t four s i g n i f i c a n t figures, in reagent water. Add 1 0 . 0 mL c o n c e n t r a t e d HNO, and d i l u t e t o volume i n a l-L v o l u m e t r i c f l a s k with reagent water.

7.8.29

Tin s o l u t i o n , s t o c k , 1 mL = 1000 pg Sn: Dissolve 1.000 g Sn s h o t , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n an a c i d mixture of 10.0 mL c o n c e n t r a t e d HC1 and 2 . 0 mL ( l t l ) HNO, with h e a t i n g t o e f f e c t d i s s o l u t i o n . Let s o l u t i o n c o o l , add 200 mL c o n c e n t r a t e d HC1, and d i l u t e t o volume in a l-L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r . R e v i s i o n 4 . 4 May1994

48

Methods for the Determination 7.8.30

Titanium solution, ctock, 1 mL = 1000 pg Ti: DO NOT DRY. (Ti fraction = 0.1629), Dissolve 6.138 g (Nli,),TiO(CZO ),*H,O weighed accurately t o a t least four significant figures, in 100 mL reagent water. Dilute to volume in a 1-L volumetric flask with reagent water.

7.8.31

Vanadium solution, stock, 1 mL = 1000 pg V : Dissolve 1.000 g V metal, acid cleaned with ( 1 t 9 ) HN03, weighed accurately to at least four significant figures, in 50 mL ( l t l ) HNO with heating to effect dissolution. Let solution cool and dilute with reagent water to volume in a l-L volumetric flask.

7.9

7.8.32

Yttrium solution, stock 1 mL = 1000 pg Y : Dissolve 1.270 g Y,O, (Y fraction = 0.7875), weighed accurately to at least heating to four significant figures, in 50 mL ( l t l ) HNO,, effect dissolution. Cool and dilute to volume in a l - L volumetric flask with reagent water.

7.8.33

Zinc solution, stock, 1 mL = 1000 pg Zn: Dissolve 1.000 g Zn metal, acid cleaned with ( 1 t 9 ) HNO,, weighed accurately to at least four significant figures, in 50 mL ( l t l ) HNO, .with heating to effect dissolution. Let solution cool and dilute with reagent water to volume in a l-L volumetric flask.

Mixed Calibration Standard Solutions - For the analysis of total recoverable digested samples prepare mixed calibration standard solutions (see Table 3 ) by combining appropriate volumes of the stock solutions in 500-mL volumetric flasks containing 20 mL ( l t l ) HNO, and 20 mL ( l t l ) HC1 and dilute to volume with reagent water. Prior to preparing the mixed standards, each stock solution should be analyzed separately to determine possible spectral interferences or the presence of impurities. Care should be taken when preparing the mixed standards to ensure that the elements are compatible and stable together. To minimize the opportunity for contamination by the containers, it is recommended to transfer the mixed-standard solutions to acid-cleaned, never-used FEP fluorocarbon (FEP) bottles for storage. Fresh mixed standards should be prepared, as needed, with the realization that concentrations can change on aging. Calibration standards not prepared from primary standards must be initially verified using a certified reference solution. For the recommended wavelengths listed in Table 1 some typical calibration standard combinations are given in Table 3 .

NOTE:

If the addition of silver to the recommended mixed-acid calibration standard results in an initial precipitation, add 15 mL of reagent water and warm the flask until the solution clears. For this acid combination, the silver concentration should be limited to 0 . 5 mg/L.

7.10 Blanks - Four types of blanks are required for the analysis.

The calibration blank is used in establishing the analytical curve, the laboratory reagent blank i s used to assess possible contamination from the sample preparation procedure, the laboratory fortified blank is used to assess routine l a b o r a t o r y performance and a rinse blank is Revision 4 . 4 May 1994

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used t o f l u s h t h e i n s t r i r m e n t u p t a k e system and n e b u l i z e r between standards, check solutions, and samples t o reduce memory interferences. 7 . 1 0 . 1 The c a l i b r a t i o n b l a n k f o r aqueous samples and e x t r a c t s i s prepared by a c i d i f y i n g reagent water to the same c o n c e n t r a t i o n s o f t h e a c i d s as used f o r t h e standards. The c a l i b r a t i o n b l a n k s h o u l d be s t o r e d i n a FEP b o t t l e . 7.10.2

The l a b o r a t o r y r e a g e n t b l a n k (LRB) must r e a g e n t s i n t h e same volumes as used i n t h e samples. The LRB must be c a r r i e d t h r o u g h p r e p a r a t i o n scheme as t h e samples i n c l u d i n g when appl icab1 e.

7.10.3

The l a b o r a t o r y f o r t i f i e d b l a n k (LFB) i s p r e p a r e d by f o r t i f y i n g an a l i q u o t o f t h e l a b o r a t o r y r e a g e n t b l a n k w i t h a l l a n a l y t e s t o a s u i t a b l e c o n c e n t r a t i o n u s i n g t h e f o l l o w i n g recommended c r i t e r i a : Ag 5 0 . 1 mg/L, 2 K 5 . 0 mg/L and a l l o t h e r a n a l y t e s 0.2 mg/L o r a c o n c e n t r a t i o n a p p r o x i m a t e l y 100 t i m e s t h e i r r e s p e c t i v e MDL, whichever i s g r e a t e r . The LFB must be c a r r i e d t h r o u g h t h e same e n t i r e p r e p a r a t i o n scheme as t h e samples i n c l u d i n g sample d i g e s t i o n , when a p p l i c a b l e .

7.10.4

The r i n s e b l a n k i s p r e p a r e d by a c i d i f y i n g reagent w a t e r t o t h e same c o n c e n t r a t i o n s o f a c i d s as used i n t h e c a l i b r a t i o n b l a n k and s t o r e d i n a c o n v e n i e n t manner.

contain a l l the processing o f the t h e same e n t i r e sample d i g e s t i o n ,

7.11 I n s t r u m e n t Performance Check (IPC) S o l u t i o n - The I P C s o l u t i o n i s used t o p e r i o d i c a l l y v e r i f y i n s t r u m e n t performance d u r i n g a n a l y s i s . It s h o u l d be p r e p a r e d i n t h e same a c i d m i x t u r e as t h e c a l i b r a t i o n standards by combining method a n a l y t e s a t a p p r o p r i a t e c o n c e n t r a t i o n s . S i l v e r must be l i m i t e d t o < 0.5 mg/L; w h i l e p o t a s s i u m and phosphorus because o f h i g h e r MDLs and s i l i c a because o f p o t e n t i a l c o n t a m i n a t i o n s h o u l d be a t c o n c e n t r a t i o n s o f 10 mg/L. For other analytes a c o n c e n t r a t i o n o f 2 mg/L i s recommended. The I P C s o l u t i o n s h o u l d be p r e p a r e d f r o m t h e same s t a n d a r d s t o c k s o l u t i o n s used t o p r e p a r e t h e c a l i b r a t i o n standards and s t o r e d i n an FEP b o t t l e . Agency programs may s p e c i f y o r r e q u e s t t h a t a d d i t i o n a l i n s t r u m e n t performance check s o l u t i o n s be p r e p a r e d a t s p e c i f i e d c o n c e n t r a t i o n s i n o r d e r t o meet p a r t i c u l a r program needs.

7 . 12 Q u a l i t y C o n t r o l Sample (QCS) - A n a l y s i s o f a QCS i s r e q u i r e d f o r i n i t i a l and p e r i o d i c v e r i f i c a t i o n o f c a l i b r a t i o n standards o r s t o c k s t a n d a r d s o l u t i o n s i n o r d e r t o v e r i f y i n s t r u m e n t performance. The QCS must be o b t a i n e d f r o m an o u t s i d e source d i f f e r e n t from t h e s t a n d a r d s t o c k s o l u t i o n s and p r e p a r e d i n t h e same a c i d m i x t u r e as t h e c a l i b r a t i o n s t a n d a r d s . The c o n c e n t r a t i o n o f t h e a n a l y t e s i n t h e QCS s o l u t i o n s h o u l d be 2 1 mg/L, e x c e p t s i l v e r , which must be l i m i t e d t o a c o n c e n t r a t i o n o f 0 . 5 mg/L f o r s o l u t i o n s t a b i l i t y . The QCS s o l u t i o n s h o u l d be s t o r e d i n a FEP b o t t l e and analyzed as needed t o meet d a t a q u a l i t y needs. A f r e s h s o l u t i o n s h o u l d be p r e p a r e d q u a r t e r l y o r more f r e q u e n t l y as needed. R e v i s i o n 4.4 Hay 1994

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7.13 Spectral

Interference Check ( S I C ) Solutions - When interelement corrections are applied, S I C solutions are needed containing concentrations of the interfering elements at levels that will provide an adequate test of the correction factors. 7.13.1

SIC solutions containing (a) 300 mg/L Fe; (b) 200 mg/L AL; (c) 50 mg/L Ba; (d) 50 mg/L Be; (e) 50 mg/L Cd; (f) 50 mg/L Ce; (9) 50 mg/L Co; (h) 50 mg/L Cr; ( i )50 mg/L Cu; (j) 50 mg/L Mn; (k) 50 mg/L Mo; (1) 50 mg/L Ni; (m) 50 mg/L Sn; (n) 50 mg/L SiO,; ( 0 ) 50 mg/L Ti; (p) 50 mg/L T1 and ( 4 ) 50 mg/L V should be prepared in the same acid mixture as the calibration standards and stored in FEP bottles. These solutions can be used to periodically verify a partial list of the on-line (and possible off-1 ine) interelement spectral correction factors for the recommended wavelengths given in Table 1. Other solutions could achieve the same objective as well. (Multielement SIC solutions3 may be prepared and substituted for the single element solutions provided an analyte i s nat subject to interference from more than one interferant in the sol ut i on. ) NOTE:

If wavelengths other than those recommended in Table 1 are used, other solutions different from those above (a thru q) may be required.

7.13.2

For interferences from iron and aluminum, only those correction factors (positive or negative) when multiplied by 100 to calculate apparent analyte concentrations that exceed the determined analyte IDL or fall below the lower 3-sigma control limit of the calibration blank need be tested on a dai 1 y basi s.

7.13.3

For the other interfering elements, only those correction factors (positive or negative) when multiplied by 10 to calculate apparent analyte concentrations that exceed the determined analyte IDL or fall below the lower 3-sigma control limit o f the calibration blank need be tested on a daily basis.

7.13.4

If the correction routine is operating properly, the determined apparent analyte(s) concentration from analysis of each interference solution (a thru q) should fall within a specific concentration range bracketing the calibration blank. This concentration range is calculated by multiplying the concentration of the interfering element by the value of the correction factor being tested and dividing by 10. If after subtraction of the calibration blank the apparent analyte concentration is outside (above or below) this range, a change in the correction factor of more than 10% should be suspected. The cause of the change should be determined and corrected and the correction factor should be updated. NOTE:

The SIC solution should be analyzed more than once to confirm a change has occurred with adequate rinse time Revision 4.4 May 1994

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between s o l u t i o n s and b e f o r e subsequent a n a l y s i s o f t h e c a l i b r a t i o n blank.

7.13.5

I f t h e c o r r e c t i o n f a c t o r s t e s t e d on a d a i l y b a s i s a r e found t o be w i t h i n t h e 10% c r i t e r i a f o r 5 c o n s e c u t i v e days, t h e r e q u i r e d v e r i f i c a t i o n frequency o f those f a c t o r s i n compliance may be extended t o a weekly b a s i s . A l s o , i f t h e n a t u r e o f t h e samples analyzed i s such ( e . g . , f i n i s h e d d r i n k i n g w a t e r ) t h a t t h e y do n o t c o n t a i n c o n c e n t r a t i o n s o f t h e i n t e r f e r i n g elements a t t h e lO-mg/L l e v e l , d a i l y v e r i f i c a t i o n i s n o t r e q u i r e d ; however, a1 1 i n t e r e l e m e n t s p e c t r a l c o r r e c t i o n f a c t o r s must be v e r i f i e d a n n u a l l y and updated, i f necessary.

7.13.6

I f t h e i n s t r u m e n t does n o t d i s p l a y n e g a t i v e c o n c e n t r a t i o n values, f o r t i f y t h e SIC s o l u t i o n s w i t h t h e elements o f i n t e r e s t a t 1 mg/L and t e s t f o r a n a l y t e r e c o v e r i e s t h a t a r e below 95%. I n t h e absence o f measurable a n a l y t e , overc o r r e c t i o n c o u l d go u n d e t e c t e d because a n e g a t i v e v a l u e c o u l d be r e p o r t e d as zero.

7.14 F o r i n s t r u m e n t s w i t h o u t i n t e r e l e m e n t c o r r e c t i o n c a p a b i l i t y o r when i n t e r e l e m e n t c o r r e c t i o n s a r e n o t used, SIC s o l u t i o n s ( c o n t a i n i n g s i m i l a r c o n c e n t r a t i o n s o f t h e m a j o r components i n t h e samples, e.g., can s e r v e t o v e r i f y t h e absence o f e f f e c t s a t t h e wavelengths s e l e c t e d . These d a t a must be k e p t on f i l e w i t h t h e sample a n a l y s i s d a t a . I f t h e SIC s o l u t i o n c o n f i r m s an o p e r a t i v e i n t e r f e r e n c e t h a t i s 2 10% o f t h e a n a l y t e c o n c e n t r a t i o n , t h e a n a l y t e must be d e t e r m i n e d u s i n g a wavelength and background c o r r e c t i o n l o c a t i o n f r e e o f t h e i n t e r f e r e n c e o r by a n o t h e r approved t e s t procedure. Users a r e a d v i s e d t h a t h i g h s a l t c o n c e n t r a t i o n s can cause a n a l y t e s i g n a l suppressions and confuse i n t e r f e r e n c e t e s t s . 2 10 mg/L)

7.15 Plasma S o l u t i o n - The plasma s o l u t i o n i s used f o r d e t e r m i n i n g t h e optimum v i e w i n g h e i g h t o f t h e plasma above t h e work c o i l p r i o r t o u s i n g t h e method ( S e c t . 10.2). The s o l u t i o n i s p r e p a r e d by adding a 5-mL a l i q u o t f r o m each o f t h e s t o c k s t a n d a r d s o l u t i o n s o f a r s e n i c , l e a d , selenium, and t h a l l i u m t o a m i x t u r e o f 20 mL (ltl) n i t r i c a c i d and 20 mL (ltl) h y d r o c h l o r i c a c i d and d i l u t i n g t o 500 mL w i t h r e a g e n t w a t e r . S t o r e i n a FEP b o t t l e . 8.0

SAMPLE COLLECTION, PRESERVATION, AND STORAGE

8.1

P r i o r t o t h e c o l l e c t i o n o f an aqueous sample, c o n s i d e r a t i o n s h o u l d be given t o t h e type o f data required, (i.e., dissolved o r t o t a l r e c o v e r a b l e ) , so t h a t a p p r o p r i a t e p r e s e r v a t i o n and p r e t r e a t m e n t steps can be t a k e n . The pH o f a l l aqueous samples must be t e s t e d i m m e d i a t e l y p r i o r t o a1 i q u o t i n g f o r p r o c e s s i n g o r " d i r e c t a n a l y s i s " t o ensure t h e sample has been p r o p e r l y p r e s e r v e d . If properly acid preserved, t h e sample can be h e l d up t o 6 months b e f o r e a n a l y s i s .

8.2

F o r t h e d e t e r m i n a t i o n o f t h e d i s s o l v e d elements, t h e sample must be f i l t e r e d t h r o u g h a 0.45-pm p o r e d i a m e t e r membrane f i l t e r a t t h e t i m e o f c o l l e c t i o n o r as soon t h e r e a f t e r as p r a c t i c a l l y p o s s i b l e . (Glass o r p l a s t i c f i l t e r i n g apparatus a r e recommended t o a v o i d p o s s i b l e R e v i s i o n 4.4 Hay 1994

52

Methods for the Determination contamination. Only p l a s t i c apparatus should be used when t h e d e t e r m i n a t i o n s o f boron and s i l i c a a r e c r i t i c a l . ) Use a p o r t i o n o f t h e f i l t e r e d sample t o r i n s e t h e f i l t e r f l a s k , d i s c a r d t h i s p o r t i o n and c o l l e c t t h e r e q u i r e d volume o f f i l t r a t e . A c i d i f y t h e f i l t r a t e w i t h (It\) n i t r i c a c i d i m m e d i a t e l y f o l l o w i n g f i ' \ t r a t i o n t o pH < 2. 8.3

F o r t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e elements i n aqueous samples, samples a r e n o t f i l t e r e d , b u t a c i d i f i e d w i t h ( l t l ) n i t r i c a c i d t o pH < 2 ( n o r m a l l y , 3 mL o f ( l t l ) a c i d p e r l i t e r o f sample i s s u f f i c i e n t f o r most ambient and d r i n k i n g w a t e r samples). P r e s e r v a t i o n may be done a t t h e t i m e o f c o l l e c t i o n , however, t o a v o i d t h e hazards o f s t r o n g a c i d s i n t h e f i e l d , t r a n s p o r t r e s t r i c t i o n s , and p o s s i b l e c o n t a m i n a t i o n i t i s recommended t h a t t h e samples be r e t u r n e d t o t h e l a b o r a t o r y w i t h i n two weeks o f c o l l e c t i o n and a c i d p r e s e r v e d upon r e c e i p t i n t h e l a b o r a t o r y . F o l l o w i n g a c i d i f i c a t i o n , t h e sample s h o u l d be mixed, h e l d f o r s i x t e e n hours, and t h e n v e r i f i e d t o be pH < 2 j u s t p r i o r w i t h d r a w i n g an a l i q u o t f o r p r o c e s s i n g o r " d i r e c t a n a l y s i s " . I f f o r some reason such as h i g h a l k a l i n i t y t h e sample pH i s v e r i f i e d t o be > 2 , more a c i d must be added and t h e sample h e l d f o r s i x t e e n hours u n t i l v e r i f i e d t o be pH < 2. See S e c t i o n 8.1.

NOTE:

9.0

When t h e n a t u r e o f t h e sample i s e i t h e r unknown o r i s known t o be hazardous, a c i d i f i c a t i o n s h o u l d be done i n a fume hood. See S e c t i o n 5 . 2 .

8.4

S o l i d samples r e q u i r e no p r e s e r v a t i o n p r i o r t o a n a l y s i s o t h e r t h a n s t o r a g e a t 4°C. There i s no e s t a b l i s h e d h o l d i n g t i m e l i m i t a t i o n f o r s o l i d samples.

8.5

For aqueous samples, a f i e l d b l a n k should be prepared and analyzed as r e q u i r e d by t h e d a t a u s e r . Use t h e same c o n t a i n e r and a c i d as used i n sample c o l l e c t i o n .

QUALITY CONTROL 9.1

Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a f o r m a l qua1 i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f t h i s program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y , and t h e p e r i o d i c a n a l y s i s o f l a b o r a t o r y r e a g e n t blanks, f o r t i f i e d b l a n k s and o t h e r l a b o r a t o r y s o l u t i o n s as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n performance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f t h e d a t a t h u s generated.

9.2

I n i t i a l Demonstration o f Performance (mandatory), 9.2.1

The i n i t i a l d e m o n s t r a t i o n o f performance i s used t o c h a r a c t e r i z e i n s t r u m e n t performance ( d e t e r m i n a t i o n o f l i n e a r dynamic ranges and a n a l y s i s o f q u a l i t y c o n t r o l samples) and l a b o r a t o r y performance ( d e t e r m i n a t i o n o f method d e t e c t i o n l i m i t s ) p r i o r t o analyses conducted by t h i s method.

9.2.2

L i n e a r dynamic range (LDR) - The upper l i m i t o f t h e LDR must be e s t a b l i s h e d f o r each wavelength u t i l i z e d . I t must be R e v i s i o n 4.4 Hay 1994

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d e t e r m i n e d f r o m a l i n e a r c a l i b r d t i o n p r e p a r e d i n t h e normal manner u s i n g t h e e s t a b l i s h e d a n a l y t i c a l o p e r a t i n g p r o c e d u r e f o r t h e i n s t r u m e n t . The LDR s h o u l d be d e t e r m i n e d b y a n a l y z i n g succeedingly higher standard concentrations o f the analyte u n t i l t h e o b s e r v e d a n a l y t e c o n c e n t r a t i o n i s no more t h a n 10% below t h e s t a t e d c o n c e n t r a t i o n o f t h e standard. Determined LDRs must be documented and k e p t on f i l e . The LDR w h i c h may be u s e d f o r t h e a n a l y s i s o f samples s h o u l d be j u d g e d b y t h e a n a l y s t f r o m t h e r e s u l t i n g d a t a . D e t e r m i n e d sample a n a l y t e c o n c e n t r a t i o n s t h a t a r e g r e a t e r t h a n 90% o f t h e d e t e r m i n e d u p p e r LDR l i m i t must be d i l u t e d and r e a n a l y z e d . The LDRs s h o u l d be v e r i f i e d a n n u a l l y o r whenever, i n t h e judgement o f t h e a n a l y s t , a change i n a n a l y t i c a l p e r f o r m a n c e caused by e i t h e r a change i n i n s t r u m e n t h a r d w a r e o r o p e r a t i n g c o n d i t i o n s w o u l d d i c t a t e t h e y be r e d e t e r m i n e d .

9.2.3

Q u a l i t y c o n t r o l sample ( Q C S ) - When b e g i n n i n g t h e use o f t h i s method, on a q u a r t e r l y b a s i s , a f t e r t h e p r e p a r a t i o n o f s t o c k o r c a l i b r a t i o n s t a n d a r d s o l u t i o n s o r as r e q u i r e d t o meet d a t a qua1 i t y needs, v e r i f y t h e c a l i b r a t i o n s t a n d a r d s and a c c e p t a b l e i n s t r u m e n t p e r f o r m a n c e w i t h t h e p r e p a r a t i o n and a n a l y s e s o f a QCS ( S e c t . 7 . 1 2 ) . To v e r i f y t h e c a l i b r a t i o n s t a n d a r d s t h e d e t e r m i n e d mean c o n c e n t r a t i o n s f r o m 3 a n a l y s e s o f t h e QCS must be w i t h i n _+ 5% o f t h e s t a t e d v a l u e s . I f the calibration s t a n d a r d c a n n o t be v e r i f i e d , . p e r f o r m a n c e o f t h e d e t e r m i n a t i v e s t e p o f t h e method i s u n a c c e p t a b l e . The s o u r c e o f t h e p r o b l e m must be i d e n t i f i e d and c o r r e c t e d b e f o r e e i t h e r p r o c e e d i n g on w i t h t h e i n i t i a l d e t e r m i n a t i o n o f method d e t e c t i o n l i m i t s o r c o n t i n u i n g w i t h on-going analyses.

9.2.4

Method d e t e c t i o n l i m i t (MDL) - MDLs m u s t be e s t a b l i s h e d f o r a l l wavelengths u t i l i z e d , u s i n g reagent water (blank) f o r t i f i e d a t a concentration o f twy5 t o three times t h e estimated instrument detection l i m i t . To d e t e r m i n e MDL v a l u e s , t a k e seven r e p l i c a t e a l i q u o t s o f t h e f o r t i f i e d r e a g e n t w a t e r and p r o c e s s t h r o u g h t h e e n t i r e a n a l y t i c a l method. P e r f o r m a l l c a l c u l a t i o n s d e f i n e d i n t h e method and r e p o r t t h e c o n c e n t r a t i o n v a l u e s i n t h e a p p r o p r i a t e u n i t s . C a l c u l a t e t h e MDL as f o l l o w s : MDL

=

( t ) x (S)

where: t

S

Note:

s t u d e n t s ’ t v a l u e f o r a 99% c o n f i d e n c e l e v e l and a standard d e v i a t i o n e s t i m a t e w i t h n-1 degrees o f freedom [ t = 3 . 1 4 f o r seven r e p l i c a t e s ] .

=

=

standard d e v i a t i o n o f t h e r e p l i c a t e analyses.

I f additional confirmation i s desired, reanalyze the seven r e p 1 i c a t e a1 i q u o t s on t w o more n o n c o n s e c u t i v e d a y s and a g a i n c a l c u l a t e t h e MDL v a l u e s f o r each day. An a v e r a g e o f t h e t h r e e MDL v a l u e s f o r each a n a l y t e If may p r o v i d e f o r a more a p p r o p r i a t e MDL e s t i m a t e . t h e r e l a t i v e s t a n d a r d d e v i a t i o n (RSD) f r o m t h e a n a l y s e s R e v i s i o n 4 . 4 May1994

54

Methods for the Determination o f t h e seven a l i q u o t s i s < l o % , t h e c o n c e n t r a t i o n used t o d e t e r m i n e t h e a n a l y t e MDL may have been inappropr i a t e l y h i g h f o r t h e d e t e r m i n a t i o n . I f so, t h i s c o u l d r e s u l t i n t h e c a l c u l a t i o n o f an u n r e a l i s t i c a l l y l o w MDL. C o n c u r r e n t l y , d e t e r m i n a t i o n o f MDL i n r e a g e n t w a t e r r e p r e s e n t s a b e s t case s i t u a t i o n and does n o t r e f l e c t p o s s i b l e m a t r i x e f f e c t s o f r e a l w o r l d samples. However, s u c c e s s f u l analyses o f LFMs ( S e c t . 9.4) and the analyte a d d i t i o n t e s t described i n Section 9.5.1 can g i v e c o n f i d e n c e t o t h e MDL v a l u e determined i n r e a g e n t w a t e r . T y p i c a l s i n g l e l a b o r a t o r y MDL v a l u e s u s i n g t h i s method a r e g i v e n i n Table 4 . The MDLs must be s u f f i c i e n t t o d e t e c t a n a l y t e s a t t h e r e q u i r e d l e v e l s a c c o r d i n g t o compliance m o n i t o r i n g r e g u l a t i o n (Sect. 1 . 2 ) . MDLs s h o u l d be d e t e r m i n e d a n n u a l l y , when a new o p e r a t o r b e g i n s work o r whenever, i n t h e judgement o f t h e a n a l y s t , a change i n a n a l y t i c a l performance caused by e i t h e r a change i n i n s t r u m e n t hardware o r o p e r a t i n g c o n d i t i o n s would d i c t a t e t h e y be r e d e t e r m i n e d . 9.3

Assessing L a b o r a t o r y Performance (mandatory) 9.3.1

L a b o r a t o r y r e a g e n t b l a n k (LRB) - The l a b o r a t o r y must analyze a t l e a s t one LRB ( S e c t . 7.10.2) w i t h each b a t c h of 20 o r fewer samples o f t h e same m a t r i x . LRB d a t a a r e used t o assess c o n t a m i n a t i o n f r o m t h e l a b o r a t o r y environment. LRB v a l u e s t h a t exceed t h e MDL i n d i c a t e l a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n s h o u l d be suspected. When LRB v a l u e s c o n s t i t u t e 10% o r more o f t h e a n a l y t e l e v e l determined f o r a sample o r i s 2.2 t i m e s t h e a n a l y t e MDL whichever i s g r e a t e r , f r e s h a l i q u o t s o f t h e samples must be p r e p a r e d and analyzed a g a i n f o r t h e a f f e c t e d a n a l y t e s a f t e r t h e source o f c o n t a m i n a t i o n has been c o r r e c t e d and a c c e p t a b l e LRB v a l u e s have been o b t a i n e d .

9.3.2

L a b o r a t o r y f o r t i f i e d b l a n k (LFB) - The l a b o r a t o r y must analyze a t l e a s t one LFB ( S e c t . 7.10.3) w i t h each b a t c h o f samples. C a l c u l a t e accuracy as p e r c e n t r e c o v e r y u s i n g t h e f o l l o w i n g equation:

R =

LFB - LRB

x

100

S

where:

R LFB LRB

= =

s

=

=

percent recovery. l a b o r a t o r y f o r t i f i e d blank. l a b o r a t o r y reagent blank. concentration equivalent o f analyte added t o f o r t i f y t h e LBR s o l u t i o n .

I f t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e r e q u i r e d c o n t r o l l i m i t s o f 85-115%, t h a t a n a l y t e i s judged o u t o f R e v i s i o n 4 . 4 Hay 1994

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55

c o n t r o l , and t h e source o f t h e problem s h o u l d be i d e n t i f i e d and resolved before continuing analyses. 9.3.3

The l a b o r a t o r y must use LFB analyses d a t a t o assess l a b o r a t o r y performance a g a i n s t t h e r e q u i r e d c o n t r o l l i m i t s o f 85-115% ( S e c t . 9 . 3 . 2 ) . When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e ( u s u a l l y a minimum o f t w e n t y t o t h i r t y a n a l y s e s ) , o p t i o n a l c o n t r o l l i m i t s can be developed from t h e mean p e r c e n t r e c o v e r y ( x ) and t h e s t a n d a r d d e v i a t i o n ( S ) o f t h e mean p e r c e n t r e c o v e r y . These d a t a can be used t o e s t a b l i s h t h e upper and l o w e r c o n t r o l l i m i t s as f o l l o w s :

UPPER CONTROL L I M I T LOWER CONTROL LIMIT

= =

x t 3s x - 3s

The o p t i o n a l c o n t r o l 1 i m i t s must be equal t o o r b e t t e r t h a n t h e r e q u i r e d c o n t r o l l i m i t s o f 85-115%. A f t e r each f i v e t o t e n new r e c o v e r y measurements, new c o n t r o l 1 i m i t s can be c a l c u l a t e d u s i n g o n l y t h e most r e c e n t t w e n t y t o t h i r t y d a t a p o i n t s . Also, t h e s t a n d a r d d e v i a t i o n ( S ) d a t a s h o u l d be used t o e s t a b l i s h an on-going p r e c i s i o n statement f o r t h e l e v e l o f c o n c e n t r a t i o n s i n c l u d e d i n t h e LFB. These d a t a must be k e p t on f i l e and be a v a i l a b l e f o r review. 9.3.4

I n s t r u m e n t performance check (IPC) s o l u t i o n - For a l l d e t e r m i n a t i o n s t h e l a b o r a t o r y must analyze t h e I P C s o l u t i o n ( S e c t . 7.11) and a c a l i b r a t i o n b l a n k immediately f o l l o w i n g daily calibration, a f t e r e v e r y t e n t h sample ( o r more f r e q u e n t l y , i f r e q u i r e d ) and a t t h e end o f t h e sample r u n . A n a l y s i s o f t h e c a l i b r a t i o n b l a n k s h o u l d always be < t h e a n a l y t e IDL, b u t > t h e l o w e r 3-sigma c o n t r o l l i m i t o f t h e c a l i b r a t i o n b l a n k . A n a l y s i s o f t h e I P C s o l u t i o n immediately f o l l o w i n g c a l i b r a t i o n must v e r i f y t h a t t h e i n s t r u m e n t i s w i t h i n k 5% o f c a l i b r a t i o n w i t h a r e l a t i v e s t a n d a r d d e v i a t i o n < 3% f r o m r e p l i c a t e i n t e g r a t i o n s 2 4. Subsequent analyses o f t h e I P C s o l u t i o n must be w i t h i n k 10% o f c a l i b r a t i o n . I f the c a l i b r a t i o n cannot be v e r i f i e d w i t h i n t h e s p e c i f i e d l i m i t s , r e a n a l y z e e i t h e r o r b o t h t h e I P C s o l u t i o n and t h e c a l i b r a t i o n I f t h e second a n a l y s i s o f t h e I P C s o l u t i o n or t h e blank. c a l i b r a t i o n b l a n k c o n f i r m c a l i b r a t i o n t o be o u t s i d e t h e l i m i t s , sample a n a l y s i s must be d i s c o n t i n u e d , t h e cause determined, A l l samples c o r r e c t e d and/or t h e i n s t r u m e n t r e c a l i b r a t e d . f o l l o w i n g t h e l a s t a c c e p t a b l e I P C s o l u t i o n must be r e a n a l y z e d . The a n a l y s i s d a t a o f t h e c a l i b r a t i o n b l a n k and I P C s o l u t i o n must be k e p t on f i l e w i t h t h e sample analyses d a t a .

9.3.5

Spectral i n t e r f e r e n c e check (SIC) s o l u t i o n - F o r a l l d e t e r m i n a t i o n s t h e l a b o r a t o r y must p e r i o d i c a l l y v e r i f y t h e i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e c o r r e c t i o n r o u t i n e by a n a l y z i n g SIC s o l u t i o n s . The p r e p a r a t i o n and r e q u i r e d p e r i o d i c a n a l y s i s o f S I C s o l u t i o n s and t e s t c r i t e r i a f o r v e r i f y i n g t h e interelement i n t e r f e r e n c e c o r r e c t i o n r o u t i n e are given i n S p e c i a l cases where on-going v e r i f i c a t i o n i s Section 7.13. r e q u i r e d a r e d e s c r i b e d i n S e c t i o n 7.14. R e v i s i o n 4.4 Hay 1994

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Methods for the Determination

9.4

Assessing Analyte R e c n v i l r y arid D a t a Qua1i t y 9.4.1

Sample homoqeiwiiy ‘itid t h e chemical n a t u r e of t h e sample m a t r i x can a f f e c t a n a l y t e recovery and t h e q u a l i t y o f t h e d a t a . Taking s e p a r a t e a l i q u o t s from t h e sample f o r r e p l i c a t e and f o r t i f i e d a n a l y s e s can i n some c a s e s a s s e s s t h e e f f e c t . Unless o t h e r w i s e s p e c i f led by t h e d a t a u s e r , l a b o r a t o r y o r program, t h e f o l l o w i n g 1aborat.nt-y f o r t i f i e d m a t r i x ( L F M ) procedure ( S e c t 9 . 4 . 2 ) i s r e q u i r e d . Also, o t h e r t e s t s such a s t h e a n a l y t e a d d i t i o n t e s t ( S e c t . 9 . 5 . 1 ) and sample d i l u t i o n t e s t ( S e c t . 9 . 5 . 2 ) can i n d i c a t e i f m a t r i x e f f e c t s a r e o p e r a t i v e .

9.4.2

The l a b o r a t o r y must add a known amount of each a n a l y t e t o a minimum of 10% of t h e r o u t i n e samples. I n each c a s e t h e LFM a l i q u o t must be a d u p l i c a t e of t h e a l i q u o t used f o r sample a n a l y s i s and f o r t o t a l r e c o v e r a b l e d e t e r m i n a t i o n s added p r i o r t o sample p r e p a r a t i o n . For water samples, t h e added a n a l y t e c o n c e n t r a t i o n must be t h e same a s t h a t used i n t h e l a b o r a t o r y f o r t i f i e d blank ( S e c t . 7 . 1 0 . 3 ) . For s o l i d samples, however, t h e c o n c e n t r a t i o n added should be e x p r e s s e d a s mg/kg and i s c a l c u l a t e d f o r a one gram a l i q u o t by m u l t i p l y i n g t h e added a n a l y t e c o n c e n t r a t i o n (mg/L) i n s o l u t i o n by t h e conversion f a c t o r 100 (mg/L x O.lL/O.OOlkg = 100, S e c t . 1 2 . 5 ) . ( F o r n o t e s on Ag, Ba, and Sn s e e S e c t s . 1 . 7 & 1 . 8 . ) Over t i m e , samples from a l l r o u t i n e sample s o u r c e s should be f o r t i f i e d . NOTE:

The c o n c e n t r a t i o n o f c a l c i u m , magnesium, sodium and s t r o n t i u m in environmental w a t e r s , along with i r o n and aluminum i n s o l i d s can vary g r e a t l y and a r e not necessarily predictable. Fortifying these analytes in r o u t i n e samples a t the same c o n c e n t r a t i o n used f o r the LFB may prove t o be o f l i t t l e use i n a s s e s s i n g d a t a q u a l i t y f o r t h e s e a n a l y t e s . For t h e s e a n a l y t e s sample d i l u t i o n and r e a n a l y s i s u s i n g t h e c r i t e r i a given i n S e c t i o n 9 . 5 . 2 i s recommended. Also, i f s p e c i f i e d by t h e d a t a u s e r , l a b o r a t o r y o r program, samples can be f o r t i f i e d a t h i g h e r c o n c e n t r a t i o n s , b u t even major c o n s t i t u e n t s should be l i m i t e d t o < 25 mg/L so a s n o t t o a l t e r t h e sample m a t r i x and a f f e c t t h e a n a l y s i s .

9 . 4 . 3 C a l c u l a t e the percent recovery f o r each a n a l y t e , c o r r e c t e d f o r background c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o t h e d e s i g n a t e d LFM r e c o v e r y range of 70-130% o r a 3 sigma recovery ra:$e c a l c u l a t e d from t h e r e g r e s s i o n e q u a t i o n s given i n Table 9 . Recovery c a l c u l a t i o n s a r e n o t r e q u i r e d i f t h e c o n c e n t r a t i o n added i s l e s s than 30% o f t h e sample background c o n c e n t r a t i o n . Percent r e c o v e r y may be c a l c u l a t e d i n u n i t s a p p r o p r i a t e t o t h e m a t r i x , using the following equation:

Revision 4 . 4 Hay 1994

Metals where:

9.5

R C, C s

= = = =

57

percent recovery. f o r t i f i e d sample c o n c e n t r a t i o n . sample background c o n c e n t r a t i o n . concentration equivalent o f analyte added t o f o r t i f y t h e sample.

9.4.4

I f t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e d e s i g n a t e d LFM r e c o v e r y range, and t h e l a b o r a t o r y performance f o r t h a t a n a l y t e i s shown t o be i n c o n t r o l ( S e c t . 9 . 3 ) , t h e r e c o v e r y problem encountered w i t h t h e f o r t i f i e d sample i s judged t o be m a t r i x r e l a t e d , n o t system r e l a t e d . The d a t a u s e r s h o u l d be i n f o r m e d t h a t t h e r e s u l t f o r t h a t a n a l y t e i n t h e u n f o r t i f i e d sample i s suspect due t o e i t h e r t h e heterogeneous n a t u r e o f t h e sample or m a t r i x e f f e c t s and a n a l y s i s by method o f s t a n d a r d a d d i t i o n o r t h e use o f an i n t e r n a l s t a n d a r d ( s ) ( S e c t . 11.5) should be considered.

9.4.5

Where r e f e r e n c e m a t e r i a l s a r e a v a i l a b l e , t h e y s h o u l d be analyzed t o p r o v i d e a d d i t i o n a l performance d a t a . The a n a l y s i s o f r e f e r e n c e samples is a v a l u a b l e t o o l f o r d e m o n s t r a t i n g t h e a b i l i t y t o p e r f o r m t h e method a c c e p t a b l y . Reference m a t e r i a l s c o n t a i n i n g h i g h c o n c e n t r a t i o n s o f a n a l y t e s can p r o v i d e a d d i t i o n a l i n f o r m a t i o n on t h e performance o f t h e s p e c t r a l interference correction routine.

Assess t h e p o s s i b l e need f o r t h e method o f s t a n d a r d a d d i t i o n s (MSA) o r i n t e r n a l s t a n d a r d elements by t h e f o l l o w i n g t e s t s . Directions f o r u s i n g MSA o r i n t e r n a l s t a n d a r d ( s ) a r e g i v e n i n S e c t i o n 11.5. 9.5.1

A n a l y t e a d d i t i o n t e s t : An a n a l y t e ( s ) s t a n d a r d added t o a p o r t i o n o f a p r e p a r e d sample, o r i t s d i l u t i o n , s h o u l d be The r e c o v e r e d t o w i t h i n 85% t o 115% o f t h e known v a l u e . a n a l y t e ( s ) a d d i t i o n s h o u l d produce a minimum l e v e l o f 20 t i m e s and a maximum o f 100 t i m e s t h e method d e t e c t i o n l i m i t . I f t h e a n a l y t e a d d i t i o n i s < 20% o f t h e sample a n a l y t e c o n c e n t r a t i o n , t h e f o l l o w i n g d i l u t i o n t e s t s h o u l d be used. I f r e c o v e r y o f t h e analyte(s) i s not w i t h i n the specified l i m i t s , a matrix e f f e c t s h o u l d be suspected, and t h e a s s o c i a t e d d a t a f l a g g e d accordingly. The method o f a d d i t i o n s o r t h e use o f an a p p r o p r i a t e i n t e r n a l s t a n d a r d element may p r o v i d e more a c c u r a t e data.

9.5.2

D i l u t i o n test: I f the analyte concentration i s s u f f i c i e n t l y h i g h ( m i n i m a l l y , a f a c t o r o f 50 above t h e i n s t r u m e n t d e t e c t i o n l i m i t i n t h e o r i g i n a l s o l u t i o n b u t < 90% o f t h e l i n e a r l i m i t ) , an a n a l y s i s of a 1t4 d i l u t i o n s h o u l d agree ( a f t e r c o r r e c t i o n f o r t h e f i v e f o l d d i l u t i o n ) w i t h i n f 10% o f t h e o r i g i n a l determination. I f n o t , a chemical o r p h y s i c a l i n t e r f e r e n c e e f f e c t s h o u l d be suspected and t h e a s s o c i a t e d d a t a f l a g g e d a c c o r d i n g l y . The method o f s t a n d a r d a d d i t i o n s o r t h e use o f an i n t e r n a l - s t a n d a r d element may p r o v i d e more a c c u r a t e d a t a f o r samples f a i l i n g t h i s t e s t . R e v i s i o n 4.4 May 1994

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Methods for the Determination

10.0 CALIBRATION AND STANDARDIZATION

1 0 . 1 S p e c i f i c w a v e l e n g t h s a r e l i s t e d i n T a b l e 1. O t h e r w a v e l e n g t h s may be s u b s t i t u t e d i f t h e y can p r o v i d e t h e needed s e n s i t i v i t y and a r e corrected f o r spectral interference. However, because o f t h e d i f f e r e n c e among v a r i o u s makes and models o f s p e c t r o m e t e r s , s p e c i f i c i n s t r u m e n t o p e r a t i n g c o n d i t i o n s c a n n o t be g i v e n . The i n s t r u m e n t and o p e r a t i n g c o n d i t i o n s u t i l i z e d f o r d e t e r m i n a t i o n must be c a p a b l e o f p r o v i d i n g d a t a o f a c c e p t a b l e q u a l i t y t o t h e p r o g r a m and d a t a u s e r . The a n a l y s t s h o u l d f o l l o w t h e i n s t r u c t i o n s p r o v i d e d b y t h e i n s t r u m e n t manufacturer unless other conditions provide s i m i l a r o r b e t t e r p e r f o r m a n c e f o r a t a s k . O p e r a t i n g c o n d i t i o n s f o r aqueous s o l u t i o n s u s u a l l y v a r y f r o m 1100 t o 1200 w a t t s f o r w a r d power, 1 5 - t o 16-mm v i e w i n g h e i g h t , 15 t o 19 l i t e r s / m i n a r g o n c o o l a n t f l o w , 0 . 6 t o 1 L / m i n a r g o n a e r o s o l f l o w , 1 t o 1.8 mL/min sample pumping r a t e w i t h a l - m i n p r e f l u s h t i m e and measurement t i m e n e a r 1 s p e r w a v e l e n g t h peak ( f o r s e q u e n t i a l i n s t r u m e n t s ) and n e a r 10 s p e r sample ( f o r s i m u l t a n e o u s instruments). Use o f t h e Cu/Mn i n t e n s i t y r a t i o a t 324.754 nm and 257.610 nm (by a d j u s t i n g t h e a r g o n a e r o s o l f l o w ) has been recommended as a way t o a c h i e v e r e p e a t a b l e i n t e r f e r e n c e c o r r e c t i o n f a c t o r s . ” 10.2 P r i o r t o u s i n g t h i s method o p t i m i z e t h e plasma o p e r a t i n g c o n d i t i o n s . The f o l l o w i n g p r o c e d u r e i s recommended f o r v e r t i c a l l y c o n f i g u r e d plasmas. The p u r p o s e o f plasma o p t i m i z a t i o n i s t o p r o v i d e a maximum signal-to-background r a t i o f o r t h e l e a s t s e n s i t i v e elgment i n t h e a n a l y t i c a l a r r a y . The use o f a mass f l o w c o n t r o l l e r t o r e g u l a t e t h e n e b u l i z e r gas f l o w r a t e g r e a t l y f a c i l i t a t e s t h e p r o c e d u r e . 1 0 . 2 . 1 I g n i t e t h e plasma and s e l e c t an a p p r o p r i a t e i n c i d e n t r f power w i t h minimum r e f l e c t e d power. A l l o w t h e i n s t r u m e n t t o become thermally stable before beginning. This usually requires a t l e a s t 30 t o 60 m i n u t e s o f o p e r a t i o n . While a s p i r a t i n g t h e 1000-pg/mL s o l u t i o n o f y t t r i u m ( S e c t . 7.8.32), follow the i n s t r u m e n t m a n u f a c t u r e r ’ s i n s t r u c t i o n s and a d j u s t t h e a e r o s o l c a r r i e r gas f l o w r a t e t h r o u g h t h e n e b u l i z e r so a d e f i n i t i v e b l u e e m i s s i o n r e g i o n o f t h e plasma e x t e n d s a p p r - t x i m a t e l y f r o m 5 t o 20 mm above t h e t o p o f t h e w o r k c o i l . Record t h e n e b u l i z e r gas f l o w r a t e o r p r e s s u r e s e t t i n g f o r f u t u r e reference. 10.2.2 A f t e r e s t a b l i s h i n g t h e n e b u l i z e r gas f l o w r a t e , d e t e r m i n e t h e s o l u t i o n u p t a k e r a t e o f t h e n e b u l i z e r i n mL/min by a s p i r a t i n g a known volume c a l i b r a t i o n b l a n k f o r a p e r i o d o f a t l e a s t 3 m i n u t e s . D i v i d e t h e s p e n t volume by t h e a s p i r a t i o n t i m e ( i n m i n u t e s ) and r e c o r d t h e u p t a k e r a t e . S e t t h e p e r i s t a l t i c pump t o d e l i v e r t h e u p t a k e r a t e i n a s t e a d y even f l o w . 10.2.3 A f t e r h o r i z o n t a l l y a l i g n i n g t h e plasma a n d / o r o p t i c a l l y p r o f i l i n g t h e s p e c t r o m e t e r , use t h e s e l e c t e d i n s t r u m e n t c o n d i t i o n s f r o m S e c t i o n s 1 0 . 2 . 1 and 10.2.2, and a s p i r a t e t h e plasma s o l u t i o n ( S e c t . 7 . 1 5 ) , c o n t a i n i n g 10 pg/mL each o f A s , Pb, Se and T1. C o l l e c t i n t e n s i t y d a t a a t t h e w a v e l e n g t h peak f o r each a n a l y t e a t 1 mm i n t e r v a l s f r o m 14 t o 18 mm above t h e t o p o f t h e work c o i l . ( T h i s r e g i o n o f t h e plasma i s commonly R e v i s i o n 4.4 May 1994

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r e f e r r e d t o a s t h e a n a l y t i c a l zone.)'' Repeat t h e process u s i n g t h e c a l i b r a t i o n b l a n k . Determine t h e n e t s i g n a l t o b l a n k i n t e n s i t y r a t i o f o r each a n a l y t e f o r each v i e w i n g h e i g h t s e t t . i n y . Choose t h e h e i g h t f o r v i e w i n g t h e plasma t h a t p r o v i d e s t h e l a r g e s t i n t e n s i t y r a t i o f o r t h e l e a s t s e n s i t i v e element o f t h e f o u r a n a l y t e s . I f more t h a n one p o s i t i o n p r o v i d e s t h e same r a t i o , s e l e c t the p o s i t i o n t h a t provides the highest n e t i n t e n s i t y c o u n t s f o r t h e l e a s t s e n s i t i v e element o r accept a compromise p o s i t i o n o f t h e i n t e n s i t y r a t i o s o f a l l f o u r analytes. 10.2.4 The i n s t r u m e n t o p e r a t i n g c o n d i t i o n f i n a l l y s e l e c t e d as b e i n g optimum should p r o v i d e t h e l o w e s t r e l i a b l e i n s t r u m e n t d e t e c t i o n l i m i t s and method d e t e c t i o n l i m i t s . R e f e r t o Tables 1 and 4 f o r comparison o f I D L s and MDLs, r e s p e c t i v e l y . 10.2.5 I f e i t h e r t h e i n s t r u m e n t o p e r a t i n g c o n d i t i o n s , such as i n c i d e n t power and/or n e b u l i z e r gas f l o w r a t e a r e changed, o r a new t o r c h i n j e c t o r tube having a d i f f e r e n t o r i f i c e i . d . i s i n s t a l l e d , t h e plasma and plasma v i e w i n g h e i g h t should be reoptimized. 10.2.6 B e f o r e d a i l y c a l i b r a t i o n and a f t e r t h e i n s t r u m e n t warmup p e r i o d , t h e n e b u l i z e r gas f l o w must be r e s e t t o t h e determined o p t i m i z e d f l o w . I f a mass .flow c o n t r o l l e r i s b e i n g used, i t s h o u l d be r e s e t t o t h e r e c o r d e d o p t i m i z e d f l o w r a t e . I n o r d e r t o m a i n t a i n Val i d s p e c t r a l i n t e r e l e m e n t c o r r e c t i o n r o u t i n e s t h e n e b u l i z e r gas f l o w r a t e s h o u l d be t h e same from day-to-day (<2% change). The change i n s i g n a l i n t e n s i t y w i t h a change i n n e b u l i z e r gas f l o w r a t e f o r b o t h " h a r d " (Pb 220.353 nm) and " s o f t " (Cu 324.754) l i n e s i s i l l u s t r a t e d i n F i g u r e 1. 10.3 B e f o r e u s i n g t h e procedure ( S e c t i o n 11.0) t o analyze samples, t h e r e must be d a t a a v a i l a b l e documenting i n i t i a l d e m o n s t r a t i o n o f performance. The r e q u i r e d d a t a and procedure i s d e s c r i b e d i n S e c t i o n 9.2. T h i s d a t a must be g e n e r a t e d u s i n g t h e same i n s t r u m e n t o p e r a t i n g c o n d i t i o n s and c a l i b r a t i o n r o u t i n e (Sect. 11.4) t o be used f o r sample a n a l y s i s . These documented d a t a must be k e p t on f i l e and be a v a i l a b l e f o r r e v i e w by t h e d a t a u s e r . 10.4 A f t e r c o m p l e t i n g t h e i n i t i a l d e m o n s t r a t i o n of performance, b u t b e f o r e a n a l y z i n g samples, t h e l a b o r a t o r y must e s t a b l i s h and i n i t i a l l y v e r i f y an i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e c o r r e c t i o n r o u t i n e t o be used d u r i n g sample a n a l y s i s . A general d e s c r i p t i o n concerning spectral i n t e r f e r e n c e and t h e a n a l y t i c a l r e q u i r e m e n t s f o r background c o r r e c t i o n and f o r c o r r e c t i o n o f i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e i n p a r t i c u l a r a r e g i v e n i n S e c t i o n 4.1. To d e t e r m i n e t h e a p p r o p r i a t e l o c a t i o n f o r background c o r r e c t i o n and t o e s t a b l i s h t h e i n t e r e l e m e n t i n t e r f e r e n c e c o r r e c t i o n r o u t i n e , r e p e a t e d s p e c t r a l scan about t h e a n a l y t e wavelength and r e p e a t e d analyses o f t h e s i n g l e element s o l u t i o n s may be r e q u i r e d . C r i t e r i a f o r d e t e r m i n i n g an i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e i s an apparent p o s i t i v e o r n e g a t i v e c o n c e n t r a t i o n on t h e a n a l y t e t h a t i s o u t s i d e t h e 3-sigma c o n t r o l l i m i t s o f t h e c a l i b r a t i o n b l a n k f o r t h e a n a l y t e . (The u p p e r - c o n t r o l l i m i t i s t h e a n a l y t e I D L . ) Revision 4.4 Hay 1994

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Methods for the Determination Once established, the entire routine must be initially and periodically verified annually, or whenever there is a change in instrument operating conditions ( S e c t 10.2.5). Only a portion of the correction routine must be verified more frequently or on a daily basis. Test criteria and required solutions are described in Section 7.13. Initial and periodic verification data of the routine should be kept on file. Special cases where on-going verification are required is described in Section 7 . 1 4 .

11.0 PROCEDURE

11.1 Aqueous Sample Preparation - Dissolved Analytes 11.1.1 For the determination of dissolved analytes in ground and surface waters, pipet an aliquot ( 2 20 mL) o f the filtered,

acid preserved sample into a 50-mL polypropylene centrifuge tube. Add an appropriate volume of ( l t l ) nitric acid to adjust the acid concentration of the aliquot to approximate a 1% (v/v) nitric acid solution (e.g., add 0.4 mL ( l t l ) HNO, to a 20 mL aliquot of sample). Cap the tube and mix. The sample is now ready for analysis (Sect. 1 . 3 ) . Allowance for sample dilution should be made in the calculations. (If mercury is to be determined, a separate aliquot must be additionally acidified to contain 1% (v/v) HC1 to match the signal response of mercury in the calibration standard and reduce memory "interference effects. Sect. 1.9) NOTE:

If a precipitate is formed during acidification, transport, or storage, the sample aliquot must be treated using the procedure described in Sections 11.2.2 thru 1 1 . 2 . 7 prior to analysis.

11.2 Aqueous Sample Preparation - Total Recoverable Analytes 1 1 . 2 . 1 For the "direct analysis" of total recoverable analytes in drinking water samples containing turbidity < 1 NTU, treat an

unfiltered acid preserved sample aliquot using the sample preparation procedure described in Section 11.1.1 while making allowance for sample dilution in the data calculation (Sect. 1 . 2 ) . For the determination of total recoverable analytes in all other aqueous samples or for preconcentrating drinking water samples prior to analysis follow the procedure given in Sections 11.2.2 through 1 1 . 2 . 7 . 1 1 . 2 . 2 For the determination of total recoverable analytes in aqueous samples (other than drinking water with < 1 NTU turbidity), transfer a 100-mL (+ 1 mL) aliquot from a well mixed, acid preserved sample to a 250-mL Griffin beaker (Sects. 1 . 2 , 1 . 3 , 1.6, 1 . 7 , 1 . 8 , & 1 . 9 ) . (When necessary, smaller sample aliquot

volumes may be used.) NOTE:

If the sample contains undissolved solids > 1%, a well mixed, acid preserved aliquot containing no more than 1 g particulate material should be cautiously Revision 4.4 May 1994

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evaporated to near 10 mL and extracted using the acidmixture procedure described in Sections 1 1 . 3 . 3 thru 11.3.6.

11.2.3 Add 2 mL ( l t l ) nitric acid and 1.0 nil o f

(1t1) hydrochloric acid to the beaker containing the measured volume of sample. Place the beaker on the hot plate for solution evaporation. The hot plate should be located in a fume hood and previously adjusted to provide evaporation at a temperature o f approximately but no higher than 85'C. (See the following note.) The beaker should be covered with an elevated watch glass or other necessary steps should be taken to prevent sample contamination from the fume hood environment.

NOTE:

For proper heating adjust the temperature control of the hot plate such that an uncovered Griffin beaker containing 50 mL of water placed in the center of the hot plate can be maintained at a temperature approximately but no higher than 85'C. (Once the beaker is covered with a watch glass the temperature of the water will rise to approximately 95OC.)

11.2.4 Reduce the volume of the sample aliquot to about 20 mL by gentle heating at 85°C. DO NOT BOIL. This step takes about 2 h for a 100 mL aliquot with. the rate of evaporation rapidly

increasing as the sample volume approaches 20 mL. (A spare beaker containing 20 mL of water can be used as a gauge.) 11.2.5 Cover the lip of the beaker with a watch glass to reduce

additional evaporation and gently reflux the sample for 30 minutes. (Slight boiling may occur, but vigorous boiling must be avoided to prevent loss of the HC1-H,O azeotrope.) 11.2.6

Allow the beaker to cool. Quantitatively transfer the sample solution to a 50-mL volumetric flask, make to volume with reagent water, stopper and mix.

11.2.7 Allow

any undissolved material to settle overnight, or centrifuge a portion of the prepared sample until clear. (If after centrifuging or standing overnight the sample contains suspended solids that would clog the nebulizer, a portion of the sample may be filtered for their removal prior to analysis. However, care should be exercised to avoid potential contamination from filtration.) The sample is now ready for analysis. Because the effects of various matrices on the stability of diluted samples cannot be characterized, all analyses should be performed as soon as possible after the completed preparation.

11.3 Sol id Sample Preparation - Total Recoverable Analytes 11.3.1 For the determination o f total recoverable analytes in solid

samples, mix the sample thoroughly and transfer a portion ( > 20 9) t o tared weighing dish, weigh the sample and record Revision 4.4 Hay 1994

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Methods for the Determination the w e t weight ( W W ) . ( F o r samples w i t h < 35% m o i s t u r e a 20 g For samples w i t h m o i s t u r e > 35% a portion i s sufficient. l a r g e r a l i q u o t 50-100 g i s r e q u i r e d . ) Dry t h e sample t o a c o n s t a n t w e i g h t a t 6OoC and r e c o r d t h e d r y w e i g h t (DW) f o r c a l c u l a t i o n o f percent s o l i d s (Sect. 12.6). (The sample i s d r i e d a t 6OoC t o p r e v e n t t h e l o s s o f mercury and o t h e r p o s s i b l e v o l a t i l e m e t a l l i c compounds, t o f a c i l i t a t e s i e v i n g , and t o ready t h e sample f o r g r i n d i n g . ) 11.3.2 To a c h i e v e homogeneity, s i e v e t h e d r i e d sample u s i n g a 5-mesh p o l y p r o p y l e n e s i e v e and g r i n d i n a m o r t a r and p e s t l e . (The s i e v e , m o r t a r and p e s t l e should be cleaned between samples.) From t h e d r i e d , ground m a t e r i a l weigh a c c u r a t e l y a r e p r e s e n t a t i v e 1.0 f 0 . 0 1 g a l i q u o t ( W ) o f t h e sample and t r a n s f e r t o a 250-mL P h i l l i p s beaker f o r a c i d e x t r a c t i o n ( S e c t s . l . 6 , 1.7, 1.8, & 1 . 9 ) . 11.3.3 To t h e beaker add 4 mL o f ( l t l ) HNO, and 10 mL o f ( 1 t 4 ) HC1. Cover t h e l i p o f t h e beaker w i t h a watch g l a s s . Place t h e beaker on a h o t p l a t e f o r r e f l u x e x t r a c t i o n o f t h e a n a l y t e s . The h o t p l a t e s h o u l d be l o c a t e d i n a fume hood and p r e v i o u s l y adjusted t o provide a r e f l u x temperature o f approximately 95OC. (See t h e f o l l o w i n g n o t e . ) NOTE:

For p r o p e r h e a t i n g a d j u s t t h e temperatur-e c o n t r o l o f t h e h o t p l a t e such t h a t an uncovered G r i f f i n beaker c o n t a i n i n g 50 mL o f w a t e r p l a c e d i n t h e c e n t e r o f t h e h o t p l a t e can be m a i n t a i n e d a t a t e m p e r a t u r e a p p r o x i m a t e l y b u t no h i g h e r t h a n 85OC. (Once t h e beaker i s covered w i t h a watch g l a s s t h e t e m p e r a t u r e o f t h e w a t e r w i l l r i s e t o a p p r o x i m a t e l y 95OC.) A l s o , a b l o c k d i g e s t e r capable o f m a i n t a i n i n g a t e m p e r a t u r e o f 95OC and equipped w i t h 250-mL c o n s t r i c t e d v o l u m e t r i c d i g e s t i o n t u b e s may be s u b s t i t u t e d f o r t h e h o t p l a t e and c o n i c a l beakers i n t h e e x t r a c t i o n s t e p .

Very s l i g h t 11.3.4 Heat t h e sample and g e n t l y r e f l u x f o r 30 min. b o i l i n g may occur, however v i g o r o u s b o i l i n g must be avoided t o p r e v e n t l o s s o f t h e HC1-H 0 azeotrope. Some s o l u t i o n e v a p o r a t i o n w i l l o c c u r (3 t o mL) .

5

11.3.5 A l l o w t h e sample t o c o o l and q u a n t i t a t i v e l y t r a n s f e r t h e e x t r a c t t o a 100-mL v o l u m e t r i c f l a s k . D i l u t e t o volume w i t h r e a g e n t w a t e r , s t o p p e r and m i x . 11.3.6 A l l o w t h e sample e x t r a c t s o l u t i o n t o s t a n d o v e r n i g h t t o separate i n s o l u b l e m a t e r i a l o r c e n t r i f u g e a p o r t i o n o f t h e sample s o l u t i o n u n t i l c l e a r . ( I f after centrifuging or s t a n d i n g o v e r n i g h t t h e e x t r a c t s o l u t i o n c o n t a i n s suspended s o l i d s t h a t would c l o g t h e n e b u l i z e r , a p o r t i o n o f t h e e x t r a c t s o l u t i o n may be f i l t e r e d f o r t h e i r removal p r i o r t o a n a l y s i s . However, c a r e s h o u l d be e x e r c i s e d t o a v o i d p o t e n t i a l c o n t a m i n a t i o n from f i l t r a t i o n . ) The sample e x t r a c t i s now ready f o r a n a l y s i s . Because t h e e f f e c t s o f v a r i o u s m a t r i c e s on R e v i s i o n 4 . 4 May 1994

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the stability o f diluted samples cnnnot be characterized, all analyses should be performed as soon as possible after the completed preparation. 11.4 Sample Analysis 1 1 . 4 . 1 Prior to daily calibration of the instrument inspect, the sample

introduction system including the nebulizer, torch, injector tube and uptake tubing for salt deposits, dirt and debris that would restrict solution flow and affect instrument performance. Clean the system when needed or on a daily basis. 11.4.2 Configure the instrument system to the selected power and

operating conditions as determined in Sections 10.1 and 10.2. 11.4.3

The instrument must be allowed to become thermally stable before calibration and analyses. This usually requires at least 30 to 60 minutes of operation. After instrument warmup, complete any required optical profiling or a1 ignment particular to the instrument.

1 1 . 4 . 4 For initial

and daily operation calibrate the instrument according to the instrument manufacturer's recommended procedures, using mixed calibration standard solutions (Sect. 7 . 9 ) and the calibration blank (Sect. 7.10.1). A peristaltic pump must be used to introduce all solutions to the nebulizer. To allow equilibrium to be reached in the plasma, aspirate all solutions for 3 0 sec after reaching the plasma before beginning integration of the background corrected signal to accumulate data. When possible, use the average value of replicate integration periods of the signal to be correlated to the analyte concentration. Flush the system with the rinse blank (Sect. 7 . 1 0 . 4 ) for a minimum of 60 seconds (Sect. 4 . 4 ) between each standard. The calibration line should consist of a minimum of a calibration blank and a high standard. Replicates of the blank and highest standard provide an optimal distribution of calibration standards to minimize the confidence band for a straigh;;line calibration in a response region with uniform variance.

1 1 . 4 . 5 After completion of the initial requirements of this method (Sects. 10.3 and 1 0 . 4 ) , samples should be analyzed in the same

operational manner used in the calibration routine with the rinse blank also being used between all sample solutions, LFBs, LFMs, and check solutions (Sect. 7 . 1 0 . 4 ) . 1 1 . 4 . 6 During the analysis of samples, the laboratory must comply with the required quality control described in Sections 9.3 and 9 . 4 .

Only for the determination of dissolved analytes or the "direct analysis" of drinking water with turbidity o f < 1 NTU is the sample digestion step o f the L R B , LFB, and LFM not required. 1 1 . 4 . 7 Determined sample analyte concentrations that are 90% or more of the upper limit of the analyte LDR must be diluted with

Revision 4 . 4 May 1994

64 Methods for the Determination reagent water that has been acidified in the same manner as calibration blank and reanalyzed (see Sect. 1 1 . 4 . 8 ) . Also, for the interelement spectral interference correction routines to remain valid during sample analysis, the interferant concentration must not exceed its LDR. If the interferant LDR is exceeded, sample dilution with acidified reagent water and In these circumstances analyte reanalysis i s required. detection limits are raised and determination by another approved test procedure that is either more sensitive and/or interference free is recommended. 11.4.8 When it i s necessary to assess an operative matrix interference

(e.g., signal reduction due to high dissolved solids), the tests described in Section 9 . 5 are recommended. 11.4.9 11.5

Report data as directed in Section 12.

If the method of standard additions (MSA) is used, standards are added at one o r more levels to portions of a prepared sample. This technique2' compensates for enhancement or depression of an analyte signal by a matrix. It will not correct for additive interferences such as contamination, interelement interferences, or baseline shifts. This technique i s valid in the linear range when the interference effect i s constant over the range, the added analyte responds the same as the endogenous analyte, and the signal is corrected for additive interferences. The simplest version of this technique is the singleaddition method. This procedure calls for two identical aliquots of the sample solution to be taken. To the first aliquot, a small volume of standard is added; while to the second aliquot, a volume of acid blank is added equal to the standard addition. The sample concentration is calculated by the following:

s, x v, x c Sample Conc = (mg/L or mg/kg) where: C

=

(S,-S,)

x

v,

Concentration of the standard solution (mg/L)

S, = Signal for fortified aliquot S,

V, V,

= = =

Signal for unfortified aliquot Volume of the standard addition (L) Volume of the sample aliquot (L) used for MSA

For more than one fortified portion of the prepared sample, linear regression analysis can be applied using a computer or calculator program to obtain the concentration of the sample solution. An alternative to using the method of standard additions is use of the internal standard technique by adding one or more elements (not in the samples and verified not to cause an uncorrected interelement spectral interference) at the same concentration (which is sufficient for optimum precision) to the prepared samples (blanks and standards) that are affected the same as the analytes by the sample matrix. Use the ratio o f analyte signal to the internal standard signal for calibration and quantitation. Revision 4.4 May 1994

Metals

65

12.0 D A T A A N A L Y S I S AND C A L C U L A T I O N S 12.1 Sample data should be reported in units of mg/L for aqueous samples and m g / k g dry weight for solid samples. 12.2 For dissolved aqueous analytes (Sect. 11.1) report the data generated directly from the instrument with allowance for sample dilution. Do

not report analyte concentrations below the IDL. 12.3 For total recoverable aqueous analytes (Sect. 1 1 . 2 ) , multiply solution analyte concentrations by the dilution factor 0 . 5 , when 100 mL aliquot is used to produce the 50 mL final solution, and report data as instructed in Section 12.4. If a different aliquot volume other than 100 mL is used for sample preparation, adjust the dilution factor accordingly. Also, account for any additional dilution o f the

prepared sample solution needed to complete the determination of analytes exceeding 90% or more o f the LDR upper limit. Do not report data below the determined analyte MDL concentration or below an adjusted detection limit reflecting smaller sample aliquots used in processing or additional dilutions required to complete the analysis. 12.4 For analytes with MDLs < 0.01 mg/L, round the data values to the

thousandth place and report analyte concentrations up to three significant figures. For analytes with MDLs 2 0.01 mg/L round the data values to the hundredth place-and report analyte concentrations up to three significant figures. Extract concentrations for sol ids data should be rounded in a similar manner before calculations in Section 12.5 are performed. 12.5 For total recoverable analytes in solid samples (Sect. 11.3), round

the solution analyte concentrations (mg/L) as 12.4. Report the data up to three significant weight basis unless specified otherwise by the Calculate the concentration using the equation

instructed in Section figures as mg/kg dryprogram or data user. below:

C x V x D Sample Conc. (mg/kg) dry-weight basis where: C

V D W

= = =

=

=

W

Concentration in extract (mg/L) Volume o f extract (L, 100 mL = 0.1L) Dilution factor (undiluted = 1) Weight o f sample aliquot extracted (g x 0.001

=

kg)

Do not report analyte data below the estimated solids MDL or an adjusted MDL because of additional dilutions required to complete the analysis. 12.6 To report percent solids in solid samples (Sect. 11.3) calculate as

fol 1 ows :

Revision 4.4 Hay 1994

66

Methods for the Determination

DW % solids (S)

where: IW WW NOTE:

= =

=

~

ww

x 100

Sample w e i g h t ( g ) d r i e d a t 6OoC Sample w e i g h t ( 9 ) b e f o r e d r y i n g

I f t h e d a t a u s e r , program o r l a b o r a t o r y r e q u i r e s t h a t t h e r e p o r t e d p e r c e n t sol i d s be determined by d r y i n g a t 105OC, r e p e a t t h e procedure g i v e n i n S e c t i o n 1 1 . 3 u s i n g a s e p a r a t e p o r t i o n ( > 20 g ) o f t h e sample and d r y t o c o n s t a n t w e i g h t a t 103-105°C.

12.7 The QC d a t a o b t a i n e d d u r i n g t h e analyses p r o v i d e an i n d i c a t i o n o f t h e q u a l i t y o f t h e sample d a t a and should be p r o v i d e d w i t h t h e sample results. 13.0 METHOD PERFORMANCE

13.1 L i s t e d i n Table 4 a r e t y p i c a l s i n g l e l a b o r a t o r y t o t a l r e c o v e r a b l e MDLs determined f o r t h e recommended wavelengths u s i n g simultaneous ICP-AES and t h e o p e r a t i n g c o n d i t i o n s g i v e n i n T a b l e 5. The MDLs were determined i n r e a g e n t b l a n k m a t r i x ( b e s t case s i t u a t i o n ) . PTFE beakers were used t o a v o i d boron and s i l i c a c o n t a m i n a t i o n f r o m glassware w i t h t h e f i n a l d i l u t i o n t o 50 mL completed i n p o l y p r o p y l e n e c e n t r i f u g e d t u b e s . The l i s t e d MDLs f o r s o l i d s a r e e s t i m a t e s and were c a l c u l a t e d f r o m t h e aqueous MDL d e t e r m i n a t i o n s . 13.2 Data o b t a i n e d f r o m s i n g l e l a b o r a t o r y method t e s t i n g a r e summarized i n Table 6 f o r f i v e t y p e s o f w a t e r samples c o n s i s t i n g o f d r i n k i n g water, s u r f a c e w a t e r , ground w a t e r , and two wastewater e f f l u e n t s . The d a t a p r e s e n t e d c o v e r a l l a n a l y t e s except c e r i u m and t i t a n i u m . Samples were p r e p a r e d u s i n g t h e procedure d e s c r i b e d i n Sect. 11.2. F o r each m a t r i x , f i v e r e p l i c a t e a1 i q u o t s were prepared, analyzed and t h e average of t h e f i v e d e t e r m i n a t i o n s used t o d e f i n e t h e sample background c o n c e n t r a t i o n o f each a n a l y t e . I n a d d i t i o n , two p a i r s o f d u p l i c a t e s were f o r t i f i e d a t d i f f e r e n t c o n c e n t r a t i o n l e v e l s . For each method a n a l y t e , t h e sample background c o n c e n t r a t i o n , mean p e r c e n t r e c o v e r y , s t a n d a r d d e v i a t i o n o f t h e p e r c e n t r e c o v e r y , and r e l a t i v e p e r c e n t d i f f e r e n c e between t h e d u p l i c a t e f o r t i f i e d samples a r e 1 i s t e d i n Table 6. The v a r i a n c e o f t h e f i v e r e p l i c a t e sample background determinations i s included i n t h e c a l c u l a t e d standard d e v i a t i o n o f t h e p e r c e n t r e c o v e r y when t h e a n a l y t e c o n c e n t r a t i o n i n t h e sample was g r e a t e r t h a n t h e MDL. The t a p and w e l l w a t e r s were processed i n T e f l o n and q u a r t z beakers and d i l u t e d i n p o l y p r o p y l e n e c e n t r i f u g e d tubes. The nonuse o f b o r o s i l i c a t e glassware i s r e f l e c t e d i n t h e p r e c i s i o n and r e c o v e r y d a t a f o r boron and s i l i c a i n t h o s e two sample types. 1 3 . 3 Data o b t a i n e d from s i n g l e l a b o r a t o r y method t e s t i n g a r e summarized i n Table 7 f o r t h r e e s o l i d samples c o n s i s t i n g o f EPA 884 Hazardous S o i l , SRM 1645 R i v e r Sediment, and EPA 286 E l e c t r o p l a t i n g Sludge. Samples were prepared u s i n g t h e procedure d e s c r i b e d i n Sect. 1 1 . 3 . F o r each method a n a l y t e , t h e sample background c o n c e n t r a t i o n , mean p e r c e n t R e v i s i o n 4.4 May 1994

Metals

67

recovery o f the f o r t i f i e d a d d i t i o n s , the standard d e v i a t i o n o f the p e r c e n t r e c o v e r y , and r e l a t i v e p e r c e n t d i f f e r e n c e between d u p l i c a t e a d d i t i o n s were determined as d e s c r i b e d i n S e c t . 1 3 . 2 . Data p r e s e n t e d a r e f o r a l l a n a l y t e s e x c e p t cerium, s i l i c a and t i t a n i u m . Limited c o m p a r a t i v e d a t a t o o t h e r methods and SRM m a t e r i a l s a r e p r e s e n t e d i n r e f e r e n c e 23 o f S e c t i o n 1 6 . 0 . 13.4 Performance d a t a f o r aqueous s o l u t i o n s independent o f sampJe p r e p a r a t i o n f r o m a m u l t i l a b o r a t o r y s t u d y a r e p r o v i d e d i n Table 8 . 13.5 L i s t e d i n Table 9 a r e r e g r e s s i o n e q u a t i o n s f o r p r e c i s i o n and b i a s f o r 25 a n a l y t e s a b s t r a c t e d from EPA MFthod Study 27, a m u l t i l a b o r a t o r y v a l i d a t i o n s t u d y o f Method 200.7. These e q u a t i o n s were developed f r o m d a t a r e c e i v e d from 12 l a b o r a t o r i e s u s i n g t h e t o t a l r e c o v e r a b l e sample p r e p a r a t i o n procedure on r e a g e n t w a t e r , d r i n k i n g water, s u r f a c e w a t e r and 3 i n d u s t r i a l e f f l u e n t s . F o r a complete r e v i e w and d e s c r i p t i o n o f t h e s t u d y see r e f e r e n c e 16 o f S e c t i o n 16.0.

14.0 POLLUTION PREVENTION 14.1 P o l l u t i o n p r e v e n t i o n encompasses any t e c h n i q u e t h a t reduces o r e l i m i n a t e s t h e q u a n t i t y o r t o x i c i t y o f waste a t t h e p o i n t o f g e n e r a t i o n . Numerous o p p o r t u n i t i e s f o r p o l l u t i o n p r e v e n t i o n e x i s t i n l a b o r a t o r y o p e r a t i o n . The EPA has e s t a b l i s h e d a p r e f e r r e d h i e r a r c h y o f e n v i r o n m e n t a l management t e c h n i q u e s t h a t p l a c e s p o l 1u t i o n Whenever p r e v e n t i o n as t h e management o p t i ' o n o f f i r s t c h o i c e . f e a s i b l e , l a b o r a t o r y p e r s o n n e l s h o u l d use p o l l u t i o n p r e v e n t i o n t e c h n i q u e s t o address t h e i r waste g e n e r a t i o n ( e . g . , S e c t . 7 . 8 ) . When wastes cannot be f e a s i b l y reduced a t t h e source, t h e Agency recommends r e c y c l i n g as t h e n e x t b e s t o p t i o n . 14.2 F o r i n f o r m a t i o n about p o l l u t i o n p r e v e n t i o n t h a t may be a p p l i c a b l e t o l a b o r a t o r i e s and r e s e a r c h i n s t i t u t i o n s , c o n s u l t Less i s Better: Laboratory Chemical Management for W a s t e Reduction, a v a i l a b l e from t h e American Chemical S o c i e t y ' s Department o f Government R e l a t i o n s and Science P o l i c y , 1155 1 6 t h S t r e e t N.W., Washington D.C. 20036, (202)872-4477.

15.0 WASTE MANAGEMENT 15.1 The Environmental P r o t e c t i o n Agency r e q u i r e s t h a t l a b o r a t o r y waste management p r a c t i c e s be conducted c o n s i s t e n t w i t h a l l a p p l i c a b l e r u l e s and r e g u l a t i o n s . The Agency u r g e s l a b o r a t o r i e s t o p r o t e c t t h e a i r , w a t e r , and l a n d by m i n i m i z i n g and c o n t r o l l i n g a l l r e l e a s e s f r o m hoods and bench o p e r a t i o n s , c o m p l y i n g w i t h t h e l e t t e r and s p i r i t o f any sewer d i s c h a r g e p e r m i t s and r e g u l a t i o n s , and by complying w i t h a l l s o l i d and hazardous waste r e g u l a t i o n s , p a r t i c u l a r l y t h e hazardous waste i d e n t i f i c a t i o n r u l e s and l a n d d i s p o s a l r e s t r i c t i o n s . For f u r t h e r i n f o r m a t i o n on waste management c o n s u l t The W a s t e Management Manual for Laboratory Personnel, a v a i l a b l e f r o m t h e American Chemical S o c i e t y a t t h e address l i s t e d i n t h e S e c t i o n 14.2. R e v i s i o n 4.4 May 1994

68

Methods for the Determination

16.0

REFERENCES 1.

U . S . Environmental Protection Agency. Inductively Coupled PlasmaAtomic Emission Spectrometric Method for Trace Element Analysis of Water and Wastes-Method 200.7, Dec. 1982. EPA-600/4-79-020, revised March 1983.

2.

U . S . Environmental Protection Agency. Inductively Coupled Plasma Atomic Emission Spectroscopy Method 6010, SW-846 Test Methods for Evaluating Solid Waste, 3rd Edition, 1986.

3.

U.S. Environmental Protection Agency. Method 200.7: Determination of Metals and Trace Elements in Water and Wastes by Inductively Coupled Plasma-Atomic Emission Spectrometry, revision 3.3, EPA 600 4-91/010 June 1991.

4.

U . S . Environmental Protection Agency. Inductively Coupled Plasma Atomic Emission Spectrometry Method for the Analysis o f Waters and Solids, EMMC, July 1992.

5.

Fassel, V.A. et a?. Simultaneous Determination of Wear Metals in Lubricating Oils by Inductively-Coupled Plasma Atomic Emission Spectrometry. Anal. Chem. @:516-519, 1976.

6.

Merryfield, R.N. and R.C. Loyd. Simultaneous Determination of Metals in Oil by Inductively Coupled Plasma Emission Spectrom'etry. Anal. Chem. =:1965-1968, 1979.

7.

Winge, R.K. et al. Inductively Coupled Plasma-Atomic Emission Spectroscopy: An At1 as of Spectral Information, Physical Science Data 20. Elsevier Science Publishing, New York, New York, 1985.

8.

Boumans, P.W.J.M. Line Coincidence Tables for Inductively Coupled Plasma Atomic Emission Spectrometry, 2nd edition. Pergamon Press, Oxford, United Kingdom, 1984.

9.

Carcinogens - Working With Carcinogens, Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, Publication No. 77-206, Aug. 1977. Available from the National Technical Information Service (NTIS) as PB-277256.

10. OSHA Safety and Health Standards, General Industry, (29 CFR 1910), Occupational Safety and Health Administration, OSHA 2206, (Revised, January 1976). 11. Safety in Academic Chemistry Laboratories, American Chemical Society Publication, Committee on Chemical Safety, 3rd Edition, 1979. 12. Proposed OSHA Safety and Health Standards, Laboratories, Occupational Safety and Health Administration, Federal Register, July 24, 1986.

Revision 4.4 Hay 1994

Metals

69

13

Rohrbough, W.G. e t a l . Reagent Chemicals, American Chemical S o c i e t y S p e c i f i c a t i o n s , 7 t h e d i t i o n . American Chemical S o c i e t y , Washington, DC, 1986.

14.

American S o c i e t y f o r T e s t i n g and M a t e r i a l s . Standard S p e c i f i c a t i o n f o r Reagent Water, D1193-77. Annual Book o f ASTM Standards, V o l . 11.01. P h i l a d e l p h i a , PA, 1991.

15.

Code o f Federal R e g u l a t i o n s 40, Ch. 1, P t . 136 Appendix B

16.

M a x f i e l d , R. and b. Mindak. EPA Method Study 27, Method 200.7 Trace M e t a l s by I C P , Nov. 1983. A v a i l a b l e f r o m N a t i o n a l Technical I n f o r m a t i o n S e r v i c e (NTIS) as PB 85-248-656.

17.

Botto, R . I . Q u a l i t y Assurance i n O p e r a t i n g a M u l t i e l e m e n t Emission Spectrometer. Spectrochim. Acta, 398(1):95-113, 1984.

18.

Wallace, G . F . , Some F a c t o r s A f f e c t i n g t h e Performance o f an I C P Sample I n t r o d u c t i o n System. Atomic Spectroscopy, V o l . 4, p . 188-192, 1983.

19.

K o i r t y o h a n n , S . R . e t a l . Nomenclature System f o r t h e Low-Power Argon I n d u c t i v e l y Coupled Plasma, Anal. Chem. x : 1 9 6 5 , 1980

20.

Deming, S.N. and S.L. Morgan. E x p e r i m e n t a l Design f o r Q u a l i t y and P r o d u c t i v i t y i n Research, Development, and M a n u f a c t u r i n g , P a r t 111, pp 119-123. S h o r t c o u r s e p u b l i c a t i o n ' by S t a t i s t i c a l Designs, 9941 R o w l e t t , S u i t e 6, Houston, TX 77075, 1989.

21.

Winefordner, J.D., Trace A n a l y s i s : Spectroscopic Elements, Chemical A n a l y s i s , V o l . 46, pp. 41-42.

22.

Jones, Plasma 3050. Vegas,

23.

M a r t i n , T.D., E.R. M a r t i n and S.E. Long. Method 200.2: Sample P r e p a r a t i o n Procedure f o r Spectrochemical Analyses o f T o t a l Recoverable Elements, EMSL ORD, USEPA, 1989.

Methods

ICP

for

C.L. e t a l . An I n t e r l a b o r a t o r y Study o f I n d u c t i v e l y Coupled Atomic Emission Spectroscopy Method 6010 and D i g e s t i o n Method EPA-600/4-87-032, U . S . Environmental P r o t e c t i o n Agency, Las Nevada, 1987.

R e v i s i o n 4.4 May 1994

70

Methods for the Determination

17.0 TABLES, DIAGRAMS. FLOWCHARTS, AND VALIDATION DATA

TABLE 1:

Anal yte

A1 urninum Anti rnony Arsenic Barium Beryl 1 ium Boron Cadmi urn Calcium Cerium Chromi um Cobalt Copper Iron Lead Lithium Magnesi um Manganese Mercury Molybdenum Nickel Phosphorus Potass iurn Sel eni urn Silica (SiO,) S i 1 ver Sod i urn Stronti urn Thal 1 i urn Tin Titanium Vanadium Zinc

WAVELENGTHS, ESTIMATED INSTRUMENT DETECTION L I M I T S , AND RECOMMENDED CALIBRATION

Wave1 engtha (nm) 308.215 206.833 193.759 493.409 313.042 249.678 226.502 315.887 413.765 205.552 228.616 324.754 259.940 220.353 670.784 279.079 257.610 194.227 203.844 231.604 214.914 766.491 196.090 251.611 328.068 588.995 421.552 190.864 189.980 334.941 292.402 213.856

E st i mated Detection Limi tb (P3/L)

45 32 53 2.3 0.27 5.7 3.4 30 48 6.1 7.0 5.4 6.2 42 3.1d 30 1.4 2.5 12 15 76 700e 75 26d (SiO,) 7.0 29 0.77 40 25 3.8 7.5 1.8

Cal i brate' to (mg/L) 10 5 10 1 1 1 2 10 2 5 2

2

10 10 5 10 2 2 10 2 10 20 5 10 0.5 10 1 5 4 10 2 5

a

The wavelengths listed are recommended because of their sensitivity and overall acceptability. Other wavelengths may be substituted if they can provide the needed sensitivity and are treated with the same corrective techniques for spectral interference (see Section 4.1). These estimated 3-sigma instrumental detection 1 imits16 are provided only as a guide to instrumental limits. The method detection limits are Revision 4.4 May 1994

Metals

71

sample dependent and may vary as t h e sample m a t r i x v a r i e s . D e t e c t i o n l i m i t s f o r s o l i d s c an be estimated by d i v i d i n g these values by t h e grams e x t r a c t e d oer l i t e r . which depends upon t h e e x t r a c t i o n procedure. D i v i d e s o l u t i o n d b t e c t i o n ii m i t s by 10 f o r 1 g e x t r a c t e d t o 100 mL f o r s o l i d detection l i m i t s . Suggested c o n c e n tra ti o n f o r instrument c a 1 i b r a t i o n e 2 Other c a l i b r a t i o n l i m i t s i n t h e l i n e a r ranges may be used. Calcula te d f r o m 2-sigma data. 5 H i g h l y dependent on o p e r a t i n g c o n d i t i o n s and plasma p o s i t i o n .

Revision 4 . 4 May 1994

72

Methods for the Determination TABLE 2: ON-LINE METHOD INTERELEMENT SPECTRAL INTERFERENCES ARISING FROM INTERFERANTS AT THE lOO-mg/L LEVEL Wave1 eng t h

Analyte

I nt e r f e r a n t *

(nm) ~

A9 A1 As B Ba Be Ca Cd Ce co Cr

cu Fe Hg K Li Mg Mn Mo Na Ni P Pb Sb Se SiO, Sn Sr

11 Ti V Zil

~~

328.068 308.2 15 193.759 249.678 493.409 313.042 315.887 226.502 413.765 228.616 205.552 324.754 259.940 194.227 766.491 670.784 279.079 257.610 203.844 588.995 231.604 214.914 220.353 206.833 196.099 251.611 189.980 421.552 190.864 334.941 292.402 213.856

~

~

Ce,Ti ,Mn V,Mo,Ce,Mn V,A1 ,Co,Fe,Ni None None V,Ce Co,Mo, Ce N i , T i ,Fe,Ce None Ti,Ba,Cd,Ni,Cr,Mo,Ce Be,Mo,Ni, Mo,Ti None V,Mo None None Ce Ce Ce None co, 11 Cu,Mo Co,A1 ,Ce,Cu,Ni , T i ,Fe Cr,Mo,Sn,Ti,Ce,Fe Fe None Mo,Ti,Fe,Mn,Si None Ti,Mo,Co,Ce,Al,V,Mn None Mo,Ti,Cr,Fe,Ce N i ,Cu,Fe

* These o n - l i n e i n t e r f e r e n c e s f r o m method a n a l y t e s and t i t a n i u m o n l y were observed u s i n g an i n s t r u m e n t w i t h 0.035-nm r e s o l u t i o n (see Sect. 4.1.2). I n t e r f e r a n t ranked by magnitude o f i n t e n s i t y w i t h t h e most severe i n t e r f e r a n t l i s t e d f i r s t i n t h e row.

Revision 4.4 May 1994

Metals TABLE 3:

Solution

I I1 111 IV

V

73

MIXED STANDARD SOLUTIONS

Ana 1y t e s Ag, As, B, Ba, Ca, Cd, Cu, Mn, Sb, and Se K , L i , Mo, Na, Sr, and T i Co, P , V , and Ce A l , Cr, Hg, SiO,, Sn, and Zn Be, F e , Mg, N i , Pb, and T1

Revision 4.4 Hay 1994

74

Methods for the Determination TABLE 4:

TOTAL RECOVERABLE METHOD DETECTION LIMITS (MDL) MDLs

Anal vte Ag A1 As

B Ba Be Ca Cd Ce co

Cr cu

Fe Hg K

Li Mg Mn Mo Na Ni P

Pb Sb

Se SiO, Sn Sr

Aaueous, 0.002 0.02 0.008 0.003 0.001

0.0003 0.01 0.001 0.02 0.002 0.004 0.002 0.03 0.007 0.3 0.001 0.02 0.001 0.004 0.03 0.005 0.06 0.01 0.008

Ti T1

0.02 0.02 0.007 0.0003 0.001 0.02

V

0.003

Zn

0.002

-

mq/L”’

Sol ids,

mq/kq‘*’

0.3 3 2

-

0.2 0.1 2 0.2

3

0.4 0.8 0.5 6 2 60 0.2 3 0.2

1 6 1 12 2 2

5

-

2 0.1 0.2 3 1 0.3

(1)

MDL concentrations are computed for original matrix with allowance for

(2)

Estimated, calculated from aqueous MDL determinations.

-

Boron not reported because of glassware contamination. Silica not determined in solid samples.

*

Elevated value due t o fume-hood contamination.

2x

sample preconcentration during preparation. Samples were processed in PTFE and diluted in 50-mL plastic centrifuge tubes.

Revision4.4 May1994

Metals TABLE 5:

75

INDUCTIVELY COUPLED PLASMA INSTRUMENT OPERATING CONDITIONS

I n c i d e n t r f power

1100 w a t t s

R e f l e c t e d r f power

< 5 watts

Viewing h e i g h t above work c o i l I n j e c t o r tube o r i f i c e i.d. Argon s u p p l y

15 mm 1 mm l i q u i d argon

Argon p r e s s u r e

40 p s i

Coolant argon f l o w r a t e

19 L/min

Aerosol c a r r i e r argon flow rate

620 mL/min

Auxi 1 ia r y ( p l asma) argon f l o w r a t e

300 mL/min

Sample u p t a k e r a t e controlled t o

1 . 2 mL/min

R e v i s i o n 4.4 May 1994

76

Methods for the Determination TABLE 6:

PRECISION AND RECOVERY DATA I N AQUEOUS MATRICES TAP WATER -

SAMPLE CONC mg/L

LOW SPIKE mg/L

Ag A1 As B Ba

t o . 002

0.05 0.05 0.05 0.1 0.05

Be Ca Cd co Cr

to. 0003

ANALYTE

0.7 8.8 1.4 0.2 1.6

2.1 1.7 3.7 0.0 2.2

0.2 0.2 0.2 0.4 0.2

96 05 01 98 98

0.0 3.0 0.7 0.2 0.4

0.0 3.1 2.0 0.5 0.8

0.01 5.0 0.01 0.02 0.01

100 101 105 100 110

0.0 8.8 3.5 0.0 0.0

0.0 1.7 9.5 0.0 0.0

0.1 20.0 0.1 0.2 0.1

99 03 98 99

0.0

102

2.0 0.0 0.5 0.0

0.0 0.9 0.0 1.5 0.0

0.02 0.1 0.05 5.0 0.02

103 106 103 109 103

1.8 1 .o 0.7 1.4 6.9

4.9 1.8 1.9 2.3 3.8

0.2 0.4

101 105 100 107 110

1.2 0.3 0.4 0.7 1.9

3.5 0.5 1.o 1.7 4.4

104 100 95 99 108

2.2 0.0

1.5 0.0 10.5 2.0 4.7

20.0 0.1 0.2 20.0 0.2

100

10.3
5.0 0.01 0.02 5.0 0.02

0.7 0.0 0.5 1.o 1.1

1.1 0.0 1.4 1.6 2.9

0.045 t0.01 to. 008 t o . 02 6.5

0.1 0.05 0.05 0.1 5.0

102 95 99 87 104

13.1 0.7 0.7 1.1 3.3

9.4 2.1 3.5 3.4

0.4 0.2 0.2 0.4 20.0

102 99 96

3.2 0.2 0.7 0.8 1.1

1.3 0.5 2.0 2.3 2.3

to.007

0.05 0.1 0.1 0.05 0.05

103 102 101 101 101

2.1 3.3 3.9 0.7 3.7

5.8 2.1 10.9 2.0 9.0

0.2 0.4 0.4 0.2 0.2

101 105 101 99 98

1.8 0.8 0.1 0.2 0.9

5.0 1 .o 0.3 0.5 2.5

8.08

Sb Se Si02

*

95 98 108 98 102

0.008 to. 007 1.98 0.006

Pb

t

mg/L

to. 003

P

S(R) RPD

RPD

35.2 t o . 001 t o . 002
Mg Mn Mo Na Ni

Sn Sr T1 V Zn

S(R)

AVERAGE RECOVERY R(%)

0.185 to.008 0.023 0.042

cu Fe Hg K Li

AVERAGE RECOVERY R(%)

0.181 t0.02
HIGH SPIKE

3.5 3.0 1.8

2.0

0.2 20.0

0.2

,

99 108 106 104 104 100

S(R)

RPD

Standard d e v i a t i o n o f p e r c e n t r e c o v e r y . R e l a t i v e p e r c e n t d i f f e r e n c e between d u p l i c a t e s p i k e d e t e r m i n a t i o n s Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t . Spike c o n c e n t r a t i o n (10% o f sample background c o n c e n t r a t i o n .

R e v i s i o n 4.4 May 1994

Metals TABLE 6 :

77

PRECISION AND RECOVERY DATA I N AQUEOUS MATRICES ( C o n t ’ d . ) POND WATER HIGH AVERAGE SPIKE RECOVERY mg/L R(%) S(R)

LOW SPIKE mg/L

AVERAGE RECOVERY R(%)

0.05 0.2 0.05 0.1 0.05

92 88 102 111 96

0.0 10.0 0.0 8.9 0.9

0.0 5.0 0.0 6.9 0.0

0.2 0.8 0.2 0.4 0.2

94 100 98 103 97

0.0 2.9 1.4 2.0 0.3

0.0 3.7 4.1 0.0 0.5

0.4

107 100 105

0.0

co Cr

0.01 5 0.01 0.02 0.01

95

53.9 t o . 001 t o . 002 10.004

2.7 3.5

1.1 0.7 0.0 7.5 9.5

0.1 20.0 0.1 0.2 0.1

95 100 97 97 103

0.0 2.0 0.0 0.7 1.1

0.0 1.5 0.0 2.1 2.9

cu Fe Hg K Li

0.003 0.875 t o . 007 2.48 t o . 001

0.02 0.2 0.05 5 0.02

98 95 97 106 10

2.1 8.9 3.5. 0.3 0.0

4.4 2.8 10.3 0.1 0.0

0.2 0.8 0.2 20.0 0.2

100 97 98 103 106

0.5 3.2 0.0 0.2 0.2

1.5 3.6 0.0 0.4 0.5

Mg Mn Mo Na Ni

10.8 0.632 to. 004 17.8
5 0.01 0.02 5 0.02

02

*

0.5

05 03 96

3.5 1.3 5.6

0.0 0.2 9.5

0.4 9.1

20.0 0.1 0.2 20.0 0.2

96 97 103 94 100

0.7 2.3 0.4 0.3 0.7

1.3 0.3 1 .o 0.0 1.5

P Pb Sb Se Si02

0.196 tO.O1 to. 008 t o . 02 7.83

0.1 0.05 0.05 0.1 5

91 96 02 04 51

14.7 2.6 2.8 2.1 1.6

0.3 7.8 7.8 5.8 1.3

0.4 0.2 0.2 0.4 20.0

108 100 104 103 117

3.9 0.7 0.4 1.6 0.4

1.3 2.0 1 .o 4.4 0.6

Sn Sr T1 V Zn

to. 007

0.05 0.1 0.1 0.05 0.05

98 105 103 94 97

0.0 0.4 1.1 0.4 1.6

0.0 0.0 2.9 0.0 1.8

0.2 0.4 0.4 0.2 0.2

99 99 97 98 94

1.1 0.1 1.3 0.1 0.4

3.0 0.2 3.9 0.0 0.0

ANALYTE

Ag A1 As

B Ba Be Ca

Cd

S(R) RPD t

*

SAMPLE CONC mg/L

t o . 002 0.819 to. 008 0.034 0.029 t o .0003

0.129 t o . 02 0.003 0.006

*

S(R)

*

*

RPD

RPD

Standard d e v i a t i o n o f percent recovery. R e l a t i v e p e r c e n t d i f f e r e n c e between d u p l i c a t e s p i k e d e t e r m i n a t i o n s . Sample c o n c e n t r a t i o n b e l o w e s t a b l i s h e d method d e t e c t i o n l i m i t . S p i k e c o n c e n t r a t i o n t10% o f sample b a c k g r o u n d c o n c e n t r a t i o n .

R e v i s l o n 4 . 4 May1994

78

Methods for the Determination

TABLE 6: PRECISION AND RECOVERY DATA IN AQUEOUS MATRICES (Cont’d.) WELL WATER SAMPLE CONC

ANALYTE

mg/L

LOW SPIKE mg/L

AVERAGE RECOVERY R(%)

S(R)

RPD

H IGH SPIKE mg/L

AVERAGE RECOVERY R(%) S(R)

RPD

Ag A1 As B Ba

0.05 0.05 0.05 0.1 0.05

97 07 07 97 02

0.7 7.6 0.7 0.6 3.0

2.1 10.1 1.9 0.7 0.0

0.2 0.2 0.2 0.4 0.2

96 01 04 98 99

0.2 1.1 0.4 0.8 0.9

0.5 0.8 1.o 2.1 1.o

Be Ca Cd co Cr

0.01 5.0 0.01 0.02 0.01

00

0.0

0.0 0.4 7.1

0.1 20.0 0.1 0.2 0.1

00 00

90 94 00

0.0 2.1 0.0 1.1 20.0

96 94 100

0.0 4.1 0.0

0.0 0.1 0.0 1.1

cu Fe Hg K Li

0.005 0.042
0.02 0.1 0.05 5.0 0.02

00 99 94 96 100

1.1 2.3 2.8 3.4 7.6

0.4 1.4 8.5 3.6 9.5

0.2 0.4 0.2 20.0 0.2

96 97 93 101 104

0.5 1.4 1.2

Mg Mn Ma Na Ni

24.5 2.76 (0.004 35.0 (0.005

5.0 0.01 0.02 5.0 0.02

95

5.6

1.6

1.8 11.4 1.8

20.0 0.1 0.2 20.0 0.2

93

108 101 112

0.3 0.4 4.7 0.8 4.4

101 100 96

0.2 3.1 0.2

1.2 0.1 0.5 1.5 0.5

0.197

0.1 0.05 0.05 0.1 5.0

95 87 98 102 93

12.7 4.9 2.8 0.4 4.8

1.9 16.1 8.2 1.0 2.8

0.4 0.2 0.2 0.4 20.0

98 95 99 94 99

3.4 0.2 1.4 1.1 0.8

0.9 0.5 4.0 3.4 0.0

0.05 0.1 0.1 0.05 0.05

98 94 92 98

2.8 5.7 0.4 0.0

8.2 2.7 1.1 0.0 0.7

0.2 0.4 0.4 0.2 0.2

94 95 95 99 99

0.2 1.7 1.1 0.4 2.5

0.5 2.2 3.2 1.o 1.1

P Pb Sb

Se Si02

Sn Sr T1 V Zn S(R) RPD

<

*

t o . 01

0.274
*

*

*

*

*

*

*

0.4 0.4

1.2 1 .o

*

1.o

1.5 3.3 3.8 2.3 1.9

Standard d e v i a t i o n o f p e r c e n t r e c o v e r y . R e l a t i v e p e r c e n t d i f f e r e n c e between d u p l i c a t e s p i k e d e t e r m i n a t i o n s Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t . Spike c o n c e n t r a t i o n (10% o f sample background c o n c e n t r a t i o n .

R e v i s i o n 4.4 May 1994

79

Metals T A B L E 6:

P R E C I S I O N AND RECOVERY DATA

IN AQUEOUS M A T R I C E S

(Cont’d.)

SEWAGE TREATMENT PRIMARY EFFLUENT H I G H AVERAGE S P I K E RECOVERY mg/L R(%)

LOW SPIKE mg/L

AVERAGE RECOVERY R(%)

S(R)

RPD

0.009 1.19 to. 008 0.226 0.189

0.05 0.05 0.05 0.1 0.05

92

*

1.5

99 217 90

2.1 16.3 6.8

3.6 0.9 6.1 9.5 1.7

0.2 0.2 0.2 0.4 0.2

to. 0003

0.01 5.0 0.01 0.02 0.01

94

*

0.4

87.9 0.009 0.016 0.128

89 95

2.6 3.1

1.1 0.6 2.3 0.0 1.5

0.1 20.0 0.1

0.174 1.28
0.02 0.1 0.05 5.0 0.02

0.2

1.4, 2.8 8.5

4.7 2.8 3.9 1.3 3.2

22.7 0.199 0.125 236 0.087

5.0 0.01 0.02 5.0 0.02

*

4.4

0.0

10

*

21.2

22

10.7

2.0 6.8 0.0 4.5

20.0 0.1 0.2 20.0 0.2

0.1 0.05 0.05 0.1 5.0

*

* 3.5 0.7 3.9 4.0

0.4 0.2 0.2 0.4 20.0

*

91 97 108 124

2.6 5.0 2.1 10.0 0.9

*

Si02

4.71 0.015
96 103 101 108

1.3 1.1 2.6 1.1

1.4 2.9 2.9 7.2 0.8

Sn Sr T1 V Zn

0.016 0.515 <0.02 0.003 0.160

0.05 0.1 0.1 0.05 0.05

90 103 105 93 98

3.8 6.4 0.4 0.9 3.3

0.0 0.5 1 .o 2.0 1.9

0.2 0.4 0.4 0.2 0.2

95 96 95 97 101

1 .o 1.6 0.0 0.2 1 .o

0.0 0.2 0.0 0.5 1.4

ANALYTE Ag

A1

AS B Ba Be Ca

Cd co Cr cu Fe Hg K

Li Mg

Mn

Mo Na Ni P Pb Sb Se

S(R) RPD

<

*

SAMPLE CONC mg/L

*

98

*

102 104 03 00

*

*

*

33.1

*

* *

0.2

0.1 0.4 0.2

20.0 0.2

S(R)

RPD

95 113 93 119 99

0.1 12.4 2.1 13.1 1.6

0.0

2.1 6.5 20.9 0.5

100 101 97 93 97

0.4 3.7 0.4 0.4 2.4

1 .o 0.0 1 .o 0.5 2.7

98 111 98 101 105

3.0 7.0 0.5 0.6 0.8

1.4 0.6 1.5 0.0 0.5

92 104 102

1.1 1.9 1.3

98

0.8

0.2 0.3 0.9 0.4 1.1

*

*

Standard d e v i a t i o n o f p e r c e n t r e c o v e r y . R e l a t i v e p e r c e n t d i f f e r e n c e between d u p l i c a t e s p i k e d e t e r m i n a t i o n s . Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t . S p i k e c o n c e n t r a t i o n < l o % o f sample background c o n c e n t r a t i o n .

R e v i s i o n 4 . 4 May1994

80

Methods for the Determination TABLE 6 :

P R E C I S I O N AND RECOVERY DATA IN AQUEOUS MATRICES (Cont’d.) INDUSTRIAL EFFLUENT

SAMPLE CONC ANALYTE

mg/L

mg/L

AVERAGE RECOVERY R(%)

Ag

t o . 003

0.05 0.05 0.05 0.1 0.05

A1 As

B Ba

H I G H AVERAGE S P I K E RECOVERY mg/L R(%)

S(R)

RPD

88 88 82 162 86

0.0 11.7 2.8 17.6 8.2

0.0 12.2 9.8 13.9 1.6

0.2 0.2 0.2 0.4 0.2 0.1 20.0 0.1 0.2 0.1

S(R)

RPD

84 90 88 92 85

0.9 3.9 0.5 4.7 2.3

3.0 8.1 1.7 9.3 2.4

82

1.4

82 83 106

1.4 0.4 6.6

4.9 2.3 4.4 1.2 5.6

Be Ca Cd co Cr

t o . 0006

0.01 5.0 0.01 0.02 0.01

94

0.4

500 0.008 t o . 004 0.165

85 93

4.7 1.8

*

1.1 2.8 6.1 5.4 4.5

cu Fe

0.095 0.315 tO.O1 2.87 0.069

0.02 0.1 0.05 5.0 0.02

93 88 87 101 103

23.3 16.4 0.7 3.4 24.7

0.9 1.o 2.3 2.4 5.6

0.2 0.4 0.2 20.0 0.2

95 99 fl6 100 104

2.7 6.5 0.4 0.8 2.5

2.8 8.0 1.2 0.4 2.2

6.84 0.141 1.27 1500 0.014

5.0 0.01 0.02 5.0 0.02

87

3.1

0.9 6.6 15.0

4.4

20.0 0.1 0.2 20.0 0.2

87 89 100

98

0.0 1.2 0.0 2.7 3.0

87

0.5

1.2 4.8 2.7 2.0 1.1

0.326 0.251 2.81 0.021 6.83

0.1 0.05 0.05 0.1 5.0

105 80

16.0 19.9

3.9 5.0

2.6 6.8

0.4 0.2 0.2 0.4 20.0

97 88

106 99

4.7 1.4 0.4 3.2 1.7

105 100

1.9 2.2

<0.01 6.54 to. 03 to. 005 0.024

0.05 0.1 0.1 0.05 0.05

87

*

0.7

0.4

1.8 1.4 6.0

0.2 0.4 0.4 0.2 0.2

86

87 90 89

2.3 2.0 5.8 4.4 4.4

84 84 91

1.1 1.1 3.5

Hg

K

Li Mg

Mn

Mo Na

Ni P

Pb Sb

Se Si02

Sn Sr

T1 V

Zn S(R) RPD

<

*

0.054 t o * 02 0.17 0.083

LOW SPIKE

*

*

* * *

*

*

* * *

*

*

*

*

*

*

*

*

*

*

1.4 0.9 2.0 4.6 3.0 1.2 2.7 3.6 3.6 8.9

Standard deviation o f percent recovery. Relative percent difference between duplicate spike determinations. Sample concentration below established method detection limit. Spike concentration
Revision 4 . 4 May 1994

Metals TABLE 7 :

81

P R E C I S I O N AND RECOVERY DATA I N S O L I D MATRICES EPA HAZARDOUS SOIL #884

ANALYTE

SAMPLE CONC mg/kg

LOW' SPIKE mg/kg

AVERAGE RECOVERY R(%)

S(R)

100 100 100 400 100

96

0.2

96 100 97

1.4 2.1 10.0

0.6 5.4 3.6 5.5 1 .o

100

99

0.1

0.2

0.7 3.5 28.8

2.0 1 .o 7.7 16.5

100 100 100

94 93 104

0.2 0.8 1.3

0.4 2.1 1.1

16.2

4.4

100

104

4.0

4.2

2.5, 1.3 3.5

7.7 0.0 4.4

40 2000 40

98 107 106

0.0 0.9 0.6

0.0 1.8 0.6

* *

* *

2000 100

88 02 100

5.3 2.2 1.8

8.4 8.5 13.2 2.4 0.0

500 20 20 20 20

106 88 83 79 91

13.4 51.8 3.9 14.7 34.6

100 20 20 20

84 92 104 103

9.6 4.8 4.2 31.2

1.1 5080 5.7 20.4 111

20 20 20 100 20

98

*

0.7

95 93 98

5.4 2.7 71.4

Be Ca Cd co Cr

0.66 85200 2

20 20 20 20

97 93 96 87

0.7

cu Fe Hg K Li

113 16500 tl.4 621 6.7

20

110

10 500 10

92 21 13

Mg Mn Mo Na Ni

24400 343 5.3 195 15.6

500 20 20 500 20

P Pb Sb Se Sn

595 145 6.1 <5 16.6

Sr

102 t4 16.7 131

T1 V Zn S(R) RPD

<

*

t

5.5

RPD

1 .o 7.2 10.6 5.3 22.2

Ag A1 As B Ba

79.7

RPD

HIGH+ AVERAGE S P I K E RECOVERY rng/kg R(%) S(R)

-

-

*

-

-

-

-

-

*

-

-

*

-

-

-

-

*

*

2000 100

95 91 100 94

11.0 1.4 1.5 1.5

10.1 1.6 4.1 3.7 3.6

8.0 17.9 7.5 52.4 5.8

2000 100 100 100 80

103 108 81 99 112

3.2 15.6 1.9 0.7 8.7

2.7 17.4 5.9 2.1 2.8

10.8 14.6 5.4 7.3

400 100 100

94 91 99 104

2.5 1.5 0.8 7.2

4.6 4.6 1.7 6.4

100

100

Standard d e v i a t i o n o f p e r c e n t r e c o v e r y . R e l a t i v e p e r c e n t d i f f e r e n c e between d u p l i c a t e s p i k e d e t e r m i n a t i o n s . Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t . S p i k e c o n c e n t r a t i o n t10% o f sample background c o n c e n t r a t i o n . Not s p i k e d . Equivalent

R e v i s i o n 4.4 May 1994

82

Methods for the Determination TABLE 7:

PRECISION AND RECOVERY DATA I N SOLID MATRICES ( C o n t . )

EPA ELECTROPLATING SLUDGE #286

ANALYTE Ag

A1 As B

Ba Be Ca

Cd co Cr

cu Fe Hg K Li

Mg Mn MO

Na Ni

P Pb

Sb Se Sn Sr

T1 V Zn S(R) RPD t

* t

SAMPLE CONC mg/kg

LOW'

SPIKE mg/kg

AVERAGE RECOVERY R(%)

HIGH+ AVERAGE

SPIKE RECOVERY R(%)

S(R)

RPD

93

0.1

97 98 0

0.7 1.9 1.6

0.4 5.6 1.6 3.5 5.7

100

101

0.7

2.0

S(R)

RPD

mg/kg

100 100 100 400 100

6 4980 32 210 39.8

20 20 20 100 20

96

0.2

94 113 0

1.3 2.0 6.8

0.4 4.4 0.8 1.6 0.3

0.32 48500 108 5.9 7580

20

96

0.2

0.5

20 20 20

98 93

2.5 2.9

*

0.8 5.7 0.7

100 100 100

96 93

0.5 0.6

*

0.5 1.5 1.3

806 31100 6.1 2390 9.1

20

*

*

-

-

-

1.5

100

94

8.3

0.7

10 500 10

90 75 101

2.5

4.0

40

8.3

4.0 0.5

2000 40

97 94 106

1.7 2.9 1.6

4.3 3.8 3.1

1950 262 13.2 73400 456

500 20 20 500 20

110

*

2.0

92

* *

2.1

0.8 1.8 2.9 1.7 0.4

2000 100 100 2000 100

108 91 92

2.3 1.2 0.3

88

2.7

3.2 0.9 0.0 1.4 0.9

9610 1420 t2 6.3 24.0

500 20 20 20 20

* *

*

7.4

0.9 9.0 4.0

2000 100 100 100 100

114

76 86 87

2.9 2.1 3.3 16.6 2.7

75 103 92

2.8 1.6 0.7

145 16 21.7 12500

100 20 20 20

90 89 95

4.6

8.1 5.3 1. o

400 100 100 100

93 92 96

2.4 0.8 0.4

-

*

-

*

*

*

-

2.8

*

* * *

8.1 1.2

*

-

-

0.8

-

-

*

-

* -

*

*

*

*

-

-

* *

*

-

-

3.4 1.3 10.7 2.7 0.0 4.6 0.9 0.9 0.8

S t a n d a r d d e v i a t i o n of p e r c e n t r e c o v e r y . R e l a t i v e percent d i f f e r e n c e between d u p l i c a t e s p i k e d e t e r m i n a t i o n s . Sample c o n c e n t r a t i o n b e l o w e s t a b l i s h e d method d e t e c t i o n l i m i t . Spike concentration ~ 1 0 % o f sample b a c k g r o u n d c o n c e n t r a t i o n . Not spiked. EquiVal e n t R e v i s i o n 4.4 May 1994

Metals TABLE 7:

83

PRECISION AND RECOVERY DATA I N SOLID MATRICES ( C o n t . ) NBS 1645 R I V E R SEDIMENT

ANALYTE

SAMPLE CONC mg/kg

LOW' SPIKE mg/kg

Ag A1 As 6 Ba

1.6 5160 62.8 31.9 54.8

20 20 20 100 20

Be Ca co Cr

0.72 28000 9.7 9.4 28500

cu Fe Hg K Li

109 84800 3.1 452 3.7

Mg

Mo Na Ni

6360 728 17.9 1020 36.2

500 20 20 500 20

P Pb Sb Se Sn

553 707 22.8 6.7 309

Sr

782 t4 20.1 1640

Cd

Mn

T1 V Zn S(R) RPD

<

* t

AVERAGE RECOVERY

R(%)

HIGH' AVERAGE S P I K E RECOVERY mg/kg R(%) S(R)

S(R)

RPD

92

*

0.4

89 116 95

14.4 7.1 6.1

1 .o 8.4 9.7 13.5 2.8

100 100 100 400 100

20 20 20 20

101 100 98

0.4

1 .o

100

1.1 3.8

*

0.0 4.8 0.4

100 100 100

20

115

0.0

100

-

8.5

-

10 500 10

99 98 101

4.1 2.0

* *

*

97 92 94

12.5 2.6 5.9

500 20 20 20 20

102

*

1.4

86 103

2.3 14.3

100 20 20 20

91 90 89

12.3

*

*

*

*

-

4 .3, *

*

*

0.0

5.4

*

-

7.7 2.0 0.7

-

-

40 2000 40

RPD

0.9 2.4 5.0 1.5 1.3

96

*

0.3

97 95 98

2.9 0.6 1.2

103 101 98

1.4 0.7 0.9

*

3.9 1.8 1.8 0.7

102

1.8

1 .o

*

*

96 106 108

0.7 1.4 1.3

1 .o 2.3 3.0

2.7 12.4 0.6 1.1 1.1

1 .o 2.2 0.0 1.7 1.5

-

1.8 3.5 18.5 0.0 4.0

2000 100 100 2000 100

93 97 98 97 100

0.9 0.8 0.0 27.1 1 .o

2000 100 100 100 100

100 103 88 98 101

0.8 5.9 0.6 3.1 7.9

1.6 0.4 0.9 7.6 2.7

3.0 0.0 5.8 1.8

400

96 95 98

3.3 1.3 0.7

2.6 4.0 0.0 1.1

100

100 100

*

*

Standard d e v i a t i o n o f p e r c e n t r e c o v e r y . R e l a t i v e p e r c e n t d i f f e r e n c e between d u p l i c a t e s p i k e d e t e r m i n a t i o n s . Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t . S p i k e c o n c e n t r a t i o n t10% o f sample background c o n c e n t r a t i o n . Not s p i k e d . Equivalent R e v i s i o n 4.4 May 1994

84

Methods for the Determination TABLE 8:

Element A1 Sb As Ba Be Cd Ca Cr Co CU

Fe Pb Mg Mn Mo Ni K Se Na T1 V Zn

ICP-AES INSTRUMENTAL P R E C I S I O N AND ACCURACY FOR AQUEOUS SOLUTIONS'

Mean Conc (mq/L)

14.8 15.1 14.7 3.66 3.78 3.61 15.0 3.75 3.52 3.58 14.8 14.4 14.1 3.70 3.70 3.70 14.1 15.3 14.0 15.1 3.51 3.57

RSD

Nb

(%I

a

6.3 7.7 6.4 3.1 5.8 7.0 7.4 8.2 5.9 5.6 5.9 5.9 6.5 4.3 6.9 5.7 6.6 7.5 4.2 8.5 6.6

8

8.3

8 8 7 7 8

a

8 8 8 8 8 7 8 8 8 7 8 8 8 7

Ac c u r ac yc

I% o f Nominal 1 100 102 99 99 102 97 101 101 95 97 100 97 96 100 100 100 95 104 95 102 95 96

These performance v a l u e s a r e independent o f sample p r e p a r a t i o n because t h e l a b s analyzed p o r t i o n s o f t h e same s o l u t i o n s u s i n g s e q u e n t i a l o r simultaneous i n s t r u m e n t s . 22

a

N

=

Number o f measurements f o r mean and r e l a t i v e s t a n d a r d d e v i a t i o n (RSD).

Accuracy i s expressed as a p e r c e n t a g e o f t h e nominal v a l u e f o r each a n a l y t e i n t h e a c i d i f i e d , mu1t i - e l ement s o l u t i o n s .

R e v i s i o n 4.4 May 1994

Metals

TABLE 9:

MULTILABORATORY

CI P

PRECISION

Concentration Analyte A1 umi num

69-4792 77-1406

x =

0.9380(C) O.O481(X)

t t

22.1 18.8

=

0.8908(C) O.O682(X)

t t

0.9 2.5

X = SR =

1.0175(C) O.O643(X)

t t

3.9 10.3

x =

0.8380(C) O.O826(X)

t t

1.68 3.54

1.0177(C) O.O445(X)

-

0.55 0.10

0.9676(C) O.O743(X)

t

X = SR

Arsenic

69- 1887

B a r i urn

9-377

SR

B e r y l 1 iurn

3-1906 19-5189 9-1943

Chromi urn Cobalt

17-47170 13- 1406 17-2340

Copper

8-1887

Iron

13-9359

=

x = SR

Cal c i urn

=

X = SR

Cadmi urn

=

x = SR

Boron

=

X =

42-4717

X C SR

1.0137(C) O.O332(X)

t

18.7 21.1 0.65 0.90

0.9658(C) t O.O327(X) t

0.8 10.1

X = SR =

1.0049(C) O.O571(X) t

1.2

X = SR =

0.9278(C) O.O407(X) t

1.5 0.4

X = SR =

0.9647(C) O.O406(X)

t

3.64 0.96

X =

0.9830(C) O.O790(X)

t t

5.7 11.5

1.0056(C) O.O448(X)

t t

4.1 3.5

x = SR

*

t

SR =

SR = Lead

AND ACCURACY DATA*

T o t a l Recoverable D i g e s t i o n P/ L

SR = Ant imony

85

=

1.0

- Regression e q u a t i o n s a b s t r a c t e d f r o m Reference 16. =

Mean Recovery, pg/L

= True Value f o r t h e C o n c e n t r a t i o n , ,ug/L = S i n g l e - a n a l y s t Standard D e v i a t i o n , pg/L

R e v i s i o n 4.4 May 1994

86

Methods for the Determination

TABLE 9:

MULTILABORATORY ICP PRECISION AND ACCURACY DATA* (Cont. )

Analyte

Concentration MIL

T o t a l Recoverable D i g e s t i o n P IL

Magnesium

34-13868

X = SR =

0.9879(C) O.O268(X)

t t

2.2 8.1

Manganese

4-1887

X = SR =

0.9725(C) O.O400(X)

t t

0.07 0.82

Molybdenum

17-1830

X = SR =

0.9707(C) O.O529(X)

+

2.1

X = SR =

0.9869(C) O.O393(X)

t t

1.5 2.2

X = SR =

0.9355(C) O.O329(X)

t

X = SR =

0.9737(C) O.O443(X)

t

X = SR =

0.9737(C) - 60.8 0.2133(X) t 22.6

Nickel

17-47170

Pot ass ium 347-14151 Selenium

69-1415

Silicon

189-9434

S i 1v e r

8-189

Sod ium

35-47 170

Thallium

79-1434

X =

Zinc

13-4698 7-7076

-183.1 60.9

-

1.0 6.6

SR =

0.3987(C) t 0.1836(X) -

X = SR =

1.0526(C) t 26.7 O.O884(X) t 50.5

X =

0.9238(C) t 5.5 -O.O106(X) t 48.0

SR Van ad ium

- 2.3

=

X =

8.25

0.27

SR =

0.9551(C) t O.O472(X) t

0.4 0.5

X = SR =

0.9500(C) + O.O153(X) t

1.82 7.78

- Regression e q u a t i o n s a b s t r a c t e d from Reference 16.

X C

=

SR

=

=

Mean Recovery, pg/L True Value f o r t h e C o n c e n t r a t i o n , pg/L S i n g l e - a n a l y s t Standard D e v i a t i o n , kg/L R e v i s i o n 4.4 Hay 1994

Metals

87

Pb-Cu ICP-AES EMISSION PROFILE Net Emision Intensity Counts (X103) 32

30

28

26

24

22

20

18

16

14

12 475

525

575

625

675

725

775

825

Nebulizer Argon Flow Rate - mL/min Figure 1 200 7 - 5 7

Revision 4.4 May 1994

88

Methods for the Determination METHOD 200.8 DETERMINATION OF TRACE ELEMENTS I N WATERS AND WASTES BY INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETRY

Revision 5.4 EMMC V e r s i o n

S.E. Long (Technology A p p l i c a t i o n s I n c . ) , T.D. M a r t i n , and E.R. M a r t i n Method 200.8, R e v i s i o n s 4.2 and 4.3 (1990)

S.E. Long (Technology A p p l i c a t i o n s I n c . ) and T.D. R e v i s i o n 4.4 (1991) J.T. Creed, C.A. (1994)

M a r t i n - Mgthod 200.8,

Brockhoff, and T.D. M a r t i n - Method 200.8, R e v i s i o n 5.4

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHO I 45x8

Metals

89

METHOD 200.8 DETERMINATION OF TRACE ELEMENTS IN WATERS AND WASTES BY INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETRY 1.0

SCOPE AND APPLICATION 1.1

This method provides procedures for determination of dissolved elements in ground waters, surface waters and drinking water. It may also be used for determination of total recoverable element concentrations in these waters as well as wastewaters, sludges and soils samples. This method is applicable to the following elements:

Analyte A1 umi num Ant i mony Arsenic Bar i um Beryl 1 i um Cadmi um Chromi um Cobalt Copper Lead Manganese Mercury Ma 1 ybden um Nickel Sel eni um Si 1 ver Thall ium Thorium Urani um Vanadium Zinc

Chemical Abstract Services Registry Numbers (CASRN) 7429-90-5 7440-36-0 7440-38-2 7440-39-3 7440-41-7 7440-43-9 7440-47-3 7440-48-4 7440-50-8 7439-92-1 7439-96-5 7439-97-6 7439-98-7 7440-02-0 7782-49-2 7440-22-4 7440-28-0 7440-29-1 7440-61-1 7440-62-2 7440-66-6

Estimated instrument detection 1 imits (IDLs) for these elements are listed in Table 1. These are intended as a guide to instrumental limits typical of a system optimized for multielement determinations and employing commercial instrumentation and pneumatic nebulization sample introduction. However, actual method detection limits (MDLs) and linear working ranges will be dependent on the sample matrix, instrumentation and selected operating conditions. Given in Table 7 are typical MDLs for both total recoverable determinations by "direct analysis" and where sample digestion i s employed. Revision 5 . 4 May 1994

90

Methods for the Determination 1.2

For reference where this method i s approved for use in compliance monitoring programs [e.g., Clean Water Act (NPDES) or Safe Drinking Water Act (SDWA)] consult both the appropriate sections of the Code of Federal Regulation (40 CFR Part 136 Table 1B for NPDES, and Part 141 9 141.23 for drinking water), and the latest Federal Register announcements.

1.3

Dissolved elements are determined after suitable filtration and acid preservation. In order to reduce potential interferences, dissolved solids should not exceed 0.2% (w/v) (Sect. 4 . 1 . 4 ) .

1.4

With the exception of silver, where this method is approved for the determination of certain metal and metalloid contaminants in drinking water, samples may be analyzed directly by pneumatic nebulization without acid digestion if the samples have been properly preserved with acid and have turbidity of < 1 NTU at the time of analysis. This total recoverable determination procedure is referred to as "direct analysis".

1.5

for the determination of total recoverable analytes in aqueous and solid samples a digestion/extraction is required prior to analysis when the elements are not in solution (e.g., soils, sludges, sediments and aqueous samples that may contain particulate and suspended sol ids). Aqueous samples containing suspended or particulate material 2 1% (w/v) should be extracted as a solid type samp1.e (Sect. 1 1 . 2 . 2 ) .

1.6 The total recoverable sample digestion procedure given in this method i s not suitable for the determination of volatile organo-mercury compounds. However, for "direct analysis" of drinking water (turbidity < 1 NTU), the combined concentrations of inorganic and organo-mercury in solution can be determined by "direct analysis" pneumatic nebulization provided gold is added to both samples and standards alike to eliminate memory interference effects. 1.7

Silver is only slightly soluble in the presence of chloride unless there is a sufficient chloride concentration to form the soluble chloride complex. Therefore, low recoveries of silver may occur in samples, fortified sample matrices and even fortified blanks if determined as a dissolved analyte or by "direct analysis" where the sample has not been processed using the total recoverable mixed acid digestion. For this reason it is recommended that samples be digested prior to the determination of silver. The total recoverable sample digestion procedure given in this method is suitable for the determination o f silver in aqueous samples containing concentrations up to 0.1 mg/L. For the analysis of wastewater samples containing higher concentrations of silver, succeeding smaller volume, well mixed sample aliquots must be prepared until the analysis solution contains < 0 . 1 mg/L silver. The extraction of solid samples containing concentrations of silver > 50 mg/kg should be treated in a similar manner.

1.8

The total recoverable sample digestion procedure given in this method will solubilize and hold in solution only minimal concentrations of Revision 5.4 May 1994

Metals

91

barium in the presence of free sulfate. For the analysis of barium in samples having varying and unknown concentrations of sulfate, analysis should be completed as soon as possible after sample preparation. 1.9

This method should be used by analysts experienced in the use of inductively coupled plasma mass spectrometry ( I C P - M S ) , the interpretation of spectral and matrix interferences and procedures for their correction. A minimum of six months experience with commercial instrumentation is recommended.

1.10 Users o f the method data should state the data-quality objectives

prior to analysis. Users of the method must document and have on file the required initial demonstration performance data described in Section 9.2 prior to using the method for analysis. 2.0

SUMMARY OF METHOD

2.1 An aliquot of a well mixed, homogeneous aqueous or solid sample is accurately weighed or measured for sample processing. For total recoverable analysis of a solid or an aqueous sample containing undissolved material, analytes are first solubil ized by gentle refluxing with nitric and hydrochloric acids. After cooling, the sample is made up to volume, is mixed and centrifuged or allowed to settle overnight prior to analysis. For the determination of dissolved analytes in a filtered aqueous sample aliquot, or for the "direct analysis" total recoverable determination of analytes in drinking water where sample turbidity is < 1 NTU, the sample is made ready for analysis by the appropriate addition of nitric acid, and then diluted t o a predetermined volume and mixed before analysis. 2.2

The method describes the mu1 ti-element determination of trace elements by I C P - M S . ' ' 3 Sample material in solution is introduced by pneumatic nebulization into a radiofrequency plasma where energy transfer processes cause desolvation, atomization and ionization. The ions are extracted from the plasma through a differentially pumped vacuum interface and separated on the basis of their mass-to-charge ratio by a quadrupole mass spectrometer having a minimum resolution capability of 1 amu peak width at 5% peak height. The ions transmitted through the quadrupole are detected by an electron multiplier or Faraday detector and the ion information processed by a data handling system. Interferences relating to the technique (Sect. 4 ) must be recognized and corrected for. Such corrections must include compensation for isobaric elemental interferences and interferences from polyatomic ions derived from the plasma gas, reagents or sample matrix. Instrumental drift as well as suppressions or enhancements of instrument response caused by the sample matrix must be corrected for by the use of internal standards.

3.0 DEFINITIONS 3.1

Calibration Blank - A volume of reagent water acidified with the same acid matrix as in the calibration standards. The calibration blank is a zero standard and is used to calibrate the I C P instrument (Sect. 7.6.1).

Revision 5.4 May 1994

92

Methods for the Determination

3.2

C a l i b r a t i o n Standard (CAL) - A s o l u t i o n prepared from t h e d i l u t i o n o f s t o c k s t a n d a r d s o l u t i o n s . The CAL s o l u t i o n s a r e used t o c a l i b r a t e t h e instrument response w i t h r e s p e c t t o a n a l y t e c o n c e n t r a t i o n (Sect. 7.4).

3.3

D i s s o l v e d A n a l y t e - The c o n c e n t r a t i o n o f a n a l y t e i n an aqueous sample t h a t w i l l pass t h r o u g h a 0.45-pm membrane f i l t e r assembly p r i o r t o sample a c i d i f i c a t i o n ( S e c t . 11.1).

3.4

F i e l d Reagent B l a n k (FRB) - An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i x t h a t i s p l a c e d i n a sample c o n t a i n e r i n t h e l a b o r a t o r y and t r e a t e d as a sample i n a l l r e s p e c t s , i n c l u d i n g s h i p m e n t t o t h e sampling s i t e , exposure t o t h e sampling s i t e c o n d i t i o n s , storage, p r e s e r v a t i o n , and a l l a n a l y t i c a l p r o c e d u r e s . The p u r p o s e o f t h e FRB i s t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e f i e l d environment (Sect 8.5).

3.5

I n s t r u m e n t D e t e c t i o n L i m i t ( I D L ) - The c o n c e n t r a t i o n e q u i v a l e n t t o t h e a n a l y t e s i g n a l which i s equal t o t h r e e times t h e standard d e v i a t i o n o f a s e r i e s o f t e n r e p l i c a t e measurements o f t h e c a l i b r a t i o n b l a n k s i g n a l a t t h e s e l e c t e d a n a l y t i c a l mass(es). ( T a b l e 1).

3.6

I n t e r n a l S t a n d a r d - Pure a n a l y t e ( s ) added t o a sample, e x t r a c t , o r s t a n d a r d s o l u t i o n i n known amount(s) and u s e d t o measure t h e r e l a t i v e r e s p o n s e s o f o t h e r method a n a l y t e s t h a t a r e components o f t h e same sample o r s o l u t i o n . The i n t e r n a l s t a n d a r d must be an a n a l y t e t h a t i s n o t a sample component ( S e c t s . 7.5 & 9 . 4 . 5 ) .

3.7

L a b o r a t o r y D u p l i c a t e s (LD1 and LD2) - Two a l i q u o t s o f t h e same sample t a k e n i n t h e l a b o r a t o r y and a n a l y z e d s e p a r a t e l y w i t h i d e n t i c a l p r o c e d u r e s . A n a l y s e s o f LD1 and LD2 i n d i c a t e s p r e c i s i o n a s s o c i a t e d w i t h l a b o r a t o r y procedures, b u t n o t w i t h sample c o l l e c t i o n , preservation, o r storage procedures.

3.8

L a b o r a t o r y F o r t i f i e d B l a n k (LFB) - An a l i q u o t o f LRB t o w h i c h known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB i s a n a l y z e d e x a c t l y l i k e a sample, and i t s p u r p o s e i s t o d e t e r m i n e w h e t h e r t h e m e t h o d o l o g y i s i n c o n t r o l and w h e t h e r t h e l a b o r a t o r y i s c a p a b l e o f m a k i n g a c c u r a t e and p r e c i s e measurements ( S e c t s . 7.9 & 9.3.2).

3.9

L a b o r a t o r y F o r t i f i e d Sample M a t r i x (LFM) - An a l i q u o t o f an e n v i r o n m e n t a l sample t o w h i c h known q u a n t i t i e s o f t h e method a n a l y t e s The LFM i s a n a l y z e d e x a c t l y l i k e a a r e added i n t h e l a b o r a t o r y . sample, and i t s p u r p o s e i s t o d e t e r m i n e w h e t h e r t h e sample m a t r i x contributes bias t o the analytical results. The b a c k g r o u n d c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be d e t e r m i n e d i n a s e p a r a t e a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s (Sect. 9 . 4 ) .

3.10 L a b o r a t o r y Reagent B l a n k (LRB) - An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y as a sample i n c l u d i n g e x p o s u r e t o a l l g l a s s w a r e , equipment, s o l v e n t s , r e a g e n t s , and i n t e r n a l s t a n d a r d s t h a t a r e used w i t h o t h e r samples. The LRB i s used t o R e v i s i o n 5.4

Hay 1994

Metals

93

determine if method analytes or other interferences are present in the laboratory environment, reagents, or apparatus (Sects. 7.6.2 & 9.3.1). 3.11 Linear Dynamic Range (LDR) - The concentration range over which the instrument response to an analyte is linear (Sect. 9.2.2). 3.12 Method Detection Limit (MDL) - The minimum concentration of an analyte that can be identified, measured, and reported with 99% confidence that the analyte concentration is greater than zero (Sect. 9.2.4 and Table 7). 3.13 Quality Control Sample (QCS) - A solution of method analytes of known concentrations which is used to fortify an aliquot of LRB or sample matrix. The QCS is obtained from a source external to the laboratory and different from the source of calibration standards. It is used to check either laboratory or instrument performance (Sects. 7.8 & 9.2.3). 3.14 Solid Sample - For the purpose of this method, a sample taken from material classified as either soil, sediment or sludge. 3.15 Stock Standard Solution - A concentrated solution containing one or more method analytes prepared in the laboratory using assayed reference materials or purchased from a reputable commercial source (Sect. 7.3). 3.16 Total Recoverable Analyte - The concentration of analyte determined either by "direct analysis" of an unfiltered acid preserved drinking water sample with turbidity of < 1 NTU (Sect. 11.2.1), or by analysis of the solution extract of a solid sample or an unfiltered aqueous sample following digestion by refluxing with hot dilute mineral acid(s) as specified in the method (Sects. 11.2 & 11.3).

3.17 Tuning Solution - A solution which is used to determine acceptable instrument performance prior to calibration and sample analyses (Sect. 7.7). 3.18 Water Sample - For the purpose of this method, a sample taken from one of the following sources: drinking, surface, ground, storm runoff, industrial or domestic wastewater. 4.0

INTERFERENCES 4.1 Several interference sources may cause inaccuracies determination of trace elements by ICP-MS. These are: 4.1.1

in

the

Isobaric elemental interferences - Are caused by isotopes of different elements which form singly or doubly charged ions of the same nominal mass-to-charge ratio and which cannot be resolved by the mass spectrometer in use. All elements determined by this method have, at a minimum, one isotope free of isobaric elemental interference. Of the analytical isotopes recommended for use with this method (Table 4), only molybdenum-98 (ruthenium) and seleni um-82 (krypton) have isobaric Revision 5 . 4 May 1994

94

Methods for the Determination elemental interferences. If alternative analytical isotopes having higher natural abundance are selected in order to achieve greater sensitivity, an isobaric interference may occur. All data obtained under such conditions must be corrected by measuring the signal from another isotope of the interfering element and subtracting the appropriate signal ratio from the isotope of interest. A record of this correction process should be included with the report o f the data. It should be noted that such corrections will only be as accurate as the accuracy of the isotope ratio used in the elemental equation for data calculations. Relevant isotope ratios should be established prior to the application of any corrections. 4.1.2

Abundance sensitivity - Is a property defining the degree to which the wings of a mass peak contribute to adjacent masses. The abundance sensitivity i s affected by ion energy and quadrupole operating pressure. Wing overlap interferences may result when a small ion peak i s being measured adjacent to a large one. The potential for these interferences should be recognized and the spectrometer resolution adjusted to minimize them.

4.1.3

Isobaric polyatomic ion interferences - Are caused by ions consisting of more than one atom which have the same nominal mass-to-charge ratio as the isotope of interest, and which cannot be resolved by the mass spectrometer in use. These ions are commonly formed in the plasma or interface system from support gases or sample componen;s. Most of the common interferences have been identified , and these are listed in Table 2 together with the method elements affected. Such interferences must be recognized, and when they cannot be avoided by the selection of a1 ternative analytical isotopes, appropriate corrections must be made to the data. Equations for the correction of data should be established at the time of the analytical run sequence as the polyatomic ion interferences will be highly dependent on the sample matrix and chosen instrument conditions. In particular, the common '*Kr interference that affects the determination of both arsenic and selenium, can be greatly reduced with the use of high purity krypton free argon.

4.1.4

Physical interferences - Are associated with the physical processes which govern the transport of sample into the plasma, sample conversion processes in the plasma, and the transmission o f ions through the plasma-mass spectrometer interface. These interferences may result in differences between instrument responses for the sample and the calibration standards. Physical interferences may occur in the transfer of solution to the nebulizer (e.g., viscosity effects), at the point of aerosol formation and transport to the plasma (e.g., surface tension), or during excitation and ionization processes within the plasma itself. High levels o f dissolved solids i n the sample may contribute deposits o f material on the Revision 5.4 May 1994

Metals

95

e x t r a c t i o n and/or skimmer cones r e d u c i n g t h e e f f e c t i v e d i a m e t e r o f t h e o r i f i c e s and t h e r e f o r e i o n t r a n s m i s s i o n . Dissolve s o l i d s l e v e l s n o t exceeding 0.2% ( w / v ) have been recommended t o reduce such e f f e c t s . I n t e r n a l s t a n d a r d i z a t i o n may be e f f e c t i y l y used t o compensate f o r many p h y s i c a l i n t e r f e r e n c e effects. I n t e r n a l standards i d e a l l y should have s i m i l a r a n a l y t i c a l b e h a v i o r t o t h e elements b e i n g determined.

4.1.5

5.0

Memory i n t e r f e r e n c e s - R e s u l t when i s o t o p e s o f elements i n a p r e v i o u s sample c o n t r i b u t e t o t h e s i g n a l s measured i n a new sample. Memory e f f e c t s can r e s u l t from sample d e p o s i t i o n on t h e sampler and skimmer cones, and from t h e b u i l d u p o f sample m a t e r i a l i n t h e plasma t o r c h and spray chamber. The s i t e where t h e s e e f f e c t s o c c u r i s dependent on t h e element and can be m i n i m i z e d by f l u s h i n g t h e system w i t h a r i n s e b l a n k between samples (Sect. 7.6.3). The p o s s i b i l i t y o f memory i n t e r f e r e n c e s s h o u l d be r e c o g n i z e d w i t h i n an a n a l y t i c a l r u n and s u i t a b l e r i n s e t i m e s s h o u l d be used t o reduce them. The r i n s e t i m e s necessary f o r a p a r t i c u l a r element should be e s t i m a t e d p r i o r t o analysis. T h i s may be achieved by a s p i r a t i n g a s t a n d a r d c o n t a i n i n g elements c o r r e s p o n d i n g t o t e n t i m e s t h e upper end o f t h e l i n e a r range f o r a normal sample a n a l y s i s p e r i o d , f o l l o w e d by a n a l y s i s o f t h e r i n s e b l a n k a t d e s i g n a t e d i n t e r v a l s . The l e n g t h o f t i m e r e q u i r e d t o reduce a n a l y t e s i g n a l s t o w i t h i n a f a c t o r o f t e n o f t h e methGd d e t e c t i o n l i m i t , should be noted. Memory i n t e r f e r e n c e s may a l s o be assessed w i t h i n an a n a l y t i c a l r u n by u s i n g a minimum o f t h r e e r e p l i c a t e i n t e g r a t i o n s f o r d a t a acquisition. I f the i n t e g r a t e d s i g n a l v a l u e s drop c o n s e c u t i v e l y , t h e a n a l y s t s h o u l d be a l e r t e d t o t h e p o s s i b i l i t y o f a memory e f f e c t , and s h o u l d examine t h e a n a l y t e conc e n t r a t i o n i n t h e p r e v i o u s sample t o i d e n t i f y i f t h i s was h i g h . I f a memory i n t e r f e r e n c e i s suspected, t h e sample s h o u l d be reanalyzed a f t e r a long r i n s e period. I n the determination o f mercury, which s u f f e r s f r o m severe memory e f f e c t s , t h e a d d i t i o n o f 100 p g / L g o l d w i l l e f f e c t i v e l y r i n s e 5 pg/L mercury i n approximately 2 minutes. Higher concentrations w i l l r e q u i r e a longer r i n s e time.

SAFETY

5.1

The t o x i c i t y o r c a r c i n o g e n i c i t y o f r e a g e n t s used i n t h i s method have n o t been f u l l y e s t a b l i s h e d . Each chemical should be r e g a r d e d as a p o t e n t i a l h e a l t h hazard and exposure t o t h e s e compounds s h o u l d be as low as r e a s o n a b l y a c h i e v a b l e . Each l a b o r a t o r y i s r e s p o n s i b l e f o r m a i n t a i n i n g a c u r r e n t awareness f i l e o f OSHA r e g u l a t i o n s r e g a r d i n 2 t h e s a f e h a n d l i n g of t h e chemicals s p e c i f i e d i n t h i s method. A r e f e r e n c e f i l e o f m a t e r i a l d a t a h a n d l i n g sheets should a l s o be a v a i l able t o a l l personnel i n v o l v e d i n t h e chemical a n a l y s i s . S p e c i f i c a l l y , c o n c e n t r a t e d n i t r i c and h y d r o c h l o r i c a c i d s p r e s e n t v a r i o u s hazards and a r e m o d e r a t e l y t o x i c and e x t r e m e l y i r r i t a t i n g t o s k i n and mucus membranes. Use t h e s e r e a g e n t s i n a fume hood whenever

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Methods for the Determination possible and if eye or skin contact occurs, flush with large volumes of water. Always wear safety glasses or a shield for eye protection, protective clothing and observe proper mixing when working with these reagents. 5.2 The acidification of samples containing reactive materials may result in the release of toxic gases, such as cyanides or sulfides. Acidification of samples should be done in a fume hood. 5.3 All personnel handling environmental samples known to contain or to have been in contact with human waste should be immunized against known disease causative agents. 5.4 Analytical plasma sources emit radiofrequency radiation in addition to intense UV radiation. Suitable precautions should be taken to protect personnel from such hazards. The inductively coupled plasma should only be viewed with proper eye protection from UV emissions. 5.5

6.0

It is the responsibility of the user of this method to comply with relevant disposal and waste regulations. For guidance see Sections 14.0 and 15.0.

EQUIPMENT AND SUPPLIES

6.1 Inductively coupled plasma mass spectrometer: 6.1.1

Instrument capable of scanning the mass range 5-250 amu with a minimum resolution capability of 1 amu peak width at 5% peak height. Instrument may be fitted with a conventional or extended dynamic range detection system. NOTE: If an electron multiplier detector is being used, precautions should be taken, where necessary, to prevent exposure to high ion flux. Otherwise changes in instrument response or damage to the multiplier may result.

6.1.2 Radio-frequency generator compliant with FCC regulations. 6.1.3

Argon gas supply - High purity grade (99.99%). When analyses are conducted frequently, liquid argon is more economical and requires less frequent rep1 acement of tanks than compressed argon in conventional cylinders (Sect. 4.1.3).

6.1.4

A variable-speed peristaltic pump i s required for solution delivery to the nebulizer.

6.1.5 A mass-flow controller on the nebulizer gas supply is required. A water-cooled spray chamber may be of benefit in reducing some types of interferences (e.g., from polyatomic oxide species). 6.1.6 If an electron multiplier detector is being used, precautions should be taken, where necessary, to prevent exposure to high ion flux. Otherwise changes in instrument response or damage to the multiplier may result. Samples having high

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c o n c e n t r a t i o n s o f elements beyond t h e l i n e a r range o f t h e i n s t r u m e n t and w i t h isotoDes f a l l i n q w i t h i n scanning windows should be d i l u t e d p r i o r t o a n a l y s i s . 6.2

A n a l y t i c a l balance, w i t h c a p a b i l i t y t o measure t o 0.1 mg f o r use i n w e i g h i n g s o l i d s , f o r p r e p a r i n g standards, and f o r d e t e r m i n dissolved solids i n digests o r extracts.

6.3

A temperature a d j u s t a b l e t e m p e r a t u r e o f 95OC.

6.4

(optional) A t e m p e r a t u r e a d j u s t a b l e b l o c k d i g e s t e r capable o f m a i n t a i n i n g a t e m p e r a t u r e o f 95OC and equipped w i t h 250-mL c o n s t r i c t e d d i g e s t i o n tubes.

6.5

( o p t i o n a l ) A s t e e l c a b i n e t c e n t r i f u g e w i t h guard bowl, e l e c t r i c t i m e r and b r a k e .

6.6

A g r a v i t y c o n v e c t i o n d r y i n g oven w i t h t h e r m o s t a t i c c o n t r o l capable o f m a i n t a i n i n g 105OC f 5OC.

6.7

( o p t i o n a l ) An a i r d i s p l a c e m e n t p i p e t t e r capable o f d e l i v e r i n g volumes r a n g i n g f r o m 0 . 1 t o 2500 p L w i t h an assortment o f h i g h q u a l i t y disposable p i p e t t i p s .

6.8

M o r t a r and p e s t l e , ceramic o r n o n m e t a l l i c m a t e r i a l .

6.9

P o l y p r o p y l e n e s i e v e , 5-mesh ( 4 mm opening).

hot

plate

capable

of

ma n t a i n i n g

a

6.10 Labware - For d e t e r m i n a t i o n o f t r a c e l e v e l s o f elements, c o n t a m i n a t i o n and l o s s a r e o f p r i m e c o n s i d e r a t i o n . P o t e n t i a l c o n t a m i n a t i o n sources i n c l u d e i m p r o p e r l y c l e a n e d l a b o r a t o r y apparatus and g e n e r a l c o n t a m i n a t i o n w i t h i n t h e l a b o r a t o r y environment f r o m d u s t , e t c . A c l e a n 1 a b o r a t o r y work a r e a d e s i g n a t e d f o r t r a c e element sample h a n d l i n g must be used. Sample c o n t a i n e r s can i n t r o d u c e p o s i t i v e and n e g a t i v e e r r o r s i n t h e d e t e r m i n a t i o n o f t r a c e elements by ( 1 ) c o n t r i b u t i n g contaminants through surface desorption o r leaching, (2) d e p l e t i n g element c o n c e n t r a t i o n s t h r o u g h a d s o r p t i o n processes. A l l r e u s a b l e labware ( g l a s s , q u a r t z , p o l y e t h y l e n e , PTFE, FEP, e t c . ) s h o u l d be s u f f i c i e n t l y c l e a n f o r t h e t a s k o b j e c t i v e s . Several procedures found t o p r o v i d e c l e a n l a b w a r e i n c l u d e soaking o v e r n i g h t and t h o r o u g h l y washing w i t h l a b o r a t o r y - g r a d e d e t e r g e n t and water, r i n s i n g w i t h t a p w a t e r , and s o a k i n g f o r f o u r hours o r more i n 20% ( V / V ) n i t r i c a c i d o r a m i x t u r e o f d i l u t e n i t r i c and h y d r o c h l o r i c a c i d (1+2+9), f o l l o w e d by r i n s i n g w i t h r e a g e n t grade w a t e r and s t o r i n g c l e a n . NOTE:

Chromic a c i d must n o t be used f o r c l e a n i n g glassware.

6.10.1 Glassware - V o l u m e t r i c f l a s k s , graduated c y l i n d e r s , f u n n e l s and c e n t r i f u g e tubes ( g l a s s and/or metal f r e e p l a s t i c ) . 6.10.2 A s s o r t e d c a l i b r a t e d p i p e t t e s .

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Methods for the Determination 6 . 1 0 . 3 C o n i c a l P h i l l i p s beakers ( C o r n i n g 1080-250 o r e q u i v a l e n t ) , 250mL w i t h 50-mm watch g l a s s e s . 6 . 1 0 . 4 G r i f f i n beakers, 250-mL w i t h 75-mm watch g l a s s e s and ( o p t i o n a l ) 75-mm r i b b e d watch g l a s s e s . 6.10.5 ( o p t i o n a l ) PTFE and/or q u a r t z beakers, 250-mL w i t h PTFE c o v e r s . 6.10.6 E v a p o r a t i n g d i s h e s o r h i g h - f o r m c r u c i b l e s , p o r c e l a i n , 100 mL capacity. 6.10.7 Narrow-mouth s t o r a g e b o t t l e s , FEP ( f l u o r i n a t e d e t h y l e n e p r o p y l e n e ) w i t h ETFE ( e t h y l e n e t e t r a f l u o r e t h y l e n e ) screw c l o s u r e , 125-mL t o 250-mL c a p a c i t i e s . 6.10.8 One-piece capacity.

7.0

stem FEP wash b o t t l e w i t h screw c l o s u r e ,

125-mL

REAGENTS AND STANDARDS 7.1

Reagents may c o n t a i n e l e m e n t a l i m p u r i t i e s t h a t m i g h t a f f e c t t h e i n t e g r i t y o f a n a l y t i c a l d a t a . Owing t o t h e h i g h s e n s i t i v i t y o f I C P MS, h i g h - p u r i t y r e a g e n t s s h o u l d be used whenever p o s s i b l e . A l l a c i d s used f o r t h i s method must be o f u l t r a h i g h - p u r i t y grade. S u i t a b l e a c i d s a r e a v a i l a b l e from a number o f m a n u f a c t u r e r s or,may be p r e p a r e d by s u b - b o i l i n g d i s t i l l a t i o n . N i t r i c a c i d i s p r e f e r r e d f o r ICP-MS i n o r d e r t o m i n i m i z e p o l y a t o m i c i o n i n t e r f e r e n c e s . Several p o l y a t o m i c i o n i n t e r f e r e n c e s r e s u l t when h y d r o c h l o r i c a c i d i s used ( T a b l e 2 ) , however, i t s h o u l d be n o t e d t h a t h y d r o c h l o r i c a c i d i s r e q u i r e d t o m a i n t a i n s t a b i l i t y i n s o l u t i o n s c o n t a i n i n g antimony and s i l v e r . When h y d r o c h l o r i c a c i d i s used, c o r r e c t i o n s f o r t h e c h l o r i d e p o l y a t o m i c i o n i n t e r f e r e n c e s must be a p p l i e d t o a l l . d a t a . 7.1.1

N i t r i c acid, concentrated (sp.gr.

1.41).

7.1.2

N i t r i c a c i d ( l t l ) - Add 500 mL conc. n i t r i c a c i d t o 400 mL o f r e g e n t grade w a t e r and d i l u t e t o 1 L.

7.1.3

N i t r i c a c i d ( 1 t 9 ) - Add 100 mL conc. n i t r i c a c i d t o 400 mL o f r e a g e n t grade w a t e r and d i l u t e t o 1 L.

7.1.4

Hydrochloric acid, concentrated (sp.gr.

7.1.5

H y d r o c h l o r i c a c i d ( l t l ) - Add 500 mL conc. h y d r o c h l o r i c a c i d t o 400 mL o f r e a g e n t g r a d e w a t e r and d i l u t e t o 1 L .

7.1.6

H y d r o c h l o r i c a c i d ( 1 t 4 ) - Add 200 mL conc. h y d r o c h l o r i c a c i d t o 400 mL o f r e a g e n t grade w a t e r and d i l u t e t o 1 L.

7.1.7

Ammonium h y d r o x i d e , c o n c e n t r a t e d ( s p . g r . 0.902).

7.1.8

T a r t a r i c a c i d (CASRN 87-69-4).

1.19).

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7.2

Reagent w a t e r - A l l r e f e r e n c e s t o r e a g e n t g r a d e w a t e r i n t h i s method r e f e r t o ASTM t y p e I w a t e r (ASTM 01193). S u i t a b l e w a t e r may be p r e p a r e d by p a s s i n g d i s t i l l e d w a t e r t h r o u g h a mixed bed o f a n i o n and c a t i o n exchange r e s i n s .

7.3

Standard Stock S o l u t i o n s - Stock standards may be purchased from a r e p u t a b l e commercial source o r p r e p a r e d f r o m u l t r a h i g h - p u r i t y grade chemicals o r m e t a l s (99.99 - 99.999% p u r e ) . A l l s a l t s s h o u l d be d r i e d f o r 1 h a t 1050C, u n l e s s o t h e r w i s e s p e c i f i e d . Stock s o l u t i o n s should be s t o r e d i n FEP b o t t l e s . Replace s t o c k standards when succeeding d i l u t i o n s f o r p r e p a r a t i o n o f t h e m u l t i e l e m e n t s t o c k standards can n o t be v e r i f i e d . CAUTION:

Many m e t a l s a l t s a r e e x t r e m e l y t o x i c i f i n h a l e d swallowed. Wash hands t h o r o u g h l y a f t e r h a n d l i n g .

or

The f o l l o w i n g procedures may be used f o r p r e p a r i n g s t a n d a r d s t o c k solutions:

NOTE:

Some m e t a l s , p a r t i c u l a r l y t h o s e which f o r m s u r f a c e o x i d e s r e q u i r e c l e a n i n g p r i o r t o b e i n g weighed. T h i s may be achieved by p i c k l i n g t h e s u r f a c e o f t h e metal i n a c i d . An amount i n excess o f t h e d e s i r e d w e i g h t s h o u l d be p i c k l e d r e p e a t e d l y , r i n s e d w i t h w a t e r , d r i e d and weighed u n t i l t h e d e s i r e d w e i g h t i s achieved.

7.3.1

Aluminum s o l u t i o n , s t o c k 1 mL = 1000 p g A l : P i c k l e aluminum metal i n warm (ltl) HC1 t o an e x a c t w e i g h t o f 0.100 g . D i s s o l v e i n 10 mL conc. HC1 and 2 mL conc. n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Continue h e a t i n g u n t i l volume i s reduced t o 4 mL. Cool and add 4 m L r e a g e n t grade w a t e r . Heat u n t i l t h e volume i s reduced t o 2 mL. Cool and d i l u t e t o 100 mL w i t h r e a g e n t grade w a t e r .

7.3.2

Antimony s o l u t i o n , s t o c k 1 mL = 1000 p g Sb: D i s s o l v e 0.100 g antimony powder i n 2 mL (ltl) n i t r i c a c i d and 0.5 mL conc. h y d r o c h l o r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool, add 20 mL r e a g e n t g r a d e w a t e r and 0.15 g t a r t a r i c a c i d . Warm t h e s o l u t i o n t o d i s s o l v e t h e w h i t e p r e c i p i t a t e . Cool and d i l u t e t o 100 mL w i t h r e a g e n t grade w a t e r .

7.3.3

A r s e n i c s o l u t i o n , s t o c k 1 mL = 1000 1-19 As: D i s s o l v e 0.1320 g As,O, i n a m i x t u r e o f 50 mL r e a g e n t grade w a t e r and 1 mL conc. ammonium h y d r o x i d e . Heat g e n t l y t o d i s s o l v e . Cool and a c i d i f y t h e s o l u t i o n w i t h 2 mL conc. n i t r i c a c i d . D i l u t e t o 100 mL w i t h r e a g e n t grade w a t e r .

7.3.4

Barium s o l u t i o n , s t o c k 1 mL = 1000 p g Ba: D i s s o l v e 0.1437 g BaCO, i n a s o l u t i o n m i x t u r e o f 10 mL r e a g e n t grade w a t e r and 2 mL conc. n i t r i c a c i d . Heat and s t i r t o e f f e c t s o l u t i o n and degassing. D i l u t e t o 100 mL w i t h r e a g e n t grade w a t e r .

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Methods for the Determination

7.3.5

B e r y l l i u m s o l u t i o n , s t o c k 1 mL = 1000 pg Be: D i s s o l v e 1.965 g BeS0,.4H 0 (DO NOT DRY) i n 50 mL r e a g e n t grade w a t e r . Add 1 mL conc. n i i r i c a c i d . D i l u t e t o 100 mL w i t h r e a g e n t grade w a t e r .

7.3.6

Bismuth s o l u t i o n , s t o c k 1 mL = 1000 p g B i : D i s s o l v e 0.1115 g B i 0, i n 5 m L conc. n i t r i c a c i d . Heat t o e f f e c t s o l u t i o n . Cool an% d i l u t e t o 100 mL w i t h r e a g e n t grade w a t e r .

7.3.7

Cadmium s o l u t i o n , s t o c k 1 mL = 1000 p g Cd: P i c k l e cadmium metal i n ( 1 t 9 ) n i t r i c a c i d t o an e x a c t w e i g h t o f 0.100 g . D i s s o l v e i n 5 mL ( 1 t 1 ) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h r e a g e n t grade w a t e r .

7.3.8

Chromium s o l u t i o n , s t o c k 1 mL = 1000 p g C r : D i s s o l v e 0.1923 g C r O i n a s o l u t i o n m i x t u r e of 10 mL r e a g e n t grade w a t e r and 1 conc. n i t r i c a c i d . D i l u t e t o 100 rnL w i t h r e a g e n t grade water.

mt

7.3.9

C o b a l t s o l u t i o n , s t o c k 1 mL = 1000 p g Co: P i c k l e c o b a l t metal i n ( 1 t 9 ) n i t r i c a c i d t o an e x a c t w e i g h t o f 0.100 g . D i s s o l v e i n 5 mL ( l t l ) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h r e a g e n t grade w a t e r .

7.3.10 Copper s o l u t i o n , s t o c k 1 mL = 1000 p g Cu: P i c k l e copper metal i n ( 1 t 9 ) n i t r i c a c i d t o an e x a c t w e i g h t o f 0.laO g . D i s s o l v e i n 5 mL ( l t l ) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h r e a g e n t grade w a t e r . 7.3.11 Gold s o l u t i o n , s t o c k 1 mL = 1000 pg Au: D i s s o l v e 0,100 g h i g h p u r i t y (99.9999%) Au shot i n 10 mL o f h o t conc. n i t r i c a c i d by dropwise a d d i t i o n o f 5 mL conc. HC1 and t h e n r e f l u x t o expel o x i d e s o f n i t r o g e n and c h l o r i n e . Cool and d i l u t e t o 100 mL w i t h r e a g e n t grade water.

7.3.12 I n d i u m s o l u t i o n , s t o c k 1 mL = 1000 p g I n : P i c k l e i n d i u m metal i n ( l t l ) n i t r i c a c i d t o an e x a c t w e i g h t o f 0.100 g. D i s s o l v e i n 10 mL ( l t l ) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h r e a g e n t grade w a t e r . 7.3.13 Lead s o l u t i o n , s t o c k 1 mL = 1000 p g Pb: D i s s o l v e 0.1599 g PbNO, i n 5 mL (1+1) n i t r i c a c i d . D i l u t e t o 100 rnL w i t h r e a g e n t g r a d e water.

7.3.14 Magnesium s o l u t i o n , s t o c k 1 mL = 1000 p g Mg: D i s s o l v e 0.1658 g MgO i n 10 mL ( l t l ) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h r e a g e n t grade w a t e r . 7.3.15 Manganese s o l u t i o n , s t o c k 1 mL = 1000 p g Mn: P i c k l e manganese f l a k e i n ( 1 t 9 ) n i t r i c a c i d t o an e x a c t w e i g h t o f 0.100 g. D i s s o l v e i n 5 rnL ( l t l ) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h r e a g e n t grade w a t e r .

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7.3.16 Mercury s o l u t i o n , s t o c k , 1 m L = 1000 pg Hg: DO NOT DRY. CAUTION: h i g h l y t o x i c e l e m e n t . D i s s o l v e 0.1354 g HgC1, i n r e a g e n t w a t e r . Add 5 . 0 mL c o n c e n t r a t e d HNO, and d i l u t e t o 100 mL w i t h r e a g e n t w a t e r . 7.3.17 Molybdenum s o l u t i o n , s t o c k 1 mL = 1000 pg Mo: D i s s o l v e 0.1500 g MOO, i n a s o l u t i o n m i x t u r e of 10 m L r e a g e n t g r a d e water and 1 mL conc. ammonium h y d r o x i d e . , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h r e a g e n t g r a d e w a t e r . 7.3.18 Nickel s o l u t i o n , s t o c k 1 mL = 1000 p g N i : D i s s o l v e 0.100 g n i c k e l powder i n 5 mL conc. n i t r i c a c i d , h e a t i n q t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h r e a g e n t g r a d e water. 7.3.19 Scandium s o l u t i o n , s t o c k 1 mL = 1000 pg Sc: D i s s o l v e 0 1534 g Sc,O, i n 5 mL (ltl) n i t r i c a c i d , h e a t i n g t o e f f e c t so u t i o n . Cool and d i l u t e t o 100 mL w i t h r e a g e n t g r a d e w a t e r . 7.3.20 Selenium s o l u t i o n , s t o c k 1 mL = 1000 pg Se: D i s s o l v e 0 1405 g SeO i n 20 mL ASTM- t y p e I w a t e r . D i l u t e t o 100 mL with r e a g e n t g r a i e water. 7.3.21 S i l v e r s o l u t i o n , s t o c k 1 mL = 1000 pg Ag: D i s s o l v e 0.100 g s i l v e r metal i n 5 mL (1t1) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t*o 100 mL w i t h r e a g e n t g r a d e w a t e r . Store in dark container. 7.3.22 Terbium s o l u t i o n , s t o c k 1 mL = 1000 p g T b : D i s s o l v e 0.1176 g Tb,O, i n 5 mL conc. n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL with r e a g e n t g r a d e w a t e r . 7.3.23 Thallium s o l u t i o n , s t o c k 1 mL = 1000 p g T1: D i s s o l v e 0.1303 g TINO, i n a s o l u t i o n m i x t u r e o f 10 mL r e a g e n t g r a d e w a t e r and 1 mL conc. n i t r i c a c i d . D i l u t e t o 100 mL with r e a g e n t g r a d e water. 7.3.24 Thorium s o l u t i o n , s t o c k 1 mL = 1000 p g T h : D i s s o l v e 0.2380 g Th(N0,),.4H 0 (DO NOT DRY) i n 20 mL r e a g e n t g r a d e w a t e r . D i l u t e t o f00 mL with r e a g e n t g r a d e w a t e r . 7.3.25 Uranium s o l u t i o n , s t o c k 1 mL = 1000 p g U : D i s s o l v e 0.2110 g UO (N0,),.6H 0 (DO NOT DRY) i n 20 mL r e a g e n t g r a d e w a t e r and d i j u t e t o 180 mL w i t h r e a g e n t g r a d e w a t e r . 7.3.26 Vanadium metal i n Dissolve Cool and

s o l u t i o n , s t o c k 1 mL = 1000 pg V: P i c k l e vanadium (1t9) n i t r i c a c i d t o an e x a c t weight o f 0.100 g . i n 5 mL (1t1) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . d i l u t e t o 100 mL w i t h r e a g e n t g r a d e w a t e r .

7.3.27 Yttrium s o l u t i o n , s t o c k 1 mL = 1000 p g Y : D i s s o l v e 0.1270 g Y,O i n 5 mL (1t1) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Coo? and d i l u t e t o 100 mL w i t h r e a g e n t g r a d e w a t e r . Revision 5 . 4

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Methods for the Determination

m L = 1000 1-19 Zn: Pickle zinc metal in (1t9) nitric acid to an exact weight o f 0.1009. Dissolve in

7 . 3 . 2 8 Zinc solution, stock 1

5 mL (1t1) nitric acid, heating to effect solution. Cool and dilute to 100 m L with reagent grade water. 7.4 Multielement Stock Standard Solutions - Care must be taken in the preparation o f multielement stock standards that the elements are compatible and stable. Originating element stocks should be checked for the presence of impurities which might influence the accuracy of the standard. freshly prepared standards should be transferred to acid cleaned, not previously used FEP fluorocarbon bottles for storage and monitored periodically for stability. The following combinations of elements are suggested:

Standard Solution A

A1 umi num Ant i mony Arsenic Beryl 1 i um Cadmi um Chromi urn Cobalt Copper Lead Manganese

Mercury Mo 1 y bdenum Nickel Sel en i um Thallium Thori um Urani um Vanadi um Zinc

Standard Solution B Bari um Si 1 ver

Except for selenium and mercury, mu1 tielement stock standard solutions B (1 mL = 10 pg) may be prepared by diluting 1.0 mL o f each single element stock standard in the combination list to 100 mL with reagent water containing 1% (vfv) nitric acid. For mercury and selenium in solution A, aliquots of 0.05 mL and 5.0 mL o f the respective stock standards should be diluted to the specified 100 mL ( 1 ml = 0.5 pg Hg and 50 pg Se). Replace the multielement stock standards when succeeding dilutions for preparation of the calibration standards cannot be verified with the quality control sample.

A and

7.4.1

Preparation o f calibration standards - fresh multielement calibration standards should be prepared every two weeks or as needed. Dilute each of the stock multielement standard solutions A and B to levels appropriate to the operating range of the instrument using reagent water containing I% (v/v) nitric acid. The element concentrations in the standards should be sufficiently high to produce good measurement precision and to accurately define the slope of the response curve. Depending on the sensitivity of the instrument, concentrations ranging from 10 gg/L to 200 pg/L are suggested, except mercury, which should be limited to 5 5 pg/L. It should be noted the selenium concentration is always a factor of 5 > the other analytes. If the direct addition procedure is being used (Method A , Sect. 1 0 . 3 ) , add internal standards (Sect. 7.5) to the calibration standards and store in FEP bottles, Calibration standards

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should be v e r i f i e d i n i t i a l l y u s i n g a q u a l i t y c o n t r o l sample (Sect. 7.8). 7.5

I n t e r n a l Standards Stock S o l u t i o n - 1 mL = 100 p g . D i l u t e 10 mL o f scandium, y t t r i u m , indium, t e r b i u m and b i s m u t h s t o c k standards ( S e c t . 7.3) t o 100 mL w i t h r e a g e n t w a t e r , and s t o r e i n a FEP b o t t l e . Use t h i s s o l u t i o n c o n c e n t r a t e f o r a d d i t i o n t o b l a n k s , c a l i b r a t i o n stand a r d s and samples, o r d i l u t e by an a p p r o p r i a t e amount u s i n g 1% ( v / v ) n i t r i c a c i d , i f t h e i n t e r n a l standards a r e b e i n g added by p e r i s t a l t i c pump (Method B, S e c t . 1 0 . 3 ) .

NOTE:

7.6

I f mercury i s t o be determined by t h e " d i r e c t a n a l y s i s " procedure, add an a l i q u o t o f t h e g o l d s t o c k s t a n d a r d ( S e c t . 7.3.11) t o t h e i n t e r n a l s t a n d a r d s o l u t i o n s u f f i c i e n t t o p r o v i d e a c o n c e n t r a t i o n o f 100 p g / L i n f i n a l t h e d i l u t i o n o f a l l b l a n k s , c a l i b r a t i o n standards, and samples.

Blanks - Three t y p e s o f b l a n k s a r e r e q u i r e d f o r t h i s method. A c a l i b r a t i o n b l a n k i s used t o e s t a b l i s h t h e a n a l y t i c a l c a l i b r a t i o n c u r v e , t h e l a b o r a t o r y r e a g e n t b l a n k i s used t o assess p o s s i b l e c o n t a m i n a t i o n from t h e sample p r e p a r a t i o n p r o c e d u r e and t o assess s p e c t r a l background and t h e r i n s e b l a n k i s used t o f l u s h t h e i n s t r u m e n t between samples i n o r d e r t o reduce memory i n t e r f e r e n c e s . 7.6.1

C a l i b r a t i o n b l a n k - C o n s i s t s o f 1% ( v / v ) n i t r i c a c i d i n reagent grade w a t e r . I f t h e d i r e c t a d d i t i o n procedure (Method A , Sect. 10.3) i s b e i n g used, add i n t e r n a l s t a n d a r d s .

7.6.2

L a b o r a t o r y r e a g e n t b l a n k (LRB) - Must c o n t a i n a l l t h e reagents i n t h e same volumes as used i n p r o c e s s i n g t h e samples. The LRB must be c a r r i e d t h r o u g h t h e same e n t i r e p r e p a r a t i o n scheme as t h e samples i n c l u d i n g d i g e s t i o n , when a p p l i c a b l e . If the d i r e c t a d d i t i o n procedure (Method A , Sect. 10.3) i s b e i n g used, add i n t e r n a l standards t o t h e s o l u t i o n a f t e r p r e p a r a t i o n i s compl e t e .

7.6.3

Rinse b l a n k - C o n s i s t s o f 2% ( v / v ) n i t r i c a c i d i n r e a g e n t grade water.

NOTE:

I f mercury i s t o be d e t e r m i n e d by t h e " d i r e c t a n a l y s i s " procedure, add g o l d ( S e c t . 7.3.11) t o t h e r i n s e b l a n k t o a c o n c e n t r a t i o n o f 100 pg/L.

7.7

Tuning S o l u t i o n - T h i s s o l u t i o n i s used f o r i n s t r u m e n t t u n i n g and mass c a l i b r a t i o n p r i o r t o analysis. The s o l u t i o n i s p r e p a r e d by m i x i n g b e r y l l i u m , magnesium, c o b a l t , i n d i u m and l e a d s t o c k s o l u t i o n s ( S e c t . 7.3) i n 1% ( v / v ) n i t r i c a c i d t o produce a c o n c e n t r a t i o n o f 100 pg/L o f each element. I n t e r n a l standards a r e n o t added t o t h i s solution. (Depending on t h e s e n s i t i v i t y o f t h e i n s t r u m e n t , t h i s s o l u t i o n may need t o be d i l u t e d 10 f o l d . )

7.8

Q u a l i t y C o n t r o l Sample (QCS) - The QCS s h o u l d be o b t a i n e d from a source o u t s i d e t h e l a b o r a t o r y . The c o n c e n t r a t i o n o f t h e QCS s o l u t i o n Revision 5.4

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Methods for the Determination a n a l y z e d w i l l d(1l,cirid on t h e s e n s i t i v i t y o f t h e i n s t r u m e n t . To p r e p a r e t h e QCS d i l u 1 . e an a p p r o p r i a t e a l i q u o t o f a n a l y t e s t o a c o n c e n t r a t i o n < 100 p g / L i n 1 % ( v / v ) n i t r i c a c i d . Hecatrsc o f l o w e r s e n s i t i v i t y , s e l e n i u m may be d i l u t e d t o a c o n c e n t r a t i o n o f < 500 p g / l , however, i n a l l c a s e s , m e r c u r y s h o u l d be l i m i t e d t o a c o n c e n t r a t i o n o f 5 5 fig/L. I f t h e d i r e c t . a d d i t i o n p r o c e d u r e (Method A , S e c t . 1 0 . 3 ) i s b e i n g used, add i n t e r n a l s t a n d a r d s a f t e r d i l u t i o n , m i x and s t o r e i n a FEP b o t t l e . The QCS s h o u l d be a n a l y z e d as needed t o meet. d a t a - q u a l i t y needs and a f r e s h s o l u t i o n L h o i i l d be p r e p a r e d q u a r t e r l y o r more f r e q u e n t l y as needed,

7.9

8.0

l a b o r a t o r y F o r t i f i e d B l a n k (LFB) - To an a l i q u o t o f LRB, add a l i q u o t s f r o m m u l t i e l e m e n t s t o c k s t a n d a r d s A and B ( S e c t . 7 . 4 ) t o p r e p a r e d t h e LFB. Depending on t h e s e n s i t i v i t y o f t h e i n s t r u m e n t , t h e f o r t i f i e d c o n c e n t r a t i o n used s h o u l d r a n g e f r o m 40 p g / L t o 100 p g / L f o r each a n a l y t e , e x c e p t s e l e n i u m and m e r c u r y . F o r s e l e n i u m t h e c o n c e n t r a t i o n s h o u l d r a n g e f r o m 200 p g / L t o 500 p g / L , w h i l e t h e c o n c e n t r a t i o n r a n g e m e r c u r y s h o u l d be l i m i t e d t o 2 p g / L t o 5 p g / L . The LFB must be c a r r i e d t h r o u g h t h e same e n t i r e p r e p a r a t i o n scheme as t h e samples i n c l u d i n g sample d i g e s t i o n , when a p p l i c a b l e . I f t h e d i r e c t a d d i t i o n p r o c e d u r e (Method A , S e c t . 10.3) i s b e i n g used, add i n t e r n a l s t a n d a r d s t o t h i s s o l u t i o n a f t e r p r e p a r a t i o n has been c o m p l e t e d .

SAMPLE COLLECTION, PRESERVATION, AND STORAGE

8.1

P r i o r t o t h e c o l l e c t i o n of an aqueous sample, c o n s i d e r a t i o n s h o u l d be given t o the type o f data required, (i.e., dissolved o r t o t a l r e c o v e r a b l e ) , so t h a t a p p r o p r i a t e p r e s e r v a t i o n and p r e t r e a t m e n t s t e p s can be t a k e n . The pH o f a l l aqueous samples must be t e s t e d i m m e d i a t e l y p r i o r t o a1 i q u o t i n g f o r p r o c e s s i n g o r " d i r e c t a n a l y s i s " t o e n s u r e t h e sample h a s been p r o p e r l y p r e s e r v e d . If properly acid p r e s e r v e d , t h e sample c a n be h e l d up t o 6 months b e f o r e a n a l y s i s .

8.2

F o r t h e d e t e r m i n a t i o n o f d i s s o l v e d e l e m e n t s , t h e sample must be f i l t e r e d t h r o u g h a 0.45-pm p o r e d i a m e t e r membrane f i l t e r a t t h e t i m e o f c o l l e c t i o n o r as soon t h e r e a f t e r as p r a c t i c a l l y p o s s i b l e . Use a p o r t i o n o f t h e sample t o r i n s e t h e f i l t e r f l a s k , d i s c a r d t h i s p o r t i o n and c o l l e c t t h e r e q u i r e d volume o f f i l t r a t e . Acidify the f i l t r a t e w i t h ( 1 t 1 ) n i t r i c a c i d i m m e d i a t e l y f o l l o w i n g f i l t r a t i o n t o pH < 2 .

8.3

F o r t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e e l e m e n t s i n aqueous samples, samples a r e not f i l t e r e d , b u t a c i d i f i e d w i t h ( l t l ) n i t r i c a c i d t o pH < 2 ( n o r m a l l y , 3 mL o f ( l t l ) a c i d p e r l i t e r o f sample i s s u f f i c i e n t f o r most a m b i e n t and d r i n k i n g w a t e r s a m p l e s ) . P r e s e r v a t i o n may be done a t t h e t i m e o f c o l l e c t i o n , however, t o a v o i d t h e h a z a r d s o f s t r o n g a c i d s i n t h e f i e l d , t r a n s p o r t r e s t r i c t i o n s , and p o s s i b l e c o n t a m i n a t i o n i t i s recommended t h a t t h e samples be r e t u r n e d t o t h e l a b o r a t o r y w i t h i n two weeks o f c o l l e c t i o n and a c i d p r e s e r v e d upon r e c e i p t i n t h e l a b o r a t o r y . F o l l o w i n g a c i d i f i c a t i o n , t h e sample s h o u l d be m i x e d , h e l d f o r s i x t e e n h o u r s , and t h e n v e r i f i e d t o be pH < 2 j u s t p r i o r w i t h d r a w i n g an a l i q u o t f o r p r o c e s s i n g o r " d i r e c t a n a l y s i s " . I f f o r some r e a s o n such as h i g h a l k a l i n i t y t h e sample pH i s v e r i f i e d t o

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be > 2, more a c i d must be added and t h e sample h e l d f o r s i x t e e n h o u r s u n t i l v e r i f i e d t o be pH < 2 . See S e c t i o n 8 . 1 . NOTE:

8.4

When t h e n a t u r e o f t h e sample i s e i t h e r unknown o r known t o be hazardous, a c i d i f i c a t i o n s h o u l d be done i n a fume hood. See S e c t i o n 5.2.

S o l i d samples r e q u i r e no p r e s e r v a t i o n p r i o r t o a n a l y s i s o t h e r t h a n s t o r a g e a t 4 ° C . There i s no e s t a b l i s h e d h o l d i n g t i m e l i m i t a t i o n f o r s o l i d samples.

8.5 F o r aqueous samples, a f i e l d b l a n k s h o u l d be p r e p a r e d and analyzed as r e q u i r e d by t h e d a t a u s e r . sample c o l l e c t i o n . 9.0

Use t h e same c o n t a i n e r and a c i d as used i n

QUALITY CONTROL

9.1

Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a f o r m a l q u a l i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f t h i s program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y , and t h e p e r i o d i c a n a l y s i s o f l a b o r a t o r y r e a g e n t b l a n k s , f o r t i f i e d b l a n k s and c a l i b r a t i o n s o l u t i o n s as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n performance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f t h e d a t a t h u s generated.

9.2

I n i t i a l Demonstration o f Performance (mandatory) 9.2.1

The i n i t i a l d e m o n s t r a t i o n o f performance i s used t o c h a r a c t e r i z e i n s t r u m e n t performance ( d e t e r m i n a t i o n o f l i n e a r c a l ib r a t i o n ranges and a n a l y s i s o f qua1 it y c o n t r o l samples) and l a b o r a t o r y performance ( d e t e r m i n a t i o n o f method d e t e c t i o n l i m i t s ) p r i o r t o analyses conducted by t h i s method.

9.2.2

L i n e a r c a l i b r a t i o n ranges - L i n e a r c a l i b r a t i o n ranges a r e primarily detector limited. The upper l i m i t o f t h e l i n e a r c a l i b r a t i o n range s h o u l d be e s t a b l i s h e d f o r each a n a l y t e by d e t e r m i n i n g t h e s i g n a l responses f r o m a minimum o f t h r e e d i f f e r e n t c o n c e n t r a t i o n standards, one o f w h i c h i s c l o s e t o t h e upper l i m i t o f t h e l i n e a r range. Care s h o u l d be t a k e n t o a v o i d p o t e n t i a l damage t o t h e d e t e c t o r d u r i n g t h i s process. The l i n e a r c a l i b r a t i o n range which may be used f o r t h e a n a l y s i s o f samples s h o u l d be j u d g e d by t h e a n a l y s t f r o m t h e r e s u l t i n g d a t a . The upper LDR l i m i t s h o u l d be an observed s i g n a l no more t h a n 10% below t h e l e v e l e x t r a p o l a t e d f r o m l o w e r standards. Determined sample a n a l y t e c o n c e n t r a t i o n s t h a t a r e g r e a t e r t h a n 90% o f t h e d e t e r m i n e d upper LDR l i m i t must be d i l u t e d and reanalyzed. The LDRs s h o u l d be v e r i f i e d whenever, i n t h e judgement o f t h e a n a l y s t , a change i n a n a l y t i c a l performance caused by e i t h e r a change i n i n s t r u m e n t hardware o r o p e r a t i n g c o n d i t i o n s would d i c t a t e t h e y be r e d e t e r m i n e d .

9.2.3

Q u a l i t y c o n t r o l sample (QCS) - When b e g i n n i n g t h e use o f t h i s method, on a q u a r t e r l y b a s i s o r as r e q u i r e d t o meet d a t a Revision 5.4

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q u a 1 i t y needs, v e r i f y t h e c a l i b r a t i o n s t a n d a r d s and a c c e p t a b l e instrument performance w i t h t h e p r e p a r a t i o n and a n a l y s e s of a QCS ( S e c t . 7 . 8 ) . To v e r i f y t h e c a l i b r a t i o n s t a n d a r d s t h e determined mean c o n c e n t r a t i o n from 3 a n a l y s e s of t h e QCS must be w i t h i n f 10% of t h e s t a t e d QCS v a l u e . I f t h e QCS i s used f o r determining a c c e p t a b l e on-going instrument performance, a n a l y s i s of t h e QCS prepared t o a c o n c e n t r a t i o n of 100 pg/L must be w i t h i n f 10% of t h e s t a t e d value o r w i t h i n the acceptance l i m i t s l i s t e d i n Table 8 , whichever i s t h e g r e a t e r . ( I f t h e QCS i s not w i t h i n t h e r e q u i r e d l i m i t s , an immediate second a n a l y s i s of t h e QCS i s recommended t o confirm unacceptable performance.) I f t h e c a l i b r a t i o n s t a n d a r d s and/or a c c e p t a b l e instrument performance cannot be v e r i f i e d , t h e source of t h e problem must be i d e n t i f i e d and c o r r e c t e d before e i t h e r proceeding on with t h e i n i t i a l d e t e r m i n a t i o n of method d e t e c t i o n l i m i t s o r c o n t i n u i n g with on-going a n a l y s e s . 9.2.4

Method d e t e c t i o n l i m i t s (MDL) should be e s t a b l i s h e d f o r a l l a n a l y t e s , using reagent water ( b l a n k ) f o r t i f i e d a t a c o n c e n t r a t i o n of two t o f i v e times t h e e s t i m a t e d d e t e c t i o n l i m i t . 7 To determine MDL v a l u e s , t a k e seven r e p l i c a t e a l i q u o t s of t h e f o r t i f i e d reagent water and process through the e n t i r e a n a l y t i c a l method. Perform a l l c a l c u l a t i o n s d e f i n e d i n t h e method and r e p o r t t h e c o n c e n t r a t i o n v a l u e s i n t h e a p p r o p r i a t e u n i t s . C a l c u l a t e t h e MDL a s follows:

MDL where:

Note:

=

( t ) x (S)

t

=

S t u d e n t ’ s t value f o r a 99% confidence l e v e l and a s t a n d a r d d e v i a t i o n e s t i m a t e with n-1 degrees o f freedom [ t = 3.14 f o r seven r e p l i c a t e s ] .

S

=

s t a n d a r d d e v i a t i o n of the r e p l i c a t e a n a l y s e s .

I f a d d i t i o n a l confirmation i s d e s i r e d , r e a n a l y z e t h e seven rep1 i c a t e a1 i q u o t s on two more nonconsecutive days and again c a l c u l a t e t h e MDL v a l u e s f o r each day. An average of the t h r e e MDL v a l u e s f o r each a n a l y t e may provide f o r a more a p p r o p r i a t e MDL e s t i m a t e . I f t h e r e l a t i v e s t a n d a r d d e v i a t i o n (RSD) from the a n a l y s e s of the seven a l i q u o t s i s < lo%, the c o n c e n t r a t i o n used t o determine t h e a n a l y t e MDL may have been I f so, i n a p p r o p r i a t e l y high f o r the d e t e r m i n a t i o n . t h i s could r e s u l t i n t h e c a l c u l a t i o n of an u n r e a l i s t i c a l l y low MDL. Concurrently, d e t e r m i n a t i o n of MDL i n reagent water r e p r e s e n t s a b e s t c a s e s i t u a t i o n and does not r e f l e c t p o s s i b l e matrix e f f e c t s o f r e a l world samples. However, s u c c e s s f u l a n a l y s e s of LFMs ( S e c t . 9.4) can g i v e confidence t o t h e MDL value determined i n reagent w a t e r . Typical s i n g l e l a b o r a t o r y MDL v a l u e s using t h i s method a r e given i n Table 7 .

The MDLs must be s u f f i c i e n t t o d e t e c t a n a l y t e s a t t h e r e q u i r e d l e v e l s according t o compliance monitoring r e g u l a t i o n ( S e c t . Revision 5 . 4

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1 . 2 ) . MDLs should be determined begins work o r whenever, i n the change i n a n a l y t i c a l performance i n s t r u m e n t hardware o r o p e r a t i n g be redeterini ned. 9.3

107

a n n u a l l y , when a new o p e r a t o r judgement of t h e a n a l y s t , a caused by e i t h e r a change i n c o n d i t i o n s would d i c t a t e t h e y

Assessing Laboratory Performance (mandatory) 9.3.1

Laboratory reiigent blank ( L R B ) - The l a b o r a t o r y must analyze a t l e a s t one LRU ( S e c t . 7 . 6 . 2 ) w i t h each batch of 20 o r fewer o f samples of t h e same m a t r i x . LRB d a t a a r e used t o a s s e s s contamination from t h e l a b o r a t o r y environment and t o c h a r a c t e r i z e s p e c t r a l background from t h e r e a g e n t s used in sample p r o c e s s i n g . L R B v a l u e s t h a t exceed t h e MDL i n d i c a t e l a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n should be s u s p e c t e d . When L R B v a l u e s c o n s t i t u t e 10% o r more o f t h e a n a l y t e l e v e l determined f o r a sample o r i s 2 . 2 times t h e a n a l y t e MDL whichever i s g r e a t e r , f r e s h a l i q u o t s of t h e samples must be prepared and analyzed again f o r t h e a f f e c t e d a n a l y t e s a f t e r t h e s o u r c e of c o n t a m i n a t i o n has been c o r r e c t e d and a c c e p t a b l e LRB v a l u e s have been o b t a i n e d .

9.3.2

Laboratory f o r t i f i e d blank ( L F B ) - The l a b o r a t o r y must analyze a t l e a s t one LFB ( S e c t . 7 . 9 ) with each batch o f samples. C a l c u l a t e accuracy a s p e r c e n t r e c o v e r y using t h e f o l l o w i n g equation:

R =

LFB - LRB -~

x 100

S

where:

R LFB LRB s

=

= =

=

percent recovery. l a b o r a t o r y f o r t i f i e d blank. laboratory reagent blank. c o n c e n t r a t i o n e q u i v a l e n t of a n a l y t e added t o f o r t i f y t h e L R B s o l u t i o n .

I f t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e r e q u i r e d c o n t r o l l i m i t s o f 85-115%, t h a t a n a l y t e i s judged o u t o f c o n t r o l , and t h e s o u r c e o f t h e problem should be i d e n t i f i e d and resolved before continuing analyses. 9.3.3

The l a b o r a t o r y must use LFB a n a l y s e s d a t a t o a s s e s s l a b o r a t o r y performance a g a i n s t t h e r e q u i r e d c o n t r o l l i m i t s o f 85-115% ( S e c t . 9 . 3 . 2 ) . When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e ( u s u a l l y a minimum o f twenty t o t h i r t y a n a l y s e s ) , o p t i o n a l c o n t r o l l i m i t s can be developed from t h e mean p e r c e n t recovery ( x ) and t h e s t a n d a r d d e v i a t i o n ( S ) o f t h e mean p e r c e n t r e c o v e r y . These d a t a can be used t o e s t a b l i s h t h e upper and lower c o n t r o l l i m i t s a s f o l l o w s : UPPER CONTROL LIMIT LOWkR CONTROL LIMIT

= =

x t 3s x - 3s

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Methods for the Determination Ihe optional control limit\ nilrst be equal to or better than the required control limits o f 85-115%. After each five to ten new recovery measurements, new control 1 imits can be calculated using only the most recent twenty to thirty data points. Also, the standard deviation (S) data should be used to establish an on-going precision statement for the level of concentrations included in the LFB. These data must be kept on file and be available for review. 9.3.4

9.4

Instrument performance - For all determinations the laboratory must check instrument performance and verify that the instrument is properly calibrated on a continuing basis. To verify calibration run the calibration blank and calibration standards as surrogate samples immediately following each calibration routine, after every ten analyses and at the end of the sample run. The results of the analyses of the standards will indicate whether the calibration remains valid. The analysis of all analytes within the standard solutions must be within f 10% of calibration. If the calibration cannot be verified within the specified limits, the instrument must be recal ibrated. (The instrument responses from the calibration check may be used for recalibration purposes, however, it must be verified before continuing sample analysis.) If the continuing calibration check is not confirmed within k 15%, the previous ten samples must be reanalyzed after recalibration. If the sample matrix is responsible for the calibration drift, it is recommended that the previous ten samples are reanalyzed in groups of five between calibration checks to prevent a similar drift situation from occurring.

Assessing Analyte Recovery and Data Quality 9.4.1

Sample homogeneity and the chemical nature of the sample matrix can affect analyte recovery and the quality of the data. Taking separate aliquots from the sample for replicate and fortified analyses can in some cases assess the effect. Unless otherwise specified by the data user, laboratory or program, the following laboratory fortified matrix (LFM) procedure (Sect 9 . 4 . 2 ) is required.

9.4.2

The laboratory must add a known amount of analyte to a minimum of 10% of the routine samples. In each case the LFM aliquot must be a duplicate of the aliquot used for sample analysis and for total recoverable determinations added prior to sample preparation. For water samples, the added analyte concentration must be the same as that used in the laboratory For solid samples, the fortified blank (Sect. 7.9). concentration added should be 100 mg/kg equivalent (200 p g / L in the analysis solution) except silver which should be limited to 50 mg/kg (Sect 1 . 8 ) . Over time, samples from all routine sample sources should be fortified.

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Metals

9.4.3

109

C a l c u l a t e t h e p e r c e n t r e c o v e r y f o r each a n a l y t e , c o r r e c t e d f o r background c o n c e n t r a t i o n s measured in t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o t h e d e s i g n a t e d LFM recovery range of 70-130%. Recovery c a l c u l a t i o n s a r e not r e q u i r e d i f t h e c o n c e n t r a t i o n of t h e a n a l y t e added i s l e s s than 30% of t h e sample background c o n c e n t r a t i o n . Percent recovery may be c a l c u l a t e d in u n i t s a p p r o p r i a t e t o t h e m a t r i x , using t h e f o l lowing e q u a t i o n : R =

cs

-

x 100

~

S

where:

R

=

percent recovery.

Cs = f o r t i f i e d sample c o n c e n t r a t i o n .

C s

10.0

= =

sample background c o n c e n t r a t i o n . c o n c e n t r a t i o n e q u i v a l e n t of a n a l y t e added t o f o r t i f y t h e sample.

9.4.4

I f r e c o v e r y of any a n a l y t e f a l l s o u t s i d e the d e s i g n a t e d range and l a b o r a t o r y performance f o r t h a t a n a l y t e i s shown t o be i n c o n t r o l ( S e c t . 9 . 3 ) , t h e r e c o v e r y problem encountered with t h e f o r t i f i e d sample i s judged t o be mqtrix r e l a t e d , not system r e l a t e d . The d a t a u s e r should be informed t h a t t h e r e s u l t f o r t h a t a n a l y t e i n t h e u n f o r t i f i e d sample i s s u s p e c t due t o e i t h e r t h e heterogeneous n a t u r e o f t h e sample o r an u n c o r r e c t e d m a t r i x effect.

9.4.5

I n t e r n a l s t a n d a r d s r e s p o n s e s - The a n a l y s t i s expected t o monitor t h e r e s p o n s e s from t h e i n t e r n a l s t a n d a r d s throughout t h e sample s e t being a n a l y z e d . R a t i o s o f the i n t e r n a l s t a n d a r d s r e s p o n s e s a g a i n s t each o t h e r should a l s o be monitored r o u t i n e l y . T h i s i n f o r m a t i o n may be used t o d e t e c t p o t e n t i a l problems caused by mass dependent d r i f t , e r r o r s i n c u r r e d in adding t h e i n t e r n a l s t a n d a r d s o r i n c r e a s e s i n the c o n c e n t r a t i o n s of i n d i v i d u a l i n t e r n a l s t a n d a r d s caused by background c o n t r i b u t i o n s from t h e sample. The a b s o l u t e r e s p o n s e of any one i n t e r n a l s t a n d a r d must not d e v i a t e more t h a n 60-125% o f the o r i g i n a l response i n t h e c a l i b r a t i o n blank. I f d e v i a t i o n s g r e a t e r t h a n t h e s e a r e observed, f l u s h t h e i n s t r u m e n t w i t h t h e r i n s e blank and monitor t h e r e s p o n s e s i n t h e c a l i b r a t i o n blank. I f t h e r e s p o n s e s of t h e i n t e r n a l s t a n d a r d s a r e now w i t h i n the l i m i t , t a k e a f r e s h a l i q u o t of t h e sample, d i l u t e by a f u r t h e r f a c t o r o f two, add t h e i n t e r n a l s t a n d a r d s and r e a n a l y z e . I f a f t e r f l u s h i n g t h e response o f t h e i n t e r n a l s t a n d a r d s i n t h e c a l i b r a t i o n blank a r e o u t of l i m i t s , t e r m i n a t e t h e a n a l y s i s and determine t h e c a u s e o f t h e d r i f t . P o s s i b l e c a u s e s o f d r i f t may be a p a r t i a l l y blocked sampling cone o r a change i n t h e t u n i n g c o n d i t i o n of t h e i n s t r u m e n t .

CALIBRATION AND STANDARDIZATION 10.1 Operating

c o n d i t i o n s - Because of t h e d i v e r s i t y of instrument hardware, no d e t a i l e d i n s t r u m e n t o p e r a t i n g c o n d i t i o n s a r e provided. Revision 5 . 4

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Methods for the Determination The analyst is advised to follow the recommended operating conditions provided by the manufacturer. It is the responsibility of the analyst to verify that the inst.runient configuration and operating conditions satisfy the analytical requirements and to maintain quality control data verifying instrument performance and analytical results. Instrument operating conditions which were used to generate precision and recovery data for this method (Sect. 13) are included in Table 6. 1 0 . 2 Precal ibratiori routine

- The following precalibration routine must be completed prior to calibrating the instrument until such time it can be documented with periodic performance data that the instrument meets the criteria listed below without daily tuning.

1 0 . 2 . 1 Initiate proper operating configuration o f instrument and data system. Allow a period of not less than 3 0 min for the

instrument to warm up. During this process conduct mass calibration and resolution checks using the tuning solution. Resolution at low mass is indicated by magnesium isotopes 24,25,26. Resolution at high mass is indicated by lead isotopes 206,207,208. For good performance adjust spectrometer resolution to produce a peak width of approximately 0.75 amu at 5% peak height. Adjust mass calibration if it has shifted by more than 0.1 arnu from unit mass. 1 0 . 2 . 2 Instrument stability must be demonstrated by running the tuning solution (Sect. 7 . 7 ) a minimum of five times with resulting

relative standard deviations of absolute signals for all analytes of less than 5%. - Internal standardization must be used in all analyses to correct for instrument drift and physical interferences. A list of acceptable internal standards is provided in For full mass range scans, a minimum of three internal Table 3 . standards must be used. Procedures described in this method for general application, detail the use of five internal standards; scandium, yttrium, indium, terbium and bismuth. These were used to generate the precision and recovery data attached to this method. Internal standards must be present in all samples, standards and blanks at identical levels. This may be achieved by directly adding an aliquot of the internal standards to the CAL standard, blank or sample solution (Method A, Sect. 1 0 . 3 ) , or alternatively by mixing with the solution prior to nebulization using a second channel o f the The peristaltic pump and a mixing coil (Method B, Sect. 10.3). concentration of the internal standard should be sufficiently high that good precision is obtained in the measurement of the isotope used for data correction and to minimize the possibility of correction errors if the internal standard is naturally present in the sample. Depending on the sensitivity of the instrument, a concentration range of 20 pg/L to 200 pg/L o f each internal standard is recommended.

10.3 Internal Standardization

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Internal standards should be added to blanks, samples and standards in a like manner, so that dilution effects resulting from the addition may be disregarded. 10.4 Calibration - Prior to initial calibration, set up proper instrument

software routines for quantitative analysis. The instrument must be calibrated using one of the internal standard routines (Method A or B ) described in Section 1 0 . 3 . The instrument must be calibrated for the analytes to be determined using the calibration blank (Sect. 7 . 6 . 1 ) and calibration standards A and B (Sect. 7 . 4 . 1 ) prepared at one or more concentration levels. A minimum of three rep1 icate integrations are required for data acquisition. Use the average of the integrations for instrument calibration and data reporting. 10.5 The rinse blank should be used to flush the system between solution

changes for blanks, standards and samples. Allow sufficient rinse time to remove traces of the previous sample (Sect. 4 . 1 . 5 ) . Solutions should be aspirated for 30 sec prior to the acquisition of data to allow equilibrium to be established. 11.0 PROCEDURE

11.1 Aqueous Sample Preparation - Dissolved Anglytes 1 1 . 1 . 1 For the determination of dissolved analytes in ground and surface waters, pipet an aliquot ( 2 20 mL) of the filtered,

acid preserved sample into a 50-mL polypropylene centrifuge tube. Add an appropriate volume of ( l t l ) nitric acid to adjust the acid concentration of the aliquot to approximate a 1% (v/v) nitric acid solution (e.g., add 0.4 mL ( l t l ) HNO, to a 20 mL aliquot of sample). If the direct addition procedure (Method A, Sect. 10.3) is being used, add internal standards, cap the tube and mix. The sample i s now ready for analysis (Sect. 1 . 2 ) . Allowance for sample dilution should be made in the cal cul at i ons . NOTE:

If a precipitate is formed during acidification, transport, or storage, the sample aliquot must be treated using the procedure in Section 11.2 prior to analysis.

11.2 Aqueous Sample Preparation - Total Recoverable Analytes 1 1 . 2 . 1 For the "direct analysis" of total recoverable analytes in drinking water samples containing turbidity < 1 NTU, treat an

unfiltered acid preserved sample aliquot using the sample preparation procedure descri bed in Section 11.1.1 whi 1 e making allowance for sample dilution in the data calculation. For the determination of total recoverable analytes in all other aqueous samples or for preconcentrating drinking water samples prior to analysis follow the procedure given in Sections 11.2.2 through 1 1 . 2 . 8 .

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Methods for the Determination 11.2.2

F o r t h e d e t e r m i r i d t i o n o f t o t a l r e c o v e r a b l e a n a l y t e s i n aqueous samples ( o t h e r t h a n d r i n k i n g w a t e r w i t h < I NTU t u r b i d i t y ) , t r a n s f e r a 100-tnL ( t 1 mL) a l i q u o t f r o m a w e l l m i x e d , a c i d p r e s e r v e d sample t o a 250-mL G r i f f i n b e a k e r ( S e c t s . 1 . 2 , 1.3, 1.7, & 1 . 8 ) . (When n e c e s s a r y , s m a l l e r sample a l i q u o t volumes may be u s e d . )

NOTE:

I f t h e sample c o n t a i n s u n d i s s o l v e d s o l i d s > 1%, a w e l l m i x e d , a c i d p r e s e r v e d a l i q u o t c o n t a i n i n g no more t h a n 1 g particulate material s h o u l d be c a u t i o u s l y e v a p o r a t e d t o n e a r 10 mL and e x t r a c t e d u s i n g t h e a c i d m i x t u r e procedure d e s c r i b e d i n Sections 11.3.3 t h r u 11.3.7.

11.2.3 Add 2 mL ( l t l ) n i t r i c a c i d and 1 . 0 m t o f ( l t l ) h y d r o c h l o r i c a c i d t o t h e b e a k e r c o n t a i n i n g t h e measured volume o f sample. P l a c e t h e b e a k e r on t h e h o t p l a t e f o r s o l u t i o n e v a p o r a t i o n . The h o t p l a t e s h o u l d be l o c a t e d i n a fume hood and p r e v i o u s l y adjusted t o provide evaporation a t a temperature o f a p p r o x i m a t e l y b u t no h i g h e r t h a n 85°C. (See t h e " f o l 1 o w i n g note.) The b e a k e r s h o u l d be c o v e r e d w i t h an e l e v a t e d w a t c h g l a s s o r o t h e r n e c e s s a r y s t e p s s h o u l d be t a k e n t o p r e v e n t sample c o n t a m i n a t i o n f r o m t h e fume hood e n v i r o n m e n t .

NOTE:

11.2.4

For proper h e a t i n g a d j u s t t h e temperature c o n t r o l o f t h e h o t p l a t e such t h a t an u n c o v e r e d G r i f f i n b e a k e r c o n t a i n i n g 50 mL o f w a t e r p l a c e d i n t h e c e n t e r of t h e h o t p l a t e can be m a i n t a i n e d a t a t e m p e r a t u r e a p p r o x i m a t e l y but n o h i g h e r t h a n 8 5 O C . (Once t h e b e a k e r i s covered w i t h a watch g l a s s t h e temperature o f t h e w a t e r w i l l r i s e t o a p p r o x i m a t e l y 95°C.)

Reduce t h e volume o f t h e sample a l i q u o t t o a b o u t 20 mL b y g e n t l e h e a t i n g a t 85°C. DO NOT BOIL. T h i s s t e p t a k e s a b o u t 2 h f o r a 100 mL a l i q u o t w i t h t h e r a t e o f e v a p o r a t i o n r a p i d l y i n c r e a s i n g as t h e sample volume approaches 20 mL. (A s p a r e b e a k e r c o n t a i n i n g 20 mL o f w a t e r can be used as a g a u g e . )

11.2.5 C o v e r t h e l i p o f t h e b e a k e r w i t h a w a t c h g l a s s t o r e d u c e a d d i t i o n a l e v a p o r a t i o n and g e n t l y r e f l u x t h e sample f o r 30 m i n u t e s . ( S l i g h t b o i l i n g may o c c u r , b u t v i g o r o u s b o i l i n g must be a v o i d e d t o p r e v e n t l o s s o f t h e HC1-H,O a z e o t r o p e . ) 11.2.6 A l l o w t h e b e a k e r t o c o o l . Q u a n t i t a t i v e l y t r a n s f e r t h e sample s o l u t i o n t o a 50-mL v o l u m e t r i c f l a s k o r 50-mL c l a s s A s t o p p e r e d g r a d u a t e d c y l i n d e r , make t o volume w i t h r e a g e n t w a t e r , s t o p p e r and m i x . 11.2.7 A l l o w any u n d i s s o l v e d m a t e r i a l t o s e t t l e o v e r n i g h t , o r c e n t r i f u g e a p o r t i o n o f t h e p r e p a r e d sample u n t i l c l e a r . ( I f a f t e r c e n t r i f u g i n g o r s t a n d i n g o v e r n i g h t t h e sample c o n t a i n s suspended s o l i d s t h a t w o u l d c l o g t h e n e b u l i z e r , a p o r t i o n o f

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t h e sample may be f i l t e r e d f o r t h e i r removal p r i o r t o a n a l y s i s . However, c a r e s h o u l d be e x e r c i s e d t o a v o i d p o t e n t i a l c o n t a m i n a t i o n from f i l t r a t i o n . ) 11.2.8 P r i o r t o a n a l y s i s , a d j u s t t h e c h l o r i d e c o n c e n t r a t i o n by p i p e t t i n g 20 mL o f t h e p r e p a r e d s o l u t i o n i n t o a 50-mL v o l u m e t r i c f l a s k , d i l u t e t o volume w i t h r e a g e n t w a t e r and mix. ( I f t h e d i s s o l v e d s o l i d s i n t h i s s o l u t i o n a r e > 0.2%, a d d i t i o n a l d i l u t i o n may be r e q u i r e d t o p r e v e n t c l o g g i n g o f t h e e x t r a c t i o n and/or skimmer cones. If the d i r e c t addition procedure (Method A, Sect. 10.3) i s b e i n g used, add i n t e r n a l s t a n d a r d s and m i x . The sample i s now ready f o r a n a l y s i s . Because t h e e f f e c t s o f v a r i o u s m a t r i c e s on t h e s t a b i l i t y o f d i l u t e d samples cannot be c h a r a c t e r i z e d , a l l analyses should be performed as soon as p o s s i b l e a f t e r t h e completed p r e p a r a t i o n . 11.3 S o l i d Sample P r e p a r a t i o n - T o t a l Recoverable A n a l y t e s 11.3.1 F o r t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e a n a l y t e s i n s o l i d samples, m i x t h e sample t h o r o u g h l y and t r a n s f e r a p o r t i o n ( > 20 g ) t o t a r e d w e i g h i n g d i s h , weigh t h e sample and r e c o r d t h e wet w e i g h t ( W W ) . ( F o r samples w i t h < 35% m o i s t u r e a 20 g portion i s sufficient. F o r samples w i t h m o i s t u r e > 35% a l a r g e r a l i q u o t 50-100 g i s r e q u i r e d . ) Dry t h e sample t o a c o n s t a n t w e i g h t a t 6OoC and r e c o r d t h e d r y w e i g h t (DW) f o r c a l c u l a t i o n o f p e r c e n t s o l i d s ( S e c t . 12.6). (The sample i s d r i e d a t 6OoC t o p r e v e n t t h e l o s s o f mercury and o t h e r p o s s i b l e v o l a t i l e m e t a l l i c compounds, t o f a c i l i t a t e s i e v i n g , and t o r e a d y t h e sample f o r g r i n d i n g . ) 11.3.2 To a c h i e v e homogeneity, s i e v e t h e d r i e d sample u s i n g a 5-mesh p o l y p r o p y l e n e s i e v e and g r i n d i n a m o r t a r and p e s t l e . (The s i e v e , m o r t a r and p e s t l e s h o u l d be c l e a n e d between samples.) From t h e d r i e d , ground m a t e r i a l weigh a c c u r a t e l y a r e p r e s e n t a t i v e 1.0 f 0.01 g a l i q u o t ( W ) o f t h e sample and t r a n s f e r t o a 250-mL P h i l l i p s beaker f o r a c i d e x t r a c t i o n . 11.3.3 To t h e beaker add 4 mL o f ( l t l ) HNO, and 10 mL o f ( 1 t 4 ) HC1. Cover t h e l i p o f t h e beaker w i t h a watch g l a s s . Place t h e beaker on a h o t p l a t e f o r r e f l u x e x t r a c t i o n o f t h e a n a l y t e s . The h o t p l a t e s h o u l d be l o c a t e d i n a fume hood and p r e v i o u s l y adjusted t o provide a r e f l u x temperature o f approximately 95OC. (See t h e f o l l o w i n g n o t e . )

NOTE:

F o r p r o p e r h e a t i n g a d j u s t t h e temperature c o n t r o l o f t h e h o t p l a t e such t h a t an uncovered G r i f f i n beaker c o n t a i n i n g 50 mL o f w a t e r p l a c e d i n t h e c e n t e r o f t h e h o t p l a t e can be m a i n t a i n e d a t a temperature a p p r o x i m a t e l y b u t no h i g h e r t h a n 85OC. (Once t h e beaker i s covered w i t h a watch g l a s s t h e t e m p e r a t u r e o f t h e w a t e r w i l l r i s e t o a p p r o x i m a t e l y 95OC.) A l s o , a b l o c k d i g e s t e r capable o f m a i n t a i n i n g a temperature o f 95OC

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and

equipped

with

250-mL

constricted

volumetric

d i g e s t i o n t u b e s may b e s u b s t i t u t e d f o r t h e hot plate

and conical beakers in the extraction step. 1 1 . 3 . 4 Heat the sample and gently reflux for 30 min.

Very slight boiling may occur, however vigorous boiling must be avoided to Some solution prevent loss of the HC1-H 0 azeotrope. evaporation will occur ( 3 to f m l ) .

11.3.5 Allow the sample to cool and quantitatively transfer the

extract to a 100-mL volumetric flask. Dilute to volume with reagent water, stopper and mix. 11.3.6 Allow the sample extract solution to stand overnight to

separate insoluble material or centrifuge a portion of the sample solution until clear. (If after centrifuging or standing overnight the extract solution contains suspended solids that would clog the nebulizer, a portion o f the extract solution may be filtered for their removal prior to analysis. However, care should be exercised to avoid potential cont ami nat i on from f i 1 trat i on. ) 11.3.7 Prior to analysis, adjust the chloride concentration

by pipetting 20 mL of the prepared solution into a 100-mL volumetric flask, dilute to volume with reagent water and mix. (If the dissolved solids in this solution are > 0.2%, additional dilution may be required to prevent clogging of the If the direct addition extraction and/or skimmer cones. procedure (Method A , Sect. 10.3) is being used, add internal standards and mix. The sample extract is now ready for analysis. Because the effects of various matrices on the stabi 1 i ty of di 1 uted samples cannot be characterized, a1 1 analyses should be performed as soon as possible after the completed preparation. NOTE:

Determine the percent solids in the sample for use in calculations and for reporting data on a dry weight basis.

11 4 Sample Analysis 1 1 . 4 . 1 For every new or unusual matrix, it is highly recommended that

a semi-quantitative analysis be carried out to screen the sample for elements at high concentration. Information gained from this may be used to prevent potential damage to the detector during sample analysis and to identify elements which may be higher than the linear range. Matrix screening may be carried out by using intelligent software, if available, or by diluting the sample by a factor o f 500 and analyzing in a semiquantitative mode. The sample should also be screened for background levels of all elements chosen for use as internal standards in order to prevent b i a s in the calculation of the analytical data. Revision 5 . 4

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11.4.2 I n i t i a t e i n s t r u m e n t o p e r a t i n g c o n f i g u r a t i o n . Tune and c a l i b r a t e the instrument f o r the analytes o f i n t e r e s t (Sect. 10.0).

11.4.3 E s t a b l i s h i n s t r u m e n t s o f t w a r e r u n procedures f o r q u a n t i t a t i v e analysis. For a l l sample analyses, a minimum o f t h r e e r e p l i c a t e i n t e g r a t i o n s a r e r e q u i r e d f o r d a t a a c q u i s i t i o n . Use t h e average o f t h e i n t e g r a t i o n s f o r d a t a r e p o r t i n g . 11.4.4 A l l masses which m i g h t a f f e c t d a t a q u a l i t y must be m o n i t o r e d during the a n a l y t i c a l run. A s a minimum, t h o s e masses p r e s c r i b e d i n T a b l e 4 must be m o n i t o r e d i n t h e same scan as i s used f o r t h e c o l l e c t i o n o f t h e d a t a . T h i s i n f o r m a t i o n s h o u l d be used t o c o r r e c t t h e d a t a f o r i d e n t i f i e d i n t e r f e r e n c e s . 11.4.5 D u r i n g t h e a n a l y s i s o f samples, t h e l a b o r a t o r y must comply w i t h t h e r e q u i r e d q u a l i t y c o n t r o l d e s c r i b e d i n S e c t i o n s 9.3 and 9.4. Only f o r t h e determination o f dissolved analytes o r t h e " d i r e c t a n a l y s i s " o f d r i n k i n g w a t e r w i t h t u r b i d i t y o f < 1 NTU i s t h e sample d i g e s t i o n s t e p o f t h e LRB,*LFB, and LFM n o t r e q u i r e d . 11.4.6 The r i n s e b l a n k s h o u l d be used t o f l u s h t h e system between samples. A l l o w s u f f i c i e n t t i m e t o remove t r a c e s o f t h e p r e v i o u s sample o r a minimum o f one m i n u t e ( S e c t . 4.1.5). Samples s h o u l d be a s p i r a t e d f o r 30 sec p r i o r t o t h e c o l l e c t i o n o f data. 11.4.7 Samples h a v i n g c o n c e n t r a t i o n s h i g h e r t h a n t h e e s t a b l i s h e d l i n e a r dynamic range s h o u l d be d i l u t e d i n t o range and r e a n a l y z e d . The sample s h o u l d f i r s t be analyzed f o r t h e t r a c e elements i n t h e sample, p r o t e c t i n g t h e d e t e c t o r f r o m t h e h i g h c o n c e n t r a t i o n elements, i f necessary, by t h e s e l e c t i o n o f a p p r o p r i a t e scanning windows. The sample s h o u l d t h e n be d i l u t e d f o r t h e d e t e r m i n a t i o n o f t h e r e m a i n i n g elements. A l t e r n a t i v e l y , t h e dynamic range may be a d j u s t e d by s e l e c t i n g an a1 t e r n a t i v e i s o t o p e o f l o w e r n a t u r a l abundance, p r o v i d e d qua1 i t y c o n t r o l d a t a f o r t h a t i s o t o p e have been e s t a b l i s h e d . The dynamic r a n g e must n o t be a d j u s t e d by a l t e r i n g i n s t r u m e n t c o n d i t i o n s t o an u n c h a r a c t e r i z e d s t a t e .

12.0 DATA ANALYSIS AND CALCULATIONS 12.1 Elemental e q u a t i o n s recommended f o r sample d a t a c a l c u l a t i o n s a r e l i s t e d i n T a b l e 5. Sample d a t a s h o u l d be r e p o r t e d i n u n i t s o f p g / L Do n o t f o r aqueous samples o r mg/kg dry w e i g h t f o r s o l i d samples. r e p o r t element c o n c e n t r a t i o n s below t h e determined MDL. 12.2 F o r d a t a v a l u e s l e s s t h a n t e n , two s i g n i f i c a n t f i g u r e s s h o u l d be used f o r r e p o r t i n g element c o n c e n t r a t i o n s . F o r d a t a v a l u e s g r e a t e r t h a n o r equal t o t e n , t h r e e s i g n i f i c a n t f i g u r e s s h o u l d be used. 12.3 F o r aqueous samples p r e p a r e d by t o t a l r e c o v e r a b l e procedure ( S e c t . 11.2), m u l t i p l y s o l u t i o n c o n c e n t r a t i o n s by t h e d i l u t i o n f a c t o r 1.25. I f a d d i t i o n a l d i l u t i o n s were made t o any samples or an aqueous sample Revision 5.4

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was prepared using the acid-mixture procedure described in Section 1 1 . 3 , the appropriate factor should be applied to the calculated sample concentrations. 12.4 For total recoverable analytes in solid samples (Sect. 11.3), round the solution analyte concentrations (pg/L in the analysis solution) as instructed in Section 12.2. Multiply the p/L concentrations in the analysis solution by the factor 0.005 to calculate the mg/L analyte concentration in the 100-mL extract solution. (If additional dilutions were made to any samples, the appropriate factor should be applied to Report calculate analyte concentrations in the extract solution.) the data up to three significant figures as mg/kg dry-weight basis unless specified otherwise by the program or data user. Calculate the concentration using the equation below: c x v Sample Conc. tmg/kg) dry-weight basis where: C

V W

= = =

=

~

W

Concentration in the extract (mg/L) Volume of extract (L, 100 mL = 0.1L) Weight of sample aliquot extracted (g x 0.001

=

kg)

Do not report analyte data below the estimated solids MDL or an adjusted MDL because of additional dilutions required to complete the analysis. 12.5 To report percent solids in solid samples (Sect. 11.3) calculate as foll ows :

DW % solids ( S )

where: DW

=

WW

=

NOTE:

=

-

ww

x 100

Sample weight (9) dried at 6OoC Sample weight (9) before drying

If the data user, program or laboratory requires that the reported percent sol ids be determined by drying at 105OC, repeat the procedure given in Section 11.3 using a separate portion ( > 20 g) of the sample and dry to constant weight at 1 03- 105OC.

12.6 Data values should be corrected for instrument drift or sample matrix induced interferences by the application of internal standardization. Corrections for characterized spectral interferences should be applied to the data. Chloride interference corrections should be made on all samples, regardless of the addition of hydrochloric acid, as the chloride ion is a common constituent of environmental samples. 12.7 If an element has more than one monitored isotope, examination of the concentration calculated for each isotope, or the isotope ratios, will provide useful information for the analyst in detecting a possible spectral interference. Consideration should therefore be given to f(f

200.8-29

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117

b o t h p r i m a r y and secondary i s o t o p e s i n t h e e v a l u a t i o n o f t h e element concentration. I n some cases, secondary i s o t o p e s may be l e s s s e n s i t i v e o r more prone t o i n t e r f e r e n c e s t h a n t h e p r i m a r y recommended i s o t o p e s , t h e r e f o r e d i f f e r e n c e s between t h e r e s u l t s do n o t n e c e s s a r i l y i n d i c a t e a problem w i t h d a t a c a l c u l a t e d f o r t h e p r i m a r y i s o t o p e s . 12.8 The QC d a t a o b t a i n e d d u r i n g t h e analyses p r o v i d e an i n d i c a t i o n o f t h e q u a l i t y o f t h e sample d a t a and s h o u l d be p r o v i d e d w i t h t h e sample results.

13.0 METHOD PERFORMANCE 13.1 I n s t r u m e n t o p e r a t i n g c o n d i t i o n s used f o r s i n g l e l a b o r a t o r y t e s t i n g o f t h e method a r e summarized i n Table 6 . T o t a l r e c o v e r a b l e d i g e s t i o n and " d i r e c t a n a l y s i s " MDLs d e t e r m i n e d u s i n g t h e procedure d e s c r i b e d i n Sect. 9 . 2 . 4 , a r e l i s t e d i n Table 7. 13.2 Data o b t a i n e d f r o m s i n g l e l a b o r a t o r y t e s t i n g o f t h e method a r e summarized i n T a b l e 9 f o r f i v e w a t e r samples r e p r e s e n t i n g d r i n k i n g w a t e r , s u r f a c e w a t e r , ground w a t e r and waste e f f l u e n t . Samples were For each p r e p a r e d u s i n g t h e procedure d e s c r i b e d i n Sect. 11.2. m a t r i x , f i v e r e p l i c a t e s were analyzed and t h e average o f t h e r e p l i c a t e s used f o r d e t e r m i n i n g t h e sample background c o n c e n t r a t i o n f o r each element. Two f u r t h e r p a i r s o f d u p l i c a t e s w e r e f o r t i f i e d a t d i f f e r e n t c o n c e n t r a t i o n l e v e l s . F o r each method element, t h e sample background c o n c e n t r a t i o n , mean p e r c e n t r e c o v e r y , t h e s t a n d a r d d e v i a t i o n o f t h e p e r c e n t r e c o v e r y and t h e r e l a t i v e p e r c e n t d i f f e r e n c e between t h e d u p l i c a t e f o r t i f i e d samples a r e l i s t e d i n Table 8. 13.3 Data o b t a i n e d f r o m s i n g l e l a b o r a t o r y t e s t i n g o f t h e method a r e summarized i n T a b l e 10 f o r t h r e e s o l i d samples c o n s i s t i n g o f SRM 1645 R i v e r Sediment, EPA Hazardous S o i l and EPA E l e c t r o p l a t i n g Sludge. Samples were p r e p a r e d u s i n g t h e procedure d e s c r i b e d i n Sect. 11.3. F o r each method element, t h e sample background c o n c e n t r a t i o n , mean p e r c e n t r e c o v e r y , t h e s t a n d a r d d e v i a t i o n o f t h e p e r c e n t r e c o v e r y and t h e r e l a t i v e p e r c e n t d i f f e r e n c e between t h e d u p l i c a t e f o r t i f i e d samples were d e t e r m i n e d as f o r Sect. 13.2. 13.4 Data o b t a i n e d f r o m s i n g l e l a b o r a t o r y t e s t i n g o f t h e method f o r d r i n k i n g w a t e r a n a l y s i s u s i n g t h e " d i r e c t a n a l y s i s " procedure (Sect. Three d r i n k i n g w a t e r samples o f 11.2.1) a r e g i v e n i n T a b l e 11. v a r y i n g hardness c o l l e c t e d f r o m Regions 4, 6, and 10 were f o r t i f i e d t o c o n t a i n 1 p g / L o f a l l m e t a l p r i m a r y contaminants, except selenium, w h i c h was added t o a c o n c e n t r a t i o n o f 20 p g / L . For each m a t r i x , f o u r r e p l i c a t e a1 i q u o t s were analyzed t o d e t e r m i n e t h e sample background c o n c e n t r a t i o n o f each a n a l y t e and f o u r f o r t i f i e d a1 i q u o t s were a n a l y z e d t o d e t e r m i n e mean p e r c e n t r e c o v e r y i n each m a t r i x . Listed i n t h e T a b l e 11 a r e t h e average mean p e r c e n t r e c o v e r y o f each a n a l y t e i n t h e t h r e e m a t r i c e s and t h e s t a n d a r d d e v i a t i o n o f t h e mean p e r c e n t recoveries. 13.5 L i s t e d i n T a b l e 12 a r e t h e r e g r e s s i o n e q u a t i o n s f o r p r e c i s i o n and b i a s developed f r o m t h e j o i n t USEPA/Association o f O f f i c i a l A n a l y t i c a l Chemists (AOAC) m u l t i l a b o r a t o r y v a l i d a t i o n s t u d y conducted on t h i s R e v i s i o n 5.4

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method. These equations were developed from data received from 13 laboratories on reagent water, drinking water and ground water. Listed in Tables 13 and 14, respectively, are the precision and recovery data from a wastewater digestate supplied to all laboratories and from a wastewater of the participant’s choice. For a complete review o f the study see reference 11. Section 16.0 of this method. 14.0 POLLUTION PREVENTION

14.1 Pollution prevention encompasses any technique that reduces or eliminates the quantity or toxicity of waste at the point of generation. Numerous opportunities for pollution prevention exist in laboratory operation. The EPA has established a preferred hierarchy of environmental management techniques that places pollution prevention as the management option of first choice. Whenever feasible, laboratory personnel should use pollution prevention techniques to address their waste generation. When wastes cannot be feasibly reduced at the source, the Agency recommends recycling as the next best option. 14.2 For information about pollution prevention that may be applicable to laboratories and research institutions, consult Less is Better: laboratory Chemical Management f o r Waste Reduction, available from the American Chemical Society’s Department of Government Relations and Science Policy, 1155 16th Street N.W., Washington D.C. 20036, (202)872-4477. 15.0 WASTE MANAGEMENT

15.1 The Environmental Protection Agency requires that laboratory waste management practices be conducted consistent with all applicable rules and regulations. The Agency urges laboratories to protect the air, water, and land by minimizing and controlling all releases from hoods and bench operations, complying with the letter and spirit of any sewer discharge permits and regulations, and by complying with all solid and hazardous waste regulations, particularly the hazardous waste identification rules and land disposal restrictions. For further information on waste management consult The W a s t e Management Manual for Laboratory Personne7, available from the American Chemical Society at the address listed in the Section 14.2. 16.0 REFERENCES

1.

Gray, A.L. and A. R. Date. Inductively Coupled Plasma Source Mass Spectrometry Using Continuum Flow Ion Extraction. Analyst 108 10331050, 1983.

2.

Houk, R . S . et al. Inductively Coupled Argon Plasma as an Ion Source for Mass Spectrometric Determination of Trace Elements. Anal Chem. 52 2283-2289, 1980.

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3.

Houk, R . S . , Mass Spectrometry o f I n d u c t i v e l y Coupled Plasmas. A n a l . Chem. 3 97A-l05A, 1986.

4.

Thompson, J.J. and R . S. Houk. A Study o f I n t e r n a l S t a n d a r d i z a t i o n i n I n d u c t i v e l y Coupled Plasma-Mass S p e c t r o m e t r y . A p p l . Spec. 41 801-806, 1987.

5.

Carcinogens - Working W i t h Carcinogens, Department o f H e a l t h , E d u c a t i o n , and W e l f a r e , P u b l i c H e a l t h S e r v i c e , Center f o r Disease C o n t r o l , N a t i o n a l I n s t i t u t e f o r O c c u p a t i o n a l S a f e t y and H e a l t h , P u b l i c a t i o n No. 77-206, Aug. 1977. A v a i l a b l e from t h e National T e c h n i c a l I n f o r m a t i o n S e r v i c e (NTIS) as PB-277256.

6.

OSHA S a f e t y and H e a l t h Standards, General I n d u s t r y , (29 CFR 1910), O c c u p a t i o n a l S a f e t y and H e a l t h A d m i n i s t r a t i o n , OSHA 2206, (Revised, January 1976).

7.

S a f e t y i n Academic Chemistry L a b o r a t o r i e s , American Chemical S o c i e t y Pub1 i c a t i o n , Committee on Chemical S a f e t y , 3 r d E d i t i o n , 1979.

8.

Proposed OSHA S a f e t y and H e a l t h Standards, L a b o r a t o r i e s , Occupational S a f e t y and H e a l t h A d m i n i s t r a t i o n , F e d e r a l R e g i s t e r , J u l y 24, 1986.

9.

American S o c i e t y f o r T e s t i n g and M a t e r i a l s . Standard S p e c i f i c a t i o n f o r Reagent Water, D1193-77. Annual Book o f ASTM Standards, V o l . 11.01. P h i l a d e l p h i a , PA, 1991.

10.

Code o f F e d e r a l R e g u l a t i o n s 40, Ch. 1, P t . 136 Appendix B.

11.

Longbottom, J.E. e t . a l . D e t e r m i n a t i o n o f Trace Elements i n Water by I n d u c t i v e l y Coupled P1 asma-Mass Spectrometry: C o l l a b o r a t i v e Study, J o u r n a l o f AOAC I n t e r n a t i o n a l 1004-1023, 1994.

12.

H i n n e r s , T.A., I n t e r f e r e n c e s i n ICP-MS by Bromine Species. Winter Conference on P1 asma S p e c t r o c h e m i s t r y , San Diego, CA, January, 10-15, 1994.

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120

Methods for the Determination

17.0 TABLES. DIAGRAMS. FLOWCHARTS, AND VALIDATION DATA TABLE 1: ESTIMATED INSTRUMENT DETECTION L I M I T S

ESTIMATED IDLs (pg/L) ELEMENT

A1 uminum Ant imony Arsenic B a r i um B e r y l 1 ium Cadmi um Chromi um Cobalt Copper Lead Manganese Mercury Molybdenum Nickel Selenium S i 1v e r Thallium Thorium Urani urn Vanadium Zinc

RECOMMENDED ANALYTICAL MASS

27 123 75 137 9 111 52 59 63 206.207,208 55 202 98 60 82 107 205 232 238 51 66

SCANNING MODE’

SELECTIVE ION MONITORING MODE^

0.05 0.08 0.9 0.5 0.1 0.1 0.07 0.03 0.03 0.08 0.1

0.02 0.008 0.02 0.03 0.02 0.02 0.04 0.002. 0.004 0.015 0.007 0.2 0.005 0.07 1.3 0.004 0.014 0.005 0.005 0.006 0.07

n.a.

0.1 0.2 5

0.05 0.09 0.03 0.02 0.02 0.2

I n s t r u m e n t d e t e c t i o n 1 i m i t s ( 3 a ) e s t i m a t e d from seven rep1 i c a t e i n t e g r a t i o n s o f t h e b l a n k (1%v / v n i t r i c a c i d ) f o l l o w i n g c a l i b r a t i o n o f t h e i n s t r u m e n t w i t h t h r e e r e p l i c a t e i n t e g r a t i o n s o f a m u l t i - e l e m e n t standard.

1

I n s t r u m e n t o p e r a t i n g c o n d i t i o n s and d a t a a c q u i s i t i o n mode a r e g i v e n i n Table 6.

2 IDLsfidetermined u s i n s t a t e - o f - t h e - a r t

i n s t r u m e n t a t i o n (1994). Data f o r As, 77Se, and 8 9Se were a c q u i r e d u s i n g a d w e l l t i m e o f 4.096 sec w i t h 1500 area count p e r sec 83Kr p r e s e n t i n argon supply. A l l other d a t a were a c q u i r e d u s i n g a d w e l l t i m e o f 1.024 sec p e r AMU m o n i t o r e d .

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121

TABLE 2: COMMON MOLECULAR ION INTERFERENCES I N ICP-MS

BACKGROUND MOLECULAR IONS

Mol ecul a r I o n NH' OH' OH,'

',C C N' CO'

N,' N,H' NO'

NOH'

02' 0,H' 36ArH+

38ArH' "ArH'

co,' C0,H'

Arc', ArO' ArN' ArNH'

ArO' ArOH'

40Ar36Ar+ 40Ar38Ar' 40

Ar, a

+

Mass

15 17 18 24 26 28 28 29 30 31 32 33 37 39 41 44 45 52 54 55 56 57 76 78 80

Element Interference"

sc Cr Cr Mn

Se

Se Se

method elements o r i n t e r n a l standards a f f e c t e d by t h e m o l e c u l a r i o n s .

Revision 5 . 4

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122

Methods for the Determination

TABLE 2 (Continued). MATRIX MOLECULAR IONS

Mol ecul ar Ion

Mass

'lBrH'

82 95 97 98

7 9 ~ r ~ +

BrO' BrOH' Ar'lBr'

121

CHLORIDE Mol ecul ar Ion

Mass

3 5 ~ 1 ~ + 3 5 ~ OH+ 1 3 7 1~O+ 3 7 ~ OH+ 1

51 52

53 54

Ar3'C1' Ar3?C1'

75 77

SULPHATE No1 ecul ar Ion

Mass

32su+

3 2 ~ ~ ~ 3 4 ~ ~ + 3 4 ~ ~ ~

so,',

s,'

+ +

48 49 50 51 64

El ement Interference Se Mo Mo Mo Sb

E 1 emen t Interference V Cr Cr Cr AS

Se

Element Interference V,Cr V

Zn

72 74

PHOSPHATE No1 ecul ar Ion

Mass

PO' POH'

47 48

PO,'

63

ArP'

71

GROUP I, I1 METALS Mol ecul ar Ion ArNa' ArK' ArCa'

Mass 63

El ement Interference

cu

Element Interference

cu

79 80

Revision 5.4 Hay 1994

Metals

123

TABLE 2 (Contl nued) . HATRXX MOLECULAR IONS

MATRIX OXIDES. Hol ecul ar Ion Ti0 ZrO MOO

*

Masses 62-66 106-112 108-116

Element Interference Ni,Cu,Zn Ag Y Cd Cd

Oxide i n t e r f e r e n c e s w i l l normally be very small and w i l l o n l y impact t h e method elements when present a t r e l a t i v e l y h i g h concentrations. Some examples o f m a t r i x oxides are l i s t e d o f which t h e analyst should be aware. It i s recommended t h a t T i and Z r isotopes are monitored i n s o l i d waste samples, which are l i k e l y t o c o n t a i n h i g h l e v e l s o f these elements. Mo i s monitored as a method analyte.

Revision 5.4

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124

Methods for the Determination TABLE 3: INTERNAL STANDARDS AND LIMITATIONS OF USE

I n t e r n a l Standard 6Li t h i um Scandi urn Yttrium Rhodi um I n d i urn T erb i urn H o l m i um Lut eti u m Bismuth

Mass

6 45 89 103

115 159 165

Possible L i m i t a t i o n a polyatomic i o n i n t e r f e r e n c e a,b i s o b a r i c i n t e r f e r e n c e by Sn

175

209

a

a May be present i n environmental samples. b I n Some instruments Y t t r i u m may form measurable amounts o f YO' (105 amu)and YOH (106 amu). I f t h i s i s t h e case, care should be taken i n t h e use o f t h e cadmium elemental c o r r e c t i o n equation.

I n t e r n a l standards recommended f o r use w i t h t h i s method are shown i n b o l d face. Prepa ra ti o n procedures f o r these are i n c l u d e d i n Section 7.3.

Revision 5.4

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125

TABLE 4: RECOMMENDED ANALYTICAL ISOTOPES AND ADDITIONAL MASSES WHICH MUST BE MONITORED

Isotope

Element of I n t e r e s t

27

A1 umi num Antimony Arsenic B a r i um B e r y l 1 iurn Cadmi urn Chromi urn Cobalt Copper Lead Manganese Molybdenum Nickel Sel en iurn S i 1v e r T h a l l ium T h o r i urn Uran ium Vanadi um

121,123

75 135,137 9 106,108,JJl, 114 52 ,53 59 63,65 206,207,208 -55 95,97,98 60,62 77,g 107,109 203,205

232 238 51 66,67,68 83 99 105 118

Zinc Krypton Rut hen iurn Palladium Tin

NOTE: I s o t o p e s recommended f o r a n a l y t i c a l d e t e r m i n a t i o n a r e under1 ined.

R e v i s i o n 5.4

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126

Methods for the Determination TABLE 5: RECOMMENDED ELEMENTAL EQUATIONS FOR DATA CALCULATIONS

Element

Elemental Equation

A1

(1 .ooo) (27c)

Sb

(~.ooo)(~~~c)

As

(l.000)(75C)-(3.127)[(nC)-(0.815)(82C)]

Ba

(1 .OOO) (137c)

Be

(1.000)(9c)

Cd

(1 .OOO) (l”C)-( 1.073) [ (lO8C)-(0 .712) ( 106C)]

Cr

(1.ooo) (52c)

co

( 1.000) (59c)

cu

(1.000)(9)

Pb

(1.000) (206c)t( 1 .OOO) (207c)t( 1 .OOO) (208c)

Mn

( 1.000)( 55c)

Mo

( 1 000) ( 98C) - ( 0.146) (99C)

Ni

(1.000)(60c)

Se

( 1 * 000)(82c)

Ag

(1.000)( ‘07C)

T1

(1.000)(205c)

Th

(~.ooo)(~~~c)

U

(1.000)(~~~c)

V

(1.000)(51c)- (3.127)[ (53c)- (0.113) (52c)3

Zn

(1 .OOO) p c )

.

Revision 5.4

May 1994

Metals

127

TABLE 5 (Continued) ~~~~~

~~

~~

INTERNAL STANDARDS Element

Elemental Equation

Bi

(1 .ooo) (*09c)

In

(1 .OOO) ("*C)- (0.016)('"C)

sc

(1.ooo)

Tb

(~.ooo)(~~~c)

Y

(1.000)(89c)

(45c)

C - calibration blank subtracted counts at specified mass. (1) - borrection for chloride interference with adjustment for Se. ArCl 75/77 ratio may be determined from the reagent blank. Isobaric mass 8 2 must be from Se only and not BrH'. (2) - correction f+or MOO interference. Isobaric mass 106 must be from Cd only not ZrO . An additional isobaric elemental correction should be made if palladium i s present. (3) - in 0.4% v/v HC1, the background from ClOH will normally be small. However the contribution may be estimated from the reagent blank. Isobaric mass must be from Cr only not Arc'. (4) - allowance for isotopic variability o f lead isotopes. (5) - isobaric elemental correction for ruthenium. (6) - some argon supplies contain krypton as an impurity. Selenium is corrected for 82Kr by background subtraction. (7) - correction for chloride interference with adjustment for 'kr. C10 51/53 ratio may be determined from the reagent blank. Isobaric mass 52 must be from Cr only not Arc'. (8) - isobaric elemental correction for tin.

Revision 5.4 May 1994

128

Methods for the Determination

TABLE 6: INSTRUMENT OPERATING CONDITIONS FOR PRECISION AND RECOVERY DATA'

Instrument P1 asma f o r w a r d power Coolant f l o w r a t e Auxiliary flow rate Nebulizer flow r a t e S o l u t i o n uptake r a t e Spray chamber t e m p e r a t u r e

VG PlasmaQuad Type I 1 . 3 5 kW 13.5 L/min 0.6 L/min 0.78 L/min 0.6 mL/min 15°C

Data A c q u i s i t i o n D e t e c t o r mode Replicate integrations Mass range Dwell t i m e Number o f MCA channels Number o f scan sweeps Total acquisition time

Pul se c o u n t i n g 3 8 - 240 amu 3 2 0 ps 2048 85 3 minutes p e r sample

1 The d e s c r i b e d i n s t r u m e n t and o p e r a t i n g c o n d i t i o n s were used t o d e t e r m i n e t h e scanning mode MDL d a t a l i s t e d i n T a b l e 7 and t h e p r e c i s i o n and r e c o v e r y d a t a g i v e n i n Tables 9 and 10.

Revision 5.4

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129

TABLE 7: METHOD DETECTION L I M I T S

'

W

SCANNING MODE' TOTAL RECOVERABLE AQUEOUS SOLIDS p g~/ L ~ mglkg

27

A1

123

Sb

1 .o 0.4

Ts

As

137

'11 52 59

63

~

SELECTIVE O I N MONITORING MODE^ TOTAL RECOVERABLE DIRECT ANALYSIS' AQUEOUS AQUEOUS ~ P9IL ~ ~ M I L~

1.7

1.4

0.4 0.2 0.6

0.04 0.4

0.04 0.02 0.1

Ba Be Cd

0.8 0.3 0.5

0.4 0.1 0.2

0.04 0.02 0.03

0.04 0.03 0.03

Cr co

0.9 0.09 0.5

0.4 0.04 0.2

0.08 0.004 0.02

0.08 0.003 0.01

0.6 0.1

0.3 0.05

0.05 0.02

n.a.

n.a.

n.a.

0.02 0.04 0.2

cu

206,207,208 pb 55 202

Mn Hg

98

Mo Ni Se

0.3 0.5 7.9

0.1 0.2 3.2

0.01 0.06 2.1

0.01 0.03 0.5

lo7

Ag

205

232

T1 Th

0.1 0.3 0.1

0.05 0.1 0.05

0.005 0.02 0.02

0.005 0.01 0.01

238

u

51

v

0.1 2.5 1.8

0.05 1.0 0.7

0.01 0.9 0.1

0.01 0.05 0.2

6o 82

66

Zn

-~ 1 Data acquisition mode given in Table 6. Total recoverable MDL concentrations are computed for original matrix with allowance for sample dilution during preparation. Listed MDLs for solids calculated from determined aqueous MDLs. 2 &DLs determined using state-of-the-art instrumentation (1994). Data for A s , nSe, and "Se were acquired using a dwell time of 4.096 sec with 1500

area count per sec 83Kr present in argon supply. All other data were acquired using a dwell time of 1.024 sec per AMU monitored. 3

MDLs were determined from analysis of 7 undigested aqueous sample aliquots.

n.a.- not applicable. Total recoverable digestion not suitable for organomercury compounds. Revision 5.4 May 1994

130

Methods for the Determination TABLE 8: ACCEPTANCE LIMITS FOR QC CHECK SAMPLE

METHOD PERFORMANCE ( F g l L ) ’

ELEMENT

Aluminum Antimony Arsenic Barium Beryllium Cadmium Chromium Cobalt Copper Lead Manganese Molybdenum Nickel Selenium Silver Thallium Thorium Uranium Vanadium Zinc

1

*3 4

5

QC Check Sample Conc.

100 100

100 100 100 100 100

100 100 100 100 100 100 100 100 100 100 100

100 100

Average Recovery

100.4 99.9 101.6 99.7 105.9 100.8 102.3 97.7 100.3 104.0 98.3

101 .o 100.1 103.5 101 .I 98.5 101.4 102.6 100.3 105.1

Standard Deviation’ (S,)

5.49 2.40 3.66 2.64 4.13 2.32 3.91 2.66 2.11 3.42 2.71 2.21 2.10 5.67 3.29 2.79 2.60 2.82 3.26 4.57

Acceptance Limits3 flg/L

84-117 93-107 91-113 92-108 88-11 24 94-1 08 91-114 90-I 06 94-I 07 94-114 90-1 06 94-1 08 94-106 86-121 91-Ill5 90-1 07 94-109 94-11 1 90-110 91-119

Method performance characteristics calculated using regression equations from collaborative study, reference 1 1. Single-analyst standard deviation, S,. Acceptance limits calculated as average recovery +3 standard deviations. Acceptance limits centered at 100% recovery. Statistics estimated from summary statistics at 48 and 64 pg/L.

Revision 5 . 4

May 1994

Metals

131

TABLE 9 : PRECISION AND RECOVERY DATA I N AQUEOUS MATRICES DRINKING WATER

Sample Element Concn. (uq/LI

A1 Sb As Ba

Be Cd Cr co cu Pb Mn Mo Ni Se Ag T1

Th U V Zn

S(R) RPD

<

175 (0.4 (1.4 43.8 t0.3 t0.5 (0.9 0.11 3.6 0.87 0.96 1.9 1.9 (7.9 t0.1 t0.3 tO.l

0.23 (2.5 5.2

Low Average Spike Recovery (uq/ L ) R (%I 50 10 50 50 10 10 10 10 10 10 10 10 10 50 50 10 10 10 50 50

115.8 99.1 99.7 94.8 113.5 97.0 111.0 94.4 101.8 97.8 96.9 99.4 100.2 99.0 100.7 97.5 109.0 110.7 101.4 103.4

High S(R)

RPD

5.9 0.7 0.8 3.9 0.4 2.8 3.5 0.4 8.8 2.0 1.8 1.6 5.7 1.8 1.5 0.4 0.7 1.4 0.1 3.3

0.4 2.0 2.2 5.8 0.9 8.3 9.0 1.1 17.4 2.8 4.7 3.4 13.5 5.3 4.2 1.0 1.8 3.5 0.4 7.7

Average Spike Recovery (uq/L) R (%) 200 100 200 200 100 100 100 100 100 100 100 100 100 200 200 100 100 100 200 200

102.7 100.8 102.5 95.6 111.0 101.5 99.5 93.6 91.6 99.0 95.8 98.6 95.2 93.5 99.0 98.5 106.0 107.8 97.5 96.4

S(R)

RPD

1.6 0.7 1.1 0.8 0.7 0.4 0.1 0.5 0.3 0.8 0.6 0.4 0.5 3.5 0.4 1.7 1.4 0.7 0.7 0.5

1.1 2.0 2.9 1.7 1.8 1.0 0.2 1.4 0.3 2.2 1.8 1.0 1.3 10.7 1.0 4.9 3.8 1.9 2.1 1.0

Standard d e v i a t i o n o f percent recovery. R e l a t i v e percent d i f f e r e n c e between d u p l i c a t e spike determinations. Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t .

Revision 5 . 4

May 1994

132

Methods for the Determination TABLE 9 : PRECISION AND RECOVERY DATA I N AQUEOUS MATRICES (Cont). WELL WATER

Sample Element Concn. (uq/L) A1 Sb As Ba Be Cd Cr

co cu Pb Mn

Mo Ni Se Ag T1 Th U V Zn S(R) RPD

<

*

34.3 0.46 tl.4 106 t0.3 1.6 t0.9 2.4 37.4 3.5 2770

2.1 11.4 t7.9 tO.l t0.3 tO.l

1.8 t2.5 554

Low Average S p i k e Recovery ( u q / L) R (%I

50 10 50 50 10 10 10 10 10 10 10 10 10 50 50 10 10 10 50 50

100.1 98.4 110.0 95.4 104.5 88.6 1 1 1 .o 100.6 104.3 95.2

*

103.8 116.5 127.3 99.2 93.9 103.0 106.0 105.3

*

S(R)

RPD

3.9 0.8 0.9 1.9 6.4 16.4 3.9 3.3 0.4 1.0 1.7 3.8 0.0 0.0 1.0 1.6 5.1 1.5 2.5 1.5 * 1.8 1.1 1.6 6.3 6.5 8.4 18.7 0.4 1.0 0.1 0.0 0.7 1.9 1.1 1.6 0.8 2.1 * 1.2

High Average S p i k e Recovery (bq/L) R (%)

200 100 200 200

100 100 100

100 100 100 100 100 100 200 200 100 100 100 200 200

S(R)

RPD

102.6 02.5 01.3 04.9 01.4 98.6 03.5 04.1 00.6 99.5

1.1 0.7 0.2 1 .o 1.2 0.6 0.4 0.4 0.8 1.4

102.9 99.6 101.3 101.5 100.4 104.5 109.7 105.8 102.1

0.7

1.3 1.9 0.5 1.6 3.3 1.6 1 .o 0.9 1.5 3.9 0.7 1.9 0.0 0.5 3.9 5.0 4.8 6.3 0.5 3.2

*

*

0.3 0.2 1.4 1.8 1.8 2.5 0.2 5.5

Standard d e v i a t i o n o f p e r c e n t r e c o v e r y . R e l a t i v e p e r c e n t d i f f e r e n c e between d u p l i c a t e s p i k e d e t e r m i n a t i o n s . Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t . S p i k e c o n c e n t r a t i o n t10% o f sample background c o n c e n t r a t i o n .

R e v i s i o n 5.4 May 1994

Metals

133

TABLE 9 : PRECISION AND RECOVERY DATA I N AQUEOUS MATRICES (Cont). POND WATER

Sample Element Concn. (uq/L)

A1 Sb As Ba Be Cd Cr co cu Pb Mn Mo Ni Se Ag

T1 Th U V Zn

S(R) RPD

<

*

610 (0.4 t1.4 28.7 (0.3 (0.5 2 .o 0.79 5.4 1.9 617 0.98 2.5 (7.9 0.12 (0.3 0.19 0.30 3.5 6.8

Low Average Spike Recovery ( u q / L) R (%I 50 10 50 50 10 10 10 10 10 10 10 10 10 50 50 10 10 10 50 50

S(R)

High Spike (bq/L)

*

*

101.1 100.8 102.1 109.1 106.6 107.0 101.6 107.5 108.4

1.1 2.0 1.8 0.4 3.2 1.0 1.1 1.4 1.5

104.2 102.0 102.7 102.5 108.5 93.1 107.0 96.1 99.8

1.4 2.3 5.6 0.8 3.2 3.5 2.8 5.2 1.7

*

RPD

*

1.7 2.9 5.6 2.4 0.9 8.3 1.6 2.7 1.9 3.2 1.1 3.5 4.7 15.4 2.1 8.3 10.5 7.3 14.2 3.1

200 100 200 200 100 100 100 100 100 100 100 100 100 200 200

100 100 100 200 200

Average Recovery R (%I 78.2 101.5 96.8 102.9 114.4 105,8 100.0 101.7 98.1 106.1 139.0 104.0 102.5 105.5 105.2 105.0 93.9 107.2 101.5 100.1

S(R) 9.2 3.0 0.9 3.7 3.9 2.8 1.4 1.8 2.5 0.0 11.1 2.1 2.1 1.4 2.7 2.8 1.6 1.8 0.2 2.8

RPD 5.5 8.4 2.6 9.0 9.6 7.6 3.9 4.9 6.8 0.0 4.0 5.7 5.7 3.8 7.1

7.6 4.8 4.7 0.5 7.7

Standard d e v i a t i o n o f percent recovery. R e l a t i v e percent d i f f e r e n c e between d u p l i c a t e spike determinations. Sample concentration below e s t a b l i s h e d method d e t e c t i o n l i m i t . Spike concentration (10% o f sample background concentration.

Revision 5.4

May 1994

Methods for the Determination

134

TABLE 9 : PRECISION AND RECOVERY DATA I N AQUEOUS MATRICES (Cont). SEWAGE TREATMENT PRIMARY EFFLUENT

Sample Element Concn. (UClIL)

A1 Sb As Ba Be Cd Cr co cu Pb Mn MO

Ni Se Ag T1 Th U

V Zn

S(R) RPD

<

*

1150 1.5 t1.4 202 t0.3 9.2 128 13.4 171 17.8 199 136 84.0 t7.9 10.9 t0.3 0.11 0.71 t2.5 163

Low Average Spike Recovery f u s l L) R (%I

50 10 50 50 10 10 10 10 10 10 10 10 10 50 50 10 10 10 50 50

* 95.7 104.2 79.2 110.5 101.2

*

95.1

*

95.7

* *

88.4 112.0 97.1 97.5 15.4 109.4 90.9 85.8

S(R)

RPD

* 3.5 0.4 0.9 4.5 12.3 9.9 2.5 1.8 4.5 1.3 0.0 * 1.5 2.7 2.2 * 2.4 3.8 1.1 * 1.5 * 1.4 16.3 4.1 10.9 27.5 0.7 1.5 0.4 1.0 1.8 30.3 1.8 4.3 0.9 0.6 3.3 0.5

High Spike

Average Recovery (usfL1 R t%1

200 100 200 200 100 100 100 100 100 100 100 100 100 200 200 100 100 100 200 200

100.0 104.5 101.5 108.6 106.4 102.3 102.1 99.1 105.2 102.7 103.4 105.7 98.0 108.8 102.6 102.0 29.3 109.3 99.4 102.0

S(R)

RPD

13.8 0.7 0.7 4.6 0.4 0.4 1.7 1.1 7.1 1.1 2.1 2.4 0.9 3.0 1.4 0.0 0.8 0.7 2.1 1.5

1.5 1.9 2.0 5.5 0.9 0.9 0.4 2.7 0.7 2.5 0.7 2.1 0.0 7.8 3.7 0.0 8.2 1.8 6.0 1.9

Standard d e v i a t i o n o f percent recovery. R e l a t i v e percent d i f f e r e n c e between d u p l i c a t e s p i k e determinations. Sample concentration below e s t a b l i s h e d method d e t e c t i o n l i m i t . Spike c o n c e n t r a t i o n
Revision 5.4

Hay 1994

Metals

135

TABLE 9 : PRECISION AND RECOVERY DATA I N AQUEOUS MATRICES ( C o n t ) . INDUSTRIAL EFFLUENT

-

Sample Element Concn. (Irq/L)

A1 Sb As Ba Be Cd Cr

co

cu Pb Mn Mo Ni Se Ag

TI Th U

V Zn

S(R) RPD

<

*

44.7 2990 (1.4 100 t0.3 10.1 171 1.3 101 294 154 1370 17.3 15.0 tO.l

t0.3 0.29 0.17 (2.5 43.4

Low Average Spike Recovery ( u q / L) R (%)

50 10 50 50 10 10 10 10 10 10 10 10 10 50 50 10 10 10 50 50

S(R)

RPD

98.8

*

8.7

75.1 96.7 103.5 106.5

1.8 5.5 1.8 4.4

90.5

3.2

5.7 0.3 6.7 3.4 4.8 2.4 0.0 8.7 0.9 2.6 2.8 1.4 5.0 15.1 1.7 5.5 2.7 6.6 0.3 0.6

* * *

* * 107.4 129.5 91.8 90.5 109.6 104. a 74.9 85.0

*

* *

*

* * 7.4 9.3 0.6 1.8 1.2 2.5 0.1 4.0

High Average Spike Recovery (uq/L) R (%I

200 100 200 200 100 100 100 100 100 100 100 100 100 200 200 100 100 100 200 200

90.4

*

75.0 102.9 100.0 97.4 127.7 90.5 92.5 108.4 103.6

*

88.2 118.3 87.0 98.3 108.7 109.3 72.0 97.6

S(R)

RPD

2.1

2.2 0.0 0.0 0.7 0.0 2.8 1.7 1.3 1.6 0.0 1.6 0.7 1.0 3.6 16.1 2.8 0.0 0.9 0.0 0.4

*

’

0.0 1.1 0.0 1.1 2.4 0.4 2.0 2.1 3.7

*

0.7 1.9 4.9 1.0 0.0 0.4 0.0 1.0

Standard d e v i a t i o n o f percent recovery. R e l a t i v e percent d i f f e r e n c e between d u p l i c a t e s p i k e determinations. Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t . Spike c o n c e n tra ti o n t 1 0 % o f sample background c o n c e n t r a t i o n .

Revision 5.4

May 1994

Methods for the Determination

136

TABLE 10 : P R E C I S I O N AND RECOVERY DATA I N S O L I D M A T R I C E S EPA HAZARDOUS SOIL #884

A1 Sb As Ba Be Cd Cr co cu

Pb Mn Mo Ni Se Ag T1 Th U V Zn S(R) RPD t

* t

5170 5.4 8.8 113 0.6 1.8 83.5 7.1 115 152 370 4.8 19.2 t3.2 1.1 0.24 1.0 1.1 17.8 128

20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20

*

*

-

69.8 104.7 54.9 100.1 97.3 86.7 98.8 86.3 85.0

2.5 5.4 63.6 0.6 1.0 16.1 1.2 13.8 45.0

95.4 101.7 79.5 96.1 94.3 69.8 100.1 109.2 87.0

1.5 3.8 7.4 0.6 1.1 0.6 0.2 4.2 27.7

4.7 9.1 18.6 1.5 1.4 8.3 1.9 3.4 13.9 12.7 2.9 1.0 26.4 0.5 3.1 1.3 0.0 2.3 5.5

*

*

100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100

*

*

-

70.4 102.2 91.0 102.9 101.7 105.5 102.9 102.5 151.7 85.2 95.2 102.3 100.7 94.8 97.9 76.0 102.9 106.7 113.4

1.8 2.2 9.8 0.4 0.4 1.3

6.5 5.4 0.5 1.0 1.0 0.0 1.8 4.6 23.7 2.2 2.0 0.8 26.5 2.3 2.9 7.9 0.0 2.4 14.1

0.7

4.2 25.7 10.4 0.7 0.8 9.4 0.8 1.0 2.2 0.0 1.3 12.9

Standard d e v i a t i o n o f percent recovery. R e l a t i v e percent d i f f e r e n c e between d u p l i c a t e s p i k e determinations. Sample co n c e n tra ti o n below e s t a b l i s h e d method d e t e c t i o n l i m i t . Spike co n c e n tra ti o n ~ 1 0 % o f sample background c o n c e n t r a t i o n . N o t determined. Equi Val e n t

.

R e v i s i o n 5.4

May 1994

Metals

137

TABLE 10 : PRECISION AND RECOVERY DATA I N SOLID MATRICES (Cont). NBS 1645 RIVER SEDIMENT

Sample Low+ Average Element Concn. Spike Recovery R (%) (mq/kq) (mq/kq)

A1 Sb As Ba Be Cd Cr

co cu Pb Mn Mo Ni Se A!3

T1 Th

U V Zn

S(R) RPD

<

* -

t

5060 21.8 67.2 54.4 0.59 8.3 29100 7.9 112 742 717 17.1 41.8 (3.2 1.8 1.2 0.90 0.79 21.8 1780

20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20

S(R)

RPD

*

*

73.9 104.3 105.6 88.8 92.9

6.5 13.0 4.9 0.2 0.4

9.3 7.6 2.8 0.5

97.6 121.0

1.3 9.1

*

* *

2.6 1.5

89.8 103.7 108.3 94.8 91.2 91.3 95.6 91.8

8.1 6.5 14.3 1.6 1.3 0.9 1.8 4.6

12.0 4.8 37.4 4.3 3.6 2.6 5.0 5.7

*

*

*

*

*

0.0

-

-

High+ Average Spike Recovery ( m q / kq 1 R (%)

100 100 100 100 100 100 100 100 100 100 100

100 100 100 100 100

100 100 100 100

S(R)

RPD

*

*

81.2 107.3 98.6 87.9 95.7

1.5 2.1 2.2 0.1 1.4

103.1 105.2

0.0 2.2

3.9 2.9 3.9 0.2 3.9 0.0 1.8 0.9 0.0 15.1 1.9 1.3 2.8 3.5 0.8

* -

98.4 102.2 93.9 96.2 94.4 92.3 98.5 100.7

*

*

0.7 0.8 5.0 0.7 0.4 0.9 1.2 0.6

*

-

Standard d e v i a t i o n o f percent recovery. R e l a t i v e percent d i f f e r e n c e between d u p l i c a t e s p i k e determinations. Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t . Spike co n c e n tra ti o n
Revision 5.4 May 1994

138

Methods for the Determination

TABLE 10

:

PRECISION AND RECOVERY DATA IN SOLID MATRICES (Cont). EPA ELECTROPLATING SLUDGE #286

Sample Low+ Average Element Concn. S p i k e Recovery S ( R ) (mq/kqI Imq/kq) R I%) A1 Sb As Ba Be Cd Cr co cu

Pb Mn Mo Ni Se Ag T1 Th

U V Zn

S(R ) RPD

<

*

t

5110 8.4 41.8 27.3 0.25 112 7980 4.1 740 1480 295 13.3 450 3.5 5.9 1.9 3.6 2.4 21.1 13300

20 20 20 20 20 20 20 20 20 20 20 20

20 20 20 20 20 20 20 20

RPD

*

*

-

55.4 91 .o 1.8 92.0 85.0

1.5 2.3 7.1 0.9 5.2

4.1 1.7 8.3 2.7 1.6

89.2

1.8

4.6 6.0

*

*

-

1.2

1.3 6.8 4.2 4.6 2.4 3.2 4.6 2.1

* * *

82.9

*

89.7 89.8 96.9 91.5 107.7 105.6

*

*

* *

*

3.7 2.1 0.9 1.3 2.0 1.8

*

-

-

High+ Average S p i k e Recovery (mq / kq I R (%I

100 100 100 100 100 100 100 100 100 100 100 100 100

100 100 100 100 100 100 100

S(R)

RPD

*

*

-

61.0 94.2 0 93.4 88.5

0.2 0.8 1.5 0.3 0.8

0.9 1.5 10.0 0.9 0.5

88.7 61.7

1.5 20.4

4.6 5.4

*

*

*

*

-

-

-

-

89.2 83.0 91.0 85.1 98.9 97.4 109.6 97.4

0.4 10.0 6.0 0.4 0.9 0.7 0.7 1.1

1.0 4.5 18.0 1.1 2.4 2.0 1.8 2.5

*

*

-

Standard d e v i a t i o n o f p e r c e n t r e c o v e r y . R e l a t i v e p e r c e n t d i f f e r e n c e between d u p l i c a t e s p i k e d e t e r m i n a t i o n s . Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t . S p i k e c o n c e n t r a t i o n t10% o f sample background c o n c e n t r a t i o n . N o t determined. Equivalent.

Revision 5 . 4 Hay 1994

Metals

139

TABLE 11 : PRIMARY DRINKING WATER CONTAMINANTS PRECISION AND RECOVERY DATA

ANALYTE Antimony Arsenic B a r i um B e r y l 1 ium Cadmi um Chromi um Copper Lead Mercury Nickel Sel e n i um Thallium

REGIONAL SAMPLE BACKGROUND CONCENTRATION, p g / L (I\) (VI) (XI

AVERAGE MEAN' Y. RECOVERY

S(R)

0.03 1 .o 14.3

114% 93

4.6

0.07 2.4 280

(*I

1.9 8.5 -

< MDL

< MDL

< MDL

0.05

0.05 5.1

0.03 0.10

100% 81 94

8.2 4.0 2.5

0.16

< MDL

0.71 208 1.2

<

MDL

1.7

< MDL < MDL

130

14.3 2.5

1.2 0.23

< MDL

3.6 4.3 0.01

< MDL < MDL

0.52

(*)

91 86

2.6 11.4

101% 98 100

11.5 8.4 1.4

1

The t h r e e r e g i o n a l w a t e r s were f o r t i f i e d w i t h 1.0 pg/L o f a l l a n a l y t e s l i s t e d , e x c e p t selenium, which was f o r t i f i e d t o 20 pg/L.

(*)

Recovery o f barium and copper was n o t c a l c u l a t e d because t h e a n a l y t e a d d i t i o n was < 20% t h e sample background c o n c e n t r a t i o n i n a l l waters. (Recovery c a l c u l a t i o n s a r e n o t r e q u i r e d i f t h e c o n c e n t r a t i o n o f t h e a n a l y t e added i s l e s s t h a n 30% o f t h e sample background c o n c e n t r a t i o n . Sect.9.4.3)

S(R)

Standard d e v i a t i o n o f t h e mean p e r c e n t r e c o v e r i e s .

R e v i s i o n 5.4 May 1994

TABLE U: SUMMARY fXATISI'ICS AND DESCRIITIVE EQUATIONS FOR TEE 20 ANALYTES l X X E D IN THE COLLABORATIVE !?IWDY 0

Reagent Water

Finished D n n h n n Water

Anaiyte

Aluminum

Antimony

Arsenii

Banurn

Bcrylliurn

Cadmium

C'

Xb

S,

S,

Regr Equations

2

+ 1.19

8 00 12.00 56.00 80.00 160.00 200.00

10.01 10.98 59.13 82.59 158.95 200.89

2.33 5.16 5.55 4.92 11.82 8.61

2.80 4.00 20.00 28.00 80.00 100.00

2.75 4.22 19.76 27.48 82.52 98.06

0.27 0.46 1.09 1.38 2.24 1.34

0.27

.% = 0 . 9 9 9 c + 0.04

0.85

S, = O.O13_X s, = 0.022x

8.00 12.00 56.00 80.00 160.00 200.00

8.64 12.58 55.44 85.15 161.80 201.52

3.01 3.18 4.64 2.54

3.02

11.15

3.96

8.01 12.00 48.00 64.00 160.00 200.00

7.58 47.32 65.52 157.09 198.53

0.50 1.05 1.60 2.90 6.53 8.28

2.80 4.00 20.00 28.00 80.00 100.00

3.31 4.45 22.38 30.02 84.18 102.88

0.81 0.73 2.76 2.86 4.79 5.90

4.00 6.00

4.01 6.32 19.81 28.33 81.28 100.11

0.34 0.49 1.12 0.94 4.91 3.24

10.00

28.00 80.00 100.00

11.81

1.74 4.19

= 0.992s

SR = 0.0565 + 2.59' S, = 0.042X + 1.27

8.90

+ 0.61' + 0.20

1.76

2 = 1.013C_ + 0.50 S, = O.O31_X

3.51

S, = 0.007X

+ 2.74

+ 2.95

10.81 0.48 1.82

X = I.OOlC_- 0.36 S, = 0.0393 0.31 S. = 0.024X + 0.25

+

4.07

0.26

2

= 1.056g

SR = 0.0673 1.00

S. = 0.038X

+ 0.32 + 0.55 + 0.11

4.02

0.20 0.86 1.33

+ 0.07 0.041_X + 0.19 s, = 0.022x + 0.1ff .%

= 1.007c

S,

=

X

z

Ground Water

-

-

Q

S,

X

Regr Equations

S,

11.18 11.02 56.97 82.73 159.89 189.98

9 02 3.02 7.14 8.01 11.94 12.97

6.34

2.73 4.10 19.17 26.48 83.43 97.19

0.29 0.47 1.37 1.72

0.17

2.05

2.46

2 = 0 954C + 2 38

s, 6.18

= 7.706S, = 0.013X

+ 6.17

10.59

2 = 0.983c + 0.03 S, = 0.0493

0.66

S, = 0.026X

+ 0.19

+ 0.08

5.31

9.00 11.37 53.77 87.72 157.56 197.99

3.13 1.77 4.12 4.14 4.83 10.66

8.21 12.56 49.13 65.30 155.25 196.52

1.21 1.79 3.72 4.16 7.82 5.70

3.15 4.45 21.27 29.57 87.59 102.64

0.47 0.51 1.23 1.67 6.89 6.27

4.11 5.87 19.57 27.68 80.62 98.15

0.88 0.58 1.45 1.27 4.45 3.60

1.96 4.07

2 = 0.993c + 0.57 S, = 0.0183 + 2.55 S, = 0.031X

+

1.65

6.30

1.11

3.77

2 = 0 . 9 9 5 c + 0.37

S, = O.O45_X + 0.97' S, = 0.040X + 0.72'

5.67

0.31 0.63

X = I.055C + 0.20 S, = 0.05% + 0.28 S. = 0.016X + 0.25

1.88

0.71

? = 0.985C_ + 0 10

1.26

S, = 0.031X S. = 0.021X

2.02

+ 0.65

f

0.61

S,

S,

Rcgr Equations

9.86 13.40 51.75 82.83 155.40 189.64

7 10 10.27 10.78 33.37 15.39 31.46

2 70

2.82 4.02 20.12 27.77 80.34 101.09

0.19 0.35 0.82 1.38 9.14 2.89

0 22

10.40 7.85 53.25 83.60 159.86 194.41

5.17 4.62 3.49 12.46 11.67 18.24

490

8.04 12.85 50.12 69.53 164.44 208.32

2.60 1.45 2.98 2.66 8.81 9.22

3.02 4.27 21.55 29.24 84.23 103.39

0.46

0.44 1.72 2.09 9.05 10.17

3.98 5.62 18.15 26.86 77.83 95.31

048 0 73 173 2.59 3 05 2.04

16.92

%

2 = 0946(3+ 2 2 0 S, = 0 1693 + 6.22' S, = 0.172X + 0.75'

19.27

0.97

xS,

= 1.003C_ + 0.01

?

=

= 0.0593 + 0.04 S, = 0.058X + 0.02

6.80

0.949c

+ 0.91

S, = 0.048T

7.88

S,

=

0.059X

+ 4.52

+ 4.29

14.94

-

2.24

X = I.O55C_- 0 21 s, = 0.0203 + 2.0s

2.19

S, = 0.014X

+ 2.08

6.61

0.22 1.10

2=

1.049c + 0.08 S, = O.OSJ_X + 0.16 S, = 0.043X + 0.06

4.32

0 14 0 88 1.88

?

=

s,

= 0 0 1 q + 1

S. =

0 9 U C _ + 0 11

w

0 029X + 0 01

TABLE 12. SUMMARY SATISLICS AND D J N X W I W E EQUATIONS FOR THE 20 ANALYTES TESTED IN Tl€E C0LLABORA"E S W D Y Finished Drinking Water

Reanent Water Analytc

Chromium

Cobalt

Copper

Lead

Manganese

C

-

X'

Ground Water

-

S,

S,

Regr. Equations

1.54

2 = 1.017c + 0.62

8.00 8.27 12.00 13.88 56.00 57.86 80.00 84.73 160.00 157.66 200.00 197.43

0.32 3.10 4.03 2.65 13.62 9.47

0.80 1.21 20.10 28.20 80.50 101.00

0.88 0.98 20.77 27.75 78.59 98.79

0.10 0.74 0.96 2.29 2.94

0.67

4.00 6.00 20.00 28.00 80.00 100.00

3.88 6.14 20.07 27.97 79.80 99.57

0.73 1.00 1.08 1.94 3.22 4.42

0.59

2 = 1.003c- 0.05

0.92

S, = 0 . 0 3 3 S, = 0.016X

4.00 6.00 20.00 28.00 80.00 100.00

4.00 5.56 20.54 30.90 80.57 102.93

1.57 2.00 2.91 4.58 3.13 6.62

1.62

0.80 1.20 20.00 28.00 80.00 100.00

0.86 1.09 20.43 27.53 79.00 97.60

0.15 0.12 0.89 0.41 3.16 2.5 1

+ 0.48

S, = 0.0665

2.68

+ 1.25

S. = 0.026X

6.97

0.05

2 = 0.977c + 0.01

+ 0.06 s, = 0.027x + 0.02 S, = 0.028_X

0.04

2.31

+ 0.64 + 0.51

1.91

2 = 1.043c- 0.31 S, = 0.064X

4.36

s, = 3 . 4 1

+ 1.43'

4.29

0.09 0.72 2.38

+ +

X = 0.983(3 0.02 S, = 0.026s 0.11 s, = 0.027x + 0.06

X

S,

S,

9.46 13.10 56.04 84.38 158.24 196.72

2.34 2.39 2.24 3.18 5.12 7.47

0.92 1.02 20.45 27.29 78.04 97.62

0.45 0.10 0.91 1.22 3.72 4.62

0.3 1

3.33 5.95 18.90 27.21 76.64 %.I7

0.85 1.78 1.64 2.76 5.30 5.64

0.99

3.44 6.84 20.18 28.08 80.92 101.60

1.15 1.10 1.20 1.57 2.30 3.23

0.96 1.13 21.06 27.60 79.57 97.97

0.32 0.38 1.32 1.47 4.18 4.10

2.08 1.29

Regr. Equations

X = 0.99W- + 1.45 S, = 0.015X + 2.19 S. = 2.18'

3.16

0.53

2 = 0.964c + 0.06 S, = O.O19_X + 0.32 S. = 0.014X + 0.30

1.84

1.51

2 = 0.976c- 0.38 S, = 0.0635 + 0.86 S. = 0.029X + 0.86

3.42

1.18 I .44

2 = 1.032c- 0.30 s, = o.ors_x + 1.06 S. = 0.011X + 1.13

2.07

0.42

2 = 0.989C_ + 0.10 S, = 0.04-

0.96 2.01

s. = 0.02IX

+ 0.29 + 0.40

X

S,

S,

Rcgr. Equations

0.37

8.98 13.42 59.35 83.90 164.58 199.88

1.47 1.13 5.99 5.70 14.11 11.19

0.85 1.04 20.81 28.07 79.26 99.41

0.13 0.18 1.11 2.16 4.66 4.22

0.09

3.86 5.96 18.97 27.44 79.30 97.54

1.40 0.95 1.68 2.58 9.05 11.16

0.71

4.20 6.27 19.57 28.55 82.47 102.47

1.13 2.38 2.72 1.73 4.38 3.58

0.64 0.90 19.61 25.65

0.22 0.21 2.60 4.10 6.13 6.74

77.38

95.86

? . = 1.026c- + 0.89

, S, 5.42

= 0.06q 0.68 S. = 0.068X - 0.37

9.80

1.12

2 = 0.989c- 0.01 S, = 0.05% + 0.09 s, = 0.012x

+ 0.-

1.34

2.32

2 = 0.977c- 0.01 S, = 0.0735 + 0.92 S, = 0.077X + 0.35

654

1.76

2 = 1.012C_+ 0.15 S, = 0.048X + 1.27

0.88

S, =

1.78'

2.69

0.17

2

= 0.954C-- 0.16

S, = 0.1035

2.62 2.90

S, = 0.U25X

+ 0.14

+ 0.W

TABLE l2: SUMMARY SI'ATISTICS AND DISCXIITWE EQUATIONS FOR THE 20 ANALYTES TJZXED IN THE COLLABORATIVE STUDY 13 Reagent Water

-

Analp

C'

Xb

Ground Water

Finished Dnnkine Water

-

Regr. Equations

S,

S,

2.80 2.63 4.00 3.85 20.00 19.75 28.00 27.87 80.00 83.07 100.00 100.08

0.32 0.31 0.64 1.07 3.07 4.32

0.16

xS,

0.64

s,

4.00 4.02 6.00 6.36 20.00 19.93 28.00 28.02 80.00 79.29 100.00 100.87

0.41 0.91 1.30 1.25 2.95 7.20

32.00 33.54 40.00 41.03 80.00 81.40 96.10 98.34 160.00 163.58 200.00 214.30

4.63 6.04 5.86 8.57 15.69 10.57

0.80 0.93 1.20 1.51 48.00 49.39 64.00 63.54 160.00 136.42 200.00 153.74

0.09 0.23 3.25 2.75 48.31 57.34

2.80 4.00 20.00 28.00 80.00 100.00

2.89 3.92 19.27 28.08 81.29 96.69

0.23 0.15 0.99 0.83 3.65 2.86

0.80 1.20 20.00 28.00 80.10 100.00

0.93 1.22 20.88 27.97 81.14 102.64

0.16 0.19 0.90 1.11 2.99 3.39

X

!7

-

S,

S,

X

Regr. Equations

S,

S,

Regr. Equations

0 blol) bdcnum

Nickel

Sc I c ni 11in

Silver

Thallium

Thorium

= 1.012c_-0.20 = 0.0323 0.22 = 0.021x 0.09

+ +

1.78

0.50 0.63

xS. = 1.ooOc+ 0.12 0.0513 + 0.31 =

S, = 0.01%

+ 0.40

2.55

1.57 5.44

2=

1.036C- 0.06 S, = O.OSl_X + 3.24 S, = 0.061X - 0.64

9.86

0.14 1.81

+

= 0.917c 0.26 S, = O.L96_X - 0.09

S, = 0.053X

+ 0.08

12.19

0.22 0.67

2 = 0.984)( + 0.08

S, = O.O35_X + 0.09 S, = 0.027X f 0.13

2.86

0.09

?. = 1.013C_+ 0.08

+ 0.13 = 0.025X + 0.07

S. = 0.0365 0.71 2.14

S,

-

2

= l.013C_-O.O7 S, = 0 . 0 3 v + 0.17 S, = 0.035X + 0.20

2.80 3.95 19.78 27.87 85.65 99.06

0.20 0.47 0.60 1.51 3.50 2.89

0.32

3.66

1.03

2 = 0.953c- 0.19

18.42 27.09 75.84 95.83

0.53 1.32 0.87 1.68 4.40 4.41

1.11

S, = 0.0463 S, = 0.023X

32.57 42.18 79.97 94.94 163.48 212.19

4.31 3.71 6.66 7.90 9.17 16.49

5.44

0.70 0.34 1.37 0.33 45.43 6.78 60.35 2.22 119.06 55.28 172.15 31.92 2.88 3.96 19.77 27.61 85.32 100.07

0.40 0.21 1.13 1.24 4.08 4.33

0.78 1.09 21.66 28.09 79.99 100.50

0.13 0.19 0.94 0.83 2.03 4.56

1.16 3.07

+ 0.56

+ 0.91

3.94

3.65 5.28

-

X = I.O22C_+ 0.14 S, = 0.056z + 2.10 S, = 0.040X + 2.15

10.06

0.34

2 = 0.888c + 0.09 S, = 0.1863

5.15

S, = 0.164X

+ 0.17

+ 0.18

36.34

0.16 0.83

2 = I.OlOc_ + 0.01

S, = 0.0405 + 0.21 S , = 0.039X + 0.02

4.05

0.07 0.54 2.60

2=

I.O19C_-0.06 S, = 0.0353 + 0.12 S, = 0.024X + 0.05

3.00 3.60 20.69 28.80 84.26 103.57

0.47 0.90 1.37 2.01 4.13 6.10

4.81 6.67 20.58 30.73 82.71 101.00

2.06 3.66 3.71 3.75 9.49 9.89

32 46

4.95

41.46

3.30

81.63 98.92 167.54 209.21

6.94 4.39 8.69 14.65

0.70 0.98 45.59 59.71 121.43 160.69

0.26 0.28 4.27 6.58 42.55 27.15

2.88 3.88 20.22 28.65 83.97 101.09

0.14 0.37 1.05 1.50 6.10 4.15

0.87 1.15 21.78 29.86 86.00 107.35

0.17 0.17 0.90 1.65 3.43 4.72

0.42 1.11

X = 103Z_C - 0 09 S , = 0.55X-+ 0 43 S, = 0.042X + 0 27

4.81

2.82 2.37

2=

1.022C_+ 0.66 S, = O.OSl_X + 2.03 S, = 0.008X + 2.75'

5.42

3 24

2

= I 045C_-0 83 = 0 03% + 2 97 S , = 0.058X + 1 0 2

s, 5.65 12.98

0.10

2.70

2

= 0.858C- 0.00 S, = 0.1693 + 0.14 S, = 0.120X - 0.01

28.19

0.12 0.65

2

= 1.023c- 0.06 S, = 0.0565 + 0 04 S, = 0.049X - 0.06

6.05

0.07

x

= 1.069c- 0.03 = 0.041& + 0 13 S, = 0.02% + 0.04

s, 0.94 1.95

TABLE U: SUMMARY mATISIICS AND DESCRWITVE EQUATIONS M)R THE 20 ANALW'ES TESlED IN THE COLLABORATIVE SrUDY Finished Drinkina Water

Reagent Water Analyte

Uranium

Vanadium

Zinc

-

Xb

C

S,

S,

0.80 1.20 20.10 28.10 80.30 100.00

0.86 1.10 21.38 28.36 82.47 103.49

0.05 0.11 0.99 1.10 4.03 5.24

0.08

32.00 40.00 80.00 96.00 160.00 200.00

31.02 38.54 79.14 93.47 162.43 208.20

2.68 2.94 4.94 3.85 5.67 2.65

2.19

8.33 8.00 15.49 12.00 56.00 56.07 85.53 80.00 160.00 165.17 200.00 207.27

2.56 4.18 2.91 5.81 7.78 14.61

0.82

Regr. Equations

2 = 1.026c- 0.02 S, = 0.0485 + 0.02 S, = 0.027X + 0.05

2.16

4.29

X = 1.025C - 2.21 s, = 3.794 S, = 3.26'

3.30

1.78 2.47 9.87

2 = 1.042c + 0.87 S, = 0.0415 + 2.60 S, = 0.030X + 1.42

-

X

S,

S,

0.09

0.85 1.05 22.30 28.89 80.31 100.70

0.15 0.13 1.40 1.47 2.00 5.30

33.15 40.20 77.83 96.32 161.89 214.91

2.51 1.88 4.18 1.34 7.63 5.89

2.28

11.60 10.21 56.83 82.88 156.69 191.59

6.18 4.96 7.66 8.34 17.01 17.21

5.72

' Tme Value for the concentration added (pglL) Mean Recovery (pg/L)

' COD, < 0.5 - Use of regression equation outside study concentration range not recommended ' COD. < 0 - Mean precision is reported. ' COD. < 0 - Unweighted linear regression equation presented.

0.46

Ground Water

-

X

Rcgr. Equations

xs,

= 1.026c- 0.04 = 0.0445 + 0.11 S, = 0.022X 0.07

+

2.71

s, 2.75

S.

= 1.022c- 0.30 = 0.0233 1.45 = 0.023X 1.38

+ +

6.56

4.56 9.48

2 = 0.943c + 2.54 S, = O.O48_X+ 5.27 S, = 0.004X + 5.66'

S,

S,

0.84 1.10 21.56 29.86 85.01 106.47

0.23 0.14 1.11 1.83 3.76 3.74

33.25 40.34 84.42 98.70 170.94 217.90

3.83 3.08 3.97 5.03 9.09 11.36

7.29 12.66 54.86 78.62 150.12 184.37

1.12 3.24 5.12 8.56 12.52 16.59

Regr.Equ.tiona

0.19 1.08

2 = 1.058c- 0.06

S, = 0.0395 + 0.17 S, = 0.028X + 0.16

2.00

1.87

? = 1.076c- 1.87

2.93

S, = 0.0333 2.25 S, = 0.049X 0.09

+ -

115 5

2.20 7.24 10.84

2 = 0.962c + 0.07 S, = 0.0935 + 0.92 S, = 0.069X + 1.55

144

Methods for the Determination

TABLE 13: BACKGROUND A N D SPIKE MEASUREMENTS IN WASTEWATER DIGESTATE'

Backaround Conc.

C o n c m h

Std Dev Spike

A&b!LurrlLL!QLL

Found

Std Dev

%Rec

~-_._ILPncwltrate2

RSD Spike

u€L!llcsll4h24Lu!alL

Found

Sld Dcv %Rec

4h

LLslluLIlL

RSD RSD,

4h%

0.0

100

94 5 11.8

94.5

12.5

125

118.1

14.7

94.5

12.4

3.5

A1

78.2 12.4

200

260.9 41.2

91.4

15.8

250

309.1

48.5

92.4

15.7

2.7

Cr

19.5

8.1

200

222.2 23.3

101.4 10.5

250

274.3

26.6 101.9

9.7

2.0

V

1.9

2.8

250

271.8 36.5

108.0 13.4

200

219.3

30.1 108.7

13.7

2.6

296.6 24.7

125

419.0 35.7

97.9

8.5

100

397.4

34.8 100.8

8.8

1.o

125

124.7 12.3

97.8

9.9

101

100.7

9.4

97.2

9.3

2.8

3.0

100

142.7

5.6

95.4

3.9

2.1

15.4

2.2

7.0

1.8

Be

Mn co

0.0

2.5

0.4

Ni

47.3

5.0

125

161.7

cu

77.4 13.2

125

194.5 29.5

93.7 15.2

100

172.3

26.6 94.9

Zn

77.4

4.9

200

257.4 16.3

90.0

6.3

250

302.5

21.1

As

0.8

1.1

200

194.9

8.0

97.1

4.1

25 0

244.7

12.8 97.6

6.0

200

194.3

4.9

91.5

9.3

90.0

5.2

3.4

94.9

4.8

3.8

4.5

6.2

250

236.8 14.2

92.9

Mo

166.1

9.4

100

269.8 19 0

103.7

7.0

125

302.0

18.0 108.7

6.0

1.5

AQ

0.6

0.7

200

176.0 14.6

87.7

8.3

250

214.6

17.8

85.6

8.3

2.3

Cd

2.7

1.1

125

117.0

4.8

91.4

4.1

100

96.6

3.2

93.9

3.3

2.9

Sb

3.3

0.2

100

100.2

4.8

96.9

4.8

125

125.9

4.3

98.1

3.4

1.8

Ba

68.6

3.3

250

321.0 19.4 101.0

6.0

200

279.3

17.2 105.4

6.2

2.5

0.1

0.1

100

103.3

103.2

7.7

125

129.2

8.9 103.3

6.9

2.1

6.3 103.4

5.7

1.8

Se

TI

8.0

Pb

6.9

0.5

125

135.1

5.8

100

110.3

Th

0.1

0.1

125

140.2 19.5 112.1 13.9

100

113.3

15.4 113.2

13.6

2.7

U

0.4

0.2

125

141.2 19.3

100

113.6

16.0 113.2

14.1

2.5

7.8 102.6

112.6 13.7

Results from 10 participating laboratories. Wastewater digestate supplied with the study materials. Mean background concentrations determined by the participants.

Revision 5 . 4

Nay 1994

-

Metals

145

TABLE 14: SPIKE MEASUREMENTS IN PARTICIPANT'S WASTEWATER'

Splke

lloLL

Found Std Dev

UaLLaLL

%Rec

4h

Conc.e.mate 2 RSD Splke

2%

Found Std Dev

UalllLSll

1LalL_

RSD

RSD,

2LJ.L

LI?L

%Rec

Be

101

103.4

12.0

103.4

11.6

125

128.2

13.6

102.6

10.6

2.4

Al

200

198.7

23.9

99.4

12.0

250

252.4

15.5

101.0

6.1

2.9

Cr

200

205.4

12.3

102.7

6.0

250

253.4

15.4

101.4

6.1

1.1

V

250

246.5

4.4

98.6

1.8

200

196.8

2.8

98.4

1.4

2.0

Mn

125

119.0

5.4

95.2

4.5

100

95.5

4.3

95.5

4.5

0.8

co

125

125.8

7.0

100.6

5.6

101

99.5

5.3

98.5

5.3

1.8

Ni

125

127.4

9.7

101.9

7.6

100

101.0

7.5

101.0

7.4

1.7

cu

125

126.8

5.3

101.4

4.2

100

105.3

3.6

105.3

3.4

2.8

Zn

200

201.4

36.7

100.7

18.2

250

246.4

29.7

98.6

12.1

2.6

AS

200

207.3

11.9

103.7

5.7

250

263.0

2.6

105.2

1.0

3.2

Se

250

256.8

26.4

102.7

10.3

200

214.

18.7

107.3

8.7

3.6

Mo

100

98.6

4.6

98.6

4.7

125

123.2

6.7

98.6

5.4

2.2

Ag

200

200.7

48.9

100.4

24.4

250

231.2

63.5

92.5

27.5

8.2

Cd

125

123.2

11.5

98.6

9.3

100

95.8

2.9

95.8

3.0

5.8

Sb

100

92.2

4.4

92.2

4.8

125

119.0

1.o

95.2

0.8

2.8

Ba

250

245.2

12.8

98.1

5.2

200

204.7

12.1

102.4

5.9

2.1

TI

100

100.0

0.9

100.0

0.9

125

128.0

6.0

102.4

4.7

3.5

Pb

125

125.8

5.1

100.6

4.1

100

100.8

2.7

100.8

2.7

2.2

Th

125

124.2

7.6

99.4

6.1

100

99.8

5.7

99.8

5.7

3.2

U

125

130.4

10.3

104.3

7.9

100

106.4

6.8

106.4

6.4

2.3

'Results from 5 participating laboratories. Mean concentrations before spiking are not listed because they varied considerably among the different wastewaters.

Revision 5 . 4 May 1994

146

Methods for the Determination

METHOD 200.9 DETERMINATION OF TRACE ELEMENTS BY STABILIZED TEMPERATURE GRAPHITE FURNACE ATOMIC ABSORPTION

Revision 2.2 EMMC V e r s i o n

J . T . Creed, T.D. Martin, L.B.

Lobring, and J.W. O’Dell

- Method 200.9,

Revision 1.2 (1991) J . T . Creed,

T.D. Martin, and J.W. O’Dell - Method 200.9, Revision 2.2 (1994)

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

Metals

147

METHOD 200.9 DETERMINATION OF TRACE ELEMENTS BY STABILIZED TEMPERATURE GRAPHITE FURNACE ATOMIC ABSORPTION

1.0

SCOPE AND APPLICATION

1.1

T h i s method' p r o v i d e s procedures f o r t h e d e t e r m i n a t i o n o f d i s s o l v e d and t o t a l r e c o v e r a b l e elements by g r a p h i t e f u r n a c e a t o m i c a b s o r p t i o n (GFAA) i n ground w a t e r , s u r f a c e w a t e r , d r i n k i n g w a t e r , s t o r m r u n o f f , i n d u s t r i a l and domestic wastewater. T h i s method i s a l s o a p p l i c a b l e t o t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e elements i n sediment, sludges, and s o i l . T h i s method i s a p p l i c a b l e t o t h e f o l l o w i n g analytes :

Anal y t e

A1 umi num Ant imony Arsenic B e r y l 1 ium Cadmi um Chromi um Cobalt Copper Iron Lead Manganese Nickel Sel e n i um Silver Thal 1 ium Tin

Chemical A b s t r a c t S e r v i c e s R e g i s t r y Numbers (CASRN)

7429-90-5 7440-36-0 7440-38-2 7440-41-7 7440-43-9 7440-47-3 7440-48-4 7440-50-8 7439-89-6 7439-92-1 7439-96-5 7440-02-0 7782-49-2 7440-22-4 7440-28-0 7440-3 1-5

1.2

F o r r e f e r e n c e where t h i s method i s approved f o r use i n compliance m o n i t o r i n g programs [e.g., Clean Water A c t (NPDES) o r Safe D r i n k i n g Water A c t (SDWA)] c o n s u l t b o t h t h e a p p r o p r i a t e s e c t i o n s o f t h e Code o f Federal R e g u l a t i o n ( 4 0 CFR P a r t 136 T a b l e 1B f o r NPDES, and P a r t 1 4 1 !j 141.23 f o r d r i n k i n g w a t e r ) , and t h e l a t e s t Federal R e g i s t e r announcements.

1.3

D i s s o l v e d a n a l y t e s can be determined i n aqueous samples a f t e r s u i t a b l e f i l t r a t i o n and a c i d p r e s e r v a t i o n .

1.4

W i t h t h e e x c e p t i o n o f s i l v e r , where t h i s method i s approved f o r t h e d e t e r m i n a t i o n o f c e r t a i n m e t a l and m e t a l l o i d contaminants i n d r i n k i n g w a t e r , samples may be analyzed by d i r e c t i n j e c t i o n i n t o t h e f u r n a c e w i t h o u t a c i d d i g e s t i o n i f t h e sample has been p r o p e r l y Revision 2.2 May 1994

148

Methods for the Determination p r e s e r v e d w i t h a c i d , has t u r b i d i t y o f < 1 NTU a t t h e t i m e o f a n a l y s i s , and i s analyzed u s i n g t h e a p p r o p r i a t e method m a t r i x modifiers. T h i s t o t a l r e c o v e r a b l e d e t e r m i n a t i o n procedure i s r e f e r r e d t o as " d i r e c t a n a l y s i s " . However, i n t h e d e t e r m i n a t i o n o f some p r i m a r y d r i n k i n g w a t e r m e t a l contaminants, such as a r s e n i c and t h a l l i u m p r e c o n c e n t r a t i o n o f t h e sample may be r e q u i r e d p r i o r t o a n a l y s i s i n o r d e r t o meet d r i n k i n g w a t e r acceptance performance c r i t e r i a (Sect. 1 0 . 5 ) . 1.5

For t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e a n a l y t e s i n aqueous and s o l i d samples a d i g e s t i o n / e x t r a c t i o n i s r e q u i r e d p r i o r t o a n a l y s i s when t h e elements a r e n o t i n s o l u t i o n (e.g., s o i l s , sludges, sediments and aqueous samples t h a t may c o n t a i n p a r t i c u l a t e and suspended s o l i d s ) . Aqueous samples c o n t a i n i n g suspended o r p a r t i c u l a t e m a t e r i a l 2 1% (w/v) s h o u l d be e x t r a c t e d as a s o l i d t y p e sampl e .

1.6

S i l v e r i s o n l y s l i g h t l y s o l u b l e i s t h e presence o f c h l o r i d e u n l e s s t h e r e i s a s u f f i c i e n t c h l o r i d e c o n c e n t r a t i o n t o form t h e s o l u b l e c h l o r i d e complex. T h e r e f o r e , l o w r e c o v e r i e s o f s i l v e r may o c c u r i n samples, f o r t i f i e d sample m a t r i c e s and even f o r t i f i e d b l a n k s i f d e t e r m i n e d as a d i s s o l v e d a n a l y t e o r by " d i r e c t a n a l y s i s " where t h e sample has n o t been processed u s i n g t h e t o t a l r e c o v e r a b l e d i g e s t i o n . For t h i s reason i t i s recommended t h a t samples be d i g e s t e d p r i o r t o t h e d e t e r m i n a t i o n o f s i l v e r . The t o t a l r e c o v e r a b l e sample d i g e s t i o n procedure g i v e n i n t h i s method i s s u i t a b l e f o r t h e d e t e r m i n a t i o n o f s i l v e r i n aqueous samples c o n t a i n i n g c o n c e n t r a t i o n s up t o 0 . 1 mg/L. For t h e a n a l y s i s o f wastewater samples c o n t a i n i n g h i g h e r c o n c e n t r a t i o n s o f s i l v e r , succeeding s m a l l e r volume, w e l l mixed a l i q u o t s s h o u l d be p r e p a r e d u n t i l t h e a n a l y s i s s o l u t i o n c o n t a i n s < 0.1 mg/L s i l v e r . The e x t r a c t i o n o f s o l i d samples c o n t a i n i n g c o n c e n t r a t i o n s o f s i l v e r > 50 mg/kg s h o u l d be t r e a t e d i n a s i m i l a r manner.

1.7

Method d e t e c t i o n l i m i t s and i n s t r u m e n t o p e r a t i n g c o n d i t i o n s f o r t h e a p p l i c a b l e elements a r e l i s t e d i n T a b l e 2. These a r e i n t e n d e d as a g u i d e and a r e t y p i c a l o f a system o p t i m i z e d f o r t h e element employing commercial i n s t r u m e n t a t i o n . However, a c t u a l method d e t e c t i o n l i m i t s and l i n e a r w o r k i n g ranges w i l l be dependent on t h e sample m a t r i x , i n s t r u m e n t a t i o n and s e l e c t e d o p e r a t i n g c o n d i t i o n s .

1.8

The s e n s i t i v i t y and l i m i t e d l i n e a r dynamic range (LDR) o f GFAA o f t e n i m p l i e s t h e need t o d i l u t e a sample p r i o r t o a n a l y s i s . The a c t u a l magnitude o f t h e d i l u t i o n as w e l l as t h e c l e a n l i n e s s o f t h e labware used t o p e r f o r m t h e d i l u t i o n can d r a m a t i c a l l y i n f l u e n c e t h e q u a l i t y o f t h e a n a l y t i c a l r e s u l t s . T h e r e f o r e , samples t y p e s r e q u i r i n g l a r g e d i l u t i o n s (>50:1) s h o u l d be analyzed by an a n o t h e r approved t e s t procedure w h i c h has a l a r g e r LDR o r which i s i n h e r e n t l y l e s s s e n s i t i v e t h a n GFAA.

1.9

Users o f t h e method d a t a s h o u l d s t a t e t h e d a t a - q u a l i t y o b j e c t i v e s p r i o r t o a n a l y s i s . Users o f t h e method must document and have on f i l e t h e r e q u i r e d i n i t i a l d e m o n s t r a t i o n performance d a t a d e s c r i b e d i n S e c t i o n 9 . 2 p r i o r t o u s i n g t h e method f o r a n a l y s i s . Revision 2.2 Hay 1994

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OF METHOD

2.1

An aliquot of a well mixed, homogeneous aqueous or solid sample is accurately weighed or measured for sample processing. For total recoverable analysis of a solid or an aqueous sample containing undissolved material, analytes are first solubilized by gentle refluxing with nitric and hydrochloric acids. After cooling, the sample is made up to volume, is mixed and centrifuged or allowed to settle overnight prior to analysis. For the determination of dissolved analytes in a filtered aqueous sample aliquot, or for the "direct analysis" total recoverable determination of analytes where sample turbidity i s < 1 NTU, the sample is made ready for analysis by the appropriate addition of nitric acid, and then diluted to a predetermined volume and mixed before analysis.

2.2

The analytes listed in this method are determined by stabilized temperature platform graphite furnace atomic absorption (STPGFAA). In STPGFAA, the sample and the matrix modifier are first pipetted onto the platform or a device which provides delayed atomization. The furnace chamber is then purged with a continuous flow of a premixed gas (95% argon - 5% hydrogen) and the sample is dried at a relatively low temperature (about 120°C) to avoid spattering. Once dried, the sample is pretreated in a char or ashing step which is designed to minimize the interference effects caused by the concomitant sample matrix. After the char step the furnace is allowed to cool prior to atomization. The atomization cycle is characterized by rapid heating of the furnace to a temperature where the metal (analyte) is atomized from the pyrolytic graphite surface into a stopped gas flow atmosphere of argon containing 5% hydrogen. (Only selenium is determined in an atmosphere of high purity argon.) The resulting atomic cloud absorbs the element specific atomic emission produced by a hollow cathode lamp (HCL) or an electrodeless discharge lamp (EDL). Following analysis the furnace is subjected to a cleanout period of high temperature and continuous argon flow. Because the resulting absorbance usually has a nonspecific component associated with the actual analyte absorbance, an instrumental background correction device is required to subtract from the total signal the component which is nonspecific to the analyte. In the absence of interferences, the background corrected absorbance is directly related to the concentration of the analyte. Interferences relating to STPGFAA (Section 4 . 0 ) must be recognized and corrected. Suppressions or enhancements of instrument response caused by the sample matrix must be corrected by the method of standard addition (Section 1 1 . 5 ) .

DEFINITIONS 3.1

Calibration Blank - A volume of reagent water acidified with the same acid matrix as in the calibration standards. The calibration blank is a zero standard and is used to auto-zero the AA instrument (Sect. 7 . 1 0 . 1 ) .

3.2

Calibration Standard (CAL) - A solution prepared from the dilution of stock standard solutions. The CAL solutions are used to Revision 2.2 May 1994

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response

with

respect

to

analyte

3.3

D i s s o l v e d A n a l y t e - The c o n c e n t r a t i o n o f a n a l y t e i n an aqueous sample t h a t w i l l pass t h r o u g h a 0.45-pm membrane f i l t e r assembly p r i o r t o sample a c i d i f i c a t i o n ( S e c t . 1 1 . 1 ) .

3.4

F i e l d Reagent B l a n k (FRB) - An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i x t h a t i s p l a c e d i n a sample c o n t a i n e r i n t h e l a b o r a t o r y and t r e a t e d as a sample i n a l l r e s p e c t s , i n c l u d i n g shipment t o t h e sampling s i t e , exposure t o t h e sampling s i t e c o n d i t i o n s , s t o r a g e , p r e s e r v a t i o n , and a l l a n a l y t i c a l procedures. The purpose o f t h e FRB i s t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e f i e l d environment ( S e c t 8 . 5 ) .

3.5

I n s t r u m e n t D e t e c t i o n L i m i t (IDL) - The c o n c e n t r a t i o n e q u i v a l e n t t o t h e a n a l y t e s i g n a l w h i c h i s equal t o t h r e e t i m e s t h e s t a n d a r d d e v i a t i o n o f a s e r i e s o f t e n r e p l i c a t e measurements o f t h e c a l i b r a t i o n b l a n k s i g n a l a t t h e same wavelength.

3.6

I n s t r u m e n t Performance Check ( I P C ) S o l u t i o n - A s o l u t i o n o f method a n a l y t e s , used t o e v a l u a t e t h e performance o f t h e i n s t r u m e n t system w i t h r e s p e c t t o a d e f i n e d s e t o f method c r i t e r i a ( S e c t s . 7.11 & 9.3.4).

3.7

L a b o r a t o r y D u p l i c a t e s (LD1 and LD2) - Two a l i q u o t s o f t h e same sample t a k e n i n t h e l a b o r a t o r y and analyzed s e p a r a t e l y w i t h i d e n t i c a l procedures. Analyses o f LD1 and LD2 i n d i c a t e s p r e c i s i o n a s s o c i a t e d w i t h 1 a b o r a t o r y procedures, b u t n o t w i t h sample c o l l e c t i o n , p r e s e r v a t i o n , o r s t o r a g e procedures.

3.8

L a b o r a t o r y F o r t i f i e d B l a n k (LFB) - An a l i q u o t o f LRB t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB i s a n a l y z e d e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e methodology i s i n c o n t r o l and whether t h e 1 a b o r a t o r y i s capable o f making a c c u r a t e and p r e c i s e measurements ( S e c t s . 7.10.3 & 9 . 3 . 2 ) .

3.9

L a b o r a t o r y F o r t i f i e d Sample M a t r i x (LFM) - An a l i q u o t o f an e n v i r o n m e n t a l sample t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFM i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e sample m a t r i x c o n t r i b u t e s b i a s t o t h e a n a l y t i c a l r e s u l t s . The background c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be determined i n a s e p a r a t e a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s ( S e c t . 9 . 4 ) .

3.10

L a b o r a t o r y Reagent B l a n k (LRB) - An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a l l glassware, equipment, s o l v e n t s , r e a g e n t s , and i n t e r n a l standards t h a t a r e used w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e 1a b o r a t o r y environment, r e a g e n t s , o r apparatus ( S e c t s . 7.10.2 & 9 . 3 . 1 ) . Revision 2.2 Ray 1994

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3.11

Linear Dynamic Range (LDR) - The concentration range over which the instrument response t o an analyte is linear (Sect. 9.2.2).

3.12

Matrix Modifier - A substance added to the graphite furnace along with the sample in order to minimize the interference effects by selective volatilization of either analyte or matrix components.

3.13

Method Detection Limit (MDL) - The minimum concentration of an analyte that can be identified, measured, and reported with 99% confidence that the analyte concentration is greater than zero (Sect. 9.2.4 and Table 2 ) .

3.14

Quality Control Sample (QCS) - A solution of method analytes of known concentrations which is used to fortify an aliquot of LRB or sample matrix. The QCS is obtained from a source external to the laboratory and different from the source of calibration standards. It i s used to check either laboratory or instrument performance (Sects. 7.12 & 9 . 2 . 3 ) .

3.15

Solid Sample - For the purpose of this method, a sample taken from material classified as either soil, sediment or sludge.

3.16

Standard Addition - The addition of a known amount of analyte to the sample in order to determine the relative response of the detector to an analyte within the sample matrix. The relative response is then used to assess either an operative matrix effect or the sample analyte concentration (Sects. 9 . 5 . 1 & 11.5).

3.17

Stock Standard Solution - A concentrated solution containing one or more method analytes prepared in the laboratory using assayed reference materials or purchased from a reputable commercial source (Sect. 7.8).

3.18

Total Recoverable Analyte - The concentration of analyte determined to be in either a solid sample or an unfiltered aqueous sample following treatment by refluxing with hot dilute mineral acid(s) as specified in the method (Sects. 11.2 & 11.3).

3.19

Water Sample - For the purpose of this method, a sample taken from one of the following sources: drinking, surface, ground, storm runoff, industrial or domestic wastewater.

INTERFERENCES 4.1

Several interference sources may cause inaccuracies in the determination of trace elements by GFAA. These interferences can be classified into three major subdivisions, namely spectral, matrix, and memory.

4.2

Spectral interferences are caused by the resulting absorbance of light by a molecule or atom which is not the analyte of interest or emission from black body radiation. 4 . 2 . 1 Spectral interferences caused by an element only occur if

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Methods for the Determination there is a spectral overlap between the wavelength of the interfering element and the analyte of interest. Fortunately, this type of interference is relatively uncommon in STPGFAA because of the narrow atomic line widths associated with In addition, the use of appropriate furnace STPGFAA. temperature programs and high spectral purity lamps as light sources can minimize the possibility of this type o f interference. However, mol ecul ar absorbances can span several hundred nanometers producing broadband spectral interferences. This type of interference is far more common in STPGFAA. The use of matrix modifiers, selective volatilization, and background correctors are all attempts to eliminate unwanted nonspecific absorbance. The nonspecific component of the total absorbance can vary considerably from sample type to sample type. Therefore, the effectiveness of a particular background correction device may vary depending on the actual analyte wavelength used as well as the nature and magnitude o f the interference. The background correction device to be used with this method is not specified, however, it must provide an analytical condition that is not subject to the occurring interelement spectral interferences of palladium on copper, iron on selenium, and aluminum on arsenic. 4.2.2 Spectral interferences are also caused by the emissions from black body radiation produced during the atomization furnace cycle. This black body emission reaches the photomultiplier tube, producing erroneous results. The magnitude of this interference can be minimized by proper furnace tube a1 ignment and monochromator design. In addition, atomization temperatures which adequately volatilize the analyte of interest without producing unnecessary black body radiation can he1 p reduce unwanted background emission during analysis. 4.3

Matrix interferences are caused by sample components which inhibit the formation of free atomic analyte atoms during the atomization CYC e. 4.3 1 Matrix interferences can be of a chemical or physical nature. In this method the use of a delayed atomization device which provides stabilized temperatures is required. These devices provide an environment which is more conducive to the formation of free analyte atoms and thereby minimize this type of interference. This type of interference can be detected by analyzing the sample plus a sample aliquot fortified with a known concentration of the analyte. If the determined concentration of the analyte addition is outside a designated range, a possible matrix effect should be suspected (Sect. 9.4.3). 4.3.2 The use o f nitric acid is preferred for GFAA analyses in order to minimize vapor state anionic chemical interferences, however, in this method hydrochloric acid is required to maintain stability in solutions containing antimony and silver. When hydrochloric acid is used, the chloride ion

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vapor state interferences must be reduced using an appropriate matrix modifier. In this method a combination modifier of palladium, magnesium nitrate and a hydrogen(5%)-argon(95%) gas mixture is used for this purpose. The effects and benefits of using this modifier are discussed in detail in reference 2 . of Section 16.0. Listed in Section 4 . 4 are some typical observed effects when using this modifier. 4. 4

Specific Element Interferences Antimyy: Antimony suffers from an interference produced by K2S0,. In the absence of hydrogen in the char cycle (13OO0C), K SO, produces a relatively high ( 1 . 2 abs) background absorbance which can produce a false signal, even with Zeeman background correction. However, this background level can be dramatically reduced ( 0 . 1 abs) by the use of a hydrogenlargon gas mixture in the char step. This reduction in background is strongly influenced by the temperature of the char step. NOTE: The actual furnace temperature may vary from instrument t o instrument. Therefore, the actual furnace

temperataure should be determined on an individual basi s . Aluminum: The palladium matrix modifier may have elevated levels of A1 which will cause elevated blank absorbances. Arsenic: The HC1 present from the digestion procedure can influence the sensitivity for A s . 20 pL of a 1%HC1 solution with Pd used as a modifier results in a 20% loss in sensitivity relative to the analyte in a 1% HNO, solution. Unfortunately, the use of Pd/Mg/H? as a modifier does not significantly reduce this suppression, and therefore, it is imperative that each sample and calibration standard a1 i ke contain the same HC1 concentration. 2 Cadmium: The HC1 present from the digestion procedure can influence the sensitivity for Cd. 20 pL of a 1% HC1 solution with Pd used as a modifier results in a 80% loss in sensitivity relative t o the analyte in a’ 1% HNO, solution. The use of Pd/Mg/H, as a matrix modifier reduces this suppression to less than lo%., Lead: The HC1 present from the digestion procedure can influence the sensitivity for Pb. 20 pL of a 1% HC1 solution with Pd used as a modifier results in a 75% loss in sensitivity relative to the analyte response in a 1% HNO, solution. The use o f Pd/Mg/H, as2a matrix modifier reduces this suppression to less than 10%. Selenium: Iron has been shown :t suppress Se response with continuum background correction. In addition, the use of hydrogen as a purge gas during the dry and char steps can cause a suppression in Se response if not purged from the Revision 2.2 Hay

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Methods for the Determination furnace p r i o r t o atomization. S i l v e r : The p a l l a d i u m used i n t h e m o d i f i e r p r e p a r a t i o n may have e l e v a t e d l e v e l s o f Ag w h i c h w i l l cause e l e v a t e d b l a n k absorbances. T h a l l i u m : The HC1 p r e s e n t f r o m t h e d i g e s t i o n procedure can i n f l u e n c e t h e s e n s i t i v i t y f o r T1. 20 pL o f a 1% HC1 s o l u t i o n w i t h Pd used as a m o d i f i e r r e s u l t s i n a 90% l o s s i n s e n s i t i v i t y r e l a t i v e t o t h e a n a l y t e i n a 1% HNO, s o l u t i o n . The use o f Pd/Mg/H, as a m a t r i x m o d i f i e r reduces t h i s s u p p r e s s i o n . t o l e s s t h a n lo%.'

4.5

5.0

Memory i n t e r f e r e n c e s r e s u l t f r o m a n a l y z i n g a sample c o n t a i n i n g a h i g h c o n c e n t r a t i o n o f an element ( t y p i c a l l y a h i g h a t o m i z a t i o n t e m p e r a t u r e element) which cannot be removed q u a n t i t a t i v e l y i n one complete s e t o f f u r n a c e s t e p s . The a n a l y t e which remains i n t h e f u r n a c e can produce f a l s e p o s i t i v e s i g n a l s on subsequent sample(s). Therefore, t h e analyst should e s t a b l i s h t h e analyte concentration which can be i n j e c t e d i n t o t h e f u r n a c e and adequately removed i n one complete s e t o f f u r n a c e c y c l e s . I f t h i s c o n c e n t r a t i o n i s exceeded, t h e sample s h o u l d be d i l u t e d and a b l a n k analyzed t o assure t h e memory e f f e c t has been e l i m i n a t e d b e f o r e r e a n a l y z i n g t h e d i l u t e d sample.

SAFETY

5.1

The t o x i c i t y o r c a r c i n o g e n i c i t y o f each r e a g e n t used i n t h i s method have n o t been f u l l y e s t a b l i s h e d . Each chemical s h o u l d be regarded as a p o t e n t i a l h e a l t h hazard and exposure t o t h e s e compounds should be as l o w as r e a s o n a b l y a c h i e v a b l e . Each l a b o r a t o r y i s r e s p o n s i b l e f o r m a i n t a i n i n g a c u r r e n t awareness f i l e o f OSHA r e g u l a t i o n s r e g a r d i r 9 t h e safe handling o f t h e chemicals s p e c i f i e d i n t h i s method. A r e f e r e n c e f i l e o f m a t e r i a l d a t a h a n d l i n g sheets should a l s o be made a v a i l a b l e t o a l l personnel i n v o l v e d i n t h e chemical a n a l y s i s . S p e c i f i c a l l y , c o n c e n t r a t e d n i t r i c and h y d r o c h l o r i c a c i d s p r e s e n t v a r i o u s hazards and a r e m o d e r a t e l y t o x i c and e x t r e m e l y i r r i t a t i n g t o s k i n and mucus membranes. Use t h e s e r e a g e n t s i n a fume hood whenever p o s s i b l e and i f eye o r s k i n c o n t a c t occurs, f l u s h w i t h l a r g e volumes o f w a t e r . Always wear s a f e t y g l a s s e s o r a s h i e l d f o r eye p r o t e c t i o n , p r o t e c t i v e c l o t h i n g and observe p r o p e r m i x i n g when w o r k i n g w i t h t h e s e r e a g e n t s .

5.2

The a c i d i f i c a t i o n o f samples c o n t a i n i n g r e a c t i v e m a t e r i a l s may r e s u l t i n t h e r e l e a s e o f t o x i c gases, such as c y a n i d e s o r s u l f i d e s . A c i d i f i c a t i o n o f samples s h o u l d be done i n a fume hood.

5.3

A l l personnel h a n d l i n g e n v i r o n m e n t a l samples known t o c o n t a i n o r t o have been i n c o n t a c t w i t h human waste s h o u l d be immunized a g a i n s t known d i s e a s e c a u s a t i v e agents.

5.4

The g r a p h i t e t u b e d u r i n g a t o m i z a t i o n e m i t s i n t e n s e UV r a d i a t i o n . S u i t a b l e p r e c a u t i o n s s h o u l d be t a k e n t o p r o t e c t personnel f r o m such a hazard. Revision 2.2 May 1994

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5.5

The use o f t h e argonlhydrogen gas m i x t u r e d u r i n g t h e d r y and c h a r Therefore, steps may e v o l v e a c o n s i d e r a b l e amount o f HC1 gas. adequate v e n t i l a t i o n i s r e q u i r e d .

5.6

I t i s t h e r e s p o n s i b i l i t y o f t h e u s e r o f t h i s method t o comply w i t h r e l e v a n t d i s p o s a l and waste r e g u l a t i o n s . F o r guidance see S e c t i o n s 14.0 and 15.0.

EOUIPMENT AND SUPPLIES 6.1

G r a p h i t e Furnace Atomic Absorbance Spectrophotometer 6 . 1 . 1 The GFAA s p e c t r o m e t e r must be capable o f programmed h e a t i n g o f t h e g r a p h i t e t u b e and t h e a s s o c i a t e d d e l a y e d a t o m i z a t i o n device. The i n s t r u m e n t must be equipped w i t h an adequate background c o r r e c t i o n d e v i c e capable o f removing u n d e s i r a b l e n o n - s p e c i f i c absorbance o v e r t h e s p e c t r a l r e g i o n o f i n t e r e s t and p r o v i d e an a n a l y t i c a l c o n d i t i o n n o t s u b j e c t t o t h e occurrence o f interelement spectral overlap interferences. The f u r n a c e d e v i c e must be capable o f u t i l i z i n g an a l t e r n a t e gas s u p p l y d u r i n g s p e c i f i e d c y c l e s o f t h e a n a l y s i s . The c a p a b i l i t y t o record r e l a t i v e l y f a s t (< 1 s) transient signals In and e v a l u a t e d a t a on a peak area b a s i s i s p r e f e r r e d . a d d i t i o n , a r e c i r c u l a t i n g r e f r i g e r a t i o n b a t h i s recommended f o r improved r e p r o d u c i b i l i t y o f f u r n a c e temperatures. 6 . 1 . 2 S i n g l e element h o l l o w cathode lamps o r s i n g l e element e l e c t r o d e l e s s d i s c h a r g e lamps a l o n g w i t h t h e a s s o c i a t e d power suppl ies

.

6 . 1 . 3 Argon gas s u p p l y ( h i g h - p u r i t y grade, 99.99%) f o r use d u r i n g t h e a t o m i z a t i o n o f selenium, f o r s h e a t h i n g t h e f u r n a c e t u b e when i n o p e r a t i o n , and d u r i n g f u r n a c e c l e a n o u t . 6 . 1 . 4 A l t e r n a t e gas m i x t u r e (hydrogen 5% - argon 95%) f o r use as a c o n t i n u o u s gas f l o w environment d u r i n g t h e dry and c h a r furnace cycles. 6 . 1 . 5 Autosampler c a p a b l e o f a d d i n g m a t r i x m o d i f i e r s o l u t i o n s t o t h e f u r n a c e , a s i n g l e a d d i t i o n o f a n a l y t e , and c o m p l e t i n g methods o f s t a n d a r d a d d i t i o n s when r e q u i r e d .

6.2

A n a l y t i c a l balance, w i t h c a p a b i l i t y t o measure t o 0 . 1 mg, f o r use i n w e i g h i n g s o l i d s , f o r p r e p a r i n g standards, and f o r d e t e r n l i n i n g dissolved solids i n digests o r extracts.

6.3

A temperature a d j u s t a b l e h o t t e m p e r a t u r e o f 95OC.

6.4

A t e m p e r a t u r e a d j u s t a b l e b l o c k d i g e s t e r capable o f (optional) m a i n t a i n i n g a t e m p e r a t u r e o f 95'C and equipped w i t h 250-mL c o n s t r i c t e d d i g e s t i o n tubes.

p l a t e capable o f maintaining a

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6.5

(optional) A steel cabinet centrifuge with guard bowl, electric timer and brake.

6.6

A gravity convection drying oven with thermostatic control capable of maintaining 18OoC k 5°C.

6.7

(optional) An air displacement pipetter capable o f delivering volumes ranging from 100 to 2500 pL with an assortment of high quality disposable pipet tips.

6.8

Mortar and pestle, ceramic or nonmetallic material.

6.9

Polypropylene sieve, 5-mesh ( 4 mm opening).

6.10 Labware - All reusable labware (glass, quartz, polyethylene, PTFE, FEP, etc.) should be sufficiently clean for the task objectives. Several procedures found to provide clean 1 abware include washing with a detergent solution, rinsing with tap water, soaking for 4 h or more in 20% (v/v) nitric acid or a mixture of diluterN0, and HC1 ( 1 + 2 + 9 ) , rinsing with reagent water and storing clean. Ideally, ground glass surfaces should be avoided to eliminate a potential source of random contamination. When this is impractical, particular attention should be given to all ground glass surfaces during cleaning. Chromic acid cleaning solutions must be avoided because chromium is an analyte.

7.0

6.10.1

Glassware - Volumetric flasks, graduated cylinders, funnels and centrifuge tubes (glass and /or metal-free plastic).

6.10.2

Assorted calibrated pipettes.

6.10.3

Conical Phillips beakers, 250-mL with 50-mm watch gl asses.

6.10.4

Griffin beakers, 250-mL with 75-mm watch glasses and (optional) 75-mm ribbed watch glasses.

6.10.5

(optional) PTFE and/or quartz Griffin beakers, 250-mL with PTFE covers.

6. 0.6

Evaporating dishes or high-form crucibles, porcelain, 100 mL capacity.

6. 0.7

Narrow-mouth storage bottles, FEP (fluorinated ethylene propylene) with screw closure, 125-mL to l-L capacities.

6. 0.8

One-piece stem FEP wash bottle with screw closure, 125mL capacity.

REAGENTS AND STANDARDS

7.1

Reagents may contain elemental impurities which might affect analytical data. Only high-purity reagents that conform to the Revision 2.2 May 1994

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American Chemical S o c i e t y s p e c i f i c a t i o n s ' s h o u l d be used whenever possible. I f the p u r i t y o f a reagent i s i n question, analyze f o r c o n t a m i n a t i o n . A l l a c i d s used f o r t h i s method must be o f u l t r a h i g h - p u r i t y grade o r e q u i v a l e n t . S u i t a b l e a c i d s a r e a v a i l a b l e f r o m a number o f m a n u f a c t u r e r s . R e d i s t i l l e d a c i d s p r e p a r e d by subb o i l i n g d i s t i l l a t i o n are acceptable.

7.2

H y d r o c h l o r i c a c i d , c o n c e n t r a t e d ( s p . g r . 1.19) - HC1.

7.2.1 H y d r o c h l o r i c a c i d (ltl) - Add 500 mL c o n c e n t r a t e d HC1 t o 400 mL r e a g e n t w a t e r and d i l u t e t o 1 L. 7.2.2 H y d r o c h l o r i c a c i d (1t4) - Add 200 mL c o n c e n t r a t e d HC1 t o 400 mL r e a g e n t w a t e r and d i l u t e t o 1 L. 7.3

N i t r i c acid, concentrated (sp.gr.

1.41)

- HNO,.

- Add 500 mL c o n c e n t r a t e d HNO, r e a g e n t w a t e r and d i l u t e t o 1 L.

7.3.1 N i t r i c a c i d (ltl)

7.3.2 N i t r i c a c i d (1t5)

t o 400 mL

- Add

50 mL c o n c e n t r a t e d HNO, t o 250 mL

- Add

10 mL c o n c e n t r a t e d HNO, t o 90 mL

reagent water.

7.3.3 N i t r i c a c i d (1t9) reagent water.

7.4

Reagent w a t e r . A l l preferences t o w a t e r i n t h i s method r e f e r t o ASTM Type I grade w a t e r .

7.5

Ammonium h y d r o x i d e , c o n c e n t r a t e d ( s p . g r . 0.902).

7.6

T a r t a r i c a c i d , ACS r e a g e n t grade.

7.7

M a t r i x M o d i f i e r , d i s s o l v e 300 mg p a l l a d i u m (Pd) powder i n conc. HNO, adding 0.1 mL o f c o n c e n t r a t e d HC1 i f necessary). (1 mL o f HNO,, Pour t h e two D i s s o l v e 200 mg o f Mg(N0 ) i n ASTM Type I w a t e r . s o l u t i o n s t o g e t h e r and d i j u i e t o 100 mL w i t h ASTM Type I w a t e r .

NOTE: I t i s recommended t h a t t h e m a t r i x m o d i f i e r be analyzed s e p a r a t e l y i n o r d e r t o assess t h e c o n t r i b u t i o n o f t h e m o d i f i e r t o t h e absorbance o f c a l i b r a t i o n and r e a g e n t b l a n k s o l u t i o n s . 7.8

Standard s t o c k s o l u t i o n s may be purchased o r p r e p a r e d f r o m u l t r a h i g h p u r i t y grade c h e m i c a l s (99.99 t o 99.999% p u r e ) . A l l compounds must be d r i e d f o r 1 h a t 1 0 5 O C , u n l e s s o t h e r w i s e s p e c i f i e d . I t i s recommended t h a t s t o c k s o l u t i o n s be s t o r e d i n FEP b o t t l e s . Replace s t o c k standards when succeeding d i l u t i o n s f o r p r e p a r a t i o n o f c a l i b r a t i o n standards can n o t be v e r i f i e d . CAUTION:

Many o f t h e s e c h e m i c a l s a r e e x t r e m e l y t o x i c i f i n h a l e d o r swallowed ( S e c t . 5 . 1 ) . Wash hands t h o r o u g h l y a f t e r hand1 ing .

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Methods for the Determination T y p i c a l s t o c k s o l u t i o n p r e p a r a t i o n procedures f o l l o w f o r l - L q u a n t i t i e s , b u t f o r t h e purpose o f p o l l u t i o n p r e v e n t i o n , t h e a n a l y s t i s encouraged t o p r e p a r e s m a l l e r q u a n t i t i e s when p o s s i b l e . C o n c e n t r a t i o n s a r e c a l c u l a t e d based upon t h e w e i g h t o f t h e p u r e element o r upon t h e w e i g h t o f t h e compound m u l t i p l i e d by t h e f r a c t i o n o f t h e a n a l y t e i n t h e compound. From pure element, w e i g h t (mg) Concentration

=

volume ( L ) From pure compound, w e i g h t (mg) x g r a v i m e t r i c f a c t o r Concentration = volume ( L ) where : gravimetric factor

=

t h e weight f r a c t i o n o f t h e analyte i n t h e compound.

7.8.1

Aluminum s o l u t i o n , s t o c k , 1 mL = 1000 p g A l : D i s s o l v e 1.000 g o f aluminum m e t a l , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n an a c i d m i x t u r e o f 4.0 mL o f ( l t l ) HC1 and 1 . 0 mL o f c o n c e n t r a t e d HNO, i n a beaker. Warm beaker slowly t o e f f e c t solution. When d i s s o l u t i o n i s complete, t r a n s f e r s o l u t i o n q u a n t i t a t i v e l y t o a 1-L f l a s k , add an a d d i t i o n a l 10.0 mL o f ( l t l ) HC1 and d i l u t e t o volume w i t h reagent water.

7.8.2

Antimony s o l u t i o n , s t o c k , 1 m L = 1000 pg Sb: D i s s o l v e 1.000 g o f antimony powder, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 20.0 mL ( l t l ) HNO, and 10.0 mL c o n c e n t r a t e d HC1. Add 100 mL r e a g e n t w a t e r and 1.50 g t a r t a r i c acid. Warm s o l u t i o n s l i g h t l y t o e f f e c t complete d i s s o l u t i o n . Cool s o l u t i o n and add r e a g e n t w a t e r t o volume i n a l-L volumetric flask.

7.8.3

A r s e n i c s o l u t i o n , s t o c k , 1 mL = 1000 p g As: D i s s o l v e 1.320 g o f As,O (As f r a c t i o n = 0.7574), weighed a c c u r a t e l y t o a t l e a s t t o u r s i g n i f i c a n t f i g u r e s , i n 100 mL o f r e a g e n t w a t e r c o n t a i n i n g 10.0 mL c o n c e n t r a t e d NH,OH. Warm t h e s o l u t i o n g e n t l y t o e f f e c t d i s s o l u t i o n . A c i d i f y t h e s o l u t i o n w i t h 20.0 mL c o n c e n t r a t e d HNO, and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h reagent water.

7.8.4

B e r y l l i u m s o l u t i o n , s t o c k , 1 mL = 1000 p g Be: DO NOT DRY. D i s s o l v e 19.66 g BeS0,*4H20 (Be f r a c t i o n = 0.0509), weighed accurately t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n reagent Revision 2.2 Hay 1994

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w a t e r , add 1 0 . 0 mL c o n c e n t r a t e d HNO,, and d i l u t e t o volume i n a 1-L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r .

7.8.5

Cadmium s o l u t i o n , s t o c k , 1 mL = 1000 p g Cd: D i s s o l v e 1.000 g Cd m e t a l , a c i d cleaned w i t h ( 1 t 9 ) HNO,, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 50 mL ( l t l ) HNO w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e w i t h r e a g e n t w a t e r i n a l-L v o l u m e t r i c f l a s k .

7.8.6

Chromium s o l u t i o n , s t o c k , 1 mL = 1000 pg C r : D i s s o l v e 1.923 g CrO, ( C r f r a c t i o n = 0.5200), weighed a c c u r a t e l y t o a t l e a s t When s o l u t i o n f o u r s i g n i f i c a n t f i g u r e s , i n 120 mL (1+5) HNO,. i s complete, d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h reagent water.

7.8.7

C o b a l t s o l u t i o n , s t o c k , 1 mL = 1000 p g Co: D i s s o l v e 1 , 0 0 0 g Co m e t a l , a c i d c l e a n e d w i t h ( 1 t 9 ) HNO,, weighed a c c u r a t e l y t o Let a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 50.0 mL (1+1) HNO,. s o l u t i o n c o o l and d i l u t e t o volume i n a l-L v o l u m e t r i c f l a s k w i t h reagent water.

7.8.8

Copper s o l u t i o n , s t o c k , 1 mL = 1000 p g Cu: D i s s o l v e 1.000 g Cu m e t a l , a c i d c l e a n e d w i t h ( 1 t 9 ) HNO,, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 50.0 mL (1+1) HNO, w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e i n a l - L v o l u m e t r i i f l a s k w i t h reagent water.

7.8.9

I r o n s o l u t i o n , s t o c k , 1 mL = 1000 pg Fe: D i s s o l v e 1.000 g Fe m e t a l , a c i d c l e a n e d w i t h ( l t l ) HC1, weighed a c c u r a t e l y t o f o u r s i g n i f i c a n t f i g u r e s , i n 100 mL ( l t l ) HC1 w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e w i t h r e a g e n t water i n a l - L volumetric f l a s k .

7.8.10

Lead s o l u t i o n , s t o c k , 1 mL = 1000 b g Pb: D i s s o l v e 1.599 g Pb(N0,) (Pb f r a c t i o n = 0 . 6 2 5 6 ) , weighed a c c u r a t e l y t o a t l e a s t t o u r s i g n i f i c a n t f i g u r e s , i n a minimum amount o f ( 1 t 1 ) Add 20.0 mL ( l t l ) HNO, and d i l u t e t o volume i n a l - L HNO,. volumetric f l a s k w i t h reagent water.

7.8.11

Manganese s o l u t i o n , s t o c k , 1 mL = 1000 pg Mn: D i s s o l v e 1.000 g o f manganese m e t a l , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 50 mL ( l t l ) HNO, and d i l u t e t o volume i n a l-L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r .

7.8.12

N i c k e l s o l u t i o n , s t o c k , 1 mL = 1000 1-19 N i : D i s s o l v e 1.000 g o f n i c k e l m e t a l , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 20.0 mL h o t c o n c e n t r a t e d HNO, c o o l , and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h reagent water.

7.8.13

Selenium s o l u t i o n , s t o c k , 1 mL = 1000 pg Se: D i s s o l v e 1.405 g SeO,,(Se f r a c t i o n = 0 . 7 1 1 6 ) , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 200 mL r e a g e n t w a t e r and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r . Revision 2.2 Nay 1994

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Methods for the Determination

7.8.14 S i l v e r s o l u t i o n , s t o c k , 1 mL

= 1000 pg Ag: D i s s o l v e 1.000 g Ag m e t a l , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 80 mL ( l t l ) HNO, w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e w i t h r e a g e n t w a t e r i n a l - L v o l u m e t r i c f l a s k . S t o r e s o l u t i o n i n amber b o t t l e o r wrap b o t t l e c o m p l e t e l y w i t h aluminum f o i l t o p r o t e c t s o l u t i o n from l i g h t .

7.8.15 T h a l l i u m s o l u t i o n , s t o c k , 1 mL = 1000 p g T1: D i s s o l v e 1.303 g TlNO, (T1 f r a c t i o n = 0.7672), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n reagent water. Add 10.0 mL c o n c e n t r a t e d HNO, and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h reagent water.

7.8.16 T i n s o l u t i o n , s t o c k , 1 mL

= 1000 p g Sn: D i s s o l v e 1.000 g Sn s h o t , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n an a c i d m i x t u r e o f 10.0 mL c o n c e n t r a t e d HC1 and 2.0 mL (ltl) HNO, w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l , add 200 mL c o n c e n t r a t e d HC1, and d i l u t e t o volume i n a l-L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r .

7.9

P r e p a r a t i o n o f C a l i b r a t i o n Standards - Fresh c a l i b r a t i o n standards (CAL S o l u t i o n ) s h o u l d be p r e p a r e d e v e r y two weeks, o r as needed. D i l u t e each ofi t h e s t o c k s t a n d a r d s o l u t i o n s t o l e v e l s a p p r o p r i a t e t o t h e o p e r a t i n g range o f t h e i n s t r u m e n t u s i n g t h e a p p r o p r i a t e a c i d d i l u e n t (see n o t e ) . The element c o n c e n t r a t i o n s i n each CAL s o l u t i o n s h o u l d be s u f f i c i e n t l y h i g h t o produce good measurement p r e c i s i o n and t o a c c u r a t e l y d e f i n e t h e s l o p e o f t h e response c u r v e . The i n s t r u m e n t c a l i b r a t i o n s h o u l d be i n i t i a l l y v e r i f i e d u s i n g a q u a l i t y c o n t r o l sample ( S e c t i o n s 7.12 & 9.2.3).

NOTE:

The a p p r o p r i a t e a c i d d i l u e n t f o r t h e d e t e r m i n a t i o n o f d i s s o l v e d elements i n w a t e r and f o r t h e " d i r e c t a n a l y s i s " o f d r i n k i n g w a t e r w i t h t u r b i d i t y < 1 NTU i s 1% HNO,. For t o t a l r e c o v e r a b l e elements i n w a t e r s , t h e a p p r o p r i a t e a c i d d i l u e n t i s 2% HNO, and 1% HC1, and t h e a p p r o p r i a t e a c i d d i l u e n t f o r t o t a l r e c o v e r a b l e elements i n s o l i d samples i s 2% HNO, and 2% HC1. The reason f o r t h e s e d i f f e r e n t d i l u e n t s i s t o match t h e t y p e s o f a c i d s and t h e a c i d c o n c e n t r a t i o n s o f t h e samples w i t h t h e a c i d p r e s e n t i n t h e standards and b l a n k s .

7.10 Blanks - Four t y p e s o f b l a n k s a r e r e q u i r e d f o r t h i s method.

A c a l i b r a t i o n b l a n k i s used t o e s t a b l i s h t h e a n a l y t i c a l c a l i b r a t i o n curve, t h e l a b o r a t o r y r e a g e n t b l a n k (LRB) i s used t o assess p o s s i b l e c o n t a m i n a t i o n f r o m t h e sample p r e p a r a t i o n procedure and t o assess s p e c t r a l background, t h e l a b o r a t o r y f o r t i f i e d b l a n k i s used t o assess r o u t i n e l a b o r a t o r y performance, and a r i n s e b l a n k i s used t o f l u s h t h e i n s t r u m e n t autosampler uptake system. A l l d i l u e n t a c i d s s h o u l d be made f r o m c o n c e n t r a t e d a c i d s ( S e c t s . 7.2 & 7.3) and ASTM Type I w a t e r .

7.10.1 The c a l i b r a t i o n b l a n k c o n s i s t s o f t h e a p p r o p r i a t e a c i d d i l u e n t i n ASTM Type I w a t e r . The ( S e c t . 7.9 n o t e ) (HCl/HNO,) c a l i b r a t i o n b l a n k should be s t o r e d i n a FEP b o t t l e . Revision 2.2 Nay 1994

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7.10.2

The l a b o r a t o r y r e a g e n t b l a n k (LRB) must c o n t a i n a l l t h e r e a g e n t s i n t h e same volumes as used i n p r o c e s s i n g t h e samples. The LRB must be c a r r i e d t h r o u g h t h e same e n t i r e p r e p a r a t i o n scheme as t h e samples i n c l u d i n g sample d i g e s t i o n , when appl icab1 e .

7.10.3

The 1 a b o r a t o r y f o r t if ied b l ank (LFB) is p r e p a r e d by f o r t if y i n g an a l i q u o t o f t h e l a b o r a t o r y r e a g e n t b l a n k w i t h a l l a n a l y t e s t o p r o v i d e a f i n a l c o n c e n t r a t i o n which w i l l produce an absorbance o f a p p r o x i m a t e l y 0 . 1 f o r each a n a l y t e . The LFB must be c a r r i e d t h r o u g h t h e same e n t i r e p r e p a r a t i o n scheme as t h e samples i n c l u d i n g sample d i g e s t i o n , when a p p l i c a b l e .

7.10.4

The r i n s e b l a n k i s p r e p a r e d as needed by adding 1.0 mL o f conc. HNO, and 1 . 0 mL conc. HC1 t o 1 l i t e r o f ASTM Type I w a t e r and s t o r e d i n a c o n v e n i e n t manner.

7.11 I n s t r u m e n t Performance Check (IPC) S o l u t i o n - The I P C s o l u t i o n i s used t o p e r i o d i c a l l y v e r i f y i n s t r u m e n t performance d u r i n g a n a l y s i s . It s h o u l d be p r e p a r e d i n t h e same a c i d m i x t u r e as t h e c a l i b r a t i o n standards ( S e c t , 7.9 n o t e ) by combining method a n a l y t e s a t a p p r o p r i a t e c o n c e n t r a t i o n s t o approximate t h e m i d p o i n t o f t h e c a l i b r a t i o n c u r v e . The I P C s o l u t i o n s h o u l d be p r e p a r e d f r o m t h e same standard s t o c k s o l u t i o n s used t o p r e p a r e t h e c a l i b r a t i o n standards and s t o r e d i n a FEP b o t t l e . Agency programs may s p e c i f y o r r e q u e s t t h a t a d d i t i o n a l i n s t r u m e n t performance check s o l u t i o n s be prepared a t s p e c i f i e d c o n c e n t r a t i o n s i n o r d e r t o meet p a r t i c u l a r program needs. 7.12 Q u a l i t y C o n t r o l Sample (QCS) - F o r i n i t i a l and p e r i o d i c v e r i f i c a t i o n o f c a l i b r a t i o n s t a n d a r d s and i n s t r u m e n t performance, a n a l y s i s o f a QCS i s required. The QCS must be o b t a i n e d f r o m an o u t s i d e source d i f f e r e n t f r o m t h e s t a n d a r d s t o c k s o l u t i o n s and prepared i n t h e same a c i d m i x t u r e as t h e c a l i b r a t i o n s t a n d a r d s ( S e c t . 7 . 9 n o t e ) . The c o n c e n t r a t i o n o f t h e a n a l y t e s i n t h e QCS s o l u t i o n s h o u l d be such t h a t t h e r e s u l t i n g s o l u t i o n w i l l p r o v i d e an absorbance r e a d i n g o f a p p r o x i m a t e l y 0.1. The QCS s o l u t i o n s h o u l d be s t o r e d i n a FEP b o t t l e and a n a l y z e d as needed t o meet d a t a - q u a l i t y needs. A f r e s h s o l u t i o n s h o u l d be p r e p a r e d q u a r t e r l y o r more f r e q u e n t l y as needed. 8.0

SAMPLE COLLECTION, PRESERVATION, AND STORAGE 8.1

P r i o r t o t h e c o l l e c t i o n o f an aqueous sample, c o n s i d e r a t i o n s h o u l d be given t o t h e type o f data required, ( i . e . , dissolved o r t o t a l r e c o v e r a b l e ) , so t h a t a p p r o p r i a t e p r e s e r v a t i o n and p r e t r e a t m e n t steps can be t a k e n . The pH o f a l l aqueous samples must be t e s t e d i m m e d i a t e l y p r i o r t o a1 i q u o t i n g f o r p r o c e s s i n g o r " d i r e c t a n a l y s i s " t o ensure t h e sample has been p r o p e r l y p r e s e r v e d . I f properly acid preserved, t h e sample can be h e l d up t o 6 months b e f o r e a n a l y s i s .

8.2

F o r t h e d e t e r m i n a t i o n o f t h e d i s s o l v e d elements, t h e sample must be f i l t e r e d t h r o u g h a 0.45-pm p o r e d i a m e t e r membrane f i l t e r a t t h e t i m e o f c o l l e c t i o n o r as soon t h e r e a f t e r as p r a c t i c a l l y p o s s i b l e . (Glass o r p l a s t i c f i l t e r i n g apparatus a r e recommended t o a v o i d p o s s i b l e contamination.) Use a p o r t i o n o f t h e f i l t e r e d sample t o r i n s e t h e Revision 2.2 May 1994

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Methods for the Determination f i l t e r f l a s k , d i s c a r d t h i s p o r t i o n and c o l l e c t t h e r e q u i r e d volume o f filtrate. A c i d i f y the f i l t r a t e w i t h ( l t l ) n i t r i c a c i d immediately f o l l o w i n g f i l t r a t i o n t o pH < 2.

8.3

For t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e elements i n aqueous samples, samples a r e n o t f i l t e r e d , b u t a c i d i f i e d w i t h ( l t l ) n i t r i c a c i d t o pH < 2 ( n o r m a l l y , 3 mL o f (1t1) a c i d p e r l i t e r o f sample i s s u f f i c i e n t f o r most ambient and d r i n k i n g w a t e r samples). P r e s e r v a t i o n may be done a t t h e t i m e o f c o l l e c t i o n , however, t o a v o i d t h e hazards o f s t r o n g a c i d s i n t h e f i e l d , t r a n s p o r t r e s t r i c t i o n s , and p o s s i b l e c o n t a m i n a t i o n i t i s recommended t h a t t h e samples be r e t u r n e d t o t h e l a b o r a t o r y w i t h i n two weeks o f c o l l e c t i o n and a c i d p r e s e r v e d upon r e c e i p t i n t h e l a b o r a t o r y . F o l l o w i n g a c i d i f i c a t i o n , t h e sample s h o u l d be mixed, h e l d f o r s i x t e e n hours, and t h e n v e r i f i e d t o be pH < 2 j u s t p r i o r w i t h d r a w i n g an a l i q u o t f o r p r o c e s s i n g o r " d i r e c t a n a l y s i s " . If f o r some reason such as h i g h a l k a l i n i t y t h e sample pH i s v e r i f i e d t o be > 2 , more a c i d must be added and t h e sample h e l d f o r s i x t e e n h o u r s u n t i l v e r i f i e d t o be pH < 2 . See S e c t i o n 8.1.

NOTE:

When t h e n a t u r e o f t h e sample i s e i t h e r unknown o r i s known t o be hazardous, a c i d i f i c a t i o n s h o u l d be done i n a fume hood. See S e c t i o n 5.2.

8.4

S o l i d samples u s u a l l y r e q u i r e no p r e s e r v a t i o n p r i o r t o a n a l y s i s o t h e r t h a n s t o r a g e a t 4°C. There i s no e s t a b l i s h e d h o l d i n g t i m e l i m i t a t i o n f o r s o l i d samples.

8.5

F o r aqueous samples, a f i e l d b l a n k s h o u l d be p r e p a r e d and a n a l y z e d as r e q u i r e d by t h e d a t a u s e r . Use t h e same c o n t a i n e r and a c i d as used i n sampl e c o l 1e c t i on.

9.0 QUALITY CONTROL 9.1

Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a f o r m a l q u a l i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f t h i s program c o n s i s t of an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y , and t h e p e r i o d i c a n a l y s i s o f l a b o r a t o r y r e a g e n t b l a n k s , f o r t i f i e d b l a n k s and o t h e r l a b o r a t o r y s o l u t i o n s as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n performance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f t h e d a t a t h u s generated.

9.2

I n i t i a l Demonstration o f Performance (mandatory)

9.2.1

The i n i t i a l d e m o n s t r a t i o n o f performance i s used t o c h a r a c t e r i z e i n s t r u m e n t performance ( d e t e r m i n a t i o n o f 1 i n e a r dynamic ranges and a n a l y s i s o f q u a l i t y c o n t r o l samples) and l a b o r a t o r y performance ( d e t e r m i n a t i o n o f method d e t e c t i o n l i m i t s ) p r i o r t o samples b e i n g analyzed by t h i s method.

9.2.2

L i n e a r dynamic range (LDR) - The upper l i m i t o f t h e LDR must be e s t a b l i s h e d f o r t h e wavelength u t i l i z e d f o r each a n a l y t e by d e t e r m i n i n g t h e s i g n a l responses from a minimum o f s i x d i f f e r e n t c o n c e n t r a t i o n standards across t h e range, two o f Revision 2.2 Nay 1994

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w h i c h a r e c l o s e t o t h e upper l i m i t o f t h e LDR. Determined LDRs must be documented and k e p t on f i l e . The l i n e a r c a l i b r a t i o n range which may be used f o r t h e a n a l y s i s o f samples s h o u l d be judged by t h e a n a l y s t from t h e r e s u l t i n g d a t a . The upper LDR l i m i t s h o u l d be an observed s i g n a l no more t h a n 10% below t h e l e v e l e x t r a p o l a t e d from t h e f o u r l o w e r standards. The LDRs s h o u l d be v e r i f i e d whenever, i n t h e judgement o f t h e a n a l y s t , a change i n a n a l y t i c a l performance caused by e i t h e r a change i n i n s t r u m e n t hardware o r o p e r a t i n g c o n d i t i o n s would d i c t a t e t h e y be r e d e t e r m i n e d .

NOTE:

M u l t i p l e c l e a n o u t f u r n a c e c y c l e s may be necessary i n o r d e r t o f u l l y d e f i n e o r u t i l i z e t h e LDR f o r c e r t a i n elements such as chromium. F o r t h i s reason t h e upper l i m i t o f t h e l i n e a r c a l i b r a t i o n range may n o t c o r r e s p o n d t o t h e upper LDR l i m i t .

Determined sample a n a l y t e c o n c e n t r a t i o n s t h a t exceed t h e upper l i m i t o f t h e l i n e a r c a l i b r a t i o n range must e i t h e r be d i l u t e d and r e a n a l y z e d w i t h concern f o r memory e f f e c t s ( S e c t . 4 . 4 ) o r a n a l y z e d by a n o t h e r approved method.

9.2.3

Q u a l i t y c o n t r o l sample (QCS) - When b e g i n n i n g t h e use o f t h i s method, on a q u a r t e r l y b a s i s o r as r e q u i r e d t o meet dataqua1 i t y needs, v e r i f y t h e c a l i b r a t i o n standards and a c c e p t a b l e i n s t r u m e n t performance w i t h t h e p r e p a r a t i o n and analyses o f a QCS ( S e c t . 7 . 1 2 ) . I f t h e determined concentrations are n o t w i t h i n _+ 10% o f t h e s t a t e d v a l u e s , performance o f t h e d e t e r m i n a t i v e s t e p o f t h e method i s u n a c c e p t a b l e . The source o f t h e problem must be i d e n t i f i e d and c o r r e c t e d b e f o r e e i t h e r p r o c e e d i n g on w i t h t h e i n i t i a l d e t e r m i n a t i o n o f method d e t e c t i o n l i m i t s o r c o n t i n u i n g w i t h on-going analyses.

9.2.4

Method d e t e c t i o n l i m i t (MDL) - MDLs must be e s t a b l i s h e d f o r a l l analytes, using reagent water (blank) f o r t i f i e d a t a concentration o f t o t h r e e times t h e estimated instrument detection l i m i t . To d e t e r m i n e MDL values, t a k e seven r e p l i c a t e a1 i q u o t s o f t h e f o r t i f i e d r e a g e n t w a t e r and process t h r o u g h t h e e n t i r e a n a l y t i c a l method. P e r f o r m a l l c a l c u l a t i o n s d e f i n e d i n t h e method and r e p o r t t h e c o n c e n t r a t i o n v a l u e s i n t h e a p p r o p r i a t e u n i t s . C a l c u l a t e t h e MDL as f o l l o w s :

20

MDL

=

( t ) x (S)

where: t

=

s t u d e n t s ’ t v a l u e f o r a 99% c o n f i d e n c e l e v e l and a s t a n d a r d d e v i a t i o n e s t i m a t e w i t h n-1 degrees o f freedom [ t = 3.14 f o r seven r e p l i c a t e s ] .

S

=

s t a n d a r d d e v i a t i o n o f t h e r e p l i c a t e analyses.

Note:

I f a d d i t i o n a l c o n f i r m a t i o n i s desired, reanalyze the seven r e p l ic a t e a1 iquot s on two more nonconsecutive days and a g a i n c a l c u l a t e t h e MDL v a l u e s f o r each day. Revision 2.2 Hay 1994

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Methods for the Determination An average o f t h e t h r e e MDL v a l u e s f o r each a n a l y t e may p r o v i d e f o r a more a p p r o p r i a t e MDL e s t i m a t e . If t h e r e l a t i v e s t a n d a r d d e v i a t i o n (RSD) from t h e analyses o f t h e seven a l i q u o t s i s < lo%, t h e c o n c e n t r a t i o n used t o d e t e r m i n e t h e a n a l y t e MDL may have been inappropr i a t e l y h i g h f o r t h e d e t e r m i n a t i o n . I f so, t h i s c o u l d r e s u l t i n t h e c a l c u l a t i o n o f an u n r e a l i s t i c a l l y l o w MDL. C o n c u r r e n t l y , d e t e r m i n a t i o n o f MDL i n r e a g e n t w a t e r r e p r e s e n t s a b e s t case s i t u a t i o n and does n o t r e f l e c t p o s s i b l e m a t r i x e f f e c t s o f r e a l w o r l d samples. However, s u c c e s s f u l analyses o f LFMs ( S e c t . 9.4) and t h e a n a l y t e a d d i t i o n t e s t d e s c r i b e d i n S e c t i o n 9.5.1 can g i v e c o n f i d e n c e t o t h e MDL v a l u e d e t e r m i n e d i n r e a g e n t w a t e r . T y p i c a l s i n g l e l a b o r a t o r y MDL v a l u e s u s i n g t h i s method a r e g i v e n i n Table 2. The MDLs must be s u f f i c i e n t t o d e t e c t a n a l y t e s a t t h e r e q u i r e d l e v e l s a c c o r d i n g t o compliance m o n i t o r i n g r e g u l a t i o n ( S e c t . 1.2). MDLs s h o u l d be determined a n n u a l l y , when a new o p e r a t o r b e g i n s work o r whenever, i n t h e judgement o f t h e a n a l y s t , a change i n a n a l y t i c a l performance caused by e i t h e r a change i n i n s t r u m e n t hardware o r o p e r a t i n g c o n d i t i o n s would d i c t a t e t h e y be r e d e t e r m i n e d .

9.3 Assessing L a b o r a t o r y Performance (mandatory) 9.3.1

L a b o r a t o r y r e a g e n t b l a n k (LRB) - The l a b o r a t o r y must a n a l y z e a t l e a s t one LRB ( S e c t . 7.10.2) w i t h each b a t c h o f 20 o r fewer samples o f t h e same m a t r i x . LRB d a t a a r e used t o assess c o n t a m i n a t i o n f r o m t h e l a b o r a t o r y environment. LRB v a l u e s t h a t exceed t h e MDL i n d i c a t e l a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n s h o u l d be suspected. When LRB v a l u e s c o n s t i t u t e 10% o r more o f t h e a n a l y t e l e v e l d e t e r m i n e d f o r a sample o r i s 2.2 t i m e s t h e a n a l y t e MDL whichever i s g r e a t e r , f r e s h a l i q u o t s o f t h e samples must be p r e p a r e d and analyzed a g a i n f o r t h e a f f e c t e d a n a l y t e s a f t e r t h e source o f c o n t a m i n a t i o n has been c o r r e c t e d and a c c e p t a b l e LRB v a l u e s have been o b t a i n e d .

9.3.2 L a b o r a t o r y f o r t i f i e d b l a n k (LFB)

- The l a b o r a t o r y must a n a l y z e a t l e a s t one LFB ( S e c t . 7.10.3) w i t h each b a t c h o f samples. C a l c u l a t e accuracy as p e r c e n t r e c o v e r y u s i n g t h e f o l l o w i n g equation:

LFB - LRB

R =

x

100

S

where:

R LFB LRB s

= = = =

percent recovery. laboratory f o r t i f i e d blank. l a b o r a t o r y reagent blank. concentration equivalent o f analyte added t o f o r t i f y t h e LRB s o l u t i o n .

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If the recovery of any analyte falls outside the required control limits of 85-115%, that analyte is judged out of control, and the source of the problem should be identified and resolved before continuing analyses. 9.3.3

The laboratory must use LFB analyses data to assess laboratory performance against the required control limits of 85-115% (Sect.9.3.2). When sufficient internal performance data become available (usually a minimum of twenty to thirty analyses), optional control limits can be developed from the mean percent recovery ( x ) and the standard deviation ( S ) of the mean percent recovery. These data can be used to establish the upper and lower control limits as follows: UPPER CONTROL LIMIT LOWER CONTROL LIMIT

= =

x t 3s

x

-

3s

The optional control limits must be equal to or better than the required control limits of 85-115%. After each five to ten new recovery measurements, new control 1 imits can be calculated using only the most recent twenty to thirty data points. Also, the standard deviation ( S ) data should be used to established an on-going precision statement for the level of concentrations included in the LFB. These data must be kept on file and be available for review. 9.3.4

9.4

Instrument performance check (IPC) solution - For all determinations the laboratory must analyze the IPC solution (Sect. 7.11) and a calibration blank immediately following each calibration, after every tenth sample (or more frequently, if required) and at the end of the sample run. Analysis of the calibration blank should always be < the IDL, but > a negative signal in concentration units equal to the IDL. Analysis of the IPC solution immediately following calibration must verify that the instrument is within f 5% of calibration. Subsequent analyses of the IPC solution must be within f 10 % of calibration. If the calibration cannot be verified within the specified limits, reanalyze either or both the IPC solution and the calibration blank. If the second analysis of the IPC solution or the calibration blank confirm the calibration to be outside the limits, sample analysis must be discontinued, the cause determined and/or in the case of drift the instrument recalibrated. All samples following the last acceptable IPC solution must be reanalyzed. The analysis data of the calibration blank and IPC solution must be kept on file with the sample analyses data.

Assessing Analyte Recovery and Data Quality 9.4.1

Sample homogeneity and the chemical nature of the sample matrix can affect analyte recovery and the quality of the data. Taking separate aliquots from the sample for replicate and fortified analyses can in sotiie cases assess these effects. Unless otherwise specified by t h e data user, laboratory or Revision 2.2 May 1994

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program, t h e f o l l o w i n g l a b o r a t o r y f o r t i f i e d m a t r i x (LFM) procedure ( S e c t . 9 . 4 . 2 ) i s r e q u i r e d . Also, t h e analyte a d d i t i o n t e s t ( S e c t . 9.5.1) can i n d i c a t e i f m a t r i x and o t h e r i n t e r f e r e n c e e f f e c t s a r e o p e r a t i v e i n s e l e c t e d samples. However, a l l samples must demonstrate a background absorbance < 1 . 0 b e f o r e t h e t e s t r e s u l t s o b t a i n e d can be c o n s i d e r e d r e 1 ia b l e . 9.4.2

The l a b o r a t o r y must add a known amount o f each a n a l y t e t o a minimum o f 10% o f t h e r o u t i n e samples. I n each case t h e LFM a l i q u o t must be a d u p l i c a t e o f t h e a l i q u o t used f o r sample a n a l y s i s and f o r t o t a l r e c o v e r a b l e d e t e r m i n a t i o n s added p r i o r t o sample p r e p a r a t i o n . F o r w a t e r samples, t h e added a n a l y t e c o n c e n t r a t i o n must be t h e same as t h a t used i n t h e l a b o r a t o r y f o r t i f i e d b l a n k ( S e c t . 9.3.2). F o r s o l i d samples, however, t h e c o n c e n t r a t i o n added s h o u l d be expressed as mg/kg and i s c a l c u l a t e d f o r a 1 g a l i q u o t by m u l t i p l y i n g t h e added a n a l y t e c o n c e n t r a t i o n (pg/L) i n s o l u t i o n by t h e c o n v e r s i o n f a c t o r 0.1 (0.001 x pg/L x O.lL/O.OOlkg = 0.1, S e c t . 12.4). Over t i m e , samples from a l l r o u t i n e sample sources s h o u l d be f o r t i f i e d .

9.4.3

C a l c u l a t e t h e p e r c e n t r e c o v e r y f o r each a n a l y t e , c o r r e c t e d f o r c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare these v a l u e s t o t h e d e s i g n a t e d LFM r e c o v e r y range o f 70-130%. Recovery c a l c u l a t i o n s a r e n o t r e q u i r e d i f t h e c o n c e n t r a t i o n added i s l e s s t h a n 25% o f t h e u n f o r t i f i e d sample c o n c e n t r a t i o n . Percent r e c o v e r y may be c a l c u l a t e d i n u n i t s a p p r o p r i a t e t o t h e m a t r i x , using t h e f o l l o w i n g equation:

c, R =

-

c x 100

~

S

where:

R C, C

s 9.4.4

percent recovery. f o r t i f i e d sample c o n c e n t r a t i o n . sample background c o n c e n t r a t i o n . = concentration equivalent o f analyte added t o f o r t i f y t h e sample. =

= =

I f t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e d e s i g n a t e d LFM r e c o v e r y range ( b u t i s s t i l l w i t h i n t h e range o f c a l i b r a t i o n ) and t h e l a b o r a t o r y performance f o r t h a t a n a l y t e i s shown t o be i n c o n t r o l ( S e c t . 9.3), t h e r e c o v e r y problem encountered w i t h t h e LFM i s judged t o be e i t h e r m a t r i x o r s o l u t i o n r e l a t e d , n o t system r e l a t e d . I f t h e a n a l y t e r e c o v e r y i n t h e LFM i s < 70% and t h e background absorbance i s < 1.0, complete t h e a n a l y t e a d d i t i o n t e s t ( S e c t . 9.5.1) on an u n d i l u t e d p o r t i o n o f t h e u n f o r t i f i e d sample a l i q u o t . The t e s t r e s u l t s s h o u l d be e v a l u a t e d as f o l l o w s : 1. I f r e c o v e r y o f t h e a n a l y t e a d d i t i o n t e s t ( < 85%) c o n f i r m s t h e a l o w r e c o v e r y f o r t h e LFM, a s u p p r e s s i v e m a t r i x i n t e r f e r e n c e i s i n d i c a t e d and t h e u n f o r t i f i e d sample a1 i q u o t

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must be analyzed by method o f s t a n d a r d a d d i t i o n s (Sect.

11.5). 2. I f t h e r e c o v e r y o f t h e a n a l y t e a d d i t i o n t e s t i s between 85% t o 115%, a l o w r e c o v e r y o f t h e a n a l y t e i n t h e LFM ( < 70%) may be r e l a t e d t o t h e heterogeneous n a t u r e o f t h e sample, t h e r e s u l t o f p r e c i p i t a t i o n l o s s d u r i n g sample p r e p a r a t i o n , o r an i n c o r r e c t a d d i t i o n p r i o r t o p r e p a r a t i o n . Report a n a l y t e d a t a determined f r o m t h e a n a l y s i s o f t h e u n f o r t i f i e d sample a l i q u o t .

9.4.5

I f l a b o r a t o r y performance i s shown t o be i n c o n t r o l (Sect. 9 . 3 ) , b u t a n a l y t e r e c o v e r y i n t h e LFM i s e i t h e r > 130% or above t h e upper c a l i b r a t i o n l i m i t and t h e background absorbance i s < 1.0, complete t h e a n a l y t e a d d i t i o n t e s t ( S e c t . 9.5.1) on a p o r t i o n o f t h e u n f o r t i f i e d sample a l i q u o t . ( I f t h e determined LFM c o n c e n t r a t i o n i s above t h e upper c a l i b r a t i o n l i m i t , d i l u t e a portion o f the u n f o r t i f i e d aliquot accordingly with a c i d i f i e d reagent water before completing t h e analyte a d d i t i o n t e s t . ) E v a l u a t e t h e t e s t r e s u l t s as f o l l o w s : 1. If t h e p e r c e n t r e c o v e r y o f t h e a n a l y t e a d d i t i o n t e s t i s > 115%, an enhancing m a t r i x i n t e r f e r e n c e ( a l b e i t r a r e ) i s i n d i c a t e d and t h e u n f o r t i f i e d sample a l i q u o t o r i t s a p p r o p r i a t e d i l u t i o n must be analyzed by method o f standard a d d i t i o n s (Sect 11.5).

2. I f t h e p e r c e n t r e c o v e r y o f t h e a n a l y t e a d d i t i o n t e s t i s between 85% t o 115%, h i g h r e c o v e r y i n t h e LFM may have been caused by random sample c o n t a m i n a t i o n , an i n c o r r e c t a d d i t i o n o f t h e a n a l y t e p r i o r t o sample p r e p a r a t i o n , o r sample heterogeneity. Report a n a l y t e d a t a determined from t h e a n a l y s i s o f t h e u n f o r t i f i e d sample a l i q u o t o r i t s appropriate d i l u t i o n .

3. I f the percent recovery o f the analyte a d d i t i o n t e s t i s < 85%, e i t h e r a case o f b o t h random c o n t a m i n a t i o n and an o p e r a t i v e m a t r i x i n t e r f e r e n c e i n t h e LFM i s i n d i c a t e d o r a more p l a u s i b l e answer i s a heterogenous sample w i t h an s u p p r e s s i v e m a t r i x i n t e r f e r e n c e . Reported d a t a should be flagged accordingly. 9.4.6

I f l a b o r a t o r y performance i s shown t o be i n c o n t r o l ( S e c t . 9 . 3 ) , b u t t h e magnitude o f t h e sample (LFM o r u n f o r t i f i e d a l i q u o t ) background absorbance i s > 1 .O, a n o n - s p e c i f i c s p e c t r a l i n t e r f e r e n c e s h o u l d be suspected. A portion o f the u n f o r t i f i e d a l i q u o t s h o u l d be d i l u t e d ( 1 t 3 ) w i t h a c i d i f i e d r e a g e n t w a t e r and r e a n a l y z e d . ( D i l u t i o n may d r a m a t i c a l l y reduce a m o l e c u l a r background t o an a c c e p t a b l e l e v e l . I d e a l l y , t h e background absorbance i n t h e u n f o r t i f i e d a1 i q u o t d i l u t e d ( 1 t 3 ) s h o u l d be < 1 . 0 . However, a d d i t i o n a l d i l u t i o n may be necessary.) I f d i l u t i o n reduces t h e background absorbance t o a c c e p t a b l e l e v e l ( < l . O ) , complete t h e a n a l y t e a d d i t i o n t e s t ( S e c t . 9 . 5 . 1 ) on a p o r t i o n o f t h e d i l u t e d u n f o r t i f i e d a l i q u o t . Revision 2.2 Hay 1994

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Methods for the Determination E v a l u a t e t h e t e s t r e s u l t s as f o l l o w s 1. I f t h e r e c o v e r y o f t h e a n a l y t e a d d i t i o n t e s t i s between 85% t o 115%, r e p o r t a n a l y t e d a t a determined on t h e d i l u t i o n o f the u n f o r t i f i e d aliquot.

2. I f the recovery o f the analyte a d d i t i o n t e s t i s outside the range o f 85% t o 115%, complete t h e sample a n a l y s i s by a n a l y z i n g t h e d i l u t i o n o f t h e u n f o r t i f i e d a l i q u o t by method o f s t a n d a r d a d d i t i o n s (Sect. 11.5).

9.5

9.4.7

I f e i t h e r t h e a n a l y s i s o f a LFM sample(s) o r a p p l i c a t i o n o f t h e analyte addition t e s t routine i n d i c a t e an o p e r a t i v e i n t e r f e r e n c e , a l l o t h e r samples i n t h e b a t c h which a r e t y p i c a l and have s i m i l a r m a t r i x t o t h e LFMs o r t h e samples t e s t e d must be analyzed i n t h e same manner. A l s o , t h e d a t a u s e r must be i n f o r m e d when a m a t r i x i n t e r f e r e n c e i s so severe t h a t i t p r e v e n t s t h e s u c c e s s f u l a n a l y s i s o f t h e a n a l y t e o r when t h e heterogeneous n a t u r e o f t h e sample p r e c l u d e s t h e use o f d u p l i c a t e analyses.

9.4.8

Where r e f e r e n c e m a t e r i a l s a r e a v a i l a b l e , t h e y s h o u l d be analyzed t o p r o v i d e a d d i t i o n a l performance d a t a . The a n a l y s i s o f r e f e r e n c e samples i s a v a l u a b l e t o o l f o r d e m o n s t r a t i n g t h e a b i l i t y t o p e r f o r m t h e method a c c e p t a b l y .

The f o l l o w i n g t e s t can be used t o assess p o s s i b l e m a t r i x i n t e r f e r e n c e e f f e c t s and t h e need t o complete t h e sample a n a l y s i s by method o f s t a n d a r d a d d i t i o n s (MSA). R e s u l t s o f t h i s t e s t s h o u l d not be c o n s i d e r e d c o n c l u s i v e u n l e s s t h e d e t e r m i n e d sample background absorbance i s < 1.0. D i r e c t i o n s f o r MSA a r e g i v e n i n S e c t i o n 11.5. 9.5.1

10.0

A n a l y t e a d d i t i o n t e s t : An a n a l y t e s t a n d a r d added t o a p o r t i o n o f a p r e p a r e d sample, o r i t s d i l u t i o n , should be r e c o v e r e d t o w i t h i n 85% t o 115% o f t h e known v a l u e . The a n a l y t e a d d i t i o n may be added d i r e c t l y t o sample i n t h e f u r n a c e and s h o u l d produce a minimum l e v e l absorbance o f 0.1. The c o n c e n t r a t i o n o f t h e a n a l y t e a d d i t i o n p l u s t h a t i n t h e sample s h o u l d n o t exceed t h e l i n e a r c a l i b r a t i o n range o f t h e a n a l y t e . If the analyte i s n o t recovered w i t h i n t h e s p e c i f i e d l i m i t s , a m a t r i x e f f e c t s h o u l d be suspected and t h e sample must be analyzed by MSA ( S e c t . 11.5).

CALIBRATION AND STANDARDIZATION 10.1 S p e c i f i c wavelengths and i n s t r u m e n t o p e r a t i n g c o n d i t i o n s a r e l i s t e d i n T a b l e 2. However, because o f d i f f e r e n c e s among makes and models o f spectrophotometers and e l e c t r o t h e r m a l f u r n a c e d e v i c e s , t h e a c t u a l i n s t r u m e n t c o n d i t i o n s s e l e c t e d may v a r y f r o m t h o s e l i s t e d . 10.2 P r i o r t o t h e use o f t h i s method t h e i n s t r u m e n t o p e r a t i n g c o n d i t i o n s must be o p t i m i z e d . The a n a l y s t s h o u l d f o l l o w t h e i n s t r u c t i o n s p r o v i d e d by t h e m a n u f a c t u r e r w h i l e u s i n g t h e c o n d i t i o n s l i s t e d i n Table 2 as a g u i d e . O f p a r t i c u l a r importance i s t h e d e t e r m i n a t i o n o f Revision 2.2 Nay 1994

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the charring temperature limit for each analyte. This limit is the furnace temperature setting where a loss in analyte will occur prior to atomization. This limit should be determined by conducting char temperature profiles for each analyte and when necessary, in the matrix of question. The charring temperature selected should minimize background absorbance while providing some furnace temperature variation without loss of analyte. For routine analytical operation the charring temperature is usually set at least 100°C below this limit. The optimum conditions selected should provide the lowest reliable MDLs and be similar to those listed in Table 2. Once the optimum operating conditions are determined, they should be recorded and avai 1 able for dai ly reference. 10.3 Prior to an initial calibration the linear dynamic range of the analyte must be determined (Sect. 9.2.2) using the optimized instrument operating conditions (Sect. 10.2). For all determinations allow an instrument and hollow cathode lamp warm up period of not less than 15 min. If an EDL is to be used, allow 30 min for warm up. 10.4 Before using the procedure (Sect. 11.0) to analyze samples, there must

be data available documenting initial demonstration of performance. The required data and procedure are described in Section 9.2. This data must be generated using the same instrument operating conditions and calibration routine (Sect. 11.4) to be used for sample analysis. These documented data must be kept on file and be available for review by the data user. 10.5 In order to meet or achieve lower MDLs than those listed in Table 2 for "direct analysis" of drinking water with turbidity < 1 NTU preconcentration of the analyte is required. This may be accomplished prior to sample introduction into the GFAA or with the use of multiple aliquot depositions on the GFAA platform or associated delayed atomization device. When using multiple depositions, the same number of equal volume aliquots alike of either the calibration standards or acid preserved samples must be deposited prior to atomization. Following each deposition the drying cycle is completed before the next subsequent deposition. The matrix modifier is added along with each deposition and the total volume of each deposition must not exceed the instrument manufactures recommended capacity of the delayed atomization device. To reduce analysis time the minimum number of depositions required to achieve the desired analytical result should be used. Use o f this procedural technique for the "direct analysis" of drinking water must be completed using determined optimized instrument operating conditions for multiple depositions (Sect.lO.2) and comply with the method requirements described in Sections 10.3 and 10.4. (See Table 3 for information and data on the determination of arsenic by this procedure.) 11.0 PROCEDURE 11.1 Aqueous Sample Preparation - Dissolved Analytes

11.1.1 For the determination of dissolved analytes in ground and surface waters, pipet an aliquot ( 2 20 mL) of the filtered,

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Methods for the Determination a c i d p r e s e r v e d sample i n t o a 50-mL p o l y p r o p y l e n e c e n t r i f u g e t u b e . Add an a p p r o p r i a t e volume o f (ltl) n i t r i c a c i d t o a d j u s t t h e a c i d c o n c e n t r a t i o n o f t h e a l i q u o t t o approximate a 1% ( v / v ) n i t r i c a c i d s o l u t i o n ( e . g . , add 0.4 mL (ltl) HNO, t o a 20 mL a l i q u o t o f sample). Cap t h e t u b e and m i x . The sample i s now ready f o r a n a l y s i s ( S e c t . 1 . 3 ) . Allowance f o r sample d i l u t i o n should be made i n t h e c a l c u l a t i o n s .

NOTE:

I f a p r e c i p i t a t e i s formed d u r i n g a c i d i f i c a t i o n , t r a n s p o r t , o r s t o r a g e , t h e sample a l i q u o t must be t r e a t e d u s i n g t h e procedure d e s c r i b e d i n S e c t i o n s 11.2.2 t h r u 11.2.7 p r i o r t o a n a l y s i s .

11.2 Aqueous Sample P r e p a r a t i o n - T o t a l Recoverable A n a l y t e s 11.2.1 F o r t h e " d i r e c t a n a l y s i s " o f t o t a l r e c o v e r a b l e a n a l y t e s i n d r i n k i n g w a t e r samples c o n t a i n i n g t u r b i d i t y < 1 NTU, t r e a t an u n f i l t e r e d a c i d p r e s e r v e d sample a l i q u o t u s i n g t h e sample p r e p a r a t i o n procedure d e s c r i b e d i n S e c t i o n 11.1.1 w h i l e making allowance f o r sample d i l u t i o n i n t h e d a t a c a l c u l a t i o n (Sects. 1.2 & 1.4). For the determination o f t o t a l recoverable a n a l y t e s i n a l l o t h e r aqueous samples f o l l o w t h e procedure g i v e n i n S e c t i o n s 11.2.2 t h r o u g h 11.2.7.

11.2.2 For t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e a n a l y t e s i n aqueous samples ( o t h e r t h a n d r i n k i n g w a t e r w i t h < 1 NTU t u r b i d i t y ) , t r a n s f e r a 100-mL ( ? 1 mL) a l i q u o t f r o m a w e l l mixed, a c i d p r e s e r v e d sample t o a 250-mL G r i f f i n beaker (Sects. 1.2, & 1.6). (When necessary, s m a l l e r sample a l i q u o t volumes may be used. )

NOTE:

I f t h e sample c o n t a i n s u n d i s s o l v e d s o l i d s > 1%, a w e l l mixed, a c i d p r e s e r v e d a l i q u o t c o n t a i n i n g no more t h a n 1 g p a r t i c u l a t e m a t e r i a l s h o u l d be c a u t i o u s l y evaporated t o near 10 mL and e x t r a c t e d u s i n g t h e a c i d m i x t u r e procedure d e s c r i b e d i n S e c t i o n s 11.3.3 t h r u

11.3.6. 11.2.3 Add 2 mL

(ltl) n i t r i c a c i d and 1.0 mL o f (1t1) h y d r o c h l o r i c a c i d t o t h e beaker c o n t a i n i n g t h e measured volume o f sample. P l a c e t h e beaker on t h e h o t p l a t e f o r s o l u t i o n e v a p o r a t i o n . The h o t p l a t e s h o u l d be l o c a t e d i n a fume hood and p r e v i o u s l y adjusted t o provide evaporation a t a temperature o f a p p r o x i m a t e l y b u t no h i g h e r t h a n 85OC. (See t h e f o l l o w i n g note.) The beaker s h o u l d be covered w i t h an e l e v a t e d watch g l a s s o r o t h e r necessary s t e p s s h o u l d be t a k e n t o p r e v e n t sample c o n t a m i n a t i o n from t h e fume hood environment.

NOTE:

For proper heating a d j u s t t h e temperature c o n t r o l o f t h e h o t p l a t e such t h a t an uncovered G r i f f i n beaker c o n t a i n i n g 50 rnL o f w a t e r p l a c e d i n t h e c e n t e r o f t h e h o t p l a t e can be m a i n t a i n e d a t a t e m p e r a t u r e a p p r o x i m a t e l y b u t no h i g h e r t h a n 85'C. (Once t h e beaker Revision 2.2 May 1994

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i s covered w i t h a watch g l a s s t h e temperature o f t h e w a t e r w i l l r i s e t o a p p r o x i m a t e l y 95OC.)

11.2.4

Reduce t h e volume o f t h e sample a l i q u o t t o about 20 mL by g e n t l e h e a t i n g a t 85°C. DO NOT BOIL. T h i s s t e p t a k e s about 2 h f o r a 100 mL a l i q u o t w i t h t h e r a t e o f e v a p o r a t i o n r a p i d l y i n c r e a s i n g as t h e sample volume approaches 20 mL. ( A spare beaker c o n t a i n i n g 20 mL o f w a t e r can be used as a gauge.)

11.2.5

Cover t h e l i p o f t h e beaker w i t h a watch - g l a s s t o reduce a d d i t i o n a l e v a p o r a t i o n and g e n t l y r e f l u x t h e sample f o r 30 m i n u t e s . ( S l i g h t b o i l i n g may occur, b u t v i g o r o u s b o i l i n g must be avoided t o p r e v e n t l o s s o f t h e HC1-H,O a z e o t r o p e . )

11.2.6 A l l o w t h e beaker t o c o o l . Q u a n t i t a t i v e l y t r a n s f e r t h e sample s o l u t i o n t o a 50-mL v o l u m e t r i c f l a s k , make t o volume w i t h r e a g e n t w a t e r , s t o p p e r and mix. 11.2.7 A l l o w any u n d i s s o l v e d m a t e r i a l t o s e t t l e o v e r n i g h t , o r c e n t r i f u g e a p o r t i o n o f t h e p r e p a r e d sample u n t i l c l e a r . ( I f a f t e r c e n t r i f u g i n g o r s t a n d i n g o v e r n i g h t t h e sample c o n t a i n s suspended s o l i d s t h a t would c l o g o r a f f e c t t h e sample i n t r o d u c t i o n system, a p o r t i o n o f t h e sample may be f i l t e r e d f o r t h e i r removal p r i o r t o a n a l y s i s . However, c a r e s h o u l d be e x e r c i s e d t o a v o i d p o t e n t i a l c o n t a m i n a t i o n from f i l t r a t i o n . ) The sample i s now r e a d y f o r a n a l y s i s . Because t h e e f f e c t s o f v a r i o u s m a t r i c e s on t h e s t a b i l i t y o f d i l u t e d samples cannot be c h a r a c t e r i z e d , a l l analyses s h o u l d be performed as soon as p o s s i b l e a f t e r t h e completed p r e p a r a t i o n . 11.3 S o l i d Sample P r e p a r a t i o n - T o t a l Recoverable A n a l y t e s 11.3.1 For t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e a n a l y t e s i n s o l i d samples, m i x t h e sample t h o r o u g h l y and t r a n s f e r a p o r t i o n ( > 20 g ) t o t a r e d w e i g h i n g d i s h , weigh t h e sample and r e c o r d ( F o r samples w i t h < 35% m o i s t u r e a 20 g t h e wet w e i g h t ( W W ) . portion i s sufficient. F o r samples w i t h m o i s t u r e > 35% a l a r g e r a l i q u o t 50-100 g i s r e q u i r e d . ) Dry t h e sample t o a c o n s t a n t w e i g h t a t 6OoC and r e c o r d t h e d r y w e i g h t (DW) f o r c a l c u l a t i o n o f p e r c e n t s o l i d s ( S e c t . 12.6). (The sample i s d r i e d a t 6OoC t o p r e v e n t t h e p o s s i b l e l o s s o f v o l a t i l e m e t a l l i c compounds, t o f a c i l i t a t e s i e v i n g , and t o r e a d y t h e sample f o r g r i n d i n g .) 11.3.2 To achieve homogeneity, s i e v e t h e d r i e d sample u s i n g a 5-mesh p o l y p r o p y l e n e s i e v e and g r i n d i n a m o r t a r and p e s t l e . (The s i e v e , m o r t a r and p e s t l e s h o u l d be c l e a n e d between samples.) From t h e d r i e d , ground m a t e r i a l weigh a c c u r a t e l y a r e p r e s e n t a t i v e 1.0 f 0.01 g a l i q u o t (W) o f t h e sample and t r a n s f e r t o a 250-mL P h i l l i p s beaker f o r a c i d e x t r a c t i o n ( S e c t . 1.6). 11.3.3 To t h e beaker add 4 mL o f ( l t l ) HNO, and 10 mL o f ( 1 t 4 ) HC1. Cover t h e l i p o f t h e beaker w i t h a watch g l a s s . Place t h e Revision 2.2 Nay 1994

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Methods for the Determination beaker on a h o t p l a t e f o r r e f l u x e x t r a c t i o n o f t h e a n a t y t e s . The h o t p l a t e s h o u l d be l o c a t e d i n a fume hood and p r e v i o u s l y adjusted t o provide a r e f l u x temperature o f approximately 95OC. (See t h e f o l l o w i n g n o t e . ) NOTE:

F o r proper heating adjust the temperature c o n t r o l o f t h e h o t p l a t e such t h a t an uncovered G r i f f i n beaker c o n t a i n i n g 50 mL o f w a t e r p l a c e d i n t h e c e n t e r o f t h e h o t p l a t e can be m a i n t a i n e d a t a temperature a p p r o x i m a t e l y b u t no h i g h e r t h a n 85'C. (Once t h e beaker i s covered w i t h a watch g l a s s t h e t e m p e r a t u r e o f t h e w a t e r w i l l r i s e t o a p p r o x i m a t e l y 95OC.) A l s o , a b l o c k d i g e s t e r capable o f m a i n t a i n i n g a t e m p e r a t u r e o f 95OC and equipped w i t h 250-mL c o n s t r i c t e d v o l u m e t r i c d i g e s t i o n tubes may be s u b s t i t u t e d f o r t h e h o t p l a t e and c o n i c a l beakers i n t h e e x t r a c t i o n s t e p .

Very s l i g h t 11.3.4 Heat t h e sample and g e n t l y r e f l u x f o r 30 min. b o i l i n g may o c c u r , however v i g o r o u s b o i l i n g must be avoided t o Some s o l u t i o n p r e v e n t l o s s o f t h e HC1-H 0 azeotrope. evaporation w i l l occur ( 3 t o mL).

5

11.3.5 A l l o w t h e sample t o c o o l and q u a n t i t a t i v e l y t r a n s f e r t h e e x t r a c t t o a 100-mL v o l u m e t r i c f l a s k . D i l u t e t o volume w i t h r e a g e n t w a t e r , s t o p p e r and m i x . 11.3.6 A l l o w t h e sample e x t r a c t s o l u t i o n t o s t a n d o v e r n i g h t t o separate i n s o l u b l e m a t e r i a l o r c e n t r i f u g e a p o r t i o n o f the sample s o l u t i o n u n t i l c l e a r . (If a f t e r centrifuging o r s t a n d i n g o v e r n i g h t t h e e x t r a c t s o l u t i o n c o n t a i n s suspended s o l i d s t h a t would c l o g o r a f f e c t t h e sample i n t r o d u c t i o n system, a p o r t i o n o f t h e e x t r a c t s o l u t i o n may be f i l t e r e d f o r t h e i r removal p r i o r t o a n a l y s i s . However, c a r e should be e x e r c i s e d t o a v o i d p o t e n t i a l c o n t a m i n a t i o n from f i l t r a t i o n . ) The sample e x t r a c t i s now r e a d y f o r a n a l y s i s . Because t h e e f f e c t s o f v a r i o u s m a t r i c e s on t h e s t a b i l i t y o f d i l u t e d samples cannot be c h a r a c t e r i z e d , a l l analyses s h o u l d be performed as soon as p o s s i b l e a f t e r t h e completed p r e p a r a t i o n . 11.4 Sample A n a l y s i s 11.4.1 P r i o r t o d a i l y c a l i b r a t i o n o f t h e i n s t r u m e n t i n s p e c t t h e g r a p h i t e f u r n a c e , t h e sample u p t a k e system and autosampler i n j e c t o r f o r any change i n t h e system t h a t would a f f e c t i n s t r u m e n t performance. Clean t h e system and r e p l a c e t h e g r a p h i t e t u b e and/or p l a t f o r m when needed o r on a d a i l y b a s i s . 11.4.2 B e f o r e b e g i n n i n g d a i l y c a l i b r a t i o n t h e i n s t r u m e n t system should be r e c o n f i g u r e d t o t h e s e l e c t e d o p t i m i z e d o p e r a t i n g c o n d i t i o n s as determined i n S e c t i o n s 10.1 and 10.2 o r 10.5 f o r t h e " d i r e c t a n a l y s i s " d r i n k i n g w a t e r w i t h t u r b i d i t y < 1 NTU. I n i t i a t e d a t a system and a l l o w a p e r i o d o f n o t l e s s t h a n 15 min f o r i n s t r u m e n t and h o l l o w cathode lamp warm up. I f an EDL i s t o be used, a l l o w 30 min f o r warm up. Revision 2.2 Hay 1994

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1 1 . 4 . 3 A f t e r t h e warm up p e r i o d b u t b e f o r e c a l i b r a t i o n , i n s t r u m e n t s t a b i l i t y must be demonstrated by a n a l y z i n g a s t a n d a r d s o l u t i o n w i t h a c o n c e n t r a t i o n 20 tiiiies t h e I D L a minimum o f f i v e t i m e s . l h e r e s u l t i n g r e l a t i v e standard d e v i a t i o n (RSD) o f absorbance s i g n a l s must be < 5%. I f t h e RSD i s > 5%, d e t e r m i n e and c o r r e c t t h e cause b e f o r e c a l i b r a t i n g t h e i n s t r u m e n t .

1 1 . 4 . 4 For i n i t i a l and d a i l y o p e r a t i o n c a l i b r a t e t h e i n s t r u m e n t a c c o r d i n g t o t h e i n s t r u m e n t m a n u f a c t u r e r ' s recommended procedures u s i n g t h e c a l i b r a t i o n b l a n k ( S e c t . 7.10.1) and c a l i b r a t i o n standards ( S e c t . 7 . 9 ) p r e p a r e d a t t h r e e o r more c o n c e n t r a t i o n s w i t h i n t h e u s a b l e l i n e a r dynamic range o f t h e a n a l y t e ( S e c t s . 4.4 & 9 . 2 . 2 ) . 11.4.5 An autosampler must be used t o i n t r o d u c e a l l s o l u t i o n s i n t o t h e g r a p h i t e furnace. Once t h e standard, sample o r QC s o l u t i o n p l u s t h e m a t r i x m o d i f i e r i s i n j e c t e d , the furnace c o n t r o l l e r completes f u r n a c e c y c l e s and c l eanout p e r i o d as programmed. A n a l y t e s i g n a l s must be i n t e g r a t e d and c o l l e c t e d as peak area measurements. Background absorbances, background c o r r e c t e d a n a l y t e s i g n a l s , and determined a n a l y t e c o n c e n t r a t i o n s on a l l s o l u t i o n s must be a b l e t o be d i s p l a y e d on a CRT f o r immediate r e v i e w by t h e a n a l y s t and be a v a i l a b l e as h a r d copy f o r documentation t o be k e p t on f i l e . F l u s h t h e autosampler s o l u t i o n u p t a k e system w i t h t h e r i n s e b l a n k ( S e c t . 7.10.4) between each s o l u t i o n i n j e c t e d . 11.4.6 A f t e r c o m p l e t i o n o f t h e i n i t i a l r e q u i r e m e n t s o f t h i s method ( S e c t s . 10.4), samples s h o u l d be analyzed i n t h e same o p e r a t i o n a l manner used i n t h e c a l i b r a t i o n r o u t i n e . 11.4.7 D u r i n g t h e a n a l y s i s o f samples, t h e l a b o r a t o r y must comply w i t h t h e r e q u i r e d q u a l i t y c o n t r o l d e s c r i b e d i n S e c t i o n s 9.3 and 9.4. Only f o r t h e d e t e r m i n a t i o n o f d i s s o l v e d a n a l y t e s or t h e " d i r e c t a n a l y s i s " o f d r i n k i n g w a t e r w i t h t u r b i d i t y o f < 1 NTU i s t h e sample d i g e s t i o n s t e p o f t h e LRB, LFB, and LFM n o t r e q u i r e d . 11.4.8 For e v e r y new o r unusual m a t r i x , when p r a c t i c a l , i t i s h i g h l y recommended t h a t an i n d u c t i v e l y coupled plasma atomic e m i s s i o n s p e c t r o m e t e r be used t o screen f o r h i g h element c o n c e n t r a t i o n . I n f o r m a t i o n g a i n e d from t h i s may be used t o p r e v e n t p o t e n t i a l damage t o t h e i n s t r u m e n t and t o b e t t e r e s t i m a t e which elements may r e q u i r e a n a l y s i s by g r a p h i t e f u r n a c e . 11.4.9 Determined sample a n a l y t e c o n c e n t r a t i o n s t h a t a r e 90% o r more o f t h e upper l i m i t o f c a l i b r a t i o n must e i t h e r be d i l u t e d w i t h a c i d i f i e d r e a g e n t w a t e r and r e a n a l y z e d w i t h concern f o r memory e f f e c t s ( S e c t . 4 . 4 ) , o r determined by a n o t h e r approved t e s t procedure t h a t i s l e s s s e n s i t i v e . Samples w i t h a background absorbance > 1 . 0 must be a p p r o p r i a t e l y d i l u t e d w i t h a c i d i f i e d r e a g e n t w a t e r and r e a n a l y z e d ( S e c t . 9 . 4 . 6 ) . I f t h e method o f standard a d d i t i o n s i s required, f o l l o w the i n s t r u c t i o n s described i n Section 11.5. Revision 2.2 May 1994

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1 1 . 4 . 1 0 When i t i s necessary t o assess an o p e r a t i v e m a t r i x i n t e r f e r e n c e (e.g.! s i g n a l r e d u c t i o n due t o h i g h d i s s o l v e d s o l i d s ) , t h e t e s t d e s c r i b e d i n S e c t i o n 9 . 5 i s recommended. 11.4.11

Report d a t a as d i r e c t e d i n S e c t i o n 1 2 .

1 1 . 5 Standard A d d i t i o n s - I f t h e method o f s t a n d a r d a d d i t i o n i s r e q u i r e d , t h e f o l l o w i n g procedure i s recommended: 1 1 . 5 . 1 The s t a n d a r d a d d i t i o n technique" i n v o l v e s p r e p a r i n g new standards i n t h e sample m a t r i x by adding known amounts o f s t a n d a r d t o one o r more a l i q u o t s o f t h e processed sample s o l u t i o n . T h i s t e c h n i q u e compensates f o r a sample c o n s t i t u e n t t h a t enhances o r depresses t h e a n a l y t e s i g n a l , t h u s p r o d u c i n g a d i f f e r e n t s l o p e f r o m t h a t o f t h e c a l i b r a t i o n s t a n d a r d s . It w i l l n o t c o r r e c t f o r a d d i t i v e i n t e r f e r e n c e , which causes a b a s e l i n e s h i f t . The s i m p l e s t v e r s i o n o f t h i s t e c h n i q u e i s t h e s i n g l e - a d d i t i o n method. The procedure i s as f o l l o w s : Two i d e n t i c a l a l i q u o t s o f t h e sample s o l u t i o n , each o f volume V , a r e t a k e n . To t h e f i r s t ( l a b e l e d A) i s added a small volume b, o f a s t a n d a r d a n a l y t e s o l u t i o n o f c o n c e n t r a t i o n C,. To t h e second ( l a b e l e d B) i s added t h e same volume V, o f t h e s o l v e n t . The a n a l y t i c a l s i g n a l s o f A and B a r e measured and c o r r e c t e d f o r nonanalyte s i g n a l s . The unknown sample c o n c e n t r a t i o n C, i s c a l c u l ated :

where, S and S, a r e t h e a n a l y t i c a l s i g n a l s ( c o r r e c t e d f o r t h e b l a n k ) o f s o l u t i o n s A and B, r e s p e c t i v e l y . V, and C, s h o u l d be chosen so t h a t S, i s r o u g h l y t w i c e S, on t h e average. It i s b e s t i f V, i s made much l e s s t h a n V,, and t h u s C i s much g r e a t e r t h a n C, t o a v o i d excess d i l u t i o n o f t h e sampfe m a t r i x . If a s e p a r a t i o n o r c o n c e n t r a t i o n s t e p i s used, t h e a d d i t i o n s a r e b e s t made f i r s t and c a r r i e d t h r o u g h t h e e n t i r e procedure. F o r t h e r e s u l t s f r o m t h i s t e c h n i q u e t o be v a l i d , t h e f o l l o w i n g 1 i m i t a t i o n s must be t a k e n i n t o c o n s i d e r a t i o n :

1.

The a n a l y t i c a l c u r v e must be l i n e a r .

2.

The chemical f o r m o f t h e a n a l y t e added must respond i n t h e same manner as t h e a n a l y t e i n t h e sample.

3.

The i n t e r f e r e n c e e f f e c t must be c o n s t a n t o v e r t h e w o r k i n g range o f concern.

4.

The s i g n a l must be c o r r e c t e d f o r any a d d i t i v e i n t e r f e r e n c e .

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12.0 DATA ANALYSIS AND CALCULATIONS 1 2 . 1 Sample d a t a s h o u l d be r e p o r t e d i n u n i t s o f pg/L f o r aqueous samples and mg/kg d r y w e i g h t f o r s o l i d samples. 12.2 F o r d i s s o l v e d aqueous a n a l y t e s ( S e c t . 1 1 . 1 ) r e p o r t t h e d a t a generated d i r e c t l y from t h e i n s t r u m e n t w i t h a l l o w a n c e f o r sample d i l u t i o n . Do n o t r e p o r t a n a l y t e c o n c e n t r a t i o n s below t h e I D L . 12.3 For t o t a l r e c o v e r a b l e aqueous a n a l y t e s ( S e c t . 11.2), m u l t i p l y s o l u t i o n a n a l y t e c o n c e n t r a t i o n s by t h e d i l u t i o n f a c t o r 0.5, when 100 mL a l i q u o t i s used t o produce t h e 50 mL f i n a l s o l u t i o n , round t h e d a t a t o t h e t e n t h s p l a c e and r e p o r t t h e d a t a i n pg/L up t o t h r e e s i g n i f i c a n t f i g u r e s . I f a d i f f e r e n t a l i q u o t volume o t h e r t h a n 100 mL i s used f o r sample p r e p a r a t i o n , a d j u s t t h e d i l u t i o n f a c t o r a c c o r d i n g l y . Also, account f o r any a d d i t i o n a l d i l u t i o n o f t h e prepared sample s o l u t i o n needed t o complete t h e d e t e r m i n a t i o n o f a n a l y t e s exceeding t h e upper l i m i t o f t h e c a l i b r a t i o n curve. Do n o t r e p o r t d a t a below t h e determined a n a l y t e MDL c o n c e n t r a t i o n o r below an a d j u s t e d d e t e c t i o n 1 i m i t r e f l e c t i n g s m a l l e r sample a1 i q u o t s used i n p r o c e s s i n g o r a d d i t i o n a l d i l u t i o n s r e q u i r e d t o complete t h e a n a l y s i s . 12.4 For t o t a l r e c o v e r a b l e a n a l y t e s i n s o l i d samples ( S e c t . 11.3), round t h e s o l u t i o n a n a l y t e c o n c e n t r a t i o n s ( p g / L ) t o t h e t e n t h s p l a c e . Report t h e d a t a up t o t h r e e s i g n i f i c a n t f i g u r e s as mg/kg d r y - w e i g h t b a s i s u n l e s s s p e c i f i e d o t h e r w i s e by t h e program o r d a t a u s e r . C a l c u l a t e t h e c o n c e n t r a t i o n u s i n g t h e e q u a t i o n below: C x V x D Sample Conc. (mg/kg) dry-weight basis

=

W

where: C = C o n c e n t r a t i o n i n e x t r a c t (pg x O.OOl/L) V = Volume o f e x t r a c t (L, 100 mL = 0.1L) D = D i l u t i o n f a c t o r ( u n d i l u t e d = 1) W = Weight o f sample a l i q u o t e x t r a c t e d ( g x 0.001 = kg) Do n o t r e p o r t a n a l y t e d a t a below t h e e s t i m a t e d s o l i d s MDL o r an a d j u s t e d MDL because o f a d d i t i o n a l d i l u t i o n s r e q u i r e d t o complete t h e analysis.

12.5 To r e p o r t p e r c e n t s o l i d s i n s o l i d samples ( S e c t . 11.3) c a l c u l a t e as f o l 1ows : DW % s o l i d s (S) =

where: DW WW

= =

- x 100

ww

Sample w e i g h t ( 9 ) d r i e d a t 6OoC Sample w e i g h t ( 9 ) b e f o r e d r y i n g Revision 2.2 Hay 1994

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reported percent solids be determined by drying at 105OC, repeat the procedure given in Section 11.3 using a separate portion ( > 20 g) of the sample and dry to constant weight at 103-105°C. 12.6 The QC data obtained during the analyses provide an indication o f the quality of the sample data and should be provided with the sample results. 13.0

BETHOD PERFORMANCE

13.1 Instrument operating conditions used for single laboratory testing of the method and MDLs are listed in Table 2. 13.2 Data obtained from single laboratory testing of the method are summarized in Table 1A-C for three solid samples consisting of SRM 1645 River Sediment, EPA Hazardous Soil, and EPA Electroplating S1 udge. Samples were prepared using the procedure described in Section 11.3. For each matrix, five replicates were analyzed, and an average of the replicates was used for determining the sample background concentration. Two other pairs o f duplicates were fortified at different concentration levels. The sample background concentration, mean spike percent recovery, the standard deviation o f the average percent recovery, and the relative percent difference between the dupl icate-fortified determinations are 1 isted in Table 1AC. In addition, Table 1D-F contains single-laboratory test data for the method in aqueous media including drinking water, pond water, and well water. Samples were prepared using the procedure described in Section 11.2. For each aqueous matrix five replicates were analyzed, and an average of the replicates was used for determining the sample background concentration. Four samples were fortified at the levels reported in Table 1D-1F. A percent relative standard deviation is reported in Table 1D-1F for the fortified samples. An average percent recovery is also reported in Tables 1D-F. NOTE: Antimony and aluminum manifest relatively low percent recoveries (see Table lA, NBS River Sediment 1645).

14.0

POLLUTION PREVENTION

14.1

Pollution prevention encompasses any technique that reduces or eliminates the quantity or toxicity of waste at the point of generation. Numerous opportunities for pollution prevention exist in laboratory operation. The EPA has established a preferred hierarchy of environmental management techniques that places pollution prevention as the management option of first choice. Whenever feasible, laboratory personnel should use pollution prevention techniques to address their waste generation. When wastes cannot be feasibly reduced at the source, the Agency recommends recycling as the next best option.

14.2 For information about pollution prevention that may be applicable to laboratories and research institutions, consult Less i s Better: Revision 2.2 May 1994

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Laboratory Chemical Management for Waste Reduction, available from the American Chemical Society’s Department of Government Relations and Science Policy, 1155 16th Street N.W., Washington D.C. 20036, (202)872-4477. 15.0

WASTE MANAGEMENT 15.1

16.0

The Environmental Protection Agency requires that laboratory waste management practices be conducted consistent with all applicable rule and regulations. The Agency urges laboratories to protect the air, water, and land by minimizing and controlling all releases from hoods and bench operations, complying with the letter and spirit of any sewer discharge permits and regulations, and by complying with all solid and hazardous waste regulations, particularly the hazardous waste identification rules and land disposal restrictions. For further information on waste management consult The Waste Management Manual f o r Laboratory Personnel, available from the American Chemical Society at the address listed in the Section 15.2.

REFERENCES 1.

Environmental Protection Agency. Method 200.9, Determination of Trace Elements by Stabilized Temperature Graphite Furnace Atomic Absorption Spectrometry, Revision 1 . 2 , 1991.

2.

Creed, J.T., T.D. Martin, L.B. Lobring and J.W. O’Dell, Environ. Sci. Technol., 26:102-106, 1992.

3.

Waltz, B., G. Schlemmar and J.R. Mudakavi,

U.S.

JAAS, 3,

695,

1988.

4.

Carcinogens - Working With Carcinogens, Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, Publication No. 77-206, Aug. 1977.

5.

OSHA Safety and Health Standards, General Industry, (29 CFR 1910), Occupational Safety and Health Administration, OSHA 2206, (Revised, January 1976).

6.

Safety in Academic Chemistry Laboratories, American Chemical Society Publication, Committee on Chemical Safety, 3rd Edition, 1979.

7.

Proposed OSHA Safety and Health Standards, Laboratories, Occupational Safety and Health Administration, Federal Register, July 24, 1986.

8.

Rohrbough, W.G. et al. Reagent Chemicals, American Chemical Society Specifications, 7th edition. American Chemical Society, Washington, DC, 1986.

Revision 2.2 May 1994

178

Methods for the Determination 9.

American Society f o r Testing and M a t e r i a l s . Standard S p e c i f i c a t i o n f o r Reagent Water, D1193-77. Annual Book o f ASTM Standards, V o l . 11.01. P h i l a d e l p h i a , PA, 1991.

10.

Code o f Federal Regulation N , Ch. 1, P t . 136, Appendix B.

11.

Winefordner, J . D . , Trace Analysis: Spectroscopic Elements, Chemical Analysis, V o l . 4 6 , pp. 41-42.

Methods f o r

Revision 2.2 May 1994

17.0 TABLES, DIAGRAMS. FLOWCHARTS. AND V A L I D A T I O N DATA

TABLE 1A.

Sol i d Sample

A1 umi num A n t i mony Arsenic Cadmi um Chromi urn Copper Manganese Sel en i um Si 1 ver Tin

Certified Value+ 22600

(51) (66) 10.2 29600 109 785 1.5 --

--

Average Sed Conc (mg/kg) 6810 25.8 69.2 10.8 32800 132 893 0.7 1.7 439

P R E C I S I O N AND RECOVERY DATA FOR NBS R I V E R SEDIMENT 1645

% RSD

4.6 8.2 3.4 3.7 1.6 4.8 5.1 20.4 3.1 4.4

Average Percent Recovery (20 mg/kg)x

* 74.9 69.8 115.3

*

99.1

*

96.0 101.8 --

S(r)

-8.3 19.0 2.6 -14.2 -15.9 3.8

--

RPD

-9.5 12.0 4.0 -0

-45.2 9.7

--

Average Percent Recovery (100 rng/kg)x

* 99.0 89.2 110.7

*

111.5 103.2 105.4 93.5 --

S(r)

RPD

__

__

1.5 4.3 0.7

2.7 7.3 1.7

__

-_

3.6 26.4 4.0 1.9 --

2.6 4.7 10.7 5.6 --

( n = 5) S ( r ) Standard Deviation of Average Percent Recovery RPD Relative Percent Difference Between Duplicate Recovery Determinations * F o r t i f i e d concentration t10% o f sample concentration -Not determined t Values in parenthesis a r e noncertified X F o r t i f i e d concentration

% RSD Percent Relative Standard Deviation

FE m

0

rt

Average Sed Conc (mg/kg)

S o l i d Sample A1 umi num Ant imony Arsenic Cadmi um Chromi urn Copper Manganese Sel e n i um S i 1v e r Tin

1

6410 4.6 8.7 1.8 84.0 127 453 0.6 0.9 18.4

Average Percent Recovery (20 mg/kg)x

% RSD

3.3 14.7 4.6 10.3 4.2 4.3 6.0 7.5 18.5 3.7

S(r)

RPD

--

--

61.4 109.8 115.4 95.5 108.0

2.7 2.1 0.8 33.8 15.2

7.4 3.5 1.4 17.9 2.6

95.0 100.1

8.4 3.8

*

*

I

--

--

-_

Average Percent Recovery (100 mg/kg)x

*

--

24.1 10.2

--

I

% RSD Percent R e l a t i v e Standard D e v i a t i o n ( n = 5)

S ( r ) Standard D e v i a t i o n of Average Percent Recovery RPD

*

-X

R e l a t i v e Percent D i f f e r e n c e Between D u p l i c a t e Recovery D e t e r m i n a t i o n s F o r t i f i e d c o n c e n t r a t i o n (10% o f sample c o n c e n t r a t i o n Not determined F o r t i f i e d concentration

60.9 103.7 99.0 120.8 117.7 99.2 96.9 93.5 --

9 0 S(r)

-1.7 1.5 4.3 6.6 5.4 13.9 3.3 1.3

--

RPD

-7.1 3.6 12.1 8.9 5.7 1.6 9.7 3.8

--

?!

$.

Fig.

TABLE 1C.

PRECISION AND RECOVERY DATA FOR EPA ELECTROPLATING SLUDGE 286

Solid Sample

A1 umi num Antimony Arsenic Cadmi um Chromi um Copper Manganese Selenium Si 1 ver Tin % RSD S(r)

RPD

*

-X

zz 6590 7.7 33.7 119 8070 887 3 20 0.8 6.5 21.8

%

RSD 2.7 3.9 2.7 1.3 4.5 1.6 1.6 6.7 2.3 3.2

Average Percent Recovery (20 mg/kg)x

* 68.6 87.6 81.9

* * *

99.4 102.8

--

S(r)

RPD

--

--

2.3 2.6 7.9

----

0.8 2.5

--

1

Average Percent ( RecovgerYg)x 100 m /k

*

5.7 1.7 3.0

60.7 100.2 112.5

2.3 5.3

99.5 101.0 96.8 92.3

-_--

--

Percent !lative StanLJrd wiation (n = 5) Standard Deviation o f Average Percent Recovery Relative Percent Difference Between Duplicate Recovery Determinations Fortified concentration 4 0 % o f sample concentration Not determined Fortified concentration

*

--

S(r)

RPD

--

--

3.1 1.5 3.9

--

21.9 6.4 0.7 1.9

--

12.8 3.1 4.7

--

6.0 4.0 1.9 5.4

--

TABLE 1D.

Element Ag

A1

As3

Be Cd co Cr cu Fe Mn

Ni Pb Sb3 se3 sn3

T1

Average Conc. pg/L t0.5 550 3.2 0.05 to. 05 t0.7 0.75 2.98 773 751 2.11 1.22 4 t0.8 t0.6 t1.7 t0.7

PRECISION AND RECOVERY DATE FOR POND WATER

% RSD

Fort i f ied, Conc. pg/L

* 1.2 4.1 36.4

* *

8.7 11.2 5.7 2.2 6.8 20.5

* *

* 75.0

% RSD at Fortifipd Conc.

1.25

--

lo 2.5 0.5 10 2.5 10 --20 25 25 25 50 50

Recovery

3.7 -0.8 14.0 4.5 2.8 1.8 2.9 --

--

1.6 1.8 0.4 1.6 3.3 5.2

< Sample concentration less than the established method detection limit.

* Not determined on sample concentrations less than the method detection limit.

' Fortified sample concentration based on 100-mL ' RSD are reported on 50-mL sample volumes. Electrodeless discharge lamps were used.

sample volumes.

107.5 -100.5 90.0 99.1 97.3 98.5 101.9

--

-105.6 101 -6 115.2 97.8 117.5 101.0

TABLE 1E.

E l ement

Average Conc. pg/L

Ag A1 As3 Be Cd

co Cr cu Fe Mn

Ni Pb Sb3 s e3 sn3 T1 t

PRECISION AND RECOVERY DATE FOR DRINKING NATER

t0.5 163.6 0.5 t0.02 to. 05
% RSD

* 2.5 10.5

* * * *

7.3 17.6 1.3 32.7

*

* * * *

Fortified, Conc. pq/L

% RSD a t F o r t if i e d Conc.

1.25 150 10 2.5 0.5 10 2.5 10 150 2.5 20 10 15 25 50 20

Average Percent Recovery

5.6 6.4 0.6 9.4 6.3 3.9 3.1 1.2 5.9 0.7 4.3 4.0 14.7 1.5 0.4 2.8

Sample c o n c e n t r a t i o n l e s s than t h e e s t a b l i s h e d method d e t e c t i o n l i m i t .

* Not determined on sample c o n c e n t r a t i o n s l e s s than t h e method d e t e c t i o n l i m i t .

' F o r t i f i e d sample

c o n c e n t r a t i o n based on 100-mL sample volumes.

RSD are r e p o r t e d on 50-mL sample volumes.

Electrode1ess discharge 1amps were used.

94.6 111.7 88.4 106.0 105.2 88.5 105.7 111.5 107.8 96.7 103.8 101.8 101.4 88.9 100.7 95.4

TABLE 1F.

P R E C I S I O N AND RECOVERY DATE FOR WELL WATER

Fortified Conc. pg/L

Average Element Ag A1 As3 Be Cd CO

Cr cu Fe Mn Ni Pb Sb3

se3 sn3

T1

Conc. pg/L

<0.5 14.4 0.9 t o . 02 1.8 4.0
%

RSD

* 26.7 14.2

*

11.9 2.9

*

1.2 6.6 2.7 3.2

1.25 150 10 2.5 0.5 10 2.5 10

---

* *

20 25 25 25

*

50

* *

% RSD at Fortififd Conc.

50

Average Percent Recovery

3.6 1.5 2.1 3.4 4.6 1.o 4.0 0.6

108.3 97.1 101.6 103.7 109.3 95.8 102.6 90.2

4.0 0.7

105.7 102.2 114.3 95.9 106. I 98.0

---

1.2 1.2 3.0 1.4

< Samp e concentration less than the establ shed method detection limit.

* Not determined on sample concentrations less than the method detection limit Fortified sample concentration based on 100-mL sample volumes.

' RSD are reported on 50-mL sample volumes. Electrodeless discharge lamps were used.

---

Metals TABLE 2.

Element

RECOMMENDED GRAPHITE FURNACE OPERATJNG CONDITIONS AND RECOMMENDED M A T R I X MODIFIER -

Wave1ength

Ag A1 As7 Be Cd co Cr cu Fe Mn Ni Pb Sb7 se7 sn7 T1 Matrix Modifier

185

328.1 309.3 193.7 234.9 228.8 242.5 357.9 324.8 248.3 279.5 232.0 283.3 217.6 196.0 286.3 276.8 =

S1 i t

0.7 0.7 0.7 0.7 0.7 0.2 0.7 0.7 0.2 0.2 0.2 0.7 0.7 2.0 0.7 0.7

Temperature Char 1000

1700 1300 1200 800

1400 1650 1300 1400 1400 1400 1250 1100 1000 14008 1000

(C)5 Atom

1800 2600 2200 2500 1600 2500 26006 26006 2400 2200 2500 2000 2000 2000 2300 1600

MDL'

0.59 7 .89 0.5 0.02 0.05 0.7 0.1 0.7

-

0.3 0.6 0.7 0.8 0.6 1.7 0.7

0.015 mg Pd t 0.01 mg Mg(NO,),.

A 5% H i n A r gas mix i s used d u r i n g t h e d r y and char steps a t 300 mL/min f o r a13 elements. A cool down step between t h e char and a t o m i z a t i o n i s recommended. Obtained usi n g a 20-pL sample s i z e and stop f l o w atomization. Act ual char and a to m i z a ti o n temperatures may v a r y from instrument t o inst rument and are b e s t determined on an i n d i v i d u a l b a s i s . The a c t u a l d r y i n g temperature may v a ry depending on t h e temperature o f t h e water used t o cool t h e furnace. 6

A 7-s at omiza ti o n i s necessary t o q u a n t i t a t i v e l y remove t h e a n a l y t e from t h e g r a p h i t e furnace.

7

An e l e c t r o d e l e s s discharge lamp was used f o r t h i s element.

8

An a d d i t i o n a l low temperature (approximately 200°C) per char i s recommended.

9

Pd m o d i f i e r was determined t o have t r a c e l e v e l contamination o f t h i s e l ement .

Revision 2.2 May 1994

186

Methods for the Determination TABLE 3 . MULTIPLE DEPOSITION

D r i n k i n g Water Source

-

ARSENIC

PRECISION

AND RECOVERY

Fortified

Average

DATA'-^ Percent Recovery

Conc. ggfL

%RSD

C i n t i . Ohio

0.3

41%

3.8

3.9%

88%

Home C i s t e r n

0.2

15%

4.1

1.7%

98%

Region I

0.7

7.3%

5.0

1.9%

108%

Region V I

2.6

3.4%

6.7

4.3%

103%

Region X

1.1

4.8%

5.0

1.7%

97%

N I S T 1643c*

3.9

7.1%

_-

95%

Conc. gg/L

-_

%RSD

1

The recommended i n s t r u m e n t c o n d i t i o n s g i v e n i n Table 2 were used i n t h i s procedure e x c e p t f o r u s i n g d i l u t e d ( 1 t 2 ) m a t r i x m o d i f i e r and s i x - 36 p L d e p o s i t i o n s (30 pL sample t 1 pL r e a g e n t w a t e r t 5 pL m a t r i x m o d i f i e r ) f o r each d e t e r m i n a t i o n ( S e c t . 10.5). The amount o f m a t r i x m o d i f i e r d e p o s i t e d on t h e p l a t f o r m w i t h each d e t e r m i n a t i o n ( 6 x 5 pL) = 0.030 mg Pd + 0.02 mg Mg(NO,),. The d e t e r m i n e d a r s e n i c MDL u s i n g t h i s procedure i s 0.1 pg/L.

*

Sample d a t a and f o r t i f i e d sample d a t a were c a l c u l a t e d f r o m f o u r and f i v e rep1 i c a t e d e t e r m i n a t i o n s , r e s p e c t i v e l y . A l l d r i n k i n g w a t e r s were f o r t i f i e d w i t h 4.0 pg/L a r s e n i c . The i n s t r u m e n t was c a l i b r a t e d u s i n g a b l a n k and f o u r s t a n d a r d s o l u t i o n s (1.0, 2.5, 5.0, and 7.5 p g / L ) . The N I S T 1643c r e f e r e n c e m a t e r i a l Trace Elements i n Water was d i l u t e d ( 1 t 1 9 ) f o r a n a l y s i s . The c a l c u l a t e d d i l u t e d a r s e n i c c o n c e n t r a t i o n i s 4.1 pg/L. The l i s t e d p r e c i s i o n and r e c o v e r y d a t a a r e f r o m 13 r e p l i c a t e d e t e r m i n a t i o n s c o l l e c t e d o v e r a p e r i o d o f f o u r days.

Revision 2.2 Hay 1994

Metals

187

Method 200.10 DETERMINATION OF TRACE ELEMENTS I N MARINE WATERS BY ON-LINE CHELATION PRECONCENTRATION AND INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY

-

Stephen E. Long Technology A p p l i c a t i o n s , Inc. and Theodore D. M a r t i n I n o r g a n i c C h e m i s t r y Branch C h e m i s t r y Research D i v i s i o n

R e v i s i o n 1.4 A p r i l 1991

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

188

Methods for the Determination METHOD 200.10 DETERMINATION OF TRACE ELEMENTS I N MARINE WATERS BY ON-LINE CHELATION PRECONCENTRATION AND INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETRY

1.

SCOPE AND APPLICATION

1.1 This method describes procedures f o r p r e c o n c e n t r a t i o n and det er m i n a ti o n o f t o t a l recoverable t r a c e elements i n marine waters, i n c l u d i n g e s t u a r i n e water, seawater and b r i n e s .

1.2 Acid s o l u b i l i z a t i o n i s r e q u i r e d p r i o r t o t h e d e t e r m i n a t i o n o f t o t a l recoverable elements t o f a c i l i t a t e breakdown o f complexes or c o l l o i d s which might i n f l u e n c e t r a c e element r e c o v e r i e s . Th i s method should o n l y be used f o r p r e c o n c e n t r a t i o n and d e t e r m i n a t i o n o f t r a c e elements i n aqueous samples.

1.3

This method i s a p p l i c a b l e t o t h e f o l l o w i n g elements: Chemical A b s t r a c t Services R e g i s t r y Numbers (CASRN)

Element Cadmium Cobalt Copper Lead Nickel Uranium Vanadium

(Cd) (CO) (CU)

(Pb) (Ni 1 (U) (V)

7440-43-9 7440-48-4 7440-50-8 7439-92-1 7440-02-0 7440-61- 1 7440-62-2

1.4 Method d e t e c t i o n l i m i t s (MDLs) f o r these elements w i l l be dependent on t h e s p e c i f i c i n s tru me n ta ti o n employed and t h e s e l e c t e d o p e r a t i n g c o n d i t i o n s . However, t h e MDLs should be e s s e n t i a l l y independent o f t h e m a t r i x because e l i m i n a t i o n o f t h e m a t r i x i s a f e a t u r e of t h e method. MDLs i n reagent water, which were determined u s i n g t h e procedure described i n Sect. 10.2.2, are l i s t e d i n Table 1.

1.5 A minimum o f s i x months experience i n t h e use o f commercial inst ru me n ta ti o n f o r i n d u c t i v e l y coupled plasma mass spectrometry (ICP-MS) i s recommended. S p e c i f i c i n f o r m a t i o n r e g a r d i n g t h e use o f ICP-MS f o r t h e d e te rm i n a ti o n o f t r a c e elements may be found i n USEPA Method 200.8"'

2.

SUMMARY OF METHOD

2.1 T his method i s used t o preconcentrate t r a c e elements u s i n g an Fo l l o w i n g a c i d imino d i a c e ta te f u n c t i o n a l i z e d c h e l a t i n g s o l u b i l i z a t i o n , t h e sample i s b u f f e r e d p r i o r t o c h e l a t i n g column

Metals

189

3.11 LABORATORY F O R T I F I E D SAMPLE M A T R I X (LFM) - An a l i q u o t o f an environmental sample t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFM i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o determine whether t h e sample m a t r i x c o n t r i b u t e s b i a s t o t h e a n a l y t i c a l r e s u l t s . The background c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be determined i n a separate a l i q u o t and t h e measured values i n t h e LFM c o r r e c t e d f o r t h e c o n c e n t r a t i o n s found. 3.12 QUALITY CONTROL SAMPLE (QCS) - A s o l u t i o n c o n t a i n i n g known c o n c e n t r a t i o n s o f method a n a l y t e s which i s used t o f o r t i f y an a l i q u o t o f LRB m a t r i x . The QCS i s o b t a i n e d from a source e x t e r n a l t o t h e l a b o r a t o r y and i s used t o check l a b o r a t o r y performance. 4.

5.

INTERFERENCES

4.1

A d i s c u s s i o n o f i n t e r f e r e n c e s r e l a t i n g t o t h e use o f ICP-MS may be found i n USEPA Method 200.8"'. A p r i n c i p a l advantage o f t h i s method i s t h e s e l e c t i v e e l i m i n a t i o n o f species g i v i n g r i s e t o p o l y a t o m i c s p e c t r a l i n t e r f e r e n c e s on c e r t a i n t r a n s i t i o n m e t a l s (e.g. removal o f t h e c h l o r i d e i n t e r f e r e n c e on vanadium). As t h e m a j o r i t y o f t h e sample m a t r i x i s removed, m a t r i x induced p h y s i c a l i n t e r f e r e n c e s a r e a l s o s u b s t a n t i a l l y reduced.

4.2

Low r e c o v e r i e s may be encountered i n t h e p r e c o n c e n t r a t i o n c y c l e i f t h e t r a c e elements a r e complexed by competing c h e l a t o r s i n t h e sample o r a r e p r e s e n t as c o l l o i d a l m a t e r i a l . A c i d s o l u b i l i z a t i o n p r e t r e a t m e n t i s employed t o improve a n a l y t e r e c o v e r y and t o m i n i m i z e a d s o r p t i o n , h y d r o l y s i s and p r e c i p i t a t i o n e f f e c t s .

4.3

Memory i n t e r f e r e n c e s f r o m t h e c h e l a t i n g system may be encountered e s p e c i a l l y a f t e r a n a l y z i n g a sample c o n t a i n i n g h i g h c o n c e n t r a t i o n s o f t h e a n a l y t e s . A t h o r o u g h column r i n s i n g sequence f o l l o w i n g e l u t i o n o f t h e a n a l y t e s i s necessary t o m i n i m i z e such i n t e r f e r e n c e s .

SAFETY

5.1

Each chemical r e a g e n t used i n t h i s method should be regarded as a p o t e n t i a l h e a l t h hazard and exposure t o t h e s e r e a g e n t s should be as l o w as r e a s o n a b l y a c h i e v a b l e . Each l a b o r a t o r y i s r e s p o n s i b l e for m a i n t a i n i n g a c u r r e n t awareness f i l e o f OSHA r e g u l a t i o n s r e a d i n g t h e s a f e h a n d l i n g o f t h e c h e m i c a l s s p e c i f i e d i n t h i s method ). A r e f e r e n c e f i l e o f m a t e r i a l d a t a h a n d l i n g sheets should a l s o be a v a i l a b l e t o a l l personnel i n v o l v e d i n t h e chemical a n a l y s i s .

9's

5.2

A n a l y t i c a l plasma sources e m i t r a d i o f r e q u e n c y r a d i a t i o n i n a d d i t i o n t o i n t e n s e UV r a d i a t i o n . S u i t a b l e p r e c a u t i o n s should be t a k e n t o p r o t e c t personnel from such hazards.

190

Methods for the Determination e n t r y u s i n g an o n - l i n e system. Group I and I 1 m e t a l s , as w e l l as most anions, a r e s e l e c t i v e l y separated from t h e a n a l y t e s by e l u t i o n w i t h ammonium a c e t a t e a t DH 5 . 5 . The a n a l y t e s a r e subsequently e l u t e d i n t o a s i m p l i f i e d m a t r i x co s i s t i n q o f d i l u t e n i t r i c a c i d and a r e determined by ICP-MS u s i n g a d r e c t l y - c o u p l e d on-1 i n e configuration.

3.

DEFINITIONS 3.1

TOTAL RECOVERABLE - The c o n c e n t r a t on o f a n a l y t e d e t e r m i n e d on an u n f i l t e r e d sample f o l l o w i n g t r e a t m e n t w i t h h o t d i l u t e m i n e r a l a c i d .

3.2 METHOD DETECTION LIMIT (MDL)

- The minimum c o n c e n t r a t i o n o f an a n a l y t e t h a t can be i d e n t i f i e d , measured and r e p o r t e d w i t h 99% confidence t h a t t h e analyte concentration i s g r e a t e r than zero.

3.3

LINEAR DYNAMIC RANGE (LDR) - The c o n c e n t r a t i o n range o v e r which t h e a n a l y t i c a l w o r k i n g c u r v e remains 1 i n e a r .

3.4

LABORATORY REAGENT BLANK (LRB) ( p r e p a r a t i o n b l a n k ) - An a l i q u o t o f reagent w a t e r t h a t i s t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a l l labware, equipment, s o l v e n t s , r e a g e n t s , and i n t e r n a l standards t h a t a r e used w i t h o t h e r samples. The LRB i s used t o determine i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e l a b o r a t o r y environment, r e a g e n t s o r apparatus.

3.5 CALIBRATION BLANK - A volume o f ASTM t y p e I w a t e r a c i d i f i e d w i t h t h e same a c i d m a t r i x as i s p r e s e n t i n t h e c a l i b r a t i o n standards.

3.6

INTERNAL STANDARD - Pure a n a l y t e ( s ) added t o a s o l u t i o n i n known amount(s) and used t o measure t h e r e l a t i v e responses o f o t h e r method a n a l y t e s t h a t a r e components o f t h e same s o l u t i o n . The i n t e r n a l s t a n d a r d must be an a n a l y t e t h a t i s n o t a sample component.

3.7

STOCK STANDARD SOLUTION - A c o n c e n t r a t e d s o l u t i o n c o n t a i n i n g one o r more a n a l y t e s prepared i n t h e l a b o r a t o r y u s i n g assayed r e f e r e n c e compounds o r purchased from a r e p u t a b l e commercial source.

3 . 8 CALIBRATION STANDARD (CAL) - A s o l u t i o n p r e p a r e d f r o m t h e s t o c k standard s o l u t i o n ( s ) which i s used t o c a l i b r a t e t h e i n s t r u m e n t response w i t h r e s p e c t t o a n a l y t e c o n c e n t r a t i o n .

3.9 TUNING SOLUTION - A s o l u t i o n which i s used t o d e t e r m i n e a c c e p t a b l e i n s t r u m e n t performance p r i o r t o c a l i b r a t i o n and sample analyses.

3.10 LABORATORY F O R T I F I E D BLANK (LFB) - An a l i q u o t which known q u a n t i t i e s o f t h e method a n a l y t e s l a b o r a t o r y . The LFB i s analyzed e x a c t l y l i k e purpose i s t o determine whether t h e method i s c o n t r o l 1i m i t s .

o f reagent water t o a r e added i n t h e a sample, and i t s w i t h i n accepted

Metals

191

6 . APPARATUS AND EOUIPMENT 6.1 PRECONCENTRATION SYSTEM - System c o n t a i n i n g no m e t a l p a r t s i n t h e analyt e f l o w path, c o n fi g u re d as shown i n Fi g u r e 1. 6.1.1

Column - Macroporous i m i n o d i a c e t a t e c h e l a t i n g r e s i n (Dionex Metpac C C - 1 o r e q u i v a l e n t ) .

6.1.2

Sample l o o p - 10 mL l o o p c o n s t r u c t e d from narrow bore, highpressure i n e r t tu b i n g , Tefzel ETFE ( e t h y l e n e t e t r a fluoroethylene) o r equivalent.

6.1.3

Eluent pumping system ( P l ) - Programmable f l o w , h i g h pressure pumping system, capable o f d e l i v e r i n g e i t h e r one o f t w o e l u e n ts a t a pressure up t o 2000 p s i and a f l o w r a t e o f 1-5 mL/mi n .

6.1.4

A u x i l i a r y pumps - On l i n e b u f f e r Dump (P21, p i s t o n pump (Dionex Q I C pump o r e q u i v a l e n t ) f o r d e l i v e r i n g 2M ammonium a c e ta te b u f f e r s o l u t i o n ; c a r r i e r DumD ( P 3 ) , p e r i s t a l t i c pump (Gi l s o n M i n i p u l s o r e q u i v a l e n t ) f o r d e l i v e r i n g 1% n i t r i c a c i d c a r r i e r s o l u t i o n ; sample DumD (P42, p e r i s t a l t i c pump f o r 1oadi ng sample 1oop .

6.1.5

C o n tro l v a l v e s - I n e r t double stack, p n e u m a t i c a l l y operated four-way s l i d e r valves w i t h connectors. 6.1.5.1 Argon gas supply r e g u l a t e d a t 80-100 p s i .

6.2

6.1.6

S o l u t i o n r e s e r v o i r s - I n e r t c o n t a i n e r s , e.g. h i g h d e n s i t y p o l y e th y l e n e (HDPE) f o r h o l d i n g e l u e n t and c a r r i e r reagents.

6.1.7

Tubing - High pressure, narrow bore, i n e r t t u b i n g (e.g. T e fz e l ETFE o r e q u i v a l e n t ) f o r i n t e r c o n n e c t i o n o f pumps/valve assemblies and a minimum l e n g t h f o r connection o f t h e p re c o n c e n tra ti o n system t o t h e ICP-MS instrument.

INDUCTIVELY COUPLED PLASMA

-

MASS SPECTROMETER

6.2.1

Instrument capable o f scanning t h e mass range 5-250 amu w i t h a minimum r e s o l u t i o n c a p a b i l i t y o f 1 amu peak w i d t h a t 5% peak h e i g h t . Instrument may be f i t t e d w i t h a conventional o r extended dynamic range d e t e c t i o n system.

6.2.2

Argon gas supply ( h i g h - p u r i t y grade, 9 9 . 9 9 % ) .

6.2.3

A mass-flow c o n t r o l l e r on t h e n e b u l i z e r gas supply i s recommended. A water-cooled spray chamber may be o f b e n e f i t i n re d u c i n g some types o f i n t e r f e r e n c e s (e.g., polyatomic o x i d e s p e c i e s ).

192

Methods for the Determination 6.2.4

6.3

6.4

Operating c o n d i t i o n s - Because o f t h e d i v e r s i t y of instrument hardware, no d e t a i l e d instrument o p e r a t i n g c o n d i t i o n s a r e provided. The a n a l y s t i s advised t o f o l l o w t h e recommended o p e ra ti n g c o n d i t i o n s provided by t h e manufacturer.

LABWARE - For th e d e te rmi n a ti o n o f t r a c e elements, contamination and l o s s are o f c r i t i c a l c o n s i d e r a t i o n . P o t e n t i a l contamination sources i n c l u d e improperly cleaned l a b o r a t o r y apparatus and general contamination w i t h i n t h e l a b o r a t o r y environment. A c l e a n l a b o r a t o r y work area, designated f o r t r a c e element sample h a n d l i n g must be used. Sample c o n ta i n e rs can i n t r o d u c e p o s i t i v e and n e g a t i v e e r r o r s i n t h e d e te rm i n a ti o n o f t r a c e elements by (1) c o n t r i b u t i n g contaminants through surface d e s o r p t i o n o r l e a c h i n g , (2) d e p l e t i n g element c o n c e n tra ti o n s through a d s o r p t i o n processes. For these reasons, b o r o s i l i c a t e g l a s s i s not recommended f o r use w i t h t h i s method. A l l labware i n c o n ta c t w i t h t h e sample should be cleaned p r i o r t o use. Labware may be soaked o v e r n i g h t and t h o r o u g h l y washed w i t h 1aboratory-grade d e te rg e n t and water, r i n s e d w i t h water, and soaked f o r 4 h i n a m i x t u r e o f d i l u t e n i t r i c and h y d r o c h l o r i c acids, f ollowe d by r i n s i n g w i t h ASTM type I water and oven d r y i n g . 6.3.1

G r i f f i n beakers, 250 mL, p o l y t e t r a f l u o r o e t h y l e n e (PTFE) o r q u a rtz .

6.3.2

Storage b o t t l e s - Narrow mouth b o t t l e s , T e f l o n FEP ( f l u o r i n a t e d e th y l e n e propylene), o r HDPE, 125 mL and 250 mL capacities.

SAMPLE PROCESSING EQUIPMENT 6.4.1

A i r displacement p i p e t t e r - D i g i t a l p i p e t system capable of d e l i v e r i n a volumes from 10 t o 2500 LIL w i t h an assortment of metal-free, disposable p i p e t t i p s . '

6.4.2

Balances - A n a l y t i c a l balance, capable o f accurate y weighing t o f 0.1 mg; t o p pan balance, accurate t o k 0.01g.

6.4.3

Hot p l a t e - Corning PClOO o r e q u i v a l e n t .

6.4.4

C e n tri fu g e - Steel c a b i n e t w i t h guard bowl, e l e c t r c t i m e r and brake.

6.4.5

D ry i n g oven - G r a v i t y convection oven w i t h t h e r m o s t a t i c c o n t r o l capable o f m a i n t a i n i n g 105°C 2 5°C.

6.4.6

pH meter - Bench mounted o r hand-held e l e c t r o d e system w i t h a r e s o l u t i o n o f f 0.1 pH u n i t s .

Metals 7.

193

REAGENTS AND CONSUMABLE MATERIALS

7.1 WATER

- For a l l sample p r e p a r a t i o n and d i l u t i o n s , ASTM t y p e I water (ASTM 01193) i s r e q u i r e d .

7.2 Reagents may c o n t a i n elemental i m p u r i t i e s which m i g h t a f f e c t t h e i n t e g r i t y o f a n a l y t i c a l d a t a . Owing t o t h e h i g h s e n s i t i v i t y o f t h i s method, u l t r a h i g h - p u r i t y r e a g e n t s must be used u n l e s s o t h e r w i s e s p e c i f i e d . To m i n i m i z e c o n t a m i n a t i o n , r e a g e n t s should be prepared d i r e c t l y i n t h e i r d e s i g n a t e d c o n t a i n e r s where p o s s i b l e .

7.2.1 A c e t i c a c i d , g l a c i a l (sp. g r . 1.05). 7.2.2 Ammonium h y d r o x i d e (20%). 7.2.3

Ammonium a c e t a t e b u f f e r lM, pH 5.5 - Add 58 mL (60.5 g) of g l a c i a l a c e t i c a c i d t o 600 mL o f ASTM t y p e I w a t e r . Add 65 mL (60 g) o f 20% ammonium h y d r o x i d e and mix. Check t h e pH o f t h e r e s u l t i n g s o l u t i o n by w i t h d r a w i n g a small a l i q u o t and t e s t i n g w i t h a c a l i b r a t e d pH meter, a d j u s t i n g t h e s o l u t i o n t o pH 5.5 t 0.1 w i t h small volumes o f a c e t i c a c i d o r ammonium h y d r o x i d e as necessary. Cool and d i l u t e t o 1 L w i t h ASTM type I water.

7.2.4 Ammonium a c e t a t e b u f f e r 2M, pH 5.5 - Prepare as f o r Sect. 7.2.3 u s i n g 116 mL (121 g) g l a c i a l a c e t i c a c i d and 130 mL (120 g) 20% ammonium h y d r o x i d e , d i l u t e d t o 1000 mL w i t h ASTM t y p e I water. NOTE: The ammonium a c e t a t e b u f f e r s o l u t i o n s may be f u r t h e r p u r i f i e d by p a s s i n g them t h r o u g h t h e c h e l a t i n g column a t a f l o w r a t e of 5.0 mL/min. W i t h r e f e r e n c e t o F i g u r e 1, pump t h e b u f f e r s o l u t i o n t h r o u g h t h e column u s i n g pump P1, w i t h v a l v e s A and B o f f and v a l v e C on. C o l l e c t t h e p u r i f i e d s o l u t i o n i n a c o n t a i n e r a t t h e waste o u t l e t . F o l l o w i n g t h i s , e l u t e t h e c o l l e c t e d contaminants f r o m t h e column u s i n g 1.25M n i t r i c a c i d f o r 5 min a t a f l o w r a t e o f 4.0 mL/min.

7.2.5

N i t r i c acid, concentrated (sp.gr.

1.41).

7.2.5.1 N i t r c a c i d 1.25M - D i l u t e 79 mL (112 g) conc. n i t r i c a c i d t o 1000 mL w i t h ASTM t y p e I w a t e r . 7.2.5.2 N i t r c a c i d 1% - D i l u t e 10 mL conc. n i t r c a c i d t o 1000 mL w i t h ASTM t y p e I w a t e r . 7.2.5.3 N i t r i c a c i d (ltl) - D i l u t e 500 mL conc. n i t r i c a c i d t o 1000 mL w i t h ASTM t y p e I water. 7.2.5.4 N i t r i c a c i d (1t9) - D i l u t e 100 mL conc. n i t r i c a c i d t o 1000 mL w i t h ASTM t y p e I w a t e r .

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Methods for the Determination

7.2.6 O x a l i c a c i d d i h y d r a t e (CASRN 6153-56-6), 0.2M - D i s s o l v e 25.2 g reagent grade CH, 0,.2H 0 i n 250 mL ASTM t y p e I water and d i l u t e t o 1000 mL w i i h A S f M t y p e I w a t e r . CAUTION O x a l i c a c i d i s t o x i c , handle w i t h care.

7.3 STANDARD STOCK SOLUTIONS - May be purchased from a r e p u t a b l e commercial source o r prepared f r o m u l t r a h i g h - p u r i t y grade chemicals o r metals (99.99 - 99.999% p u r e ) . A l l s a l t s should be d r i e d f o r one hour a t 1050C, unless otherwise s p e c i f i e d . (CAUTION - Many metal s a l t s are extremely t o x i c i f i n h a l e d o r swallowed. Wash hands thoroughly a f t e r h a n d l i n g ). Stock s o l u t i o n s should be s t o r e d i n p l a s t i c b o t t l e s . The f o l l o w i n g procedures may be used f o r p r e p a r i n g standard stock s o l u t i o n s : NOTE: Some m e t a l s , p a r t i c u l a r l y those which form surface oxides r e q u i r e c l e a n i n g p r i o r t o being weighed. Th i s may be achieved by p i c k l i n g t h e surface o f t h e metal i n a c i d . An amount i n excess o f t h e d e s i re d weight should be p i c k l e d r e p e a t e d l y , r i n s e d w i t h water, d r i e d and weighed u n t i l t h e d e s i r e d weight i s achieved.

7.3.1 Cadmium s o l u t i o n , stock 1 mL = 1000 p g Cd: P i c k l e cadmium m e t a l i n (1t9) n i t r i c a c i d t o an exact weight o f 0.100 g. D i s s o l v e i n 5 mL (ltl) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h ASTM t y p e I water. 7.3.2 Cobalt s o l u t i o n , stock 1 mL = 1000 p g Co: P i c k l e c o b a l t metal i n (1t9) n i t r i c a c i d t o an exact weight o f 0.100 g. D i s s o l v e i n 5 mL (ltl) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h ASTM t y p e I water. 7.3.3 Copper s o l u t i o n , stock 1 mL = 1000 p g Cu: P i c k l e copper metal i n (1t9) n i t r i c a c i d t o an exact weight o f 0.100 g. D i s s o l v e i n 5 mL (ltl) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h ASTM t y p e I water.

7.3.4

Indium s o l u t i o n , s to c k 1 mL = 1000 gg I n : P i c k l e indium metal i n (1t1) n i t r i c a c i d t o an e x a c t weight o f 0.100 g. D i s s o l v e i n 10 mL (ltl) n i t r i c acid, h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h ASTM t y p e I water.

7.3.5

Lead s o l u t i o n , stock 1 mL = 1000 p g Pb: D i s s o l v e 0.1599 g PbNO, i n 5 mL (ltl) n i t r i c a c i d . D i l u t e t o 100 mL w i t h ASTM ty p e I water.

7.3.6 N i c k e l s o l u t i o n , stock 1 mL = 1000 p g N i : D i s s o l v e 0.100 g n i c k e l powder i n 5 mL conc. n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h ASTM t y p e I water. 7.3.7 Terbium s o l u t i o n , stock 1 mL

= 1000 p g Tb: D i s s o l v e 0.1176 g Tb,O, i n 5 mL conc. n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL w i t h ASTM t y p e I water.

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195

7.3.8 Uranium s o l u t i o n , s t o c k 1 mL

= 1000 fig U: D i s s o l v e 0.2110 g UO (N0,),.6H 0 (DO NOT DRY) i n 20 mL ASTM t y p e I w a t e r and di!ute t o 160 mL w i t h ASTM t y p e I w a t e r .

7.3.9 Vanadium s o l u t i o n , s t o c k 1 mL = 1000 p g V : P i c k l e vanadium metal i n (lt9) n i t r i c ac d t o an e x a c t w e i g h t o f 0.100 g. D i s s o l v e i n 5 mL (ltl) n t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Cool and d i l u e t o 100 mL w i t h ASTM t y p e I water. mL = 1000 p g Y : D i s s o l v e 0.1270 g YO , i n 5 mL (ltl) n i t r i c a c i d , h e a t i n g t o e f f e c t s o l u t i o n . Coo? and d i l u t e t o 100 mL w i t h ASTM t y p e I w a t e r .

7.3.10 Y t t r i u m s o l u t i o n , s t o c k

7.4

MULTI-ELEMENT STOCK STANDARD SOLUTION - Care must be t a k e n i n t h e p r e p a r a t i o n o f m u l t i - e l e m e n t s t o c k standards t h a t t h e elements a r e c o m p a t i b l e and s t a b l e . O r i g i n a t i n g element s t o c k s should be checked f o r t h e presence o f i m p u r i t i e s which m i g h t i n f l u e n c e t h e accuracy o f t h e standard. F r e s h l y prepared standards should be t r a n s f e r r e d t o a c i d cleaned, new FEP o r HDPE b o t t l e s f o r s t o r a g e and m o n i t o r e d p e r i o d i c a l l y f o r s t a b i l i t y . A multi-element stock standard s o l u t i o n c o n t a i n i n g t h e elements, cadmium, c o b a l t , copper, l e a d , n i c k e l , uranium and vanadium (1 mL = 10 fig) may be prepared by d i l u t i n g 1 mL o f each s i n g l e element s t o c k i n t h e l i s t t o 100 mL w i t h ASTM t y p e I w a t e r c o n t a i n i n g 1% ( v / v ) n i t r i c a c i d .

7.4.1

7.5

7.6

P r e p a r a t i o n o f c a l i b r a t i o n standards - Fresh m u l t i - e l e m e n t c a l i b r a t i o n standards should be p r e p a r e d weekly. D i l u t e t h e s t o c k m u l t i - e l e m e n t s t a n d a r d s o l u t i o n i n 1% ( v / v ) n i t r i c a c i d t o l e v e l s a p p r o p r i a t e t o t h e r e q u i r e d o p e r a t i n g range. The element c o n c e n t r a t i o n s i n t h e standards should be s u f f i c i e n t l y h i g h t o produce good measurement p r e c i s i o n and t o a c c u r a t e l y d e f i n e t h e s l o p e o f t h e response c u r v e . A suggested mid-range c o n c e n t r a t i o n i s 10 pg/L.

BLANKS - I n a d d i t i o n t o t h e l a b o r a t o r y f o r t i f i e d b l a n k , two t y p e s o f b l a n k s a r e r e q u i r e d f o r t h i s method. A c a l i b r a t i o n b l a n k i s used t o e s t a b l i s h t h e a n a l y t i c a l c a l i b r a t i o n c u r v e , and t h e l a b o r a t o r y r e a q e n t b l a n k i s used t o assess D o s s i b l e c o n t a m i n a t i o n from he Sam61e p r e p a r a t i o n procedure.

7.5.1

C a l i b r a t i o n b l a n k - C o n s i s t s o f 1% ( v / v ) n i t r i c a c i d t y p e I water.

7.5.2

L a b o r a t o r y r e a g e n t b l a n k (LRB) - Must c o n t a i n a l l t h e r e a g e n t s i n t h e same volumes as used i n p r o c e s s i n g t h e samples. The LRB must be c a r r i e d t h r o u g h t h e e n t i r e sample d i g e s t i o n and p r e p a r a t i o n scheme.

n ASTM

TUNING SOLUTION - T h i s s o l u t i o n i s used f o r i n s t r u m e n t t u n i n g and mass c a l i b r a t i o n p r i o r t o a n a l y s i s ( S e c t . 9.2). The s o l u t i o n i s prepared by m i x i n g n i c k e l , y t t r i u m , indium, t e r b i u m and l e a d stock

196

Methods for the Determination s o l u t i o n s ( S e c t . 7 . 3 ) i n 1% v / v ) n i t r i c a c i d t o produce a c o n c e n t r a t i o n o f 100 pg/L o f each element.

8.

7.7

q U A L I T Y CONTROL SAMPLE (QCS) - A q u a l i t y c o n t r o l sample h a v i n g c e r t i f i e d c o n c e n t r a t i o n s o f he a n a l y t e s o f i n t e r e s t s h o u l d be o b t a i n e d from a source o u t s i d e t h e l a b o r a t o r y . D i l u t e t h e QCS i f necessary w i t h 1% n i t r i c a c i d , such t h a t t h e a n a l y t e c o n c e n t r a t i o n s f a l l w i t h i n t h e proposed i n s t r u m e n t c a l i b r a t i o n range.

7.8

LABORATORY F O R T I F I E D BLANK (LFB)- To an a l i q u o t o f LRB, add a l i q u o t s from t h e m u l t i - e l e m e n t s t o c k s t a n d a r d ( S e c t . 7.4) t o produce a f i n a l c o n c e n t r a t i o n o f 10 pg/L f o r each a n a l y t e . The f o r t i f i e d b l a n k must be c a r r i e d t h r o u g h t h e e n t i r e sample p r e t r e a t m e n t and a n a l y t i c a l scheme.

SAMPLE COLLECTION, PRESERVATION AND STORAGE

8.1

For t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e elements i n aqueous samples, a c i d i f y w i t h ( 1 t 1 ) n i t r i c a c i d a t t h e t i m e of c o l l e c t i o n t o a pH o f l e s s t h a n two. The sample should n o t be f i l t e r e d p r i o r t o analysis. NOTE: Samples t h a t cannot be a c i d p r e s e r v e d a t t h e t i m e o f c o l l e c t i o n because o f sampling l i m i t a t i o n s o r t r a n s p o r t r e s t r i c t i o n s , should be a c i d i f i e d w i t h n i t r i c a c i d t o pH < 2 upon r e c e i p t i n t h e l a b o r a t o r y . F o l l o w i n g a c i d i f i c a t i o n , t h e sample should be h e l d f o r 16 h b e f o r e w i t h d r a w i n g an a l i q u o t f o r sample processing.

9.

CALIBRATION AND STANDARDIZATION 9.1

I n i t i a t e p r o p e r o p e r a t i n g c o n f i g u r a t i o n o f ICP-MS i n s t r u m e n t d a t a system. A l l o w a p e r i o d o f n o t l e s s t h a n 30 min f o r t h e i n s t r u m e n t t o warm up. D u r i n g t h i s process conduct mass c a l and r e s o l u t i o n checks u s i n g t h e t u n i n g s o l u t i o n . R e s o l u t i o n mass i s i n d i c a t e d by n i c k e l i s o t o p e s 60,61,62. Resolution a mass i s i n d i c a t e d by l e a d i s o t o p e s 206,207,208. F o r good performance a d j u s t spectrometer r e s o l u t i o n t o produce a peak o f a p p r o x i m a t e l y 0.75 arnu a t 5% peak h e i g h t . A d j u s t mass c a l i b r a t i o n i f i t has s h i f t e d by more t h a n 0.1 amu f r o m u n i t

and bration a t low high width mass.

9.2

I n s t r u m e n t s t a b i l i t y must be demonstrated by a n a l y z i n g t h e t u n i n g s o l u t i o n ( S e c t . 7.6) a minimum o f f i v e t i m e s w i t h r e s u l t i n g r e l a t i v e standard d e v i a t i o n s o f absolute s i g n a l s f o r a l l analytes o f l e s s t h a n 5%.

9.3

P r i o r t o i n i t i a l c a l i b r a t i o n , s e t up p r o p e r i n s t r u m e n t s o f t w a r e r o u t i n e s f o r q u a n t i t a t i v e a n a l y s i s and connect t h e ICP-MS i n s t r u m e n t t o t h e p r e c o n c e n t r a t i o n apparatus. The i n s t r u m e n t must be c a l i b r a t e d f o r the analytes o f i n t e r e s t using t h e c a l i b r a t i o n blank ( S e c t . 7.5.1) and c a l i b r a t i o n s t a n d a r d (Sect. 7.4.1) p r e p a r e d a t one o r more c o n c e n t r a t i o n l e v e l s . The c a l i b r a t i o n s o l u t i o n s s h o u l d be

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processed t h r o u g h t h e p r e c o n c e n t r a t i o n system u s i n g t h e procedures d e s c r i b e d i n S e c t . 11. 9.4

9.5

10.

Demonstration and documentation o f a c c e p t a b l e i n i t i a l c a l i b r a t i o n i s r e q u i r e d b e f o r e any samples a r e analyzed and i s r e q u i r e d p e r i o d i c a l l y t h r o u g h o u t sample a n a l y s i s as d i c t a t e d by r e s u l t s o f c o n t i n u i n g c a l i b r a t i o n checks. A f t e r i n i t i a l c a l i b r a t i o n i s s u c c e s s f u l , a c a l i b r a t i o n check i s r e q u i r e d a t t h e b e g i n n i n g and end o f each p e r i o d d u r i n g which analyses a r e performed and a t r e q u i s i t e intervals . 9.4.1

A f t e r t h e c a l i b r a t i o n has been e s t a b l i s h e d , i t must be i n i t i a l l y v e r i f i e d f o r a l l a n a l y t e s by a n a l y z i n g t h e QCS (Sect. 7.7). I f measurements exceed f 15% o f t h e e s t a b l i s h e d QCS v a l u e , t h e a n a l y s i s s h o u l d be t e r m i n a t e d , t h e source o f t h e problem i d e n t i f i e d and c o r r e c t e d , t h e i n s t r u m e n t r e c a l i b r a t e d and t h e new c a l i b r a t i o n v e r i f i e d b e f o r e c o n t i n u i n g analyses.

9.4.2

To v e r i f y t h a t t h e i n s t r u m e n t i s p r o p e r l y c a l i b r a t e d on a c o n t i n u i n g b a s i s , r u n t h e c a l i b r a t i o n b l a n k ( S e c t . 7 . 5 . 1 ) and c a l i b r a t i o n standards ( S e c t . 7.4.1) as s u r r o g a t e samples a f t e r e v e r y t e n analyses. The r e s u l t s o f t h e analyses o f t h e standards w i l l i n d i c a t e whether t h e c a l i b r a t i o n remains v a l i d . I f t h e i n d i c a t e d c o n c e n t r a t i o n o f any a n a l y t e d e v i a t e s f r o m t h e t r u e c o n c e n t r a t i o n by more t h a n 15%, r e a n a l y z e t h e standard. I f t h e a n a l y t e i s a g a i n o u t s i d e t h e 15% l i m i t , t h e i n s t r u m e n t must be r e c a l i b r a t e d and t h e p r e v i o u s t e n samples r e a n a l y z e d . The i n s t r u m e n t responses from t h e c a l i b r a t i o n check may be used f o r r e c a l i b r a t i o n purposes.

INTERNAL STANDARDIZATION - I n t e r n a l s t a n d a r d i z a t i o n should be used i n a l l analyses t o c o r r e c t f o r i n s t r u m e n t d r i f t . I n t e r n a l standards may be added d i r e c t l y t o t h e samples and standards p r i o r t o p r e c o n c e n t r a t i o n o r by m i x i n g w i t h t h e c h e l a t i n g column c a r r i e r e f f l u e n t p r i o r t o n e b u l i z a t i o n u s i n g a p e r i s t a l t i c pump and a m i x i n g c o i l . I n f o r m a t i o n on t h e use o f i n t e r n a l standards may be found i n Method 200.8"'. NOTE: L i t h i u m and b i s m u t h s h o u l d n o t be used as i n t e r n a l standards u s i n g t h e d i r e c t a d d i t i o n method as t h e y a r e n o t e f f i c i e n t l y c o n c e n t r a t e d on t h e i m i n o - d i a c e t a t e column.

QUALITY CONTROL

10.1 Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a q u a l i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y , and t h e a n a l y s i s o f l a b o r a t o r y r e a g e n t b l a n k s , b l a n k s and samples as a c o n t i n u i n g check on performance. l a b o r a t o r y should m a i n t a i n performance r e c o r d s t h a t d e f i n e q u a l i t y o f t h e d a t a generated.

formal this fortified he the

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Methods for the Determination

10.2 INITIAL DEMONSTRATION OF PERFORMANCE

10.2.1 The i n i t i a l demonstration o f performance i s used t o c h a r a c t e r i z e instrument performance (method d e t e c t i o n 1i m i t s and l i n e a r c a l i b r a t i o n ranges) f o r analyses conducted by t h i s method. 10.2.2 Method d e t e c t i o n l i m i t s (MDL) should be e s t a b l i s h e d f o r a l l analytes, u s i n g reagent water ( b l a n k ) f o r t i f i e d a t a c o n c e n tra ti o n o f two t o f i v e times t h e estimated d e t e c t i o n To determine MDL values, t a k e seven r e p l i c a t e limit'6'. a l i q u o t s o f t h e f o r t i f i e d reagent water and process through t h e e n t i r e a n a l y t i c a l method. Perform a l l c a l c u l a t i o n s d e fi n e d i n t h e method and r e p o r t t h e c o n c e n t r a t i o n values i n t h e a p p ro p ri a te u n i t s . C a l c u l a t e t h e MDL as f o l l o w s : MDL = ( t ) x ( S ) where, t =

S =

Stu d e n t' s t v a l u e f o r a 99% confidence l e v e l and a standard d e v i a t i o n e s t i m a t e w i t h n-1 degrees o f freedom [ t = 3.14 f o r seven r e p l i c a t e s ] . standard d e v i a t i o n o f t h e r e p l i c a t e analyses.

MDLs should be determined every s i x months o r whenever a s i g n i f i c a n t change i n background o r instrument response i s expected.

10.2.3 L i n e a r c a l i b r a t i o n ranges - The upper l i m i t o f t h e l i n e a r c a l i b r a t i o n range should be e s t a b l i s h e d f o r each a n a l y t e . L i n e a r c a l i b r a t i o n ranges should be determined every s i x months o r whenever a s i g n i f i c a n t change i n instrument response i s expected. 10.3 ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS 10.3.1 Laboratory reagent blank (LRB) - The l a b o r a t o r y must analyze a t l e a s t one LRB (Sect. 7.5.2) w i t h each s e t o f samples. LRB d a ta are used t o assess contamination from t h e l a b o r a t o r y environment. I f an a n a l y t e value i n t h e LRB exceeds i t s determined MDL, then l a b o r a t o r y o r reagent contamination should be suspected. Any determined source o f contamination should be c o r r e c t e d and t h e samples reanalyzed.

10.3.2 Laboratory f o r t i f i e d blank (LFB) - The l a b o r a t o r y must analyze a t l e a s t one LFB (Sect. 7.8) w i t h each batch of samples Cal c u l a t e accuracy as percent recovery (Sect. 10.4.2) I f t h e recovery o f any a n a l y t e f a l l s o u t s i d e t h e c o n t r o l l i m i t s (Sect. 10.3.3), t h a t a n a l y t e i s judged o u t o f c o n t r o l , and t h e source o f t h e problem should be i d e n t i f i e d and re s o l v e d b e fo re c o n t i n u i n g analyses.

.

Metals

199

10.3.3 U n t i l s u f f c i e n t LFB d a t a become a v a i l a b l e from w i t h i n t h e 1 a b o r a t o r y ( u s u a l l y a minimum o f 20 t o 30 a n a l y s e s ) , t h e 1 a b o r a t o r y should assess l a b o r a t o r y performance a g a i n s t r e c o v e r y 1 m i t s o f 85-115%. When s u f f i c i e n t i n t e r n a l performance d a t a becomes a v a i l a b l e , d e v e l o p c o n t r o l 1 i m i t s from t h e p e r c e n t mean r e c o v e r y ( x ) and t h e s t a n d a r d d e v i a t i o n ( S ) o f t h e mean r e c o v e r y . These d a t a a r e used t o e s t a b l i s h upper and l o w e r c o n t r o l l i m i t s as f o l l o w s : UPPER CONTROL LIMIT LOWER CONTROL LIMIT

= =

x t 3s x - 3s

A f t e r each f i v e t o t e n new r e c o v e r y measurements, new c o n t r o l l i m i t s should be c a l c u l a t e d u s i n g o n l y t h e most r e c e n t t w e n t y t o t h i r t y data points.

10.4 ASSESSING ANALYTE RECOVERY - LABORATORY F O R T I F I E D SAMPLE MATRIX 10.4.1 The l a b o r a t o r y must add a known amount o f each a n a l y t e t o a minimum o f 10% o f t h e r o u t i n e samples o r one sample p e r sample s e t , whichever i s g r e a t e r . The a n a l y t e c o n c e n t r a t i o n s should be t h e same as t h o s e used i n t h e LFB ( S e c t . 10.3.2). Over t i m e , samples f r o m a l l r o u t i n e sample sources should be fortified. 10.4.2 C a l c u l a t e t h e p e r c e n t r e c o v e r y f o r each a n a l y t e , c o r r e c t e d f o r t h e c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o t h e c o n t r o l l i m i t s e s t a b l i s h e d i n Sect. 10.3.3 f o r t h e analyses o f LFBs. Recovery c a l c u l a t i o n s a r e n o t r e q u i r e d i f t h e c o n c e n t r a t i o n o f t h e a n a l y t e added i s l e s s t h a n 10% o f t h e sample c o n c e n t r a t i o n . Percent r e c o v e r y may be c a l c u l a t e d i n u n i t s a p p r o p r i a t e t o t h e m a t r i x , u s i n g t h e f o l l o w i n g equation:

c, - c R =

x 100 S

where,

10.4.3

R = percent recovery C, = f o r t i f i e d sample c o n c e n t r a t i o n C = sample c o n c e n t r a t i o n s = concentration equivalent o f f o r t i f i e r added t o sample.

I f r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e d e s i g n a t e d range and l a b o r a t o r y performance f o r t h a t a n a l y t e i s shown t o be i n c o n t r o l ( S e c t . 1 0 . 3 ) , t h e r e c o v e r y problem encountered w i t h t h e f o r t i f i e d sample i s judged t o be m a t r i x r e l a t e d , n o t system r e l a t e d . The r e s u l t f o r t h a t a n a l y t e i n t h e u n f o r t i f i e d sample must be l a b e l l e d " s u s p e c t / m a t r i x " t o i n f o r m t h e d a t a u s e r t h a t t h e r e s u l t s a r e suspect due t o matrix effects.

200

Methods for the Determination

11. PROCEDURE

11.1 SAMPLE PREPARATION - TOTAL RECOVERABLE ELEMENTS 11.1.1 For t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e elements, t a k e a 100 mL a l i q u o t from a w e l l mixed, a c i d p r e s e r v e d sample and t r a n s f e r t o a 250-mL G r i f f i n beaker. Add 1 mL o f c o n c e n t r a t e d n i t r i c a c i d and h e a t on a h o t p l a t e a t 85°C u n t i l t h e volume has been reduced t o a p p r o x i m a t e l y 25 mL, e n s u r i n g t h a t t h e sample does n o t b o i l . Cover t h e beaker w i t h a watch g l a s s and r e f l u x f o r 30 min. S l i g h t b o i l i n g may o c c u r b u t v i g o r o u s b o i l i n g should be avoided. A l l o w t o c o o l and d i l u t e t o 100 mL w i t h ASTM t y p e I w a t e r . C e n t r i f u g e t h e sample o r a l l o w t o stand o v e r n i g h t t o s e p a r a t e i n s o l u b l e material. 11.2 P r i o r t o f i r s t use, t h e p r e c o n c e n t r a t i o n system should be t h o r o u g h l y cleaned and decontaminated u s i n g 0.2M o x a l i c a c i d . 11.2.1 Place a p p r o x i m a t e l y 500 mL 0.2M o x a l i c a c i d i n t h e e l u e n t and c a r r i e r s o l u t i o n c o n t a i n e r s and f i l l t h e sample l o o p w i t h 0.2M o x a l i c a c i d u s i n g t h e sample pump (P4) a t a f l o w r a t e o f 3-5 mL/min. W i t h t h e p r e c o n c e n t r a t i o n system d i s c o n n e c t e d f r o m t h e ICP-MS i n s t r u m e n t , use t h e pump program sequence l i s t e d i n Table 2, t o f l u s h t h e complete system w i t h o x a l i c a c i d . Repeat t h e f l u s h sequence t h r e e t i m e s . 11.2.2 Repeat t h e sequence d e s c r i b e d i n Sect. 11.2.1 u s i n g 1.25M n i t r i c a c i d and a g a i n u s i n g ASTM t y p e I w a t e r i n p l a c e o f t h e 0.2M o x a l i c a c i d . 11.2.3 Rinse t h e c o n t a i n e r s t h o r o u g h l y w i t h ASTM t y p e I water, f i l l them w i t h t h e i r d e s i g n a t e d r e a g e n t s (see F i g u r e 1) and r u n t h r o u g h t h e sequence i n T a b l e 2 once t o p r i m e t h e pump and a l l eluent l i n e s w i t h t h e c o r r e c t reagents.

11.3 I n i t i a t e ICP-MS i n s t r u m e n t o p e r a t i n g c o n f i g u r a t i o n . Tune and c a l i b r a t e t h e i n s t r u m e n t f o r t h e a n a l y t e s o f i n t e r e s t (Sect. 9). 11.4 E s t a b l i s h i n s t r u m e n t s o f t w a r e r u n procedures f o r q u a n t i t a t i v e a n a l y s i s . Because t h e a n a l y t e s a r e e l u t e d f r o m t h e p r e c o n c e n t r a t i o n column i n a t r a n s i e n t manner, i t i s recommended t h a t t h e i n s t r u m e n t s o f t w a r e i s c o n f i g u r e d i n a r a p i d scan/peak hopping mode. 11.5 Reconnect t h e p r e c o n c e n t r a t i o n system t o t h e ICP-MS i n s t r u m e n t . W i t h v a l v e s A and B i n t h e o f f p o s i t i o n and v a l v e C i n t h e on p o s i t i o n , l o a d sample t h r o u g h t h e sample l o o p t o waste u s i n g pump P4 f o r 4 min a t 4 mL/min. S w i t c h on t h e c a r r i e r pump (P3) and pump 1% n i t r i c a c i d t o t h e n e b u l i z e r o f t h e ICP-MS i n s t r u m e n t a t a f l o w r a t e o f 0.8-1.0 mL/min.

Metals

201

11.6 S w i t c h on t h e b u f f e r pump (P2), and pump 2M ammonium a c e t a t e a t a

f l o w r a t e o f 1 mL/min.

11.7 P r e c o n c e n t r a t i o n o f t h e sample may be a c h i e v e d by r u n n i n g t h r o u g h an e l u e n t pump program ( P l ) sequence s i m i l a r t o t h a t i l l u s t r a t e d i n Table 2 . The e x a c t t i m i n g o f t h i s sequence s h o u l d be m o d i f i e d a c c o r d i n g t o t h e i n t e r n a l volume o f t h e c o n n e c t i n g t u b i n g and t h e s p e c i f i c hardware c o n f i g u r a t i o n used. 1 1 . 7 . 1 I n j e c t sample - W i t h v a l v e s A, 6 and C on, l o a d sample from t h e l o o p o n t o t h e column u s i n g 1M ammonium a c e t a t e f o r 4.5 min a t 4 . 0 mL/min. The a n a l y t e s a r e r e t a i n e d on t h e column, w h i l e t h e m a j o r i t y o f t h e m a t r i x i s passed t h r o u g h t o waste. 11.7.2 E l u t e a n a l y t e s - Turn o f f v a l v e s A and B and b e g i n e l u t i n g t h e a n a l y t e s by pumping 1.25M n i t r i c a c i d t h r o u g h t h e column a t 4.0 mL/min, t h e n t u r n o f f v a l v e C and pump t h e e l u t e d a n a l y t e s i n t o t h e ICP-MS i n s t r u m e n t a t 1.0 mL/min. I n i t i a t e ICP-MS s o f t w a r e d a t a a c q u i s i t i o n and i n t e g r a t e t h e e l u t e d a n a l y t e p r o f i1es. 11.7.3 Column R e c o n d i t i o n i n g - Turn on v a l v e C t o d i r e c t column e f f l u e n t t o waste, and pump 1.25M n i t r i c a c i d , 1M ammonium a c e t a t e , 1.25M n i t r i c a c i d and 1M ammonium a c e t a t e a l t e r n a t e l y t h r o u g h t h e column a t 4.0 mL/min. D u r i n g t h i s p r o c e s s , t h e n e x t sample can be l o a d e d i n t o t h e sample l o o p u s i n g t h e sample pump (P4). 11.8 Repeat t h e sequence d e s c r i b e d i n S e c t . 11.7 f o r each sample t o be analyzed. A t t h e end o f t h e a n a l y t i c a l r u n l e a v e t h e column f i l l e d w i t h 1M ammonium a c e t a t e b u f f e r u n t i l i t i s n e x t used. 11.9 Samples h a v i n g c o n c e n t r a t i o n s h i g h e r t h a n t h e e s t a b l i s h e d l i n e a r dynamic range s h o u l d be d i l u t e d i n t o range and r e - a n a l y z e d .

12. CALCULATIONS 12.1 A n a l y t i c a l i s o t o p e s and e l e m e n t a l e q u a t i o n s recommended f o r sample d a t a c a l c u l a t i o n s a r e l i s t e d i n T a b l e 3. Sample d a t a s h o u l d be r e p o r t e d i n u n i t s o f p g / L . Do n o t r e p o r t element c o n c e n t r a t i o n s below t h e d e t e r m i n e d MDL. 12.2 F o r d a t a v a l u e s l e s s t h a n t e n , two s i g n i f i c a n t f i g u r e s s h o u l d be used f o r r e p o r t i n g e ement c o n c e n t r a t i o n s . F o r d a t a v a l u e s g r e a t e r t h a n o r equal t o t e n t h r e e s i g n i f i c a n t f i g u r e s s h o u l d be used. 12.3 Reported v a l u e s shou d be c a l i b r a t i o n b l a n k s u b t r a c t e d . I f a d d i t i o n a l d i 1u t ions were made t o any samples, t h e a p p r o p r i a t e f a c t o r s h o u l d be app i e d t o t h e c a l c u l a t e d sample c o n c e n t r a t i o n s .

202

Methods for the Determination 12.4 Data values should be c o r r e c t e d f o r instrument d r i f t by t h e a p p l i c a t i o n o f i n t e r n a l s ta n d a r d i z a t i o n . C o r r e c t i o n s f o r characte ri z e d s p e c tra l i n t e r f e r e n c e s should be a p p l i e d t o t h e data.

12.5 The QC d a ta obtained d u r i n g t h e analyses p r o v i d e an i n d c a t i o n o f t he q u a l i t y o f t h e sample data and should be p r o v i d e d w t h t h e sample r e s u l t s . 13. P R E C I S I O N AND ACCURACY 13.1 Experimental c o n d i t i o n s used f o r s i n g l e l a b o r a t o r y t e s t ng o f t h e method are summarized i n Table 4.

13.2 Data ob ta i n e d from s i n g l e l a b o r a t o r y t e s t i n g o f t h e method a r e summarized i n Tables 5 and 6 f o r two r e f e r e n c e water samples c o n s i s t i n g o f N a ti o n a l Research Council Canada (NRCC), E s t u a r i n e Water (SLEW-1) and Seawater (NASS-2). The samples were prepared using t h e procedure described i n Sect. 11.2.1. For each m a t r i x , t hree r e p l i c a t e s were analyzed and t h e average o f t h e r e p l i c a t e s used f o r determining t h e sample c o n c e n t r a t i o n f o r each a n a l y t e . Two f u r t h e r s e t s o f t h r e e r e p l i c a t e s were f o r t i f i e d a t d i f f e r e n t concen tra ti o n l e v e l s , one s e t a t 0.5 pg/L, t h e o t h e r a t 10 pg/L. The sample c o n c e n tra ti o n , mean percent recovery, and t h e r e l a t i v e standard d e v i a t i o n o f t h e f o r t i f i e d rep1 i c a t e s a r e 1i s t e d f o r each method a n a l y te . The re fe re n c e m a t e r i a l c e r t i f i c a t e values a r e a l s o l i s t e d f o r comparison.

Metals 14.

203

REFERENCES 1.

USEPA Method 200.8, O f f i c e o f Research and Development, USEPA, C i n c i n n a t i , Ohio, August 1990.

2.

A. Siraraks, H.M. Kingston and J.M. R i v i e l l o , A n a l Chem. E 1185 (1990).

3.

E.M. Heithmar, T.A. Hinners, J.T. Rowan and J.M. R i v i e l l o , A n a l Chem. Q 857 (1990).

4.

“OSHA Safety and Health Standards, General Industry,” (29 CFR 1910), Occupational Safety and Health Administration, OSHA 2206, r e v i s e d January 1976.

5.

“Proposed OSHA Safety and Health Standards, Laboratories, Occupational Safety and Health Administration, Federal Register, J u l y 24, 1986.

6.

Code o f Federal Regulations 40, Ch. 1, P t . 136 Appendix B.

I‘

204

Methods for the Determination

TABLE 1: TOTAL RECOVERABLE METHOD DETECTION LIMITS FOR REAGENT WATER

ELEMENT Cadrni urn Cobalt Copper Lead Nickel Uran i urn Vanadi urn

RECOMMENDED ANALYTICAL MASS 111 59 63 206,207,208 60 238 51

MDL Pg/L 0.041 0.021 0.023 0.074 0.081 0.031 0.014

Metals

TABLE 2: Eluent PUMP PROGRAMMING SEQUENCE FOR PRECONCENTRATION OF TRACE ELEMENTS

Time (min)

F1ow mL/mi n

0.0 4.5 5.1 5.5 7.5 8.0 10.0 11.0 12.5

4.0 4.0 1.o 1.o 4.0 4.0 4.0 4.0 0.0

Eluent

1M ammonium acetate 1.25M n i t r i c a c i d 1.25M n i t r i c a c i d 1.25M n i t r i c a c i d 1.25M n i t r i c a c i d 1M ammonium acetate 1.25M n i t r i c a c i d 1M ammonium acetate

Valve A,B

Valve C

ON ON OFF OFF OFF

ON ON ON OFF ON ON ON ON ON

OFF OFF OFF OFF

205

206

Methods for the Determination

TABLE 3: RECOMMENDED ANALYTICAL ISOTOPES AND ELEMENTAL EQUATIONS FOR DATA CALCULATIONS ~

Element

Isotope

Note

Elemental Equatfon - (1.073)[ ('08C) - (0.712)('Y) ]

Cd

lO6,108,rn,114

( 1.000)("'C)

co

59

(l.ooo)(59c)

Cu

@,65

(1 .ooo)

Pb

206,207.204

Ni

60

(63c) ( 1.000) (206c)t( 1,000)(207c)t(1 (1.000)p c )

U

238

(~.ooo)(~~~c)

V

51

(1 .OOO) (51c)

f

(1)

000)(*08C)

C - calibration blank subtracted counts at specified mass. (1) - correction for MOO interference. An additional isobaric elemental correction should be made if palladium is present. (2) - allowance for isotopic variability of lead isotopes. NOTE: As a minimum, all isotopes listed should be monitored. I s o t o p e s recommended for analytical determination are under1 i ned

.

Metals TABLE 4: EXPERIMENTAL CONDITIONS FOR SINGLE LABORATORY VALIDATION

Chromatography Instrument P r e c o n c e n t r a t i o n column ICP-MS I n s t r u m e n t

Dionex c h e l a t i o n system Dionex MetPac CC-1

Conditions

Instrument P1 asma f o r w a r d power Cool a n t f l o w r a t e Auxiliary flow rate Nebulizer flow r a t e

VG PlasmaQuad Type 1.35 kW 13.5 L/min 0.6 L/min 0.78 L/min

I n t e r n a l standards

Sc, Y,

I n , Tb

Data A c q u i s i t i o n D e t e c t o r mode Mass range Dwell t i m e Number o f MCA channels Number o f scan sweeps

Pulse c o u n t i n g

45-240 arnu 160 ps

2048 2 50

I

207

208

Methods for the Determination

TABLE 6: PRECISION AND RECOVERY DATA FOR ESTUARINE WATER (SLEW-1) Analyte

Certificate (Ug/L)

Sample Concn.

(w-1 Cd co cu Pb

Ni U V

0.018 0.046 1.76 0.028 0.743

__ __

<0.041 0.078 1.6 t0.074 0.83 1.1 1.4

Spike Addition (c19/L)

0.5 0.5 0.5 0.5 0.5 0.5 0.5

Average Recovery (X)

RSD (X)

94 .8 102.8 106.0 100.2 100.0 96.7 100.0

9.8 4.0 2.7 4.0 1.5 7.4 3.2

Spike Addition (c19/L) 10 10 10 10 10 10 10

Average Recovery

RSD

(X)

(%I 99.6 96.6 96.0 106.9 102.0 98.1 97.0

1.1 1.4 4.8 5.8 2.1 3.6 4.5

-- No c e r t i f i c a t e value

TABLE 6: PRECISION AND RECOVERY DATA FOR SEAWATER (NASS-2) Analyte

Cd co cu Pb

Ni U V

--

Certificate (pg/L)

0.029 0.004 0.109 0.039 0.257 3.00

--

Sample Concn. (Pg/L)

t0.041 t0.021 0.12 t0.074 0.23 3.0 1.7

No c e r t i f i c a t e value

Spike Addition (c19/L)

0.5 0.5 0.5 0.5 0.5 0.5 0.5

Average Recovery

RSD (X)

(XI 101.8 98.9 95.8 100.6 102.2 94.0 104.0

1.o 3.0 2.3 8.5 2.3 0.7 3.4

Spike Addition (c19/L)

10 10 10 10 10 10 10

Average Recovery

RSD ( (%)

(%)

96.4 99.2 93.1 92.1 98.2 98.4 109.2

3.7 1.7 0.9 2.6 1.2 1.7 3.7

I

CHELATING COLUMN

I

BUFFER

1% NrPJC ACID

2M NH40AC

SAMPLE

i

1M NH,OAc

1.25 M NITRIC ACID

-

MIXING TEE

I

209

‘--.‘A L-

FIGURE 1. CONFIGURATION OF PRECONCENTRATION SYSTEM

OFF

Metals

i

’

ON

210

Methods for the Determination METHOD 200.11

DETERMINATION OF METALS I N FISH TISSUE BY INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY

Theodore D. M a r t i n , E l e a n o r R. H a r t i n and L a r r y 8. L o b r i n g I n o r g a n i c C h e m i s t r y Branch C h e m i s t r y Research D i v i s i o n and G e r a l d D. McKee Office o f the Director

R e v i s i o n 2.1 A p r i l 1991

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

Metals

211

METHOD 200.11 DETERMINATION OF METALS I N FISH TISSUE BY INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY

1.

SCOPE AND APPLICATION 1.1 This method i s an i n d u c t i v e l y coupled plasma (1CP)-atomic emission spectrometric procedure f o r use i n d e t e r m i n a t i o n o f n a t u r a l l y o c c u r r i n g and accumulated t o x i c metals i n t h e e d i b l e t i s s u e p o r t i o n ( f i l l e t ) o f t h e f i s h . The t i s s u e must be taken from a f r e s h , n o t p r e v i o u s l y frozen, f i s h t o prevent a n a l y t e l o s s o r t i s s u e contamination due t o c e l l l y s i s and r e s u l t i n g f l u i d exchange. The method i s n o t intended t o be used f o r a n a l y s i s o f d r i e d f i s h t i s s u e . This method i s a p p l i c a b l e t o t h e d e t e r m i n a t i o n o f t h e f o l l o w i n g metal s : Anal y t e Aluminum ( A l ) Antimony (Sb) Arsenic ( A s ) B e r y l l i u m (Be) Cadmium (Cd) Chromium ( C r ) Copper (Cu) Lead (Pb) Nicke l ( N i ) S e l eni um (Se) T hall i u m ( T l ) Zinc (Zn)

1.2

7429-90-5 7440-36-0 7440-38-2 7440-41-7 7440-43-9 7440-41 -3 7440-50-8 7439-92-1 7440-02-0 7782-49-2 7440-28-0 7440-66-6

T his method a l s o may be used f o r spectrochemical d e t e r m i n a t i o n o f o t h e r elements commonly found i n f i s h t i s s u e . S p e c i f i c a n a l y t e s inclu d e d are t h e f o l l o w i n g : Anal Yte Calcium (Ca) I r o n (Fe) Magnesium (Mg) Phosphorus (P) Potassium (K) Sodium (Na)

1.3

Chemical A b s t r a c t Services R e p i s t r y Numbers fCASRN1

Chemical A b s t r a c t Services ReQistrY Numbers [CAS RN)

7440-70-2 7439-89-6 7439-95-4 7723-14-0 7440-09-7 7440-23-5

S p e c i f i c i n s tru m e n ta l o p e ra ti n g c o n d i t i o n s are g i v e n and should be used whenever p o s s i b l e . However, because o f t h e d i f f e r e n c e s between v a ri o u s makes and models o f spectrometers, t h e a n a l y s t should f o l l o w t h e instrument m a n u f a c t u r e r ' s i n s t r u c t i o n s i n

212

Methods for the Determination adapting th e i n s tru m e n t' s o p e r a t i o n t o approximate t h e recommended c o n d i t i o n s g i v e n i n t h i s method.

2.

3.

1.4

Table 1 l i s t s t h e recommended wavelengths w i t h l o c a t i o n s f o r background c o r r e c t i o n f o r th e m e t a l s p r e s e n t l y i n c l u d e d i n t h i s method, A l s o l i s t e d i n Table 1 are t y p i c a l method d e t e c t i o n l i m i t s (MDLs) f o r c e r t a i n m e t a l s determined i n f i s h t i s s u e u s i n g conventional pneumatic n e b u l i z a t i o n f o r sample i n t r o d u c t i o n i n t o t he I C P .

1.5

Once th e t i s s u e samples have been c o l l e c t e d , approximately 20 f i s h f i l l e t samples i n c l u d i n g t h e mandatory q u a l i t y c o n t r o l samples can be analyzed u s i n g t h i s method d u r i n g t h e 1.5 day work p e r i o d r e q u i r e d t o complete t h e a n a l y s i s .

SUMMARY OF METHOD 2.1

A 1 t o 2 g sample o f f i s h t i s s u e i s taken from a f r e s h ( n o t p r e v i o u s l y fro z e n ) f i s h and t r a n s f e r r e d t o a preweighed, l a b e l e d polysu l fo n e Oak Ridge type c e n t r i f u g e tube. The t i s s u e i s d i s s o c i a t e d u s i n g tetramethylammonium hydroxide2i3, low heat and v o r t e x mixing. The f o l l o w i n g day, t h e metals i n t h e r e s u l t i n g c o l l o i d a l suspension are a c i d s o l u b i l i z e d w i t h n i t r i c a c i d and heat, and then d i l u t e d w i t h deionized, d i s t i l l e d water t o a weight volume r a t i o equal t o 1 g f i s h t i s s u e per 10 mL o f s o l u t i o n . The d i l u t e d sample i s v o r t e x mixed, c e n t r i f u g e d and f i n a l l y t h e a c i d i f i e d aqueous s o l u t i o n i s analyzed by d i r e c t a s p i r a t i o n background corre c te d I C P atomic emission spectrometry. The determined metal conce n tra ti o n i s re p o rte d as microgram/gram (pg/g) wet f i s h t i s s u e weight.

2.2

The b a s i s o f t h e method d e te rm i n a t i o n step i s t h e measurement o f atomic emission by o p t i c a l spectroscopy. The sample i s n e b u l i z e d and t h e aerosol t h a t i s produced i s t r a n s p o r t e d t o t h e plasma t o r c h where e x c i t a t i o n occurs. C h a r a c t e r i s t i c a t o m i c - l i n e emission specta are produced by a radio-frequency I C P . The s p e c t r a are dispersed by a g r a t i n g spectrometer and t h e i n t e n s i t i e s o f t h e 1 ines are monitored by p h o t o m u l t i p l i e r tubes. The p h o t o c u r r e n t s from t h e p h o t o m u l t i p l i e r tubes are processed and c o n t r o l l e d by a computer system. Background c o r r e c t i o n i s r e q u i r e d t o compensate f o r t h e v a r i a b l e background c o n t r i b u t i o n o f f i s h m a t r i x and reagents t o t h e a n a l y te d e te rm i n a t i o n . The l o c a t i o n recommended f o r background c o r r e c t i o n f o r each a n a l y t e i s g i v e n i n Table 1.

DEFINITIONS 3.1

F I S H TISSUE - The s k i n l e s s e d i b l e muscle t i s s u e o f t h e f i s h commonly r e f e r r e d t o as t h e f i l l e t .

Metals

213

3.2

METHOD DETECTION L I M I T (MDL) - The minimum c o n c e n t r a t i o n o f an a n a l y t e t h a t can be i d e n t i f i e d , measured and r e p o r t e d w i t h 99% confidence t h a t t h e analyte concentration i s g r e a t e r than zero.

3.3

CALIBRATION BLANK - A volume o f d e i o n i z e d , d i s t i l l e d w a t e r c o n t a i n i n g a l l r e a g e n t s used t o p r e p a r e t h e t i s s u e f o r analyses. The c a l i b r a t i o n b l a n k i s a z e r o s t a n d a r d and i s used t o c a l i b r a t e t h e I C P i n s t r u m e n t . ( S e c t . 7.9).

3.4

F I E L D DUPLICATES (FD1 and FD2) - Two separate samples c o l l e c t e d a t t h e same t i m e and p l a c e under i d e n t i c a l circumstances and t r e a t e d e x a c t l y t h e same t h r o u g h o u t f i e l d and l a b o r a t o r y procedures. Analyses o f FD1 and FD2 g i v e a measure o f t h e p r e c i s i o n a s s o c i a t e d w i t h sample c o l l e c t i o n , p r e s e r v a t i o n , and s t o r a g e , as w e l l as w i t h 1a b o r a t o r y procedure.

3.5

LABORATORY REAGENT BLANK (LRB) - An a l i q u o t o f tetramethylammonium h y d r o x i d e t h a t i s t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a l l glassware, equipment, and r e a g e n t s t h a t a r e used w i t h o t h e r samples. The LRB i s used t o determine i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e l a b o r a t o r y environment, r e a g e n t s , o r apparatus ( S e c t . 10.3.1)

3.6

FIELD REAGENT BLANK (FRB) - An empty Oak Ridge p o l y s u l f o n e sample t u b e (Sect. 6.2.3) i s t r e a t e d as a sample i n a l l r e s p e c t s , i n c l u d i n g exposure t o sampling s i t e c o n d i t i o n s , s t o r a g e , p r e s e r v a t i o n , and a l l a n a l y t i c a l procedures. The purpose o f t h e FRB i s t o determine i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e f i e l d environment (Sect. 10.3.2).

3.7

LABORATORY PERFORMANCE CHECK SOLUTION (LPC) - A s o l u t i o n o f method a n a l y t e s used t o e v a l u a t e t h e performance o f t h e i n s t r u m e n t system w i t h r e s p e c t t o a d e f i n e d s e t o f method c r i t e r i a (Sect. 7.10.1).

3.8

LABORATORY FORTIFIED BLANK (LFB) - An a1 i q u o t o f tetramethylammonium t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB i s analyzed e x a c t l y l i k e a sample and i t s purpose i s t o d e t e r m i n e whether t h e method i s i n c o n t r o l and whether t h e l a b o r a t o r y i s capable o f making a c c u r a t e and p r e c i s e measurements a t t h e r e q u i r e d method d e t e c t i o n l i m i t (Sect. 10.3.4).

3.9

LABORATORY FORTIFIED SAMPLE MATRIX (LFM) - An a l i q u o t o f f i s h t i s s u e t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFM i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e sample m a t r i x c o n t r i b u t e s b i a s t o t h e a n a l y t i c a l r e s u l t s . The background c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be d e t e r m i n e d i n a s e p a r a t e a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s ( S e c t . 10.4).

3.10 STOCK STANDARD SOLUTION - A c o n c e n t r a t e d s o l u t i o n c o n t a i n i n g a s i n g l e c e r t i f i e d s t a n d a r d t h a t i s a method a n a l y t e , o r a

214

Methods for the Determination concentrated s o l u t i o n o f a s i n g l e analyte prepared i n the l a b o r a t o r y w i t h an assayed r e f e r e n c e compound. Stock s t a n d a r d s o l u t i o n s a r e used t o p r e p a r e p r i m a r y d i l u t i o n standards ( S e c t . 7 . 6 ) .

3 . 1 1 PRIMARY DILUTION STANDARD SOLUTION - A s o l u t i o n o f s e v e r a l a n a l y t e s prepared i n t h e l a b o r a t o r y from s t o c k s t a n d a r d s o l u t i o n s and d i l u t e d as needed t o prepared c a l i b r a t i o n s o l u t i o n s and o t h e r needed a n a l y t e s o l u t i o n s (Sect. 7.7). 3 . 1 2 CALIBRATION STANDARD (CAL) - A s o l u t i o n p r e p a r e d from t h e p r i m a r y d i l u t i o n standard s o l u t i o n . The CAL s o l u t i o n s a r e used t o c a l i b r a t e t h e i n s t r u m e n t response w i t h r e s p e c t t o a n a l y t e c o n c e n t r a t i o n (Sect. 7.9). 3 . 1 3 QUALITY CONTROL SAMPLE (QCS) - A s o l u t i o n o f method a n a l y t e s o f known c o n c e n t r a t i o n s which i s used t o f o r t i f y an a l i q u o t o f LRB m a t r i x . The QCS i s o b t a i n e d f r o m a source e x t e r n a l t o t h e l a b o r a t o r y and used t o check l a b o r a t o r y performance w i t h e x t e r n a l l y prepared t e s t m a t e r i a l s (Sect. 1 0 . 2 . 2 ) . 4.

INTERFERENCES

4.1

Occurrences o f chromium c o n t a m i n a t i o n o f b i o l o g i c a l samples from4 t h e use o f s t a i n l e s s s t e e l have been r e p o r t e d i n t h e l i t e r a t u r e . Use o f s p e c i a l c u t t i n g implements and d i s s e c t i n g board made f r o m m a t e r i a l s t h a t a r e n o t o f i n t e r e s t i s recommended. K n i f e b l a d e s made o f t i t a n i u m w i t h T e f l o n handles have been s u c c e s s f u l l y used.

4.2

Sample c o n t a m i n a t i o n and l o s s e s a r e h e l d t o a minimum because t h e c o l l e c t e d sample i s preserved, processed and analyzed i n t h e same p o l y s u l f o n e c e n t r i f u g e tube. However, t h e s t a b i l i t y o f m e t a l s i n t h e a n a l y s i s s o l u t i o n i s n o t f u l l y documented and t h e r e f o r e , t h e sample should be analyzed w i t h i n 24 h a f t e r c o m p l e t i o n o f t h e p r e p a r a t i o n procedure (Sects. 1 1 . 2 t o 1 1 . 7 ) .

4.3

The processed sample ready f o r a n a l y s i s w i l l c o n t a i n a p r e c i p i t a t e and p o s s i b l y f l o a t a b l e s o l i d s as a s u r f a c e l a y e r p a r t i a l l y c o v e r i n g t h e analysis s o l u t i o n . Nevertheless, physical occlusion o f metals i n t h e s e s o l i d s i s n o t expected. Percent r e c o v e r i e s o f a l l m e t a l c o n c e n t r a t i o n s added, e x c e p t antimony, a r e n e a r o r exceed 90% (Sect. 1 3 . 4 . )

4.4

Because a l l samples a r e d i l u t e d t o t h e same w e i g h t volume r a t i o ( 1 9/10 mL), a l l samples o f t h e same t y p e o f f i s h t i s s u e have s i m i l a r concentrations o f t h e major c o n s t i t u e n t s i n t h e m a t r i x . These m a j o r c o n s t i t u e n t elements (Ca, K, Mg, Na and P) do n o t suppress a n a l y t e s i g n a l i n t e n s i t i e s o r cause i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e s f o r t h e wavelengths and a n a l y t i c a l c o n d i t i o n s recommended. However, t h e s e elements r e p r e s e n t a small p o r t i o n (t1500mg/L) o f t h e approximate 5% d i s s o l v e d s o l i d s i n t h e s o l u t i o n m a t r i x t h a t i s a s p i r a t e d . Tetramethylammonium h y d r o x i d e accounts f o r t h e m a j o r i t y o f t h e m a t r i x and i s b e l i e v e d t o undergo chemical

Metals

215

change d u r i n g sample p r e p a r a t i o n ( S e c t . 1 1 ) ; t h i s causes s l i g h t s h i f t s i n background i n t e n s i t y and m o l e c u l a r band c o n t r i b u t i o n t o wavelength s i g n a l s near 190 nanometers (nm). A l t h o u g h background c o r r e c t i o n a d j a c e n t t o t h e wavelength w i l l compensate f o r t h e m a j o r i t y o f t h e broad band i n t e r f e r e n c e s , LRB ( S e c t . 3 . 5 ) subt r a c t i o n must be used t o p r o v i d e t h e a d d i t i o n a l c o r r e c t i o n needed f o r t h e wavelengths o f As (193.7 nm), Se (196.0 nm) and Th (190.8 nm).

4.5

D i s s o l v e d s o l i d s exceeding 1500 t o 2000 mg/L can cause a r e d u c t i o n i n atomic e m i s s i o n s i g n a l i n t e n s i t i e s . I n t h i s method, because t h e c a l i b r a t i o n s t a n d a r d and sample s o l u t i o n s b o t h c o n t a i n a p p r o x i m a t e l y 5% d i s s o l v e d s o l i d s , any r e s u l t i n g m a t r i x e f f e c t i s m i n i m i z e d . O f g r e a t e r importance i s t h a t p a r t i a l c l o g g i n g o f t h e i n s t r u m e n t n e b u l i z e r and t o r c h i m p i n g e r t u b e does n o t o c c u r .

4.6

The number o f i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e s i n t h e f i s h t i s s u e m a t r i x i s m i n i m a l . L i s t e d below a r e a l l i n t e r e l e m e n t c o r r e c t i o n f a c t o r s determined f o r t h e wavelengths and background c o r r e c t i o n l o c a t i o n s recommended i n t h i s method. A l t h o u g h t h e s e f a c t o r s a r e o n l y a p p l i c a b l e t o t h e i n s t r u m e n t used i n t h e development o f t h i s method, t h e y can be used as a g u i d e and a r e evidence t h a t , except f o r f o r t i f i e d samples, most f i s h t i s s u e analyses do n o t r e q u i r e i n t e r e l e m e n t c o r r e c t i o n f a c t o r s . I t should be n o t e d t h a t i f a l i s t e d i n t e r f e r a n t i s p r e s e n t a t a c o n c e n t r a t i o n o f 10 p g / g o r l e s s , i t s apparent c o n c e n t r a t i o n on t h e a n a l y t e channel i s l e s s t h a n t h e a n a l y t e ' s determined MDL. INTERELEMENT CORRECTION FACTORS Anal v t e As As As Cr Cr Cr Pb Pb Sb Sb Se Zn Zn

Interferant A1 Be Ni CU

Factor to,0080

-0.0027 -0.0056 -0.0007

Ni

to. 0006

Fe A1 cu Cr Ni Fe cu Ni

-0.0003 -0.234

t o . 0008 t0.0150 -0.0087 -0.0205 t o . 0013 to. 0039

A 1 p g / g c o n c e n t r a t i o n o f i n t e r f e r a n t would e i t h e r add t o o r s u b t r a c t from t h e a n a l y t e an apparent c o n c e n t r a t i o n i n p g / g equal t o the value o f the c o r r e c t i o n f a c t o r .

216

Methods for the Determination 4.7

5.

6.

The f o l l o w i n g " o f f - t h e - l i n e " background c o r r e c t i o n l o c a t i o n s shou be avoided because o f e x i s t i n g s p e c t r a l i n t e r f e r e n c e . 4.7.1

The low s i d e ( - 0.07 nm) o f t h e 90.8 nm Th wavelength has s p e c t r a l i n t e r f e r e n c e from phosphorus.

4.7.2

Background c o r r e c t i o n on t h e l o w s i d e o f t h e 193.7 nm A s wavelength below - 0.06 nm may r e s u l t i n a severe n e g a t i v e bias.

4.7.3

The h i g h s i d e (t 0.07 nm) o f t h e 196.0 nm Se wavelength has a severe u n d e f i n e d s p e c t r a l i n t e r f e r e n c e o r i g i n a t i n g f r o m t h e tetramethylammonium h y d r o x i d e .

4.7.4

Background c o r r e c t i o n on t h e l o w s i d e o f t h e 259.9 nm Fe wavelength below - 0.06 nm may r e s u l t i n s p e c t r a l i n t e r f e r e n c e from 259.8 nm Fe wavelength.

4.7.5

The l o w s i d e ( - 0.05 nm) o f t h e 308.2 nm A1 wavelength has a s p e c t r a l i n t e r f e r e n c e f r o m argon.

4.7.6

The l o w s i d e (- 0.04 nm) o f t h e 213.8 nm Zn wavelength r e a d i n t h e 2nd o r d e r has a weak s p e c t r a l i n t e r f e r e n c e f r o m magnesium.

SAFETY

5.1

A l l personnel h a n d l i n g environmental samples known t o c o n t a i n o r t o have been i n c o n t a c t w i t h human waste should be immunized a g a i n s t known d i s e a s e c a u s a t i v e agents.

5.2

P r e c a u t i o n s s h o u l d a l s o be t a k e n t o m i n i m i z e p o t e n t i a l b a c t e r i a l i n f e c t i o n s from h a n d l i n g and d i s s e c t i n g f i s h . B a s i c good housekeeping and s a n i t a t i o n p r a c t i c e s and use o f r u b b e r o r p l a s t i c g l o v e s a r e recommended.

5.3

M o b i l e and remote sampling l o c a t i o n s s h o u l d be equipped w i t h a communication system t o summon h e l p i n case o f an emergency. It i s recommended t h a t f i e l d personnel n o t work a1 one.

5.4

M a t e r i a l s a f e t y d a t a sheets f o r a l l chemical r e a g e n t s s h o u l d be a v a i l a b l e t o and understood by a l l personnel u s i n g t h i s method. S p e c i f i c a l l y , tetramethylammonium h y d r o x i d e (25%) and c o n c e n t r a t e d n i t r i c a c i d a r e moderately t o x i c and e x t r e m e l y i r r i t a t i n g t o s k i n and mucus membranes. Use t h e s e r e a g e n t s i n a hood whenever p o s s i b l e and i f eye o r s k i n c o n t a c t occurs, f l u s h w i t h l a r g e volumes o f water. Always wear s a f e t y g l a s s e s o r a s h i e l d f o r eye p r o t e c t i o n when w o r k i n g w i t h t h e s e r e a g e n t s .

APPARATUS AND EQUIPMENT

6.1

TISSUE D I S S E C T I N G EQUIPMENT

Metals

6.2

6.3

217

6.1.1.

D i s s e c t i n g Board: Polyethylene o r o t h e r i n e r t , n o n m e t a l l i c m a t e r i a l ; any non-wetting, easy-to-clean o r disposable surface i s s u i t a b l e . Adhesive backed T e f l o n o r p l a s t i c f i l m may be convenient t o use.

6.1.2

Forceps: P l a s t i c , T e fl o n o r T e f l o n coated.

6.1.3

S u rg i c a l Blades: Disposable s t a i n l e s s s t e e l w i t h s t a i n l e s s s t e e l o r p l a s t i c handle (Sect. 4 . 1 ) .

6.1.4

Scissors:

6.1.5

P l a s t i c bags w i t h w a t e r t i g h t seal, metal f r e e .

6.1.6

Label tape: Self-adhesive, v i n y l - c o a t e d marking tape, s o l v e n t r e s i s t a n t , usable from -23°C t o 122°C.

6.1.7

P o l y v i n y l c h l o r i d e o r rubber gloves, t a l c - f r e e .

Stainless steel.

Labware - A l l reusable glassware, p o l y s u l f o n e and T e f l o n c o n t a i n e r s must be soaked and washed w i t h detergent, r i n s e d w i t h t a p water, soaked f o r 4 h i n a m i x t u r e o f d i l u t e n i t r i c and h y d r o c h l o r i c a c i d (1+2+9), r i n s e d again w i t h t a p water f o l l o w e d by deionized, d i s t i l l e d water (Sect. 7.1) and oven d r y i n g . The use o f chromic a c i d must be avoided. 6.2.1

Glassware: Class A v o l u m e t r i c f l a s k s o f v a r i o u s volumes, assorted c a l i b r a t e d p i p e t t e s and beakers.

6.2.2

Oak Ridge ty p e c e n t r i f u g e tubes: 30-mL c a p a c i t y , p o l y s u l f o n e tube w i t h polypropylene screw c l o s u r e ( a v a i l a b l e from most suppl i e r s o f l a b o r a t o r y equipment).

6.2.3

Storage b o t t l e s : Narrow-mouth b o t t l e s , T e f l o n FEP ( f l u o r i n a t e d e th y l e n e propylene) w i t h Te f z e l ETFE (e th y l e n e t e t r a f l u o r e t h y l e n e ) screw c l o s u r e , 125-mL and 250-mL c a p a c i t i e s .

6.2.4

Wash b o t t l e : One-piece stem, T e f l o n FEP b o t t l e w i t h T e fz e l ETFE screw c l o s u r e , 125-mL c a p a c i t y .

SAMPLE PROCESSING EQUIPMENT 6.3.1

A i r Displacement P i p e t t e r : D i g i t a l p i p e t capable o f d e l i v e r i n g volumes ra n g i n g from 0.1 t o 2500 m i c r o l i t e r s w i t h an assortment o f h i g h q u a l i t y disposable p i p e t t i p s .

6.3.2

Hot P l a te :

Ceramic top, graduated d i a l 90°C t o 4500C (Corning P C l O O o r e q u i v a l e n t ) .

218

Methods for the Determination 6.3.3

Test tube r a c k :

Polycarbonate t u b e s i z e 25-30 mm, 3 x 8

array.

6.4

7.

6.3.4

S i n g l e pan balance capable o f w e i g h i n g t o t h e n e a r e s t 0.01 g.

6.3.5

A n a l y t i c a l balance capable o f w e i g h i n g t o t h e n e a r e s t 0.0001 g .

6.3.6

Vortex m i x e r w i t h neoprene m i x i n g head and b u i l t - i n r h e o s t a t control.

6.3.7

C e n t r i f u g e : S t e e l c a b i n e t w i t h guard bowl, capable o f r e a c h i n g 2000 r.p.m. c o m p a t i b l e w i t h c e n t r i f u g e t u b e s ( S e c t . 6.2.3), e l e c t r i c t i m e r and brake. ( I n t e r n a t i o n a l C e n t r i f u g e , U n i v e r s a l Model UV o r e q u i v a l e n t . )

6.3.8

D r y i n g oven: G r a v i t y c o n v e c t i o n oven, w i t h t h e r m o s t a t i c c o n t r o l capable o f m a i n t a i n i n g 65°C and 100°C k 5°C w i t h an i n t e r i o r dimension o f no s m a l l e r t h a n 14" x 6" x 6 " .

ANALYTICAL INSTRUMENTATION 6.4.1

The I C P i n s t r u m e n t may be a simultaneous o r s e q u e n t i a l spectrometer system t h a t uses i o n i z e d argon gas as t h e plasma. However, t h e system and t h e p r o c e s s i n g o f background c o r r e c t e d s i g n a l s must be computer c o n t r o l l e d . The i n s t r u m e n t must be capable o f meeting and complying w i t h t h e r e q u i r e m e n t s and d e s c r i p t i o n o f t h e t e c h n i q u e g i v e n i n Sect. 2.2. The i n s t r u m e n t must be equipped w i t h a n e b u l i z e r and t o r c h i m p i n g e r t u b e t h a t has an o r i f i c e capable o f a c c e p t i n g 5% d i s s o l v e d s o l i d s .

6.4.2

A v a r i a b l e speed p e r i s t a l t i c pump i s r e q u i r e d t o d e l i v e r b o t h s t a n d a r d and sample s o l u t i o n s t o t h e n e b u l i z e r .

6.4.3

The use o f mass f l o w c o n t r o l l e r s t o r e g u l a t e t h e argon f l o w rates, e s p e c i a l l y through t h e nebulizer, are h i g h l y recommended. T h e i r use w i l l p r o v i d e more e x a c t i n g c o n t r o l o f r e p r o d u c i b l e plasma c o n d i t i o n s .

REAGENTS AND CONSUMABLE MATERIAL 7.1

Deionized, d i s t i l l e d w a t e r : Prepare by p a s s i n g d i s t i l l e d w a t e r t h r o u g h a mixed bed o f c a t i o n and a n i o n exchange r e s i n s . Use d e i o n i z e d , d i s t i l l e d w a t e r f o r t h e p r e p a r a t i o n o f a l l r e a g e n t s and as d i l u t i o n o r r i n s e w a t e r . The p u r i t y o f t h i s w a t e r must be e q u i v a l e n t t o ASTM Type I 1 r e a g e n t w a t e r o f S p e c i f i c a t i o n D 1193.'

7.2

N i t r i c a c i d (HNO,), conc. ( s p . g r . 1.41) (CASRN 7697-37-2), ACS r e a g e n t grade o r e q u i v a l e n t . R e d i s t i l l e d a c i d i s a c c e p t a b l e .

Metals

7.3

7.2.1

N i t r i c acid, ( l t l ) : Add 500 mL conc. HNO, (Sect. 7 . 2 ) t o 400 mL deionized, d i s t i l l e d w a t e r (Sect. 7 . 1 ) and d i l u t e t o 1 L .

7.2.2

N i t r i c a c i d , ( 1 t 9 ) : Add 100 mL conc. HNO (Sect. 7 . 2 ) t o 400 mL d e i o n i z e d d i s t i l l e d water (Sect. 7 . l j and d i l u t e t o 1 L.

Hydr o c h l o ri c a c i d (HCl), conc. (sp. g r . 1 . 1 9 , CASRN 7647-01-0), ACS reagent grade o r e q u i v a l e n t .

7.3.1

7.4

219

H y d ro c h l o ri c a c i d , ( l t l ) : Add 500 mL conc. HC1 (Sect. 7 . 3 ) t o 400 mL deionized, d i s t i l l e d water (Sect. 7 . 1 ) and d i l u t e t o 1 L.

Tetramethylammonium hydroxide [ (CH,),NOH], (CASRN 75-59-2), TMAH 25% aqueous s o l u t i o n , e l e c t r o n i c grade 99.9999% (metals b a s i s ) ALFA #20932 o r equi Val e n t

.

7 . 5 Ammonium hydroxide (NH OH) (CASRN 1336-21-6), equiv a l e n t (sp. g r . 0 . 4 0 2 ) . 7.6

ACS reagent grade o r

Standard s to c k s o l u t i o n s may be purchased o r prepared from u l t r a h i g h p u r i t y grade chemicals o r metals. A l l s a l t s must be d r i e d f o r 1 h a t 105°C unless s p e c i f i e d otherwise. (CAUTION: Wash hands thoroughly a f t e r h a n d l i n g ). T y p i c a l s t o c k s o l u t i o n p r e p a r a t i o n procedures f o l l o w . NOTE: Some metals, p a r t i c u l a r l y those which form surface oxides r e q u i r e c l e a n i n g p r i o r t o being weighed. Th i s may be achieved by p i c k l i n g t h e surface o f t h e metal i n a c i d . An amount i n excess o f t h e d e s i re d weight should be p i c k l e d r e p e a t e d l y , r i n s e d w i t h water, d r i e d and weighed u n t i l t h e d e s i r e d weight i s achieved.

7.6.1

Aluminum s o l u t i o n , s to c k ( 1 mL = 1000 p g A l ) - P i c k l e aluminum metal i n warm ( l t l ) h y d r o c h l o r i c a c i d t o an exact weight o f 0 . 1 0 0 g. D i s s o l v e i n an a c i d m i x t u r e o f 5 m l ( l t l ) h y d r o c h l o r i c a c i d and 1 mL conc. n i t r i c a c i d i n a beaker. Warm g e n t l y t o e f f e c t s o l u t i o n . When s o l u t i o n i s complete, t r a n s f e r q u a n t i t a t i v e l y t o a 100-mL v o l u m e t r i c f l a s k and d i l u t e t o t h e mark w i t h deionized, d i s t i l l e d water. Sto re t h e s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6 . 2 . 3 ) .

7.6.2

Antimony s o l u t i o n , s to c k (1 mL = 1000 p g Sb) - D i s s o l v e 0,100 g antimony powder (CASRN 7440-36-0) in 2 mL (1+1) n i t r i c a c i d and 0 . 5 mL conc. h y d r o c h l o r i c acid, h e a t i n g t o e f f e c t s o l u t i o n . Cool, add 20 mL deionized, d i s t i l l e d water and 0 . 1 5 g t a r t a r i c a c i d . Warm t h e s o l u t i o n t o d i s s o l v e t h e w h i t e p r e c i p i t a t e . Cool and d i l u t e t o 100 mL i n v o l u m e t r i c f l a s k w i t h d e i o n i z e d d i s t i l l e d water. Store t h e s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6 . 2 . 3 ) .

220

Methods for the Determination

7.6.3 Arsenic s o l u t i o n stock (1 mL = 1000 p g A s ) - D i s s o l v e 0.1320 g arsenic t r i o x i d e ( A s 0 ) (CASRN 1327-53-3) i n 50 mL

\

deionized, d i s t i l e d water an2 mL conc. ammonium hydroxide. Heat g e n t l y t o d ssolve. A c i d i f y t h e s o l u t i o n w i t h 2 mL conc. n i t r i c a c i d and d i l u t e t o 100 mL i n a v o l u m e t r i c f l a s k w i t h deionized, d i s t i l l e d water. Store t h e s o l u t i o n i n a screwcap T e fl o n FEP storage b o t t l e (Sect. 6.2.3).

m.

7.6.4 B e r y l l i u m s o l u t i o n stock (1 mL = 500 p g Be) D i s s o l v e 0.9830 g b e r y l l i u m s u l f a t e (BeS04-4H,0) i n deionized, d i s t i l l e d w a t e r , add 1.0 mL conc. n i t r i c a c i d and d i l u t e t o 100 mL i n a v o l u m e t r i c f l a s k w i t h deionized,

d i s t i l l e d water. Store t h e s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

7.6.5

Cadmium s o l u t i o n stock (1 mL = 1000 pg Cd) - P i c k l e cadmium metal i n (1t9) n i t r i c a c i d t o an exact weight o f 0.100 g. D i s s o l v e i n 4 mL conc. n i t r i c a c i d , d i l u t e t o 100 mL i n a v o l u me tri c f l a s k w i t h deionized, d i s t i l l e d water. S t o r e t h e s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

7.6.6 Calcium s o l u t i o n stock (1 mL = 1000 1-19 Ca) - Suspend 0.2498 g calcium carbonate (CaCO,) d r i e d a t 180°C f o r 1 h before weighing, i n deionized, d i s t i l l e d w a t e r ) . D i s s o l v e c a u t i o u s l y r e a c t i n g i s vigorous) by adding dropwise 10.0 mL (ltl) h y d r o c h l o r i c a c i d and d i l u t e t o 100 mL i n a v o l u m e t r i c f l a s k w i t h deionized, d i s t i l l e d water. S t o r e t h e s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

7.6.7

Chromium s o l u t i o n , stock (1 mL = 1000 pg C r ) - D i s s o l v e 0.1923 g chromium t r i o x i d e ( C r O ) i n deionized, d i s t i l l e d water. When s o l u t i o n i s complete, a c i d i f y w i t h 1 mL conc. n i t r i c a c i d and d i l u t e t o 100 mL i n a v o l u m e t r i c f l a s k w i t h deionized, d i s t i l l e d water. S t o r e t h e s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sec,t. 6.2.3).

7.6.8 Copper s o l u t i o n , stock (1 mL = 1000 pg Cu) - P i c k l e copper metal i n (1t9) n i t r i c a c i d t o an exact weight o f 0.100 g. D i s s o l v e i n 2 mL conc. n i t r i c a c i d . D i l u t e t o 100 mL i n a v o l u me tri c f l a s k w i t h deionized, d i s t i l l e d water. s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

7.6.9

Store t h e

I r o n s o l u t i o n , stock (1 mL = 1000 p g Fe) - P i c k l e i r o n metal i n (ltl) h y d r o c h l o r i c a c i d t o an exact weight o f 0.100 g. D i s s o l v e i n 10 mL (ltl) h y d r o c h l o r i c a c i d . D i l u t e t o 100 mL i n a v o l u me tri c f l a s k w i t h deionized, d i s t i l l e d water (Sect. 7.1). Sto re t h e s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

Metals

221

= 1000 p g Pb) - D i s s o l v e 0.1613 g l e a d n i t r a t e [Pb(NO,),] i n a minimum amount o f (ltl) n i t r i c a c i d . Add 5 mL conc. n i t r i c a c i d . D i l u t e t o 100 mL i n a v o l u m e tri c f l a s k w i t h deionized, d i s t i l l e d water. Store t h e s o l u t i o n i n screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

7.6.10 Lead s o l u t i o n , stock (1 mL

7.6.11 Magnesium s o l u t i o n , stock (1 mL = 1000 p g Mg) - D i s s o l v e 0.1658 g magnesium o x i d e (MgO i n 10 mL (1+1) n i t r i c acid, h e a ti n g t o e f f e c t s o l u t i o n . Cool and d i l u t e t o 100 mL i n a v o l u m e tri c f l a s k w i t h deionized, d i s t i l l e d water. s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

Store t h e

7.6.12 N i c k e l s o l u t i o n , stock (1 mL = 1000 p g N i ) - D i s s o l v e 0.100 g n i c k e l metal i n 5 mL h o t conc. n i t r i c a c i d . Cool and d i l u t e t o 100 mL i n a v o l u m e t r i c f l a s k w i t h deionized, d i s t i l l e d water. S to re t h e s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

7.6.13 Phosphorus s o l u t i o n , stock (1 mL = 1000 p g P) - D i s s o l v e 0.3745 g ammonium phosphate, monobasic [(NH,)H PO,,] (CASRN 7722-76-1) i n deionized, d i s t i l l e d water and t i l u t e t o 100 mL i n a v o l u m e tri c f l a s k , S t o r e t h e s o l u t i o n i n a screwcap T e fl o n FEP storage b o t t l e (Sect. 6.2.3).

7.6.14 Potassium s o l u t i o n , stock (1 mL = 1000 p g K) - D i s s o l v e 0.1907 g potassium c h l o r i d e (KC1) p r e v i o u s l y d r i e d a t 110°C f o r 3 h, i n deionized, d i s t i l l e d water, add 2 mL (1+1) h y d r o c h l o r i c a c i d and d i l u t e t o 100 mL i n a v o l u m e t r i c f l a s k . Store t h e s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

7.6.15 Selenium s o l u t i o n , s to c k (1 mL = 1000 fig Se) - D i s s o l v e 0.1414 g selenium d i o x i d e (Sea,) i n deionized, d i s t i l l e d water and d i l u t e t o 100 m L i n a v o l u m e t r i c f l a s k . Store t h e s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

7.6.16 Sodium s o l u t i o n , s to c k (1 mL = 1000 p g Na) - D i s s o l v e 0.2542 g sodium c h l o r i d e (NaC1) i n deionized, d i s t i l l e d water. Add 1.0 mL conc. n i t r i c a c i d and d i l u t e t o 100 mL i n a v o l u me tri c f l a s k w i t h deionized, d i s t i l l e d water. Store t h e s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

7.6.17 T h a l l i u m s o l u t i o n , s to c k ( mL = 1000 p g T1) - D i s s o l v e 0.1303 g t h a l l o u s n i t r a t e TlNO,) i n deionized, d i s t i l l e d water. Add 1.0 mL conc. n t r i c a c i d and d i l u t e t o 100 mL i n a v o l u me tri c f l a s k w i t h de onized, d i s t i l l e d water. Store t h e s o l u t i o n i n a screwcap Tef1o.n FEP storage b o t t l e (Sect. 6.2.3).

222

Methods for the Determination 7.6.18 Zinc s o l u t i o n , stock ( 1 mL = 1000 l g Zn) - P i c k l e z i n c metal i n ( 1 t 9 ) n i t r i c a c i d t o an exact weight o f 0.100 g. Dissolve i n 5 mL conc. n i t r i c acid. D i l u t e t o 100 mL i n a volumetric f l a s k w i t h deionized, d i s t i l l e d water. Store t h e s o l u t i o n i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

7.7

Prepare f o u r 100 mL primary standard s o l u t i o n s (Sect. 3.11) by combining a1 i q u o t s from t h e appropriate i n d i v i d u a l stock s o l u t i o n s (Sect. 7.6) i n volumetric f l a s k s and d i l u t i n g t o t h e mark w i t h deionized, d i s t i l l e d water. For t h e wavelength and background c o r r e c t i o n p o s i t i o n s recommended, prepare t h e primary standard s o l u t i o n using t h e f o l l o w i n g l i s t e d a l i q u o t volumes o f t h e i n d i v i d u a l stock standards. Transfer t h e prepared primary standard s o l u t i o n s i n screwcap T e f l o n FEP storage b o t t l e s (Sect. 6.2.3). 7.7.1

Primary standard s o l u t i o n I (Volume = 100.0 mL)

Anal v t e

Sol u t i o n

A1 iquot Vol.. mL

A1 Ca Cd cu Mg Sb Se

7.6.1 7.6.6 7.6.5 7.6.8 7.6.11 7.6.2 7.6.15

10.0 10.0 2.0 1.o 10.0 5.0 5.0

Stock

7.7.2

Primary standard s o l u t i o n I 1 (Volume Anal v t e As Cr

7.7.3

Stock Sol u t i o n 7.6.3 7.6.7

Analyte Conc. .uq/ mL 100 100 20 10 100 50 50

=

A1 iquot Vol.. mL 10.0 5.0

100.0 mL) Analyte Conc.. uq/mL 100 50

Primary standard s o l u t i o n 111 (Volume = 100.0 mL) Anal v t e

Stock Sol u t i o n

A1 iquot Vol., mL

Na Pb 11 Zn

7.6.16 7.6.10 7.6.17 7.6.18

10.0 10.0 5.0 5.0

Analyte Conc.. uql mL 100 100 50 50

Metals 7 . 7 . 4 Primary standard s o l u t i o n I V (Volume

Anal v t e Be Fe K Ni P 7.8

=

100.0 mL)

A1 iquot Vol., mL

Stock Solution 7.6.4 7.6.9 7.6.14 7.6.12 7.6.13

223

2.0 10.0 20.0 2.0 10.0

Analyte Conc.. us/ mL 10 100 200 20 100

For c a l i b r a t i n g t h e instrument, prepare f o u r CAL s o l u t i o n s (Sect. 3.12), each i n 100-mL v o l u m e t r i c f l a s k by adding 10 mL TMAH (Sect. 7.4) and 5 mL o f conc. n i t r i c a c i d t o 10 mL o f each o f t h e f o u r Drimary standard s o l u t i o n s (Sect. 7 . 7 ) and d i l u t e t o t h e mark w i t h d e i o n i i e d , d i s t i l e d water. Tr a n s f e r t h e prepared c a l i b r a t i o n standards t o screwcap T e f l o n FEP storage b o t t l e s (Sect. 6.2.3). 7.8.1 CAL s o l u t i o n I

Volume = 100.0 mL)

Anal v t e

Conc.. uq/ mL

A1 Ca Cd cu Mg Sb Se

10.0 10.0 2.0 1.o 10.0 5.0 5.0

7.8.2 CAL s o l u t i o n I 1 (Volume

=

100.0 mL)

Anal v t e

Conc.. uq/ mL

As Cr

10.0 5.0

7.8.3 CAL s o l u t i o n 111 (Volume = 100.0 mL) Anal v t e Na Pb T1 Zn

Conc.. uq/ mL 10.0 10.0 5.0 5.0

224

Methods for the Determination

7.8.4 CAL s o l u t i o n

I V (Volume

Anal v t e

100.0 mL) Conc., u q l mL 1 .o 10.0 20.0 2.0 10.0

Be Fe K Ni P 7.9

=

Prepare a c a l i b r a t i o n blank by d i l u t i n g t h e combination s o l u t i o n o f 10 mL TMAH (Sect. 7.4) and 5 mL conc. n i t r i c a c i d t o 100 mL i n a volumetric f l a s k w i t h deionized, d i s t i l l e d water. Store t h e c a l i b r a t i o n blank i n a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.4).

7.10 Prepare a l a b o r a t o r y performance check (LPC) stock s o l u t i o n i n a 100-mL volumetric f l a s k by combining t h e f o l l o w i n g l i s t e d a l i q u o t volumes o f t h e i n d i v i d u a l stock standards and d i l u t i n g t o t h e mark w i t h deionized, d i s t i l l e d water. Transfer t h e stock s o l u t i o n t o a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3). Anal v t e A1 As Be Ca Cd Cr cu Fe K Mg Na Ni P Pb Sb Se T1 Zn

Stock Sol u tion 7.6.1 7.6.3 7.6.4 7.6.6 7.6.5 7.6.7 7.6.8 7.6.9 7.6.14 7.6.11 7.6.16 7.6.12 7.6.13 7.6.10 7.6.2 7.6.15 7.6.17 7.6.18

A1 iquot Vol.. mL 1.0 1 .o 2.0 2.0 1.o 1.o 1.o 1.o 10.0 2.0 2.0 1.o 10.0 1.o 1.o 1.0 1 .o 1 .o

Analyte Conc., uql mL 10.0 10.0 10.0 20.0 10.0 10.0 10.0 10.0 100.0 20.0 20.0 10.0 100.0 10.0 10.0 10.0 10.0 10.0

7.10.1 A t t h e time o f c a l i b r a t i o n prepare t h e LPC i n a 100-mL volumetric f l a s k by adding i n t h e f o l l o w i n g order, 10 mL TMAH (Sect. 7.4) and 5 mL conc. n i t r i c a c i d t o 10 mL o f t h e LPC stock s o l u t i o n (Sect. 7.10) and d i l u t i n g t o t h e mark w i t h deionized, d i s t i l l e d water. Transfer t h e LPC t o a screwcap T e f l o n FEP storage b o t t l e (Sect. 6.2.3).

Metals

225

Calibration Check Std. Conc.. ucrlr&

Anal vte A1 As Be Ca Cd Cr cu Fe

1 .o

1 .o 1 .o 2.0 1 .o 1 .o 1 .o 1 .o

K

10.0 2.0 2.0 1 .o 10.0 1 .o 1 .o 1 .o 1 .o 1 .o

Mg Na Ni P Pb Sb Se T1 Zn

7.11 Prepare the laboratory fortifying stock solution in a 200-mL volumetric flask by combining the following listed aliquot volumes of the individual stock solution and diluting to the mark with deionized, distilled water. Transfer the laboratory fortifying stock solution to a screwcap Teflon FEP storage bottle (Sect. 6.2.3).

Anal vte AL As Be Cd Cr cu Ni Pb Sb Se T1 Zn

Stock Sol ut i on 7.6.1 7.6.3 7.6.4 7.6.5 7.6.7 7.6.8 7.6.12 7.6.10 7.6.2 7.6.15 7.6.17 7.6.18

A1 i quot Vol.. mL 10.0 10.0 1 .o 1 .o 2.0 5.0 5.0 5.0 5.0 10.0 5.0 10.0

Analyte Conc.. ucrl m L 50 50 2.5 5 10 25 25 25 25 50 25 50

7.12 Prepare an instrument wash acid solution by diluting 50 mL o f conc. nitric acid to 1 L with deionized, distilled water. Store in a convenient manner. This solution is to be used to flush the solution uptake system and nebulizer between standards and samples.

226 8.

9.

Methods for the Determination SAMPLE COLLECTION, PRESERVATION AND STORAGE 8.1

F i s h samples a r e c o l l e c t e d u s i n g a v a r i e t y o f equipment, methods and techniques such as t r o t l i n e s , t r a w l s , s e i n e s , dredges, n e t s , i c h t h y o c i d e s and e l e c t r o f i s h i n g . The t e c h n i q u e used must be f r e e from c o n t a m i n a t i o n by m e t a l s . F o r example, permanganate may be used t o d e t o x i f y Rotgnone b u t s h o u l d n o t come i n c o n t a c t w i t h t h e f i s h t o be analyzed.

8.2

A p p r o p r i a t e i n d i v i d u a l t i s s u e samples s h o u l d be t a k e n soon f f t e r If c o l l e c t i o n o f t h e f i s h and must be t a k e n p r i o r t o f r e e z i n g . d i s s e c t i o n o f t h e t i s s u e cannot be performed i m m e d i a t e l y a f t e r c o l l e c t i o n , each f i s h s h o u l d be p l a c e d i n a p l a s t i c bag ( S e c t . 6.1.5), s e a l e d and p l a c e d on i c e o r r e f r i g e r a t e d a t a p p r o x i m a t e l y 4°C.

8.3

P r i o r t o d i s s e c t i o n , t h e f i s h s h o u l d be r i n s e d w i t h m e t a l - f r e e w a t e r and b l o t t e d d r y . D i s s e c t i o n s h o u l d be performed w i t h i n 24 h o f c o l l e c t i o n . Each i n d i v i d u a l f i l l e t sample s h o u l d a l s o be r i n s e d w i t h m e t a l - f r e e w a t e r , b l o t t e d d r y , p l a c e d i n a preweighed, l a b e l e d p o l y s u l f o n e c e n t r i f u g e t u b e ( S e c t . 6.2.2) and f r o z e n a t (-20°C ( d r y i c e ) .

8.4

S k i n l e s s f i l l e t samples o f a p p r o x i m a t e l y 1-2 g (1 cm x 0.5 cm x 2 cm) s h o u l d be c u t f r o m t h e f i s h u s i n g a s p e c i a l implement ( S e c t . 4.1) and handled w i t h p l a s t i c f o r c e p s ( S e c t . 6.1.2).8,9

8.5

A maximum h o l d i n g t i m e f o r f r o z e n samples has n o t been d e t e r m i n e d .

C A L I B R A T I O N AND STANDARDIZATION 9.1

S p e c i f i c wavelengths and background c o r r e c t i o n l o c a t i o n s g i v e n i n T a b l e 1 and i n s t r u m e n t o p e r a t i n g c o n d i t i o n s g i v e n i n T a b l e 2 s h o u l d be used whenever p o s s i b l e . However, because o f t h e d i f f e r e n c e among v a r i o u s makes and models o f spectrometers, t h e analyst should f o l l o w t h e instrument manufacturer's i n s t r u c t i o n s i n a d a p t i n g t h e i n s t r u m e n t ' s o p e r a t i o n t o approximate t h e recommended o p e r a t i n g c o n d i t i o n s . O t h e r wavelengths and background c o r r e c t i o n l o c a t i o n s may be s u b s t i t u t e d i f t h e y can p r o v i d e t h e needed s e n s i t i v i t y and a r e c o r r e c t e d f o r s p e c t r a l interference.

9.2

A l l o w t h e i n s t r u m e n t t o become t h e r m a l l y s t a b l e b e f o r e b e g i n n i n g . T h i s u s u a l l y r e q u i r e s a t l e a s t 30 min o f o p e r a t i o n p r i o r t o c a l ib r a t ion.

9.3

O p t i c a l l y p r o f i l e t h e i n s t r u m e n t and a d j u s t t h e plasma t o a p r e v i o u s l y e s t a b l i s h e d c o n d i t i o n by r e g u l a t i n g t h e argon f l o w r a t e through the n e b u l i z e r w h i l e monitoring t h e i n t e n s i t y r a t i o o f s e l e c t e d a t o m / i o n wavelengths [e.g., Cu (I) 324.75 nm/Mn ( 1 1 ) 257.61 nm] .

Metals 9.4

C a l i b r a t e th e instrument according t o t h e instrument m a n u f a c t u r e r ' s i n s t r u c t i o n s u s i n g th e prepared c a l i b r a t i o n blank (Sect. 7.9) and CAL s o l u t i o n s (Sect. 7 . 8 ) .

9.5

The f o l l o w i n g o p e ra ti o n a l steps should be used f o r b o t h CAL s o l u t i o n s and s a m p l e s . 9.5.1

Using a p e r i s t a l i c pump i n t r o d u c e t h e standard ,or sample t o n e b u l i z e r a t a u n i fo rm r a t e (e.g., 1.2 mL/min.- ) .

9.5.2

To a l l o w e q u i l i b r i u m t o be reached i n t h e plasma, a s p i r a t e t h e standard o r sample s o l u t i o n f o r 30 sec a f t e r reaching t h e plasma b e f o r e beginning i n t e g r a t i o n o f t h e background c o r r e c t e d s i g n a l .

9.5.3

Use th e average value o f f o u r 4 sec background c o r r e c t e d i n t e g r a t i o n p e r i o d s a s t h e atomic emission s i g n a l ' t o be c o r r e l a t e d t o a n a l y t e c o n c e n t r a t i o n .

9.5.4

9.6

10.

227

Between each standard o r sample, f l u s h t h e n e b u l i z e r and s o l u t i o n uptake system w i t h t h e wash a c i d s o l u t i o n (Sect. 7.12) f o r 60 sec o r f o r t h e r e q u i r e d p e r i o d o f time t o ensure t h a t a n a l y te memory e f f e c t s are n o t o c c u r r i n g .

Analyze th e LPC s o l u t i o n (Sect. 7.10.1) and c a l i b r a t i o n b (Sect. 7.9) immediately f o l l o w i n g c a l i b r a t i o n , a t t h e end analyses and p e r i o d i c a l l y throughout t h e sample run. The value o f t h e LPC s o l u t i o n should be w i t h i n an i n t e r v a l o f 105% o f t h e expected value. I f t h e value i s o u t s i d e t h e t h e instrument should be r e c a l i b r a t e d and a l l samples f o l l a s t acceptable LPC s o l u t i o n should be reanalyzed.

ank o f the analyzed 95% t o nterval , owing t h e

OUALITY CONTROL 10.1

Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o operate a formal q u a l i t y c o n t r o l (QC) program. The minimum requirements o f t h i s program c o n s i s t o f an i n i t i a l demonstration o f l a b o r a t o r y c a p a b i l i t y and t h e a n a l y s i s o f reagent blanks, f o r t i f i e d blanks and samples as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n ta i n performance records t h a t d e f i n e t h e q u a l i t y o f data th u s generated.

10.2

INITIAL DEMONSTRATION OF PERFORMANCE 10.2.1

I n i t i a l demonstration o f performance i s used t o c h a ra c te ri z e d instrument and l a b o r a t o r y performance, (method d e t e c t i o n l i m i t s and q u a l i t y c o n t r o l v e r i f i c a t i o n ) f o r analyses conducted by t h i s method.

10.2.2

When beginning t h e use o f t h i s method and on a q u a r t e r l y basis, v e r i f y acceptable l a b o r a t o r y performance w i t h t h e p re p a ra ti o n and analyses o f a q u a l i t y c o n t r o l sample (QCS)

228

Methods for the Determination ( S e c t . 3 . 1 3 ) . The QCS i s c a r r i e d t h r o u g h t h e e n t i r e a n a l y t i c a l o p e r a t i o n o f t h e method. I f t h e d e t e r m i n e d c o n c e n t r a t i o n s a r e n o t w i t h i n f 5% s t a t e d v a l u e s o f 1 mg/L, l a b o r a t o r y performance i s unacceptable. The source o f t h e problem should be i d e n t i f i e d and c o r r e c t e d b e f o r e c o n t i n u i n g t h e analyses. 10.2.3

Method d e t e c t i o n l i m i t (MDL) ( S e c t . 3.2) i n p g / g must be determined f o r each o f t h e f o l l o w i n g a n a l y t e s : A l , As, Be, Cd, C r , Cu, N i , Pb, Sb, Se, T1, and Zn. Except f o r A s , Cu and Zn, t h e MDLs f o r a l l a n a l y t e s must be determined i n t h e f i s h t i s s u e m a t r i x . Because o f background c o n c e n t r a t i o n s i n f i s h t i s s u e , MDLs f o r As, Cu and Zn should be determined by f o r t i f y i n g and a n a l y z i n g t h e LRB (Sect. 3.5) m a t r i x . The MDL d e t e r m i n a t i o n s should be made u s i n g seven r e p l i c a t e samples p r e p a r e d as d e s c r i b e d i n t h e procedure ( S e c t . 11.). The c o n c e n t r a t i o n o f t h e f o r t i f i e d a n a l y t e i n t h e sample should be approximately t h r e e times t h e estimated d e t e c t i o n l i m i t . The determined MDL values t e s t e d i n T a b l e 1 can be used as a g u i d e . ( A c t u a l s o l u t i o n c o n c e n t r a t i o n i n pg/mL a r e 10% o f t h e l i s t e d values). Appropriate d i l u t i o n s o f t h e l a b o r a t o r y f o r t i f y i n g s t o c k s o l u t i o n ( S e c t . 7.11) may be used t o determine MDL. C a l c u l a t e t h e MDL as f o l l o w s : MDL = ( t ) x ( S ) where, t = S t u d e n t ' s t v a l u e f o r a 99% c o n f i d e n c e l e v e l and a s t a n d a r d d e v i a t i o n e s t i m a t e w i t h n-1 degrees o f freedom [ t = 3.14 f o r seven r e p l i c a t e s ] . S

=

standard d e v i a t i o n of t h e r e p l i c a t e analyses.

MDLs should be determined y e a r l y o r whenever t h e r e i s a s i g n i f i c a n t change i n background o r i n s t r u m e n t response. 10.3

ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS 10.3.1

A l a b o r a t o r y reagent b l a n k (LRB) (Sect. 3.5) i s t o be analyzed w i t h each group o f samples. LRB d a t a a r e used t o assess c o n t a m i n a t i o n from t h e l a b o r a t o r y environment and t o c h a r a c t e r i z e s p e c t r a l background f r o m r e a g e n t s used i n sample p r o c e s s i n g . Prepare t h e LRB by t r a n s f e r r i n g 1.0 mL TMAH (Sect. 7.4) t o a c l e a n preweighed, l a b e l e d 30-mL p o l y s u l f o n e Oak Ridge t y p e c e n t r i f u g e t u b e (Sect. 6.2.3). C a r r y t h e b l a n k t h r o u g h t h e e n t i r e procedure (Sect. 11) as a 1.0 g sample ending w i t h a f i n a l s o l u t i o n volume o f 10 mL. I f t h e v a l u e f o r one o r more o f t h e f o l l o w i n g

Metals

229

m e t a l s : A l , As, Be, Cd, C r , Cu, N i , Pb, Sb, Se, T1, and Zn exceeds i t s d e t e r m i n e d MDL o r e s t a b l i s h e d c o n t r o l l i m i t s , t h e n l a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n s h o u l d be suspected and a t t e n t i o n s h o u l d be g i v e n t o t h e c l e a n i n g p r o c e d u r e and t h e p u r i t y o f t h e r e a g e n t s s h o u l d be v e r i f i e d . The source o f c o n t a m i n a t i o n s h o u l d be c o r r e c t e d before completing a d d i t i o n a l analyses.

10.4

10.3.2

A f i e l d r e a g e n t b l a n k (FRB) ( S e c t . 3 . 6 ) t h a t accompanies each g r o u p o f samples i s t o be a n a l y z e d i n t h e same manner as t h e LRB. I t s purpose i s t o m o n i t o r sample c o l l e c t i o n and s t o r a g e c o n d i t i o n . C r i t e r i a f o r r e j e c t i o n o f analyses d a t a based on FRB d a t a have n o t been d e t e r m i n e d .

10.3.3

A l a b o r a t o r y f o r t i f i e d b l a n k (LFB) ( S e c t . 3 . 8 ) i s t o be a n a l y z e d w i t h each g r o u p o f samples. The LFB s h o u l d c o n t a i n t h e f o l l o w i n g m e t a l s : A l , As, Be, Cd, C r , Cu, N i , Pb, Sb, Se, T1, and Zn. To p r e p a r e t h e LFB, p i p e t 0 . 1 mL o f t h e l a b o r a t o r y f o r t i f y i n g s t o c k s o l u t i o n ( S e c t . 7.11) i n t o a c l e a n preweighed, l a b e l e d 30-mL p o l y s u l f o n e Oak Ridge t y p e c e n t r i f u g e t u b e ( S e c t . 6 . 2 . 2 ) . Add 1 mL o f TMAH ( S e c t . 7 . 4 ) and c a r r y t h e LFB t h r o u g h t h e e n t i r e p r o c e d u r e ( S e c t . 11) as a sample e n d i n g w i t h a f i n a l volume o f 10 mL. The analyzed v a l u e s s h o u l d be w i t h i n f 2 s t a n d a r d d e v i a t i o n s o f an e s t a b l i s h e d mean v a l u e d e t e r m i n e d f r o m seven p r i o r r e p l i c a t e a n a l y s e s . (Data i n T a b l e 3 may be used as a g u i d e u n t i l a s u f f i c i e n t number o f r e p l i c a t e s have been d e t e r m i n e d . ) I f an a n a l y z e d v a l u e i s greater than k 2 standard deviations, i t i s outside t h e warning l i m i t s . I f i t i s g r e a t e r than 2 3 standard d e v i a t i o n s , t h e a n a l y s i s i s j u d g e d t o be o u t o f c o n t r o l . When t h i s i s t h e case, t a k e a p p r o p r i a t e s t e p s t o i d e n t i f y and r e s o l v e t h e problems b e f o r e c o n t i n u i n g w i t h t h e analyses.

ASSESSING ANALYTE RECOVERY - LABORATORY FORTIFIED SAMPLE MATRIX 10.4.1

To demonstrate a n a l y t e r e c o v e r y f r o m t h e t i s s u e m a t r i x p r e p a r e and a n a l y z e a l a b o r a t o r y f o r t i f i e d m a t r i x sample (LFM) ( S e c t . 3.9) f o r each t y p e o f t i s s u e under a n a l y s i s . S e l e c t one f i s h f r o m each group o f I 20 samples and a t t h e t i m e o f d i s s e c t i o n c o l l e c t two a d j a c e n t f i l l e t o r t i s s u e a l i q u o t s o f n e a r l y equal s i z e (1 9 ) . To one o f t h e a l i q u o t s add 0.1 mL o f t h e l a b o r a t o r y f o r t i f y i n g s t o c k s o l u t i o n (Sect. 7.11). Carry both a l i q u o t s through t h e e n t i r e p r o c e d u r e ( S e c t . 11).

10.4.2

C a l c u l a t e t h e p e r c e n t r e c o v e r y f o r each a n a l y t e , c o r r e c t e d f o r background c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d a l i q u o t , and compare theses v a l u e s t o t h e c o n t r o l l i m i t s e s t a b l i s h e d i n Sect. 10.3.3 f o r t h e analyses o f LFBs.

230

Methods for the Determination Percent recovery may be c a l c u l a t e d i n u n i t s a p p r o p r i a t e t o th e m a t r i x , u s i n g th e f o l l o w i n g equation: R

=

(C,

-

C) X 100

F

where, R

C, C F

10.4.3

11.

= = = =

percent recovery. f o r t i f i e d sample c o n c e n t r a t i o n sample background c o n c e n t r a t i o n c o n c e n t r a t i o n e q u i v a l e n t o f a n a l y t e added t o sample

I f t h e recovery o f any a n a l y t e i n t h e LFM f a l l s o u t s i d e t h e designated range and t h e l a b o r a t o r y performance f o r t h a t a n a l y te i s shown t o be i n c o n t r o l (Sect. 10.3), t h e recovery problem encountered w i t h t h e f o r t i f i e d sample i s judged t o be m a t r i x r e l a t e d , n o t system r e l a t e d . See Sect. 13.4 and Table 5 f o r t y p i c a l recovery data.

PROCEDURE

11.1

A t t h e s t a r t o f sample processing, remove t h e cap from t h e preweighed, l a b e l e d c e n t r i f u g e tube (Sect. 6.2.2) c o n t a i n i n g t h e sample and reweigh t h e tube t o determine t h e weight o f t h e t i s s u e by d i f f e r e n c e . T h i s can be done u s i n g t h e a n a l y t i c a l balance (Sect. 6.3.5). Wipe t h e o u ts i d e o f t h e c e n t r i f u g e tube w i t h a Kimwipe o r s u i t a b l e paper t i s s u e and p l a c e t h e tube h o r i z o n t a l l y on t h e pan. The weight o f t h e t i s s u e should be between 1 and 2 g and expressed t o t h e nearest 10 mg. Record t h e t i s s u e weight.

11.2

Using a 2-mL graduated p i p e t o r an a i r displacement p i p e t t e r (Sect. 6.3.1), add a volume o f 25% tetramethylammonium hydroxide (TMAH) (Sect. 7 . 4 ) equal t o t h e weight o f t h e t i s s u e (1 mL TMAH = 1 g t i s s u e ) . The a l i q u o t o f TMAH should be t o t h e nearest t e n t h o f a m i l l i l i t e r equal t o t h e t i s s u e weight (e.g., 1.6 mL o f TMAH f o r 1.62 g o f t i s s u e ) . With t h e TMAH added, r e p l a c e and t i g h t e n t h e cap securely. (T h i s w i l l minimize t h e odor caused i n h e a t i n g t h e sample mi x tu re .) Place t h e sample i n an open r a c k f o r adequate heati n g and p l a c e t h e r a c k i n a d r y i n g oven preheated t o 65°C f 5°C and warm t h e sample f o r 1 h.

11.3 A f t e r an hour o f heating, remove t h e sample from t h e oven, r e t i g h t e n t h e cap i f loose, and mix t h e sample f o r a few seconds usin g a v o r t e x mixer (Sect. 6.3.6) s e t a t medium power s e t t i n g . Return t h e sample t o t h e d r y i n g oven and heat f o r an a d d i t i o n a l hour.

11.4 A f t e r t h e second hour o f h e a t i n g , again v o r t e x mix t h e sample and a l l o w t h e capped sample t o stand o v e r n i g h t a t room temperature.

Metals 11.5

231

The f o l l o w i n g morning, a c i d i f y t h e sample w i t h conc. n i t r i c a c i d (Sect. 7 . 2 ) t o between 4% and 5% ( v / v ) a c i d . The volume o f n i t r i c a c i d added t o each sample i s based on t h e f i n a l volume o f sample. The f i n a l sample volume i s c a l c u l a t e d by m u l t i p l y i n g t h e wet t i s s u e weight by 1 0 . Using a 1-mL graduated p i p e t o r an a i r displacement p i p e t t e r (Sect. 6 . 3 . 1 ) , add th e a p p r o p r i a t e volume o f n i t r i c a c i d as i n d i c a t e d i n t h e f o l l o w i n g t a b l e : Weight o f Tissue, a 0.80 - 1 . 0 4 1.05 - 1 . 2 4 1.25 - 1.44 1 . 4 5 - 1.64 1 . 6 5 - 1.84 1.85 - 2.04 2.05 - 2.24

F i n a l Sample Volume. mL 8 10 12 14 16 18 20

t o 10

to to to to to to

12 14 16 18 20 22

Volume o f Conc. HNO, Added, mL 0.4 0.5 0.6 0.7 0.8 0.9 1 .o

A f t e r t h e a c i d a d d i t i o n , recap t h e tube and l i g h t l y v o r t e x mix t h e sample. Place t h e tube t o t h e d r y i n g oven preheated t o 100°C and heat t h e sample f o r an hour t o s o l u b i l i z e t h e metals before proceeding. Note: A f t e r t h e a c i d i s added,' s o l i d s w i l l f a l l o u t o f s o l u t i o n and a p r e c i p i t a t e w i l l form. Th i s i s normal and t o be expected. 11.6

A f t e r t h e p e r i o d o f s o l u b i l i z a t i o n , cool t h e tube t o room temperature. Uncap t h e tube and p l a c e t h e tube on t h e s i n g l e pan balance (Sect. 6 . 3 . 4 ) i n a t a r e d 100-mL G r i f f i n beaker. A d j u s t t h e f i n a l volume o f t h e sample by adding deionized, d i s t i l l e d water f r o m a "squeeze" wash b o t t l e (Sect. 6 . 2 . 4 ) w h i l e weighing t h e tube t o an a p p r o p r i a t e weight t o m a i n t a i n t h e constant weight/volume r a t i o o f 1 9/10 mL. The a p p r o p r i a t e weight i s c a l c u l a t e d by m u l t i p l y i n g t h e wet t i s s u e weight by 10 and adding t h e product t o t h e recorded weight o f t h e empty tube.

11.7

A f t e r d i l u t i o n i s completed, recap t h e tube and v o r t e x mix t h e sample. A f t e r mixing, c e n t r i f u g e (Sect. 6 . 3 . 7 ) t h e sample a t 2000 rpm. f o r 10 min. A f t e r c e n t r i f u g i n g , t h e sample may c o n t a i n f l o a t a b l e s o l i d s as a s u rfa c e l a y e r as w e l l as t h e p r e c i p i t a t e . Also, some p a r t i c l e s may adhere t o t h e w a l l o f t h e tube. Th i s c o n d i t i o n i s normal and should n o t cause concern unless t h e a n a l y s i s s o l u t i o n a c t u a l l y c o n t a i n s suspended m a t e r i a l . The sample i s now ready f o r a n a l y s i s . Analyze t h e sample w i t h i n 24 h o f p r e p a r a t i o n (Sect. See 4 . 2 ) .

11.8

A s p i r a t e t h e sample i n t o t h e I C P u s i n g t h e same o p e r a t i n g c o n d i t i o n s used i n c a l i b r a t i o n (Sect. 9) w h i l e making c e r t a i n t h e p r e c i p i t a t e i s n o t d i s t u r b e d and i n a d v e r t e n t l y a s p i r a t e d . I f t h e surface o f t h e a n a l y s i s s o l u t i o n i s p a r t i a l l y covered w i t h f l o a t a b l e s o l i d s , proceed by removing t h e t i p o f t h e a s p i r a t i o n tube from t h e wash s o l u t i o n (Sect. 7.12) and a l l o w an a i r bubble

232

Methods for the Determination

segment t o form i n the sample uptake l i n e . Reverse t h e pump f l o w and, w h i l e back pumping the a i r bubble, i n s e r t t h e a s p i r a t i o n tube past the f l o a t a b l e s o l i d s i n t o t h e sample s o l u t i o n . Change t h e pump f l o w back t o uptake d i r e c t i o n and a s p i r a t e t h e sample.

12.

13.

CALCULATIONS 12.1

I f d i l u t i o n s are performed, t h e appropriate f a c t o r must be appl i e d t o sample values.

12.2

Data read from t h e instrument i n pg/mL should be rounded t o t h e thousandth place.

12.3

Subtract t h e LFB where appropriate (Sect. 4 . 4 ) .

12.4

To express t h e data i n concentrations o f pg/g wet t i s s u e weight m u l t i p l y t h e rounded n e t pg/mL data by a f a c t o r o f 10.

12.5

Report pg/g wet t i s s u e weight data up t o t h r e e s i g n i f i c a n t figures.

12.6

Do n o t r e p o r t data below t h e determined MDL.

PRECISION AND ACCURACY 13.1

The p r e c i s i o n and recovery data presented i n t h i s method are s i n g l e l a b o r a t o r y v e r i f i c a t i o n data only. The data were c o l l e c t e d u t i l i z i n g t h e recommended instrument c o n d i t i o n s described i n t h e method.

13.2

The p r e c i s i o n and recovery data presented i n Table 3 are f o r t h e LFB concentrations recommended i n t h i s method. The data can be used as a guide f o r q u a l i t y c o n t r o l l i m i t s (Sect. 10.3) u n t i l t h e time t h e method user e s t a b l i s h e s actual l i m i t s .

13.3

The comparative data f o r t h e f o u r types o f f i s h f i l l e t s ( b l u e g i l l , c a t f i s h , salmon, and tuna) presented i n Table 4 are f o r v e r i f i c a t i o n o f v e r s i o n 2 . 0 o f t h i s method. I n a # i t i o n t o v e r s i o n 2.0, data are included f o r t h e former v e r s i o n 1.3 o f t h i s method, which incorporated t h e use o f 50% hydrogen peroxide and a vigorous a c i d d i g e s t i o n procedure t h a t u t i l i z e s n i t r i c a c i d and hydrogen peroxide w i t h t h e d i g e s t a t e f i n a l l y being d i l u t e d i n 5% (v/v) h y d r o c h l o r i c acid. The analytes l i s t e d are those n a t u r a l l y o c c u r r i n g elements i n f i s h t i s s u e p l u s N i found i n t h e salmon and t h e Cd and Se found i n t h e tuna. The purpose o f t h e comparison i s t o demonstrate t h e effectiveness and usefulness o f t h e TMAH s o l u b i l i z a t i o n . For each type o f f i s h a l l f i l l e t s were taken from t h e same f i s h . Except as noted i n t h e t a b l e , Method 200.11 mean data f o r t h e analytes: As, Cd, Cu, N i , Se and Zn are from t h e analyses o f f o u r r e p l i c a t e f i l l e t s w h i l e t h e mean data f o r Ca, Fe, K, Mg, Na and P are from t h e analyses o f e i g h t r e p l i c a t e f i l l e t s .

Metals

233

The a c i d d i g e s t i o n mean d a t a f o r a l l a n a l y t e s a r e f r o m t h e analyses o f f o u r r e p l i c a t e f i l l e t s . The c a t f i s h , salmon and t u n a d a t a f o r v e r s i o n 2 . 0 o f Method 200.11 were s t a t i s t i c a l l y compared t o v e r s i o n 1 . 3 d a t a and t h e a c i d d i g e s t i o n d a t a . The comparison was made u s i n g a two t a i l S t u d e n t ’ s t t e s t a t a l p h a l e v e l 0.05. If a s t a t i s t i c a l d i f f e r e n c e was determined, t h e d a t a were t e s t e d f o r p r a c t i c a l d i f f e r e n c e by d e t e r m i n i n g t h e r e l a t i v e p e r c e n t d i f f e r e n c e between t h e two means. I f t h e r e l a t i v e p e r c e n t d i f f e r e n c e was 10% o r l e s s , i t was concluded t h a t t h e r e i s no p r a c t i c a l d i f f e r e n c e between t h e methods. L i s t e d i n S e c t . 13.3.1 a r e t h e r e l a t i v e p e r c e n t d i f f e r e n c e s f o r v e r s i o n 1.3 d a t a and i n Sect. 13.3.2 t h e r e l a t i v e percent d i f f e r e n c e s f o r t h e a c i d d i g e s t i o n d a t a f o r those a n a l y t e s where a s t a t i s t i c a l d i f f e r e n c e was proven. The l a r g e d i f f e r e n c e f o r t h e salmon d a t a between v e r s i o n 2.0 and 1.3 cannot be e x p l a i n e d . A t p r e s e n t , t h e d i f f e r e n c e s a r e a t t r i b u t e d t o t h e i n d i v i d u a l f i s h used i n t h e comparison. T h i s was concluded f r o m analyses o f o t h e r f i l l e t segments f r o m t h e same f i s h t h a t i n d i c a t e d good agreement between t h e two v e r s i o n s b u t gave e x t r e m e l y e l e v a t e d c o n c e n t r a t i o n s f o r Cu - 3 p g J g , Fe - 18 p g J g and Zn - 8 p g J g . 13.3.1

13.3.2

RELATIVE PERCENT DIFFERENCES - VERSION 1.3 ANALYTE

F I S H TISSUE

Fe K Mg Na P P Zn

Salmon Salmon Salmon Salmon Salmon Tuna Salmon

3 7% 2 1% 18% 30% 14% 6% 19%

RELATIVE PERCENT DIFFERENCES - A C I D DIGESTION ANALY TE As As cu K Mg Na P P

13.4

RELATIVE DIFFERENCE

F I S H TISSUE Catfish Salmon Catfish Tuna Tuna Salmon Catfish Tuna

RELATIVE DIFFERENCE 50% 82% 12% 11% 10%

2 7% 6% 14%

The p r e c i s i o n and r e c o v e r y d a t a f o r t h e f o u r t y p e s o f f i s h f i l l e t s ( b l u e g i l l , c a t f i s h , salmon, and t u n a ) p r e s e n t e d i n T a b l e 5 a r e f r o m t h e a n a l y s e s o f f o u r r e p l i c a t e LFMs t a k e n f r o m t h e same f i s h and f o r t i f i e d w i t h t h e same c o n c e n t r a t i o n s as t h e L F B r e p l i c a t e s l i s t e d i n T a b l e 3. Sample c o n c e n t r a t i o n s u b t r a c t e d b e f o r e c a l c u l a t i o n o f p e r c e n t r e c o v e r e d were mean v a l u e s t a k e n f r o m T a b l e 4. Except f o r

234

Methods for the Determination Sb, which shows c o n s i s t e n t l y low r e c o v e r y , a l l o t h e r a n a l y t e s have

r e c o v e r i e s t h a t range from 90 t o 112% w i t h an average o f 101% and RSD v a l u e s t h a t range from 0 . 7 t o 10.7% w i t h an average o f 3.7%, o n l y s l i g h t l y h i g h e r t h a n t h e LFB average o f 3.1% c a l c u l a t e d from Table 3 v a l u e s . 13.5

Table 6 l i s t s t h e mean, standard d e v i a t i o n , r e l a t i v e s t a n d a r d d e v i a t i o n , and p e r c e n t r e c o v e r y d a t a from t h e a n a l y s i s o f f o u r , 0.25 g a l i q u o t s o f d r i e d NBS SRM 1566 O y s t e r T i s s u e . Data f r o m t h e analyses o f r e f e r e n c e m a t e r i a l a r e i n c l u d e d f o r s u p p o r t o f t h e procedure. Except f o r C r and Fe, a l l r e c o v e r y d a t a a r e between 90 and 110%.

REFERENCES

14.

9, Ch.

1.

Code o f Federal R e g u l a t i o n s

2'

Gross, S. B,, and E, S. Parkinson, "Analyses of M e t a l s i n Human Tissues Using Base (TMAH) D i g e s t s and G r a p h i t e Furnace Atomic A b s o r p t i o n Spectrophotometry," Atomic AbsorDtion N e w s l e t t e r , V o l . 13, NO. 4, pp. 107-108, 1974.

3.

Murthy, L., E . E. Menden, P. M. E l l e r , and H. G. P e t e r i n g , "Atomic A b s o r p t i o n D e t e r m i n a t i o n o f Zinc, Copper, Cadmium and Lead i n T i s s u e s S o l u b i l i z e d by Aqueous Tetramethylammonium Hydroxide," A n a l v t i c a l B i o c h e m i s t r y , V o l . 53, pp. 365-372, 1973.

4.

V e r s i e c k , J . , and F . B a r b i e r , "Sample Contamination as A Source o f E r r o r i n Trace-Element A n a l y s i s o f B i o l o g i c a l Samples," T a l a n t a , V o l . 29, pp. 973-984, 1982.

5.

Annual Book o f ASTM Standards, Volume 11.01, American S o c i e t y f o r T e s t i n g and M a t e r i a l s , 1916 Race S t . , P h i l a d e l p h i a , Pennsylvania, 19103.

1, P t . 136 Appendix B.

6. Standard Methods f o r t h e Examination o f Water and Wastewater, 1 6 t h E d i t i o n , 1985.

P a r t 1006; "Fish: Sample C o l l e c t i o n and P r e s e r v a t i o n . "

7.

Ney, J . J . , and M. G. M a r t i n , " I n f l u e n c e s o f P r e f r e e z i n g on Heavy Metal C o n c e n t r a t i o n s i n B l u e g i l l Sunfish," Water Res., Vol. 19, No. 7, pp. 905-907, 1985.

8.

"The P i l o t N a t i o n a l Environmental Specimen Bank," NBS S p e c i a l P u b l i c a t i o n 656, U. S. Department o f Commerce, August, 1983.

9.

K o i r t y o h a n n , S. R., and H. C. Hopps, "Sample S e l e c t i o n , C o l l e c t i o n , P r e s e r v a t i o n and Storage f o r Data Bank on Trace Elements i n Human T i s s u e , " F e d e r a t i o n Proceedings, Vol. 40, No. 8, June, 1981.

10.

Method 200.11, " D e t e r m i n a t i o n o f M e t a l s i n F i s h T i s s u e by I n d u c t i v e l y Coupled Plasma-Atomic Emission Spectrometry," R e v i s i o n 1.3, A p r i l 1987. U.S. Environmental P r o t e c t i o n Agency, O f f i c e o f Research and Development, Environmental M o n i t o r i n g and Support L a b o r a t o r y , C i n c i n n a t i , Ohio 45268.

Metals

TABLE 1. RECOMMENDED WAVELENGTHS WITH LOCATIONS FOR BACKGROUND CORRECTION AND METHOD DETECTION L I M I T S (MDL)

Analyte

Location for Bkgd. Correction

MDL, Ccglg Wet Tissue Weight

t t

Be

0.061 nm 0.061 nm - 0.061 nm

0.3 0.4* 0.02

Ca Cd Cr

31 5.887 226.502 205.552 X 2

t t

0.061 nm 0.061 nm - 0.030 nm

0.02 0.05

cu Fe

324.754 259.940 766.491

- 0.061 nm t 0.061 nm - 0.061 nm

0.05*

Ni

279.079 588.995 231.604 X 2

- 0.061 nm t 0.061 nm - 0.030 nm

P Pb Sb

214.914 X 2 220.353 206.883

t t t

Se

196.026 190.864 213.856 X 2

- 0.061 nm t 0.061 nm t 0.030 nm

K Mg Na

T1

Zn

(*)

’ nm

308.215 193.696 313.042

A1 As

(1)

Wavelength,

0.030 nm 0.061 nm 0.061 nm

-

0.08

0.2 0.2 0.6 0.5 0.07*

Wavelength X 2 indicates wavelength is read in second order. MDL determined in LRB matrix.

235

236

Methods for the Determination

TABLE 2 .

INDUCTIVELY COUPLED PLASMA INSTRUMENT OPERATING CONDITIONS

Forward rf power Reflected rf power Viewing height above work coll Argon supply

1100 watts

< 5 watts 16 mm

Liquid argon

Argon pressure

40 PSI

Cool ant argon flow rate

19 L/min

Aerosol carrier argon flow rate

630 mL/mln

Auxi 1 1 ary ( p l asma) argon flow rate

300 mL/min

Sample uptake rate control 1 ed t o

1 . 2 mL/min

Metals TABLE 3.

237

PRECISION AND RECOVERY OF DATA LABORATORY F O R T I F I E D BLANK

Concentration, pglg

Analyte

The0 Value

Anal ys is Mean (1)

A1 As Be

5.00 5.00 0.25

Cd Cr cu

Std Dev

RSD

Percent Recovered

4.94 5.11 0.26

0.14 0.13 0.01

2.8% 2.5% 3.7%

99% 102% 104%

0.50 1-00 2.50

0.52 1.02 2.57

0.01 0.04 0.07

1.9% 3.9% 2.7%

104% 102% 103%

Ni Pb Sb

2.50 2.50 2.50

2.55 2.51 2.42

0.08 0.09 0.22

3.1% 3.6% 9.1%

102% 100% 97%

Se Tl Zn

5.00 2.50 5.00

5.05 2.48 5.01

0.16 0.09 0.13

3.2% 3.6% 2.6%

101% 99% 100%

(1) Data from seven r e p l i c a t e d e t e r m i n a t i o n s

238

Methods for the Determination

TABLE 4.

COMPARATIVE HETHODS DATA

Concentration, pg/g Wet Tissue Weight

Fish Tissue

Analyte

-

Blueaill F i l l e t Method 200.11 Version 1.3 Version 2.0 Mean Std Dev Mean (1) Std Dev

Acid D i g e s t i o n HNO,/H 0 Mean (1) $
As Ca cu

1.08 141 0.18

0.13 37 0.03

1.03 131 0.15

0.39 134 0.22

Fe K Mg

1.57 4690 346

0.18 300 23

1.48 4870 370

1.69 4140 340

Na P Zn

216 2640 4.74

36 200 0.07

247 2700 4.88

235 2370 4.77

(1) Data from d u p l i c a t e analyses, standard d e v i a t i o n s n o t provided

F i s h Tissue

- Catfish

Fillet

Method 200.11 Version 1.3 Version 2.0 Mean Std Dev Mean Std Dev

Acid D i g e s t i o n HNO,/H 0 Mean Dev

As Ca cu

0.45 110 0.33

0.10 5 0.09

0.47 111 0.35

0.14 15 0.10

0.20 123 0.31

0.06 2 0.01

Fe K Mg

2.01 3400 244

0.30 240 16

1.95 3260 238

0.23 370 38

2.38 3640 230

0.53 70 7

Na P Zn

460 1840 5.68

17 90 0.58

464 1750 6.02

19 200 1.07

467 1950 5.67

6 30 1.68

Analyte

!fd

Metals TABLE 4.

COMPARATIVE NETHODS DATA

239

(Continued)

Concentration, p g / g Wet Tissue Weight F i s h Tissue

-

Salmon F i l l e t Method 200.11 Version 1.3 Version 2.0 Mean Std Dev Mean Std Dev

Anal y t e

Acid D i g e s t i o n HNO,/H 0 Mean \ t d Dev

As Ca cu

0.79 118 0.70

0.03 14 0.05

0.84 98 0.69

0.13 28 0.06

0.41 114 0.57

0.07 27 0.13

Fe K Mg

3.12 3160 233

0.55 180 10

2.15 280 280

0.25 90 7

3.16 31 10 229

0.48 360 27

Na Ni P Zn

653 0.09 2090 4.37

64 0.04 100 0.40

481 0.07* 2410 3.60

22 0.04 90 0.30

496 0.07 2000 3.72

66 0.03 160 0.46

*Data below MDL, normally n o t r e p o r t e d - l i s t e d o n l y f o r comparison F i s h Tissue

Analyte

- Tuna

Fillet

Method 200.11 Version 1.3 Version 2.0 Mean Std Dev Mean S t d Dev

Acid D i g e s t i o n HNO,/H 0 Mean( 1) Dev

Ad

As Ca Cd

3.01 33.4 0.020

0.45 3.7 0.006

3.29 37.0 0.020

0.15 6.5 0.006

2.83 37.8 0.025

0.39 7.8 0.003

cu Fe K

0.23 6.14 4640

0.10 1.51 110

0.22 5.15 4530

0.04 1.01 160

0.11 7.33 4140

0.04 1.08 120

Mg Na

P

384 328 3060

8 35 50

373 360 2890

13 34 80

347 342 2670

10 39 90

Se Zn

0.95 3.12

0.22 0.24

0.73 2.83

0.05 0.09

N.D. tO .8

(1) N.D.

- Not detected below MDL

2.90

0.23

240

Methods for the Determination TABLE 5.

PRECISION AND RECOVERY DATA

Concentration, gqJq Wet Tissue Weight F i s h Tissue

-

Blued11 F i l l e t Sample Conc.

Conc. Added

A1 As Be

1.08 -

5.00 5.00 0.25

Cd

-

Cr cu

Ni Pb Sb

-

Se T1 Zn

Analyte

Analysis Mean

Std Dev

RSD

Percent Recovery

5.06 6.41 0.28

0.15 0.32 0.012

3.0% 5.0% 4.3%

101% 107% 112%

0.50

0.52

0.018

3.5%

104%

-

1.oo

0.18

2.50

1.03 2.74

0.03 0.10

2.9% 3.6%

103% 102%

-

-

2.50 2.50 2.50

2.65 2.57 2.27

0.10 0.19 0.15

3.8% 7.4% 6.6%

106% 103% 91%

0.54* 4.74

5.00 2.50 5.00

5.58 2.56 9.77

0.19 0.07 0.45

3.4% 2.7% 4.6%

112% 102% 101%

Std Dev

RSD

Percent Recovery

*Data below MDL, r e p o r t e d f o r e x p l a n a ti o n o f e l e v a t e d LFM F i s h Tissue Analyte A1 As Be Cd Cr cu

- Catfish Fillet Sample Conc.

Conc. Added

0.45

5.00 5.00 0.25

4.94 5.50 0.26

0.16 0.07 0.005

3.2% 1.3% 1.9%

99% 101% 104%

0.50 1 .oo 2.50

0.49 0.98 2.85

0.008 0.02 0.04

1.6% 2.0% 1.4%

98% 98% 101%

2.50 2.50 2.50

2.42 2.43 2.09

0.10 0.10 0.07

4.1% 4.1% 3.3%

97% 97% 84%

5.00 2.50 5.00

4.60 2.43 11.0

0.40 0.16 1.18

8.7% 6.6% 10.7%

92% 97% 106%

-

0.33

Ni Pb Sb Se T1 Zn

5.68

An a l y s i s Mean

Metals TABLE 5.

241

PRECISION AND RECOVERY DATA (Continued)

Concentration, p g / g Wet Tissue Weight

Fish Tissue - Salmon Fillet Analyte

Sample Conc.

A1 As Be

0.79 -

5.00 5.00 0.25

Cd Cr cu

-

Ni Pb Sb Se T1 Zn F i s h Tissue Analyte

0.70

0.09

-

-

4.37

- Tuna

Conc. Added

Analysis Mean

Std Dev

RSD

Percent Recovery

4.67 5.59 0.25

0.23 0.13 0.002

4.9% 2.3% 0.8%

93% 96% 100%

0.50 1 .oo 2.50

0.47 0.93 3.20

0.015 0.03 0.12

3.2% 3.2% 3.8%

94% 93% 00%

2.50 2.50 2.50

2.41 2.38 2.01

0.11 0.09 0.15

4.6% 3.8% 7.4%

93% 95% 80%

5.00 2.50 5.00

5.05 2.36 8.85

0.28 0.90 0.62

5.5% 3.8% 7.0%

0 1% 94% 90%

Anal y s is Mean

Std Dev

RSD

Percent Recovery

Fillet

Sample Conc.

Conc. Added

Be

3.01 -

5.00 5.00 0.25

5.09 8.29 0.28

0.60 0.53 0.003

1.2% 6.4% 1.1%

102% 106% 112%

Cd Cr cu

0.02 0.23

0.50 1 .oo 2.50

0.54 0.99 2.74

0.024 0.01 0.02

4.4% 1.0% 0.7%

104% 99% 100%

2.50 2.50 2.50

2.56 2.57 2.00

0.06 0.08 0.11

2.3% 3.1% 5.5%

102% 103% 80%

5.00 2.50 5.00

6.33 2.70 7.99

0.27 0.13 0.20

4.3% 3.7% 2.5%

108% 108% 97%

A1 As

Ni Pb Sb Se 11 Zn

0.95 3.12

242

Methods for the Determination TABLE 6 .

ANALYSES DATA

-

NBS SRM 1566 OYSTER TISSUE

Concentration, p g l g Dry Weight

Analyte

Certified Value

Analysis Mean (1)

Std De v

RSD

As

13.4 f 1.9

14.6

0.2

1.5%

109%

Ca

1500 f 200

1560

80

5.1%

104%

Cd

3.5

3.39

0.05

1.5%

97%

Cr

0.69 f 0.27

N. D . to.02

-

-

-

cu

63.0 f 3.5

63.0

1.5

2.4%

100%

Fe

195 f 34

128

16

13%

66%

K

9690 f 50

9860

50

0.5%

102%

Mg

1280 f 90

1270

30

2.4%

99%

Na

5100 f 300

4790

110

2.3%

94%

Ni

1.03 2 0.19

1.28

0.41

32%

124%

P

8100*

7360

180

2.4%

94%

Pb

0.48 f 0.04

N.D.
Se

2.1

Zn

852 f

(1) N . D .

f 0.4

N .D.<2.4

f 0.5

832

14

- Not detected below

MDL

*Phosphorus Val ue not certified

Percent Recovered

5

-

-

0.6%

98%

Metals

243

METHOD 200.15 DETERMINATION OF METALS AND TRACE ELEMENTS I N WATER BY ULTRASONIC NEBULIZATION INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY

R e v i s i o n 1.2 EMMC V e r s i o n

T.D. M a r t i n , C.A. ( 1994)

B r o c k h o f f , and J.T. Creed

- Method 200.15, R e v i s i o n 1.2

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U. S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

244

Methods for the Determination

METHOD 200.15 DETERMINATION OF METALS AND TRACE ELEMENTS I N WATER BY ULTRASONIC NEBULIZATION INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY

1.0

SCOPE AND APPLICATION

1.1 U1t r a s o n i c n e b u l i z a t i o n i n d u c t i v e l y c o u p l e d plasma-atomic e m i s s i o n s p e c t r o m e t r y (UNICP-AES) i s used t o d e t e r m i n e m e t a l s and some nonmetals i n s o l u t i o n . T h i s method p r o v i d e s procedures f o r t h e d e t e r m i n a t i o n o f d i s s o l v e d and t o t a l r e c o v e r a b l e elements i n ground w a t e r s and s u r f a c e waters, and t o t a l r e c o v e r a b l e elements i n d r i n k i n g w a t e r s u p p l i e s . T h i s method i s a p p l i c a b l e t o t h e f o l l o w i n g a n a l y t e s :

Analyte A1 umi num Antimony Arsenic Barium B e r y l 1ium Boron Cadmi um Calcium C e r i ma Chromi um Cobalt Copper Iron Lead Lithium Magnesi um Manganese Mercury Mol ybdenum Nickel Pot ass iurn Sel e n i um Silica S i 1v e r Sod ium

Chemical A b s t r a c t S e r v i c e s R e g i s t r y Numbers (CASRN)

7429-90-5 7440-36-0 7440-38-2 7440-39-3 7440-41-7 7440-42-8 7440-43-9 7440-70-2 7440-45-1 7440-47-3 7440-48-4 7440-50-8 7439-89-6 7439-92-1 7439-93-2 7439-95-4 7439-96-5 7439-97-6 7439-98-7 7440-02-0 7440-09-7 7782-49-2 7631-86-9 7440-22-4 7440-23-5

( c o n t i n u e s on n e x t page) Cerium has been i n c l u d e d as method a n a l y t e f o r c o r r e c t i o n o f potential interelement spectral interference.

a

R e v i s i o n 1 . 2 May1994

Metals

Analyte S t r o n t ium Thallium Tin Titanium Vanadi um Zinc

245

Chemical A b s t r a c t S e r v i c e s R e g i s t r y Numbers (CASRN) 7440-24-6 7440-28-0 7440-3 1-5 7440-32-6 7440-62-2 7440-66-6

1.2

F o r r e f e r e n c e where t h i s method i s approved f o r use i n compliance m o n i t o r i n g programs [e.g., Clean Water A c t (NPDES) o r Safe D r i n k i n g Water A c t (SDWA)] c o n s u l t b o t h t h e a p p r o p r i a t e s e c t i o n s o f t h e Code o f Federal R e g u l a t i o n (40 CFR P a r t 136 T a b l e 1B f o r NPDES, and P a r t 141 § 141.23 f o r d r i n k i n g w a t e r ) , and t h e l a t e s t Federal R e g i s t e r announcements.

1.3

D i s s o l v e d a n a l y t e s a r e determined by UNICP-AES a f t e r s u i t a b l e f i l t r a t i o n , a c i d p r e s e r v a t i o n , and r e a g e n t m a t r i x m a t c h i n g t o t h e c a l i b r a t i o n s t a n d a r d s . To reduce p o t e n t i a l i n t e r f e r e n c e s , d i s s o l v e d s o l i d s s h o u l d be < 0.2% (w/v) ( S e c t . 4 . 2 ) .

1.4

F o r t h e d e t e r m i n a t i o n o f t o t a l r e c o v e r a b l e a n a l y t e s i n aqueous samples that contain particulate or suspended solids a digestion/extraction i s required p r i o r t o analysis. I f t h e sample c o n t a i n s u n d i s s o l v e d s o l i d s > 1%, t h e sample s h o u l d be analyzed u s i n g one o f t h e o t h e r s p e c t r o c h e m i c a l methods - 200.7, 200.8, or 200.9 g i v e n i n t h i s manual.

1.5

Where t h i s method i s approved f o r t h e d e t e r m i n a t i o n o f c e r t a i n metal and m e t a l l o i d contaminants i n d r i n k i n g w a t e r , samples may be analyzed d i r e c t l y w i t h o u t a c i d d i g e s t i o n i f t h e sample has been p r o p e r l y p r e s e r v e d w i t h a c i d , has t u r b i d i t y o f < 1 NTU a t t h e t i m e o f a n a l y s i s and i s p r e s e n t e d t o t h e i n s t r u m e n t i n t h e same r e a g e n t / a c i d m a t r i x as t h e c a l i b r a t i o n standards. This t o t a l recoverable determination p r o c e d u r e i s r e f e r r e d t o as " d i r e c t a n a l y s i s " .

1.6

When d e t e r m i n i n g b o r o n and s i l i c a i n aqueous samples, o n l y p l a s t i c , PTFE o r q u a r t z labware s h o u l d be used f r o m t i m e o f sample c o l l e c t i o n t o c o m p l e t i o n o f a n a l y s i s . When p o s s i b l e , b o r o s i l i c a t e g l a s s should be avoided t o p r e v e n t c o n t a m i n a t i o n o f t h e s e a n a l y t e s .

1.7

S i l v e r i s o n l y s l i g h t l y s o l u b l e i n t h e presence o f c h l o r i d e u n l e s s t h e r e i s a s u f f i c i e n t c h l o r i d e concentration t o form the soluble c h l o r i d e complex. T h i s method i s s u i t a b l e f o r t h e t o t a l r e c o v e r a b l e d e t e r m i n a t i o n o f s i l v e r i n aqueous samples c o n t a i n i n g c o n c e n t r a t i o n s up t o 0 . 1 mg/L. F o r t h e a n a l y s i s o f w a t e r samples c o n t a i n i n g h i g h e r c o n c e n t r a t i o n s o f s i l v e r , succeeding s m a l l e r volume, w e l l mixed R e v i s i o n 1 . 2 May1994

246

Methods for the Determination

a l i q u o t s should be p r e p a r e d u n t i l t h e a n a l y s i s s o l u t i o n c o n t a i n s < 0 . 1 mg/l. s i l v e r .

1.8

The t o t a l r e c o v e r a b l e sample d i g e s t i o n procedure g i v e n i n t h i s method w i l l s o l u b i l i z e and h o l d i n s o l u t i o n o n l y minimal c o n c e n t r a t i o n s o f barium i n t h e presence o f f r e e s u l f a t e . F o r t h e a n a l y s i s o f b a r i u m i n samples h a v i n g v a r y i n g and unknown c o n c e n t r a t i o n s o f s u l f a t e , a n a l y s i s should be completed as soon as p o s s i b l e a f t e r sample p r e p a r a t i o n .

1.9

T h i s method i s n o t s u i t a b l e f o r t h e d e t e r m i n a t i o n o f organo-mercury compounds.

1.10 Sample m a t r i c e s can s i g n i f i c a n t l y a f f e c t t h e a n a l y t i c a l response o f selenium. The r e s u l t i n g e f f e c t i s s i g n a l enhancement when compared t o a s i n g l e element c a l i b r a t i o n standard, The e f f e c t can range f r o m 20% t o 60% and i s i n f l u e n c e d by b o t h t h e n a t u r e and c o n c e n t r a t i o n o f t h e o t h e r element(s) i n s o l u t i o n . The s t a n d a r d i z a t i o n r o u t i n e u t i l i z e d i n t h i s method p a r t i a l l y compensates f o r t h i s enhancement i n t h e a n a l y s i s o f ambient o r d r i n k i n g w a t e r s where t h e t o t a l c o n c e n t r a t i o n o f t h e m a t r i x c a t i o n s (Ca, K , Mg, & Na) range f r o m 10 mg/L t o 300 mg/L. However, f o r c r i t i c s 1 d e t e r m i n a t i o n s o f selenium, method o f s t a n d a r d a d d i t i o n s o r r e c o g n i z e d proven methodology such as g r a p h i t e f u r n a c e atomic a b s o r p t i o n s h o u l d be used. 1.11 U l t r a s o n i c n e b u l i z a t i o n b e i n g more e f f i c i e n t t h a n d i r e c t pneumatic n e b u l i z a t i o n a g r e a t e r p o r t i o n o f t h e sample a e r o s o l and a n a l y t e reaches t h e plasma. The i n c r e a s e d amount o f a n a l y t e causes h i g h e r s i g n a l i n t e n s i t i e s w h i c h decreases t h e l i n e a r c o n c e n t r a t i o n range. Also, i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e s become more s i g n i f i c a n t a t l o w e r c o n c e n t r a t i o n s when compared t o pneumatic n e b u l i z a t i o n . Sample a n a l y t e c o n c e n t r a t i o n s t h a t exceed 90% o f t h e determined upper 1 i m i t o f t h e l i n e a r dynamic range s h o u l d be d i l u t e d and r e a n a l y z e d . 1.12 D e t e c t i o n l i m i t s and l i n e a r ranges f o r t h e elements w i l l v a r y w i t h t h e wavelength s e l e c t e d , t h e i n s t r u m e n t system, o p e r a t i n g c o n d i t i o n s , and sample m a t r i c e s . L i s t e d i n T a b l e 4 a r e t y p i c a l method d e t e c t i o n l i m i t s d e t e r m i n e d i n r e a g e n t b l a n k m a t r i x f o r t h e recommended wavelengths w i t h background c o r r e c t i o n u s i n g t h e i n s t r u m e n t o p e r a t i n g c o n d i t i o n s g i v e n i n Table 5 . The MDLs l i s t e d a r e f o r b o t h t o t a l r e c o v e r a b l e d e t e r m i n a t i o n s by " d i r e c t a n a l y s i s " and where sample d i g e s t i o n i s employed. 1.13 Users o f t h e method d a t a s h o u l d s t a t e t h e d a t a - q u a l i t y o b j e c t i v e s p r i o r t o a n a l y s i s . Users o f t h e method must document and have on f i l e t h e r e q u i r e d i n i t i a l d e m o n s t r a t i o n performance d a t a d e s c r i b e d i n S e c t i o n 9.2 p r i o r t o u s i n g t h e method f o r a n a l y s i s . 2.0

SUMMARY OF METHOD 2.1

An a l i q u o t o f a w e l l mixed, homogeneous sample i s a c c u r a t e l y weighed o r measured f o r sample p r o c e s s i n g . For t o t a l r e c o v e r a b l e a n a l y s i s o f a sample c o n t a i n i n g u n d i s s o l v e d m a t e r i a l , a n a l y t e s a r e f i r s t s o l u b i l i z e d by g e n t l e r e f l u x i n g w i t h n i t r i c and h y d r o c h l o r i c a c i d s . A f t e r c o o l i n g , t h e sample i s made up t o volume, i s mixed and R e v i s i o n 1.2 May1994

Metals

247

centrifuged or allowed to settle overnight prior to analysis. For the determination of dissolved analytes in a filtered sample aliquot, or for the "direct analysis" total recoverable determination of analytes in drinking water where sample turbidity is < 1 NTU, the sample is made ready for analysis by the appropriate addition of acids and hydrogen peroxide, and then diluted to a predetermined volume and mixed before analysis. 2.2 The analysis described in this method involves multielemental determinations by ICP-AES using sequential or simultaneous instruments. The instruments measure characteristic atomic-line emission spectra by optical spectrometry. Samples are nebulized and the resulting aerosol is desolvated before being transported to the plasma torch. Element specific emission spectra are produced by a radio-frequency inductively coupled plasma. The spectra are dispersed by a grating spectrometer, and the intensities of the line spectra are monitored at specific wavelengths by a photosensitive device. Photocurrents from the photosensitive device are processed and controlled by a computer system. A background correction technique is required to compensate for variable background contribution to the determination of the analytes. Background must be measured adjacent to the analyte wavelength during analysis. Various interferences must be considered and addressed appropriately as discussed in Sections 4, 7, 9, 10, and 11. 3.0

DEFINITIONS 3.1

Calibration Blank - A volume of reagent water acidified with the same acid matrix as in the calibration standards. The calibration blank is a zero standard and is used to calibrate the ICP instrument (Sect. 7.11.1).

3.2

Calibration Standard (CAL) - A solution prepared from the dilution of stock standard solutions. The CAL solutions are used to calibrate the instrument response with respect to analyte concentration (Sect. 7.10).

3.3

Dissolved Analyte - The concentration o f analyte in an aqueous sample that will pass through a 0.45-pm membrane filter assembly prior to sample acidification (Sect. 11.1).

3.4

Field Reagent Blank (FRB) - An aliquot of reagent water or other blank matrix that is placed in a sample container in the laboratory and treated as a sample in all respects, including shipment to the sampling site, exposure to the sampling site conditions, storage, preservation, and all analytical procedures. The purpose of the FRB i s to determine if method analytes or other interferences are present in the field environment (Sect 8 . 4 ) .

3.5

Instrument Detection Limit (IDL) - The concentration equivalent to the analyte signal which is equal to three times the standard deviation of a series of ten rep1 icate measurements o f the calibration blank signal at the same wavelength (Table 1). Revision 1.2 May 1994

248

Methods for the Determination 3.6

I n s t r u m e n t Performance Check ( I P C ) S o l u t i o n - A s o l u t i o n o f method a n a l y t e s , used t o e v a l u a t e t h e performance o f t h e i n s t r u m e n t system w i t h r e s p e c t t o a d e f i n e d s e t o f method c r i t e r i a ( S e c t s . 7 . 1 2 & 9.3.4).

3.7

I n t e r n a l Standard - Pure a n a l y t e ( s ) added t o a sample, e x t r a c t , o r s t a n d a r d s o l u t i o n i n known amount(s) and used t o measure t h e r e l a t i v e responses o f o t h e r method a n a l y t e s t h a t a r e components o f t h e same sample o r s o l u t i o n . The i n t e r n a l s t a n d a r d must be an a n a l y t e t h a t i s n o t a sample component ( S e c t . 1 1 . 4 ) .

3.8

L a b o r a t o r y D u p l i c a t e s (LD1 and LD2) - Two a l i q u o t s o f t h e same sample t a k e n i n t h e l a b o r a t o r y and analyzed s e p a r a t e l y w i t h i d e n t i c a l procedures. Analyses o f LD1 and LO2 i n d i c a t e s p r e c i s i o n a s s o c i a t e d w i t h l a b o r a t o r y procedures, b u t n o t w i t h sample c o l l e c t i o n , p r e s e r v a t i o n , o r s t o r a g e procedures.

3.9

L a b o r a t o r y F o r t i f i e d B l a n k (LFB) - An a l i q u o t o f LRB t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e methodology i s i n c o n t r o l and whether t h e l a b o r a t o r y i s capable o f making a c c u r a t e and p r e c i s e measurements ( S e c t s . 7.11.3 & 9.3.2).

3 . 1 0 L a b o r a t o r y F o r t i f i e d Sample M a t r i x (LFM) - An a l i q u o t o f an environmental sample t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The L F M i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e sample m a t r i x contributes bias t o the analytical results. The background c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be d e t e r m i n e d i n a s e p a r a t e a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s ( S e c t . 9 . 4 ) .

3.11 L a b o r a t o r y Reagent B l a n k (LRB) - An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a l l glassware, equipment, s o l v e n t s , r e a g e n t s , and i n t e r n a l standards t h a t a r e used w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e l a b o r a t o r y environment, r e a g e n t s , o r apparatus (Sects. 7.11.2 & 9.3.1). 3.12 L i n e a r Dynamic Range (LDR) - The c o n c e n t r a t i o n range o v e r w h i c h t h e i n s t r u m e n t response t o an a n a l y t e i s l i n e a r ( S e c t . 9 . 2 . 2 ) . 3.13 Method D e t e c t i o n L i m i t (MDL) - The minimum c o n c e n t r a t i o n o f an a n a l y t e t h a t can be i d e n t i f i e d , measured, and r e p o r t e d w i t h 99% c o n f i d e n c e t h a t t h e a n a l y t e c o n c e n t r a t i o n i s g r e a t e r t h a n z e r o ( S e c t . 9 . 2 . 4 and Table 4 ) . 3 . 1 4 Plasma S o l u t i o n - A s o l u t i o n t h a t i s used t o d e t e r m i n e t h e optimum h e i g h t above t h e work c o i l f o r v i e w i n g t h e plasma (Sects. 7.16 & 10.2.2).

R e v i s i o n 1 . 2 May1994

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3.15 Q u a l i t y C o n t r o l Sample ( Q C S ) - A s o l u t i o n o f method a n a l y t e s o f known c o n c e n t r a t i o n s w h i c h i s used t o f o r t i f y an a l i q u o t o f LRB o r sample m a t r i x . The QCS i s o b t a i n e d from a source e x t e r n a l t o t h e l a b o r a t o r y and d i f f e r e n t f r o m t h e source o f c a l i b r a t i o n s t a n d a r d s . I t i s used t o check e i t h e r l a b o r a t o r y o r i n s t r u m e n t performance ( S e c t s . 7.13 & 9.2.3). 3.16 S p e c t r a l I n t e r f e r e n c e Check ( S I C ) S o l u t i o n - A s o l u t i o n o f s e l e c t e d method a n a l y t e s o f h i g h e r c o n c e n t r a t i o n s w h i c h i s used t o e v a l u a t e t h e p r o c e d u r a l r o u t i n e f o r c o r r e c t i n g known i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e s w i t h r e s p e c t t o a d e f i n e d s e t o f method c r i t e r i a (Sects. 7.14, 7.15 & 9.3.5). 3.17 Standard A d d i t i o n - The a d d i t i o n o f a known amount o f a n a l y t e t o t h e sample i n o r d e r t o d e t e r m i n e t h e r e l a t i v e response o f t h e d e t e c t o r t o an a n a l y t e w i t h i n t h e sample m a t r i x . The r e l a t i v e response i s t h e n used t o assess e i t h e r an o p e r a t i v e m a t r i x e f f e c t o r t h e sample a n a l y t e c o n c e n t r a t i o n ( S e c t s . 9.5.1 & 1 1 . 4 ) . 3.18 S t o c k S t a n d a r d S o l u t i o n - A c o n c e n t r a t e d s o l u t i o n c o n t a i n i n g one or more method a n a l y t e s p r e p a r e d i n t h e l a b o r a t o r y u s i n g assayed r e f e r e n c e m a t e r i a l s o r purchased f r o m a r e p u t a b l e commercial source (Sect. 7.9). 3.19 T o t a l Recoverable A n a l y t e - The c o n c e n t r a t i o n o f a n a l y t e determined e i t h e r by " d i r e c t a n a l y s i s " o f an u n f i l t e r e d a c i d p r e s e r v e d d r i n k i n g w a t e r sample w i t h t u r b i d i t y o f < 1 NTU ( S e c t . 11.2.1), o r by a n a l y s i s o f t h e s o l u t i o n e x t r a c t o f a s o l i d sample o r an u n f i l t e r e d aqueous sample f o l l o w i n g d i g e s t i o n by r e f l u x i n g w i t h h o t d i l u t e m i n e r a l a c i d ( s ) as s p e c i f i e d i n t h e method (Sects. 11.2). 3.20 Water Sample - F o r t h e purpose o f t h i s method, a sample t a k e n from one o f t h e f o l l o w i n g sources: d r i n k i n g , ambient s u r f a c e , o r ground w a t e r .

4.0

INTERFERENCES

4.1

S p e c t r a l i n t e r f e r e n c e s a r e caused by background e m i s s i o n from c o n t i n u o u s o r r e c o m b i n a t i o n phenomena, s t r a y l i g h t f r o m t h e l i n e e m i s s i o n o f h i g h c o n c e n t r a t i o n elements, o v e r l a p o f a s p e c t r a l l i n e f r o m a n o t h e r element, o r u n r e s o l v e d o v e r l a p o f m o l e c u l a r band s p e c t r a . 4.1.1

Background e m i s s i o n and s t r a y l i g h t can u s u a l l y be compensated f o r by s u b t r a c t i n g t h e background e m i s s i o n determined by measurement(s) a d j a c e n t t o t h e a n a l y t e wavelength peak. S p e c t r a l scans o f samples o r s i n g l e element s o l u t i o n s i n t h e a n a l y t e r e g i o n s may i n d i c a t e n o t o n l y when a l t e r n a t e wavelengths a r e d e s i r a b l e because o f severe s p e c t r a l i n t e r f e r e n c e , b u t a l s o w i l l show whether t h e most a p p r o p r i a t e e s t i m a t e o f t h e background e m i s s i o n i s p r o v i d e d by an i n t e r p o l a t i o n f r o m measurements on b o t h s i d e s o f t h e wavelength peak o r by t h e measured e m i s s i o n on one s i d e o r t h e other. The l o c a t i o n ( s ) s e l e c t e d f o r t h e measurement o f background i n t e n s i t y w i l l be determined by t h e c o m p l e x i t y o f t h e spectrum a d j a c e n t t o t h e wavelength peak. The l o c a t i o n ( s ) R e v i s i o n 1 . 2 May1994

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used for routine measurement must be free of off-line spectral interference (interelement or molecular) or adequately corrected to reflect the same change in background intensity as occurs at the wavelength peak. 4.1.2

Spectral overlaps may be avoided by using an alternate wavelength or can be compensated for by equations that correct for interelement contributions, which involves measuring the interfering elements. Some potential on-line spectral interferences observed for the recommended wavelengths are given in Table 2. When operative and uncorrected, these interferences will produce false-positive determinations and be reported as analyte concentrations. The interferences listed are only those that occur between method analytes. Only interferences o f a direct overlap nature that were observed with a single instrument having a working resolution More extensive information on of 0.035 nm are listed. interferant effects at various3 wavelengths and resolutions is avai 1 able in Boumans’ Tab1 es. Users may apply i nterel ement correction factors determined on their instruments within tested concentration ranges to compensate (off-line or online) for the effects of interfering elements.

4.1.3

When interelement corrections are applied, there is a need to verify their accuracy by analyzing spectral interference check Interelement solutions as described in Section 7.14. corrections will vary for the same emission line among instruments because of differences in resolution, as determined by the grating plus the entrance and exit slit widths, and by the order of dispersion. Interelement corrections will also vary depending upon the choice of background correction points. Selecting a background correction point where an interfering emission 1 ine may appear should be avoided when practical. Interelement corrections that constitute a major portion of an emission signal may not yield accurate data. Users should not forget that some samples may contain uncommon elements that could contribute spectral interferences .314

4.1.4

The interference effects must be evaluated for each individual instrument whether configured as a sequential or simultaneous instrument. For each instrument, intensities will vary not only with optical resolution but also with operating conditions (such as power, viewing height and argon flow rate). When using the recommended wavelengths given in Table 1, the analyst is required to determine and document for each wavelength the effect from the known interferences given in Table 2, and to utilize a computer routine for their automatic correction on all analyses. To determine the appropriate location for off-1 ine background correction, the user must scan the area on either side adjacent to the wavelength and record the apparent emission intensity from all other method analytes. This spectral information must be documented and kept on file. The location selected for background correction Revision 1.2 May1994

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must be either f r w o f off-line interelement spectral interference or a computer routine must be used for their automatic correction on all determinations. I f a wavelength other than the recommended wavelength i s used, the user must determine and document both the on-1 ine and off-1 ine spectral interference effect from all method analytes and provide for Tests to their automatic Correction on all analyses. determine the spectral interference must be done using analyte concentrations that will adequately describe the interference, but not exceed the upper LDR limit of the analyte. Normally, for ultrasonic nebulization 20 mg/L single element solutions are sufficient, however, for the major constituent analytes (calcium, magnesium, potassium and sodium) found in all waters, or other analytes encountered at elevated levels, a more appropriate test would be to use a concentration near the upper LDR limit (Sect. 9 . 2 . 2 ) . See Section 10.4 for required spectral interference test criteria. 4.1.5

When interelement corrections are not used, either on-going SIC solutions (Sect. 7.15) must be analyzed to verify the absence of interelement spectral interference or a computer software routine must be employed for comparing the determinative data to limits files for notifying the analyst when an interfering element is detected in the sample at a concentration that will produce either an apparent false positive concentration, > the analyte IDL, or false negative analyte concentration, < the 99% lower control limit of the calibration blank. When the interference accounts for 10% or more of the analyte concentration, either an alternate wavelength free of interference or another approved test procedure must be used to complete the analysis. For example, the copper peak at 213.853 nm could be mistaken for the zinc peak at 213.856 nm in solutions with high copper and low zinc concentrations. For this example, a spectral scan in the 213.8-nm region would not reveal the misidentification because a single peak near the zinc location would be observed. The possibility of this misidentification of copper for the zinc peak at 213.856 nm can be identified by measuring the copper at another emission line, e.g. 324.754 nm. Users should be aware that, depending upon the instrumental resolution, a1 ternate wavelengths with adequate sensitivity and freedom from interference may not be available for all matrices. In these circumstances the analyte must be determined using another approved test procedure.

4.2 Physical interferences are effects associated with the sample nebulization and aerosol transport processes. These effects can cause significant inaccuracies and can occur especially in samples containing high dissolved solids or high acid concentrations. Because ultrasonic nebulization provides more efficient nebulization, these effects may become more predominant at lower concentrations compared to pneumatic nebulization. I f physical interferences are present, they must be reduced by diluting the sample or u s i n g an appropriate internal standard element. Also, it has been reported that better Revision 1.2 May 1994

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control of the argon flow rates, especially f o r the nebulizer, improves instrument stability and precisian; this is accomplished with the use of mass flow controllers.

5.0

4.3

Chemical interferences include molecular-compound formation, ionization effects, and solute-vaporization effects. Normally, these effects are not significant with the I C P - A E S technique using pneumatic nebulization, but when evident, are usually matrix dependent. However, with ultrasonic nebulization the aerosol droplets are desolvated and the water vapor is removed as condensate before the analyte enters the plasma. This desolvation step changes the nature of the aerosol and affects the emission intensity of certain analytes. A difference in signal intensity has been observed between the stable valence states o f arsenic (As(II1) and A s ( V ) ) and chromium (Cr(II1) and Cr(V1)) when analyzed as a desolvated aerosol. For arsenic the higher valance state gives the more intense signal, while for chromium the opposite is true. A similar phenomenon occurs for selenium, however, in this situation signal intensity is affected by varying concentrations of other method analytes in solution. Fortunately, for arsenic and chromium the effect can be controlled by the addition of hydrogen peroxide to the mixed acid solutions of samples and calibration standards alike prior to ultrasonic nebulization. For selenium the effect is somewhat controlled by appro:imating the matrix of the calibration standard to the sample matrix. Effects observed from the plasma alone can be minimized by careful selection o f operating conditions such as incident power, observation height, and nebulizer gas flow.

4.4

Memory interferences result when analytes in a previous sample contribute to the signals measured in a new sample. Memory effects can result from sample deposition on the uptake tubing to the nebulizer, and from the buildup of sample material in the plasma torch and spray chamber. These effects can be minimized by flushing the The system with a rinse blank between samples (Sect. 7 . 1 1 . 4 ) . possibility of memory interferences should be recognized within an analytical run and suitable rinse times should be used to reduce them. The rinse times necessary for a particular element must be estimated prior to analysis. This may be achieved by nebulizing a standard containing elements corresponding to either their LDR or a concentration ten times those usually encountered. The nebulization time should be the same as a normal sample analysis period, followed by analysis of the rinse blank at designated intervals. The length o f time required to reduce analyte signals t o within a factor o f two o f the method detection limit, should be noted. Until the required rinse time is established, this method requires a rinse period of at least 60 sec between samples and standards. If a memory interference is suspected, the sample must be re-analyzed after a long rinse period.

SAFETY 5.1

The toxicity or carcinogenicity of each reagent lised in this method have not been fully established. Each chemical should be regarded as a potential health hazard and exposure to these compounds should be as low as reasonably achievable. Each laboratory is responsible for Revision1.2 May1994

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m a i n t a i n i n g a c u r r e n t awareness f i l e o f OSHA r e g u l a t i o n s r e g a r d i n ? t h e s a f e h a n d l i n g o f t h e chemicals s p e c i f i e d i n t h i s method. A r e f e r e n c e f i l e o f m a t e r i a l d a t a h a n d l i n g sheets should a l s o be made a v a i l a b l e t o a l l personnel i n v o l v e d i n t h e chemical a n a l y s i s . S p e c i f i c a l l y , c o n c e n t r a t e d n i t r i c and h y d r o c h l o r i c a c i d s p r e s e n t v a r i o u s hazards and a r e m o d e r a t e l y t o x i c and e x t r e m e l y i r r i t a t i n g t o s k i n and mucus membranes. Use t h e s e r e a g e n t s i n a fume hood whenever p o s s i b l e and i f eye o r s k i n c o n t a c t occurs, f l u s h w i t h l a r g e volumes o f w a t e r . Always wear s a f e t y g l a s s e s o r a s h i e l d f o r eye p r o t e c t i o n , p r o t e c t i v e c l o t h i n g and observe p r o p e r m i x i n g when w o r k i n g w i t h these reagents.

6.0

5.2

The a c i d i f i c a t i o n o f samples c o n t a i n i n g r e a c t i v e m a t e r i a l s may r e s u l t i n t h e r e l e a s e o f t o x i c gases, such as cyanides o r s u l f i d e s . A c i d i f i c a t i o n o f samples s h o u l d be done i n a fume hood.

5.3

A l l personnel h a n d l i n g e n v i r o n m e n t a l samples known t o c o n t a i n o r t o have been i n c o n t a c t w i t h human waste s h o u l d be immunized a g a i n s t known d i s e a s e c a u s a t i v e agents.

5.4

The i n d u c t i v e l y c o u p l e d plasma s h o u l d o n l y be viewed w i t h p r o p e r eye p r o t e c t i o n from t h e u l t r a v i o l e t emissions.

5.5

I t i s t h e r e s p o n s i b i l i t y o f t h e u s e r o f t h i s method t o comply w i t h r e l e v a n t d i s p o s a l and waste r e g u l a t i o n s . F o r guidance see S e c t i o n s 14.0 and 15.0.

EQUIPMENT AND SUPPLIES 6.1

I n d u c t i v e l y c o u p l e d plasma e m i s s i o n s p e c t r o m e t e r : 6.1.1

C o m p u t e r - c o n t r o l l e d e m i s s i o n spectrometer w i t h backgroundc o r r e c t i o n c a p a b i l i t y . The spectrometer must be capable o f meeting and complying w i t h t h e r e q u i r e m e n t s d e s c r i b e d and r e f e r e n c e d i n S e c t i o n 2.2.

6.1.2

Radio-frequency g e n e r a t o r c o m p l i a n t w i t h FCC r e g u l a t i o n s .

6.1.3

Argon gas s u p p l y - H i g h p u r i t y grade (99.99%). When analyses a r e conducted f r e q u e n t l y , l i q u i d argon i s more economical and r e q u i r e s l e s s f r e q u e n t replacement o f t a n k s t h a n compressed argon i n c o n v e n t i o n a l c y l i n d e r s .

6.1.4

A v a r i a b l e speed p e r i s t a l t i c pump i s r e q u i r e d t o d e l i v e r b o t h s t a n d a r d and sample s o l u t i o n s t o t h e n e b u l i z e r .

6.1.5

U l t r a s o n i c n e b u l i z e r - A r a d i o - f r e q u e n c y powered o s c i l l a t i n g t r a n s d u c e r p l a t e capable o f p r o v i d i n g a d e n s e l y populated, extremely f i n e desolvated aerosol.

6.1.6

( o p t i o n a l ) Mass f l o w c o n t r o l l e r s t o r e g u l a t e t h e argon f l o w r a t e s , e s p e c i a l l y t h e a e r o s o l t r a n s p o r t gas, a r e h i g h l y recommended. T h e i r use w i l l p r o v i d e more e x a c t i n g c o n t r o l o f r e p r o d u c i b l e plasma c o n d i t i o n s . R e v i s i o n 1.2 May1994

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Methods for the Determination 6.2

A n a l y t i c a l balance, w i t h c a p a b i l i t y t o measure t o 0 . 1 mg, f o r use i n p r e p a r i n g s t a n d a r d s , and f o r d e t e r m i n i n g d i s s o l v e d s o l i d s .

6.3

A temperature adjustable t e m p e r a t u r e o f 95°C.

6.4

( o p t i o n a l ) A s t e e l c a b i n e t c e n t r i f u g e w i t h g u a r d bowl, e l e c t r i c t i m e r and b r a k e .

6.5

A g r a v i t y c o n v e c t i o n d r y i n g oven w i t h t h e r m o s t a t i c c o n t r o l capable o f m a i n t a i n i n g 180°C f 5OC.

6.6

( o p t i o n a l ) An a i r displacement p i p e t t e r c a p a b l e o f d e l i v e r i n g volumes r a n g i n g f r o m 0 . 1 t o 2500 p L w i t h an assortment o f h i g h q u a l i t y disposable p i p e t t i p s .

6.7

Labware - A l l r e u s a b l e labware ( g l a s s , q u a r t z , p o l y e t h y l e n e , PTFE, FEP, e t c . ) s h o u l d be s u f f i c i e n t l y c l e a n f o r t h e t a s k o b j e c t i v e s . Several procedures found t o p r o v i d e c l e a n labware i n c l u d e washing w i t h a d e t e r g e n t s o l u t i o n , r i n s i n g w i t h t a p w a t e r , s o a k i n g f o r 4 h or more i n 20% ( v / v ) n i t r i c a c i d o r a m i x t u r e o f HNO, and HC1 (1+2+9), r i n s i n g w i t h r e a g e n t w a t e r and s t o r i n g clean.’.* Chromic a c i d c l e a n i n g s o l u t i o n s must be avoided because chromium i s an a n a l y t e .

hot

plate

capable

of

maintaining

a

6.7.1

Glassware - V o l u m e t r i c f l a s k s , g r a d u a t e d c y l i n d e r s , f u n n e l s and c e n t r i f u g e tubes ( g l a s s a n d / o r m e t a l - f r e e p l a s t i c ) .

6.7.2

Assorted c a l i b r a t e d p i p e t t e s .

6.7.3

G r i f f i n beakers, 250-mL w i t h 75-mm ( o p t i o n a l ) 75-mm r i b b e d watch g l a s s e s .

6.7.4

( o p t i o n a l ) PTFE and/or q u a r t z G r i f f i n beakers, 250-mL w i t h PTFE covers.

6.7.5

Narrow-mouth s t o r a g e b o t t l e s , FEP ( f l u o r i n a t e d e t h y l e n e p r o p y l e n e ) w i t h screw c l o s u r e , 125-mL t o l - L c a p a c i t i e s .

6.7.6

One-piece stem FEP wash b o t t l e w i t h screw c l o s u r e , capacity.

watch

glasses

and

125-mL

7.0 REAGENTS AND STANDARDS 7.1

Reagents may c o n t a i n elemental i m p u r i t i e s which m i g h t a f f e c t a n a l y t i c a l data. Only h i g h - p u r i t y r e a g g n t s t h a t conform t o t h e American Chemical S o c i e t y s p e c i f i c a t i o n s s h o u l d be used whenever possible. I f t h e p u r i t y o f a reagent i s i n question, analyze f o r c o n t a m i n a t i o n . A l l a c i d s used f o r t h i s method must be o f u l t r a h i g h p u r i t y grade o r e q u i v a l e n t . S u i t a b l e acids are a v a i l a b l e from a number o f m a n u f a c t u r e r s . R e d i s t i l l e d a c i d s p r e p a r e d by s u b - b o i l i n g d i s t i l l a t i o n are acceptable.

7.2

H y d r o c h l o r i c a c i d , c o n c e n t r a t e d ( s p . g r . 1 . 1 9 ) - HC1. R e v i s i o n 1 . 2 May1994

Metals 7.2.1

H y d r o c h l o r i c a c i d (ltl) - Add 500 mL c o n c e n t r a t e d HC1 t o 400 mL r e a g e n t w a t e r and d i l u t e t o 1 L .

7.2.2

H y d r o c h l o r i c a c i d (1t20) - Add 10 mL c o n c e n t r a t e d HC1 t o 200 mL r e a g e n t w a t e r .

7.3 N i t r i c a c i d , c o n c e n t r a t e d ( s p . g r . 1.41)

7.4

255

- HNO,.

7.3.1

N i t r i c a c i d (ltl) - Add 500 mL c o n c e n t r a t e d HNO, r e a g e n t w a t e r and d i l u t e t o 1 L .

t o 400 mL

7.3.2

N i t r i c a c i d (1t2) - Add 100 mL c o n c e n t r a t e d HNO, reagent water.

t o 200 mL

7.3.3

N i t r i c a c i d ( 1 t 5 ) - Add 50 mL c o n c e n t r a t e d HNO, reagent water.

t o 250 mL

7.3.4

N i t r i c a c i d (1t9) - Add 10 mL c o n c e n t r a t e d HNO, r e a g e n t water.

t o 90 rnL

Reagent w a t e r . All,r-eferences Type I grade w a t e r .

t o w a t e r i n t h i s method r e f e r t o ASTM

7.5 Ammonium h y d r o x i d e , c o n c e n t r a t e d (sp. g r . 0.902). 7.6 T a r t a r i c a c i d , ACS r e a g e n t grade. 7.7 Hydrogen p e r o x i d e , 30%, n o t - s t a b i l i z e d c e r t i f i e d r e a g e n t grade. 7.8 Hydrogen p e r o x i d e , SO%, s t a b i l i z e d c e r t i f i e d r e a g e n t grade. 7.9 Standard S t o c k S o l u t i o n s - S t o c k standards may be purchased o r p r e p a r e d f r o m u l t r a - h i g h p u r i t y grade chemicals (99.99 t o 99.999% pure). All compounds must be d r i e d f o r 1 h a t 105OC, u n l e s s o t h e r w i s e s p e c i f i e d . It i s recommended t h a t s t o c k s o l u t i o n s be s t o r e d i n FEP b o t t l e s . Replace s t o c k standards when succeeding d i l u t i o n s f o r p r e p a r a t i o n o f c a l i b r a t i o n standards cannot be v e r i f i e d . CAUTION:

Many o f t h e s e chemicals a r e e x t r e m e l y t o x i c i f i n h a l e d o r swallowed ( S e c t . 5.1). Wash hands t h o r o u g h l y a f t e r h a n d l i n g .

T y p i c a l s t o c k s o l u t i o n p r e p a r a t i o n procedures f o l l o w f o r l - L q u a n t i t i e s , b u t f o r t h e purpose o f p o l l u t i o n p r e v e n t i o n , t h e a n a l y s t i s encouraged t o p r e p a r e s m a l l e r q u a n t i t i e s when p o s s i b l e . C o n c e n t r a t i o n s a r e c a l c u l a t e d based upon t h e w e i g h t o f t h e pure element o r upon t h e w e i g h t o f t h e compound m u l t i p l i e d by t h e f r a c t i o n o f t h e a n a l y t e i n t h e compound. From p u r e element, w e i g h t (mg) Concentration

=

volume (L) R e v i s i o n 1.2 Hay 1994

256

Methods for the Determination From p u r e compound, w e i g h t (mg) x g r a v i m e t r i c f a c t o r Concentration

=

volume ( L ) where gravimetric factor

=

the weight f r a c t i o n o f t h e analyte i n t h e compound.

7.9.1

Aluminum s o l u t i o n , s t o c k , 1 mL = 1000 p g A l : D i s s o l v e 1.000 g o f aluminum m e t a l , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n an a c i d m i x t u r e o f 4 . 0 mL o f ( l t l ) HC1 and 1.0 mL o f c o n c e n t r a t e d HNO, i n a beaker. Warm beaker slowly t o e f f e c t solution. When d i s s o l u t i o n i s complete, t r a n s f e r s o l u t i o n q u a n t i t a t i v e l y t o a l - L f l a s k , add an a d d i t i o n a l 10.0 mL o f ( l t l ) HC1 and d i l u t e t o volume w i t h reagent water.

7.9.2

Antimony s o l u t i o n , s t o c k , 1 mL = 1000 p g Sb: D i s s o l v e 1.000 g o f antimony powder, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 20.0 mL (1t1) HNO, and 10.0 mL c o n c e n t r a t e d HC1. Add 100 mL r e a g e n t w a t e r and 1.50 g t a r t a r i c acid. Warm s o l u t i o n s l i g h t l y t o e f f e c t complete d i s s o l u t i o n . Cool s o l u t i o n and add r e a g e n t w a t e r t o volume i n a l-L volumetric flask.

7.9.3

A r s e n i c s o l u t i o n , s t o c k , 1 mL = 1000 p g As: D i s s o l v e 1.320 g o f As,O, (As f r a c t i o n = 0.7574), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 100 mL o f r e a g e n t w a t e r c o n t a i n i n g 10.0 mL c o n c e n t r a t e d NH,OH. Warm s o l u t i o n g e n t l y t o e f f e c t d i s s o l u t i o n . A c i d i f y t h e s o l u t i o n w i t h 20.0 mL c o n c e n t r a t e d HNO, and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h reagent water.

7.9.4

Barium s o l u t i o n , s t o c k , 1 mL = 1000 p g Ba: D i s s o l v e 1.437 g BaCO, (.Ba f r a c t i o n = 0.6960), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 150 mL ( 1 t 2 ) HNO, w i t h h e a t i n g and s t i r r i n g t o degas and d i s s o l v e compound. Let solution c o o l and d i l u t e w i t h r e a g e n t w a t e r i n l - L v o l u m e t r i c f l a s k .

7.9.5

B e r y l l i u m s o l u t i o n , s t o c k , 1 mL = 1000 p g Be: DO NOT DRY. D i s s o l v e 19.66 g BeS0,*4H20 (Be f r a c t i o n = 0.0509), weighed accurately t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n reagent w a t e r , add 10.0 mL c o n c e n t r a t e d HNO,, and d i l u t e t o volume i n a l - L volumetric f l a s k w i t h reagent water.

7.9.6

Boron s o l u t i o n , s t o c k , 1 mL = 1000 p g B: DO NOT DRY. D i s s o l v e 5.716 g anhydrous H,BO ( 6 f r a c t i o n = 0.1749), weighed accurately t o a t l e a s t t o u r s i g n i f i c a n t f i g u r e s , i n reagent w a t e r and d i l u t e i n a l - L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r . T r a n s f e r i m m e d i a t e l y a f t e r m i x i n g t o a c l e a n FEP b o t t l e t o R e v i s i o n 1.2 May1994

Metals

257

m i n i m i z e any l e a c h i n g o f boron froiii t h e g l a s s v o l u m e t r i c c o n t a i n e r . Use o f a nonglass v o l u m e t r i c f l a s k i s recommended t o a v o i d boron c o n t a m i n a t i o n f r o m q l a s s w a r e . 7.9.7

Cadmium s o l u t i o n , s t o c k , 1 mL = 1000 pg Cd: D i s s o l v e 1.000 g Cd m e t a l , a c i d cleaned w i t h ( 1 t 9 ) IiNO,, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 50 mL ( l t l ) HNO w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e w i t h reagent water i n a l - L volumetric f l a s k .

7.9.8

Calcium s o l u t i o n , s t o c k , 1 mL = 1000 pg C a : Suspend 2.498 g CaCO (Ca f r a c t i o n = 0.4005), d r i e d a t 180°C f o r 1 h b e f o r e weigfiing, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n r e a g e n t w a t e r and d i s s o l v e c a u t i o u s l y w i t h a Add 10.0 mL c o n c e n t r a t e d HNO minimum amount o f (1+1) HNO,. and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h r e a g e n j water.

7.9.9

Cerium s o l u t i o n , s t o c k , 1 mL = 1000 1-19 Ce: S l u r r y 1.228 g CeO, (Ce f r a c t i o n = 0.8141), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 100 mL c o n c e n t r a t e d HNO and evaporate r e s i d u e i n 20 mL 0, add 50 mL Slurry the t o dryness. c o n c e n t r a t e d HNO,, w i t h h e a t and s t i r r i n g add k0 mL 50% H202 d r o p w i s e i n 1 mL increments a l l o w i n g p e r i o d s o f s t i r r i n g between t h e 1 mL a d d i t i o n s . B o i l o f f excess H20, b e f o r e d i l u t i n g t o volume i n a l - L v o l u m e t r i c f l a s k w i t h reagent water.

d

7.9.10

Chromium s o l u t i o n , s t o c k , 1 mL = 1000 pg C r : D i s s o l v e 1.923 g CrO, .(Cr f r a c t i o n = 0.5200), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 120 mL ( 1 t 5 ) HNO,. When s o l u t i o n i s complete, d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h reagent water.

7.9.11

C o b a l t s o l u t i o n , s t o c k , 1 mL = 1000 pg Co: D i s s o l v e 1.000 g Co m e t a l , a c i d cleaned w i t h ( 1 t 9 ) HN03, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 50.0 mL ( l t l ) HNOJ. L e t s o l u t i o n c o o l and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h reagent water.

7.9.12

Copper s o l u t i o n , s t o c k , 1 mL = 1000 p g Cu: D i s s o l v e 1.000 g Cu m e t a l , a c i d c l e a n e d w i t h ( 1 t 9 ) HNO,, weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 50.0 mL ( 1 t 1 ) HNO, w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e i n a l - L volumetric f l a s k w i t h reagent water.

7.9.13

I r o n s o l u t i o n , s t o c k , 1 mL = 1000 p g Fe: D i s s o l v e 1.000 g Fe m e t a l , a c i d c l e a n e d w i t h ( l t l ) HC1, weighed a c c u r a t e l y t o f o u r s i g n i f i c a n t f i g u r e s , i n 100 mL ( l t l ) HC1 w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n cool and d i l u t e w i t h r e a g e n t water i n a l - L volumetric f l a s k .

7.9.14

Lead s o l u t i o n , s t o c k , 1 mL = 1000 pg Pb: D i s s o l v e 1.599 g Pb(NO,), (Pb f r a c t i o n = 0 . 6 2 5 6 ) , weighed a c c u r a t e l y t o a t R e v i s i o n 1 . 2 May1994

258

Methods for the Determination l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n a minimum amount o f ( l t l ) Add 20.0 mL ( 1 t 1 ) HNO, and d i l u t e t o volume i n a l - L volumetric f l a s k w i t h reagent water.

HNO,.

7.9.15

L i t h i u m s o l u t i o n , s t o c k , 1 mL = 1000 p g L i : D i s s o l v e 5.324 g ( C i f r a c t i o n = 0.1878), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n a minimum amount o f ( l t l ) HC1 and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r . Ci,CO,

7.9.16

Magnesium s o l u t i o n , s t o c k , 1 mL = 1000 p g Mg: D i s s o l v e 1.000 g c l e a n l y p o l i s h e d Mg r i b b o n , a c c u r a t e l y weighed t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n s l o w l y added 5 . 0 mL ( l t l ) HC1 (CAUTION: r e a c t i o n i s v i g o r o u s ) . Add 20.0 mL ( l t l ) HNO, and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r .

7.9.17

Manganese s o l u t i o n , s t o c k , 1 mL = 1000 p g Mn: D i s s o l v e 1.000 g o f manganese m e t a l , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 50 mL ( l t l ) HNO, and d i l u t e t o volume i n a l - L volumetric f l a s k w i t h reagent water.

7.9.18

Mercury s o l u t i o n , s t o c k , 1 mL = 1000 pg Hg: DO NOT DRY. CAUTION: h i g h l y t o x i c element. D i s s o l v e 1.354 g HgC1, (Hg f r a c t i o n = 0.7388) i n r e a g e n t w a t e r . Add 50.0 mL c o n c e n t r a t e d HNO, and d i l u t , e t o volume i n l - L v o l u m e t r i c f l a s k w i t h r e a g e n t water.

7.9.19

Molybdenum s o l u t i o n , s t o c k , 1 mL = 1000 p g Mo: D i s s o l v e 1.500 g MOO, (Mo f r a c t i o n = 0.6666), weighed a c c u r a t e l y t o a t l e a s t four s i g n i f i c a n t f i g u r e s , i n a m i x t u r e o f 100 rnL r e a g e n t w a t e r and 10.0 mL c o n c e n t r a t e d NH,OH, h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e w i t h r e a g e n t w a t e r i n a l - L v o l umet r ic f 1ask .

7.9.20

N i c k e l s o l u t i o n , s t o c k , 1 mL = 1000 p g N i : D i s s o l v e 1.000 g o f n i c k e l m e t a l , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 20.0 mL h o t c o n c e n t r a t e d HNO,, c o o l , and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h r e a g e n t water.

7.9.21

Potassium s o l u t i o n , s t o c k , 1 mL = 1000 p g K: D i s s o l v e 1.907 g KC1 (K f r a c t i o n = 0.5244) d r i e d a t l l O " C , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n r e a g e n t w a t e r , add 20 mL ( l t l ) HC1 and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h reagent water.

7.9.22

Selenium s o l u t i o n , s t o c k , 1 mL = 1000 p g Se: D i s s o l v e 1.405 g SeO, (Se f r a c t i o n = 0.7116), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 200 mL r e a g e n t w a t e r and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r .

7.9.23

S i l i c a s o l u t i o n , s t o c k , 1 mL = 1000 p g S i O : DO NOT DRY. D i s s o l v e 2.964 g (NH,),SiF6, weighed a c c u r a t e $ y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 200 mL ( 1 t 2 0 ) HC1 w i t h h e a t i n g a t R e v i s i o n 1 . 2 May1994

Metals

259

85°C t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e t o volume i n a l-L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r .

7.9.24

S i l v e r s o l u t i o n , s t o c k , 1 mL = 1000 p g Ag: D i s s o l v e 1.000 g Ag m e t a l , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 80 mL ( l t l ) HNO, w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e w i t h reagent w a t e r i n a l-L v o l u m e t r i c f l a s k . S t o r e s o l u t i o n i n amber b o t t l e o r wrap b o t t l e c o m p l e t e l y w i t h aluminum f o i l t o p r o t e c t s o l u t i o n from l i g h t .

7.9.25

Sodium s o l u t i o n , s t o c k , 1 mL = 1000 pg Na: D i s s o l v e 2.542 g NaCl (Na f r a c t i o n = 0 . 3 9 3 4 ) , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n reagent water. Add 10.0 m L c o n c e n t r a t e d HNO, and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h reagent water.

7.9.26

S t r o n t i u m s o l u t i o n , s t o c k , 1 mL = 1000 pg S r : D i s s o l v e 1.685 g SrCO,.(Sr f r a c t i o n = 0 . 5 9 3 5 ) , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 200 mL r e a g e n t w a t e r w i t h d r o p w i s e a d d i t i o n o f 100 mL ( l t l ) HC1. D i l u t e t o volume i n a l-L v o l u m e t r i c f l a s k w i t h r e a g e n t w a t e r .

7.9.27

T h a l l i u m s o l u t i o n , s t o c k , 1 mL = 1000 p g T1: D i s s o l v e 1.303 g TlNO, (T1 f r a c t i o n = 0 . 7 6 7 2 ) , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n reagent water. Add 10.0 mL c o n c e n t r a t e d HNO, and d i l u t e t o volume i n a l - L v o l u m e t r i c f l a s k w i t h reagent water.

7.9.28

T i n s o l u t i o n , s t o c k , 1 mL = 1000 p g Sn: D i s s o l v e 1.000 g Sn s h o t , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 200 mL ( l t l ) HC1 w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and d i l u t e w i t h ( l t l ) HC1 i n a l - L v o l u m e t r i c flask.

7.9.29

T i t a n i u m s o l u t i o n , s t o c k , 1 mL = 1000 pg T i : DO NOT DRY. D i s s o l v e 6.138 g (NH,),TiO(C,O ),*H,O ( T i f r a c t i o n = 0.1629), weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 100 mL r e a g e n t w a t e r . D i l u t e t o volume i n a l-L v o l u m e t r i c f l a s k w i t h reagent water.

7.9.30

Vanadium s o l u t i o n , s t o c k , 1 mL = 1000 pg V: D i s s o l v e 1.000 g V m e t a l , a c i d cleaned w i t h ( 1 t 9 ) H N 4 , weighed a c c u r a t e l y t o a t l e a s t f o u r s i g n i f i c a n t f i g u r e s , i n 50 mL ( l t l ) HNO w i t h h e a t i n g t o e f f e c t d i s s o l u t i o n . L e t s o l u t i o n c o o l and i i l u t e w i t h r e a g e n t w a t e r t o volume i n a l - L v o l u m e t r i c f l a s k .

7.9.31

Y t t r i u m s o l u t i o n , s t o c k 1 mL = 200 p g Y : D i s s o l v e 0.254 g Y,O, (Y f r a c t i o n = 0.7875), weighed a c c u r a t e l y t o a t l e a s t f o u r heating t o e f f e c t s i g n i f i c a n t f i g u r e s , i n 50 mL ( l t l ) HNO,, d i s s o l u t i o n . Cool and d i l u t e t o volume i n a l-L v o l u m e t r i c f l a s k w i t h reagent water.

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7.9.32

Zinc solution, stock, 1 mL = 1000 pg Zn: Dissolve 1.000 g Zn metal, acid cleaned with ( 1 t 9 ) HNO,, weighed accurately to at least four significant figures, in 50 mL ( l t l ) HNO, with heating to effect dissolution. Let solution cool and dilute with reagent water to volume in a 1-L volumetric flask.

7.10 Mixed Calibration Standard Solutions

Prepare mixed calibration standard solutions (see Table 3 ) by combining appropriate volumes o f the stock solutions in 500-mL volumetric flasks containing 20 mL ( l t l ) HNO,, 10 mL ( l t l ) HCl, and 2 mL 30% H,O, (not-stabilized) and dilute to volume with reagent water. Prior to preparing the mixed standards, each stock solution should be analyzed separately to determine possible spectral interferences or the presence of impurities. Care should be taken when preparing the mixed standards to ensure that the To minimize the elements are compatible and stable together. opportunity for contamination by the containers, it is recommended to transfer the mixed-standard solutions to acid-cleaned, never-used FEP fluorocarbon (FEP) bottles for storage. Fresh mixed standards should be prepared, as needed, with the realization that concentrations can change on aging. Calibration standards not prepared from primary standards must be initially verified using a certified reference solution. For the recommended wavelengths listed in Table 1 some typical calibration standard combinations are given in Table 3 .

NOTE:

If the addition of silver to the recommended acid combination results in an initial precipitation, add 15 mL of reagent water and warm the flask until the solution clears. For this acid combination, the silver concentration should be limited to 0 . 1 mg/L.

7.11 Blanks - Four types of blanks are required for the analysis.

The calibration blank is used in establishing the analytical curve, the laboratory reagent blank is used to assess possible contamination from the sample preparation procedure, the laboratory fortified blank is used to assess routine laboratory performance and a rinse blank is used to flush the instrument uptake system and nebulizer between standards, check solutions, and samples to reduce memory interferences. 7.11.1

The calibration blank is prepared by adding HNO,, HC1 and H 0, to reagent water to the same concentrations as used for the calibration standard solutions. The calibration blank should be stored in a FEP bottle.

7.11.2

The laboratory reagent blank (LRB) must contain all the reagents (HNO,, HC1, and H,O )in the same volumes as used in the processing of the samp5es. The LRB must be carried through the same entire preparation scheme as the samples including sample digestion, when applicable.

7.11.3

The laboratory fortified blank (LFB) is prepared by fortifying an aliquot of the laboratory reagent blank to a concentration of 0.2 mg/L with all analytes of interest except aluminum, calcium, iron, magnesium, potassium, selenium, silica, silver, Revision 1.2 May 1994

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and sodium. The elements of calcium, magnesium, and sodium should be added to a concentration of 10.0 mg/L each, while silica (Sect. 1 . 6 ) and potassium should be added to a concentration of 5.0mg/L, and aluminum, iron, and selenium to a concentration 0.5 mg/L. If silver is included, it should be added to a concentration of 0.05 mg/L. (The analyzed value for Se may indicate a positive bias, Sects. 1.10 & 4 . 3 . ) The LFB must be carried through the same entire preparation scheme as the samples including sample digestion, when applicable. 7.11.4

The rinse blank is prepared by acidifying reagent water to the same concentrations of the acids as used for the calibration standard solutions and stored in a convenient manner.

7 . 1 2 Instrument Performance Check (IPC) Solution - Two IPC solutions are

used to periodically verify instrument performance during analysis. They should be prepared in the same acidlhydrogen peroxide mixture as the calibration standards by combining method analytes at appropriate concentrations. The first IPC solution should contain 10 mg/L each of calcium, magnesium, and sodium and 1 . 0 mg/L of selenium. All other analytes should be combined in the second IPC solution each to a recommended concentration of 0.5 mg/L, except for potassium which should be 5.0 mg/L and silver, which must be limited to concentration < 0.1 mg/L. The IPC solution should be prepared from the same standard stock solutions used to prepare the calibration standards and stored in FEP bottles. (Following verification and if convenient, the QCS solutions required in Section 7.13 can be substituted for the IPC solutions.) Agency programs may specify or request that additional instrument performance check solutions be prepared at specified concentrations in order to meet particular program needs. 7.13 Quality Control Sample (QCS) - For initial and periodic verification

of calibration standards and instrument performance, analyses of QCS solutions are required. The QCS must be obtained from an outside source different from the standard stock solutions and prepared in the same acid/hydrogen peroxide mixture as the calibration standards. The QCS for calcium, magnesium, sodium, and selenium should be prepared as a separate solution from a single element stock solutions with Ca, Mg, and Na each at a concentration of 10.0 mg/L and Se at a concentration of 1.0 mg/L (Sects. 1.10 & 4 . 3 ) . The other analytes can be combined in a second QCS solution each at concentrations of 0.5 mg/L, except for potassium which should be 5.0 mg/L and silver, which must be limited to a concentration of 5 0 . 1 mg/L for solution stability. The QCS solutions should be stored in FEP bottles and analyzed as needed to meet data-qua1 ity needs. Fresh solutions should be prepared quarterly or more frequently as needed. 7.14 Spectral

Interference Check (SIC) Solutions - When interelement corrections are applied, SIC solutions are needed containing concentrations of the interfering elements at levels that will provide an adequate test of the correction factors. 7.14.1

SIC solutions containing (a) 30 mg/L Fe; ( b ) 20 mg/L AL; (c) 10 mg/L Ba; (d) 5 mg/L Be; (e) 5 mg/L Cd; ( f ) 5 mg/L Ce; (9) Revision 1.2 May1994

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Co; (h) 5 mg/L Cr; ( i ) 5 mg/L Cu; (j) 5 mg/L Mn; (k) Mo; ( 1 ) 5 mg/L Ni; ( m ) 5 mg/L Sn; (n) 20 mg/L SiO,; ( 0 ) Ti; (p) 5 mg/L T1 and ( 4 ) 5 mg/L V should be prepared same acidlhydrogen peroxide mixture as the calibration standards and stored in FEP bottles. These solutions can be used to periodically verify a partial list of the on-line (and possible off-1 ine) interelement spectral correction factors for the recommended wavelengths given in Table 1. Other solutions could achieve the same objective as well. (Multielement SIC solutions’ may be prepared and substituted for the single element solutions provided an analyte is not subject to interference from more than one interferant in the solution and the concentration of the interferant is not above its upper LDR limit, Sect. 9.2.2.) 5 mg/L 5 mg/L 5 mg/L in the

NOTE:

If wavelengths other than those recommended in Table 1 are used, other solutions different from those above (a thru q) may be required.

7.14.2 For interferences from iron and aluminum, only those correction factors (positive or negative) when multiplied by 100 to calculate apparent analyte concentrations that exceed the determined analyte IDL or fall below the lower 3-sigma control limit of the calibration blank need be tested on a da i 1 y bas i s . 7.14.3

For the other interfering elements, only those correction factors (positive or negative) when multiplied by 10 to calculate apparent analyte concentrations that exceed the determined analyte IDL or fall below the lower 3-sigma control limit of the calibration blank need be tested on a daily basis.

7.14.4 If the correction routine is operating properly, the determined apparent analyte(s) concentration from analysis of each interference solution (a thru q) should fall within a specific concentration range bracketing the calibration blank. The concentration range is calculated by multiplying the concentration of the interfering element by the value of the correction factor being tested and dividing by 10. If after subtraction of the calibration blank the apparent analyte concentration is outside (above or below) this range, a change in the correction factor of more than 10% should be suspected. The cause of the change should be determined and corrected and the correction factor should be updated. NOTE:

The SIC solution should be analyzed more than once to confirm a change has occurred with adequate rinse time between solutions and before subsequent analysis of the cal ibrati on bl ank.

7.14.5 If the correction factors tested on a daily basis are found to be within the 10% criteria for 5 consecutive days, the required verification frequency of those factors in compl iance Revision1.2 May1994

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may be extended to a weekly basis. Also, if the nature of the samples analyzed is such (e.g., finished drinking water) that they do not contain concentrations of the interfering elements at the l-mg/L level, daily verification is not required; however, all interelement spectral correction factors must be verified annually and updated, i f necessary. 7.14.6 If the instrument does not display negative values, fortify the SIC solution with the elements of interest at 0 . 1 or 0.2 mg/L and test for analyte recoveries that are below 95%. In the absence of measurable analyte, over-correction could go undetected because a negative value could be reported as zero. 7.15 For instruments without interelement correction capability or when interelement corrections are not used, SIC solutions (containing similar concentrations of the major components in the samples, e.g., 2 1 mg/L) can serve to verify the absence of effects at the wavelengths selected. These data must be kept on file with the sample analysis data. I f the SIC solution confirms an operative interference that is 2 10% of the analyte concentration, the analyte must be determined using a wavelength and background correction location free of the interference or by another approved test procedure. Users are advised that high salt concentrations can cause analyte signal suppressions and confuse interference tests. 7.16 Plasma Solution - The plasma solution is used for determining the optimum viewing height of the plasma above the work coil prior to using the method (Sect. 10.2). The solution is prepared by adding a 1mL aliquot from each of the stock standard solutions of arsenic, lead, selenium, and thallium to a 500-mL volumetric flask containing 20 mL (ltl) HNO , 10 mL (ltl) HC1, and 2 mL 30% HO ,, (not-stabilized) and diluting $0 volume with reagent water. Store in a FEP bottle. 8.0

SAMPLE COLLECTION, PRESERVATION, AND STORAGE

8.1

Prior to the collection of an aqueous sample, consideration should be given to the type of data required, (i.e., dissolved or total recoverable), so that appropriate preservation and pretreatment steps can be taken. The pH of all aqueous samples must be tested immediately prior to aliquoting for analysis to ensure the sample has been properly preserved. If properly acid preserved, the sample can be held up to 6 months before analysis.

8.2 For the determination o f the dissolved elements, the sample must be

filtered through a 0.45-pm pore diameter membrane filter at the time of collection or as soon thereafter as practically possible. (Glass or plastic filtering apparatus are recommended to avoid possible contamination. Only plastic apparatus should be used when the determinations of boron and silica are critical.) Use a portion of the filtered sample to rinse the filter flask, discard this portion and collect the required volume of filtrate. Acidify the filtrate with (ltl) nitric acid immediately following filtration to pH < 2.

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For the determination of total recoverable elements in aqueous samples, samples are not filtered, but acidified with ( 1 t 1 ) nitric acid to pH < 2 (normally, 3 mL of ( 1 t 1 ) acid per liter of sample is sufficient for most ambient and drinking water samples). Preservation may be done at the time of collection, however, to avoid the hazards of strong acids in the field, transport restrictions, and possible contamination it is recommended that the samples be returned to the laboratory within two weeks of collection and acid preserved upon receipt in the laboratory. Following acidification, the sample should be mixed, held for sixteen hours, and then verified to be pH < 2 just prior withdrawing an aliquot for processing or "direct analysis". If for some reason such as high alkalinity the sample pH is verified to be > 2, more acid must be added and the sample held for sixteen hours until verified to be pH < 2. See Section 8.1. NOTE:

8. 4

A field blank should be prepared and analyzed as required by the data

user. 9.0

When the nature of the sample is either unknown or i s known to be hazardous, acidification should be done in a fume hood. See Section 5.2. Use the same container and acid as used in sample collection.

QUALITY CONTROL

9.1

Each laboratory using this method is required to operate a formal qua1 ity control (QC) program. The minimum requirements of this program consist of an initial demonstration of laboratory capability, and the periodic analysis of laboratory reagent blanks, fortified blanks and other laboratory solutions as a continuing check on performance. The laboratory is required to maintain performance records that define the quality of the data thus generated.

9.2 Initial Demonstration of Performance (mandatory).

9.2.1

The initial demonstration of performance is used to characterize instrument performance (determination of linear dynamic ranges and analysis of quality control samples) and laboratory performance (determination of method detection limits) prior to analyses conducted by this method.

9.2.2

Linear dynamic range (LDR) - The upper limit of the LDR must It must be be established for each wavelength utilized. determined from a linear calibration prepared in the normal manner using the established analytical operating procedure for the instrument. The LDR should be determined by analyzing succeedingly higher standard concentrations of the analyte until the observed analyte concentration is no more than 10% below the stated concentration of the standard. Determined LDRs must be documented and kept on file. The LDR which may be used for the analysis of samples should be judged by the analyst from the resulting data. Determined sample analyte concentrations that are greater than 90% of the determined LDR limit must be diluted and reanalyzed. The LDRs should be verified annually or whenever, in the judgement of the Revision1.2 May1994

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analyst, a change in analytical performance caused by either a change in instrument hardware or operating conditions would dictate they be redetermined. 9.2.3 Quality control sample (QCS) - When beginning the use of this method, on a quarterly basis, after the preparation of stock or calibration standard solutions or as required to meet dataquality needs, verify the calibration standards and acceptable instrument performance with the preparation and analyses of QCS solutions (Sect. 7.13). To verify the calibration standards the determined mean concentrations from 3 analyses o f the QCS must be within f 5% of the stated values. If the calibration standard can not be verified, performance of the determinative step of the method is unacceptable. The source of the problem must be identified and corrected before either proceeding on with the initial determination of method detection limits or continuing with on-going analyses.

9.2.4 Method detection limit (MDL) - MDLs must be established for all wavelengths utilized, using reagent water (blank) fortified at a concentration of two to three times the estimated instrument detection limit.’* To determine MDL values, take seven repl icate a1 iquots of the fortified reagent water and process through the entire analytical method. Perform all calculations defined in the method and report the concentration values in the appropriate units. Calculate the MDL as follows: MDL

=

(t) x (S)

where: t

=

students’ t value for a 99% confidence level and a standard deviation estimate with n-1 degrees of freedom [t = 3.14 for seven replicates].

S

=

standard deviation of the replicate analyses.

Note:

If additional confirmation is desired, reanalyze the seven repl icate a1 iquots on two more nonconsecutive days and again calculate the MDL values f o r each day. An average of the three MDL values for each analyte may provide for a more appropriate MDL estimate. If the relative standard deviation (RSD) from the analyses of the seven aliquots is < l o % , the concentration used to determine the analyte MDL may have been inappropriately high for the determination. If so, this could result in the calculation of an unrealistically low MDL. Concurrently, determination of MDL in reagent water represents a best case situation and does not reflect possible matrix effects of real world samples. However, successful analyses of LFMs (Sect. 9.4) and the analyte addition test described in Section 9.5.1 can give confidence to the MDL value determined in reagent water. Typical single laboratory MDL values using this method are given in Table 4. Revision1.2 flay1994

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Methods for the Determination The MDLs must be s u f f i c i e n t t o d e t e c t a n a l y t e s a t t h e r e q u i r e d l e v e l s a c c o r d i n g t o compliance m o n i t o r i n g r e g u l a t i o n ( S e c t . MDLs s h o u l d be determined a n n u a l l y , when a new o p e r a t o r 1.2). b e g i n s work o r whenever, i n t h e judgement o f t h e a n a l y s t , a change i n a n a l y t i c a l performance caused by e i t h e r a change i n i n s t r u m e n t hardware o r o p e r a t i n g c o n d i t i o n s would d i c t a t e t h e y be r e d e t e r m i n e d . 9.3

Assessing L a b o r a t o r y Performance (mandatory) 9.3.1

L a b o r a t o r y r e a g e n t b l a n k (LRB) - The l a b o r a t o r y must a n a l y z e a t l e a s t one LRB ( S e c t . 7.11.2) w i t h each b a t c h o f 20 o r fewer samples o f t h e same m a t r i x . LRB d a t a a r e used t o assess c o n t a m i n a t i o n f r o m t h e l a b o r a t o r y environment. LRB v a l u e s t h a t exceed t h e MDL i n d i c a t e 1 a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n s h o u l d be suspected. When LRB v a l u e s c o n s t i t u t e 10% o r more o f t h e a n a l y t e l e v e l d e t e r m i n e d f o r a sample o r i s 2 . 2 t i m e s t h e a n a l y t e MDL whichever i s g r e a t e r , f r e s h a l i q u o t s o f t h e samples must be p r e p a r e d and analyzed a g a i n f o r t h e a f f e c t e d a n a l y t e s a f t e r t h e source o f c o n t a m i n a t i o n has been c o r r e c t e d and a c c e p t a b l e LRB v a l u e s have been o b t a i n e d .

9.3.2

L a b o r a t o r y f o r t i f i e d b l a n k (LFB) - The l a b o r a t o r y must a n a l y z e a t l e a s t one LFB ( S e c t . 7.11.3) w i t h each b a t c h o f samples. C a l c u l a t e accuracy as p e r c e n t r e c o v e r y u s i n g t h e f o l l o w i n g equation: LFB - LRB R =

x

100

S

where:

R = LFB = LRB =

s

=

percent recovery. l a b o r a t o r y f o r t i f i e d blank. l a b o r a t o r y reagent blank. concentration equivalent o f analyte added t o f o r t i f y t h e LRB s o l u t i o n .

I f t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e r e q u i r e d c o n t r o l l i m i t s o f 85-115%, t h a t a n a l y t e i s j u d g e d o u t o f c o n t r o l , and t h e source o f t h e problem s h o u l d be i d e n t i f i e d and r e s o l v e d b e f o r e c o n t i n u i n g analyses.

9.3.3

The l a b o r a t o r y must use LFB analyses d a t a t o assess l a b o r a t o r y performance a g a i n s t t h e r e q u i r e d c o n t r o l l i m i t s o f 85-115% (Sect.9.3.2). When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e ( u s u a l l y a minimum o f t w e n t y t o t h i r t y a n a l y s e s ) , o p t i o n a l c o n t r o l l i m i t s can be developed f r o m t h e mean p e r c e n t r e c o v e r y ( x ) and t h e s t a n d a r d d e v i a t i o n ( S ) o f t h e mean p e r c e n t r e c o v e r y . These d a t a can be used t o e s t a b l i s h t h e upper and l o w e r c o n t r o l l i m i t s as f o l l o w s : UPPER CONTROL L I M I T LOWFR CONTROL L I M I T

= =

x t 3s x - 3s

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The optional control limits must be equal to or better than the required control limits of 85-115%. After each five to ten new recovery measurements, new control 1 imits can be calculated using only the most recent twenty to thirty data points. Also, the standard deviation (S) data should be used to established an on-going precision statement for the level of concentrations included in the LFB. These data m u s t be kept on file and be available for review.

9.4

9.3.4

Instrument performance check ( I P C ) solution - For all determinations the laboratory must analyze the I P C solution (Sect. 7 . 1 2 ) and a calibration blank immediately following daily calibration, after every tenth sample (or more frequently, if required) and at the end of the sample run. Analysis of the calibration blank should always be < the analyte IDL, but > the lower 3-sigma control limit of the calibration blank. Analysis of the I P C solution immediately following calibration must verify that the instrument is within f 10% of calibration with a relative standard deviation < 3% from replicate integrations 2 4 . Subsequent analyses of the I P C solution also must be within f 10% of calibration. If the calibration cannot be verified within the specified limits, reanalyze either or both the I P C solution and the calibration blank. If the second analysis of the I P C solution or the calibration blank confirm calibration to be outside the limits, sample analysis must be discontinued, the cause determined, corrected and/or the instrument recalibrated. All samples following the last acceptable I P C solution must be reanalyzed. The analysis data of the calibration blank and I P C solution must be kept on file with the sample analyses data.

9.3.5

Spectral interference check ( S I C ) solution For all determinations the laboratory must periodically verify the interelement spectral interference correction routine by analyzing SIC solutions. The preparation and required periodic analysis o f S I C solutions and test criteria for verifying the interelement interference correction routine are given in Special cases where on-going verification is Section 7.14. required are described in Section 7 . 1 5 .

Assessing Analyte Recovery and Data Quality 9.4.1

Sample homogeneity and the chemical nature of the sample matrix can affect analyte recovery and the quality of the data. Taking separate aliquots from the sample for replicate and fortified analyses can in some cases assess the effect. Unless otherwise specified by the data user, laboratory or program, the following laboratory fortified matrix (LFM) procedure (Sect 9 . 4 . 2 ) is required. Also, other tests such as the analyte addition test (Sect. 9 . 5 . 1 ) and sample dilution test (Sect. 9 . 5 . 2 ) can indicate i f matrix effects are operative.

9.4.2

The laboratory must add a known amount of each analyte to a minimum of 10% o f the routine s a o p l e s . I n each case the LFM Revision1.2 May1994

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a l i q u o t must be a d u p l i c a t e of t h e a l i q u o t used f o r sample a n a l y s i s and f o r t o t a l r e c o v e r a b l e d e t e r m i n a t i o n s added p r i o r t o sample p r e p a r a t i o n . The added a n a l y t e c o n c e n t r a t i o n must be t h e same a s t h a t used i n the l a b o r a t o r y f o r t i f i e d blank ( S e c t . 9 . 3 . 2 ) . Over time, samples from a l l r o u t i n e sample sources should be f o r t i f i e d . NOTE:

9.4.3

The c o n c e n t r a t i o n of calcium, magnesium, sodium and s t r o n t i u m in environmental waters can vary g r e a t l y and a r e not n e c e s s a r i l y p r e d i c t a b l e . F o r t i f y i n g t h e s e a n a l y t e s in r o u t i n e samples a t t h e same c o n c e n t r a t i o n used f o r t h e LFB may prove t o be of l i t t l e use i n a s s e s s i n g d a t a q u a l i t y f o r t h e s e a n a l y t e s . For t h e s e a n a l y t e s sample d i l u t i o n and r e a n a l y s i s using t h e c r i t e r i a given i n Section 9 . 5 . 2 i s recommended. Also, i f s p e c i f i e d by the d a t a user, l a b o r a t o r y o r program, samples can be f o r t i f i e d a t d i f f e r e n t c o n c e n t r a t i o n s , but even major c o n s t i t u e n t s should be l i m i t e d t o 5 10 mg/L so a s not t o a l t e r the sample matrix and a f f e c t the analysis.

C a l c u l a t e t h e percent recovery f o r each a n a l y t e , c o r r e c t e d f o r background c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o t h e d e s i g n a t e d LFM recovery range o f 70-130%. Recovery c a l c u l a t i o n s a r e not r e q u i r e d i f the c o n c e n t r a t i o n added i s l e s s than 30% of t h e sample background c o n c e n t r a t i o n . Percent recovery may be c a l c u l a t e d using t h e following e q u a t i o n : R =

c, - c -

x 100

S

where :

R C,

C s

= = = =

p e r c e n t recovery, f o r t i f i e d sample c o n c e n t r a t i o n . sample background c o n c e n t r a t i o n . c o n c e n t r a t i o n e q u i v a l e n t of a n a l y t e added t o f o r t i f y t h e sample.

9.4.4

I f t h e recovery of any a n a l y t e f a l l s o u t s i d e t h e designated LFM recovery range, and t h e 1 aboratory performance f o r t h a t a n a l y t e i s shown t o be i n c o n t r o l ( S e c t . 9 . 3 ) , t h e recovery problem encountered with t h e f o r t i f i e d sample i s judged t o be matrix r e l a t e d , not system r e l a t e d . The d a t a u s e r should be informed t h a t the r e s u l t f o r t h a t a n a l y t e i n the u n f o r t i f i e d sample i s s u s p e c t due t o e i t h e r t h e heterogeneous n a t u r e of the sample o r m a t r i x e f f e c t s and a n a l y s i s by method of standard a d d i t i o n o r the use of an i n t e r n a l s t a n d a r d ( s ) ( S e c t . 1 1 . 4 ) should be considered.

9.4.5

Where r e f e r e n c e m a t e r i a l s a r e a v a i l a b l e , they should be analyzed t o provide a d d i t i o n a l performance d a t a . The a n a l y s i s of r e f e r e n c e samples i s a valuable tool f o r demonstrating t h e a b i l i t y t o perform t h e method a c c e p t a b l y . Reference m a t e r i a l s Revision 1.2 May1994

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c o n t a i n i n g h i g h c o n c e n t r a t i o n s o f a n a l y t e s can p r o v i d e a d d i t i o n a l i n f o r m a t i o n on t h e performance o f t h e s p e c t r a l interference correction routine. 9.5

Assess t h e p o s s i b l e need f o r t h e method o f s t a n d a r d a d d i t i o n s (MSA) o r i n t e r n a l s t a n d a r d elements by t h e f o l l o w i n g t e s t s . D i r e c t i o n s f o r u s i n g MSA o r i n t e r n a l s t a n d a r d ( s ) a r e g i v e n i n S e c t i o n 11.4. 9.5.1

A n a l y t e a d d i t i o n t e s t : An a n a l y t e ( s ) s t a n d a r d added t o a p o r t i o n o f a p r e p a r e d sample, o r i t s d i l u t i o n , should be r e c o v e r e d t o w i t h i n 85% t o 115% o f t h e known v a l u e . The a n a l y t e ( s ) a d d i t i o n should produce a minimum l e v e l o f 20 t i m e s and a maximum o f 100 t i m e s t h e method d e t e c t i o n l i m i t . If t h e a n a l y t e a d d i t i o n i s < 20% o f t h e sample a n a l y t e c o n c e n t r a t i o n , t h e f o l l o w i n g d i l u t i o n t e s t s h o u l d be used. I f r e c o v e r y o f t h e analyte(s) i s not w i t h i n the specified l i m i t s , a matrix effect s h o u l d be suspected, and t h e a s s o c i a t e d d a t a f l a g g e d accordingly. The method o f a d d i t i o n s o r t h e use o f an a p p r o p r i a t e i n t e r n a l s t a n d a r d element may p r o v i d e more a c c u r a t e data.

9.5.2

D i l u t i o n test: I f the analyte concentration i s s u f f i c i e n t l y h i g h ( m i n i m a l l y , a f a c t o r o f 50 above t h e i n s t r u m e n t d e t e c t i o n l i m i t i n t h e o r i g i n a l s o l u t i o n b u t < 90% o f t h e l i n e a r l i m i t ) , an a n a l y s i s o f a 1 t 4 d i l u t i o n s h o u l d agree ( a f t e r c o r r e c t i o n f o r the f i v e f o l d d i l u t i o n ) w i t h i n k 10% o f t h e o r i g i n a l determination. I f n o t , a chemical o r p h y s i c a l i n t e r f e r e n c e e f f e c t s h o u l d be suspected and t h e a s s o c i a t e d d a t a f l a g g e d a c c o r d i n g l y . The method o f s t a n d a r d a d d i t i o n s o r t h e use o f an i n t e r n a l - s t a n d a r d element may p r o v i d e more a c c u r a t e d a t a f o r samples f a i l i n g t h i s t e s t .

10.0 CALIBRATION AND STANDARDIZATION 10.1 S p e c i f i c wavelengths a r e l i s t e d i n Table 1. O t h e r wavelengths may be s u b s t i t u t e d i f t h e y can p r o v i d e t h e needed s e n s i t i v i t y and are corrected f o r spectral interference. However, because o f t h e d i f f e r e n c e among v a r i o u s makes and models o f spectrometers, s p e c i f i c i n s t r u m e n t o p e r a t i n g c o n d i t i o n s cannot be g i v e n . The i n s t r u m e n t and o p e r a t i n g c o n d i t i o n s u t i l i z e d f o r d e t e r m i n a t i o n must be capable o f p r o v i d i n g d a t a o f a c c e p t a b l e q u a l i t y t o t h e program and d a t a user. The a n a l y s t s h o u l d f o l l o w t h e i n s t r u c t i o n s p r o v i d e d by t h e i n s t r u m e n t manufacturer unless other c o n d i t i o n s provide s i m i l a r o r b e t t e r performance f o r a t a s k . Operating conditions using u l t r a s o n i c n e b u l i z a t i o n u s u a l l y v a r y f r o m 1100 t o 1500 w a t t s f o r w a r d power, 12-to 16-mm v i e w i n g h e i g h t , 12 t o 19 l i t e r s / m i n argon c o o l a n t flow, 0.5 t o 1 L/min argon a e r o s o l f l o w , 1.5 t o 2.5 mL/min sample pumping r a t e w i t h a 1-min p r e f l u s h t i m e and measurement t i m e near 1 s p e r wavelength peak ( f o r s e q u e n t i a l i n s t r u m e n t s ) and n e a r 10 s p e r sample ( f o r simultaneous i n s t r u m e n t s ) . The u l t r a s o n i c n e b u l i z e r i s n o r m a l l y o p e r a t e d a t < 50 w a t t s i n c i d e n t power w i t h t h e d e s o l v a t i o n temperature s e t a t 14OoC and a condenser t e m p e r a t u r e o f 5Oc.

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10.2 Prior t o using this method optimize the plasma operating conditions. The following procedure is recommended for vertically configured plasmas. The purpose o f plasma optimization is to provide a maximum signal-to-background ratio for the least sensitive element in the analytical array. The use of a mass flow controller to regulate the nebulizer gas flow rate greatly facilitates the procedure. 10.2.1 Ignite the plasma and select an appropriate incident rf power with minimum reflected power. Turn on the power to the ultrasonic nebulizer including the heating tube and chiller and allow both instruments to become thermally stable before beginning. This usually requires at least 30 to 60 minutes of operation. Set the peristaltic pump to deliver an uptake rate between 1.8 and 2.0 mL/min in a steady even flow. While nebulizing the 200-pg/mL solution of yttrium (Sect. 7.9.31), follow the instrument manufacturer’s instructions and adjust the aerosol carrier gas flow rate through the nebulizer so a definitive blue emission region of the plasma extend,: approximately from 5 to 20 mm above the top of the work coil. Record the nebulizer gas flow rate or pressure setting for future reference. 10.2.2 After horizontally aligning the plasma and/or optically profiling the spectrometer, use the selected instrument conditions from Sections 10.2.1 and nebulize the plasma solution (Sect. 7.16), containing 2.0 pg/mL each of As, Pb, Se and T1. Collect intensity data at the wavelength peak for each analyte at 1-mm intervals from 14 to 18 mm above the top of the work coil. (This region of the plasma is commonly referred to as the analytical zone.)14 Repeat the process using the calibration blank. Determine the net signal to blank intensity ratio for each analyte for each viewing height setting. Choose the height for viewing the plasma that provides the largest intensity ratio for the least sensitive element o f the four analytes. If more than one position provides the same ratio, select the position that provides the highest net intensity counts for the least sensitive element or accept a compromise position of the intensity ratios of all four analytes. 10.2.3 The instrument operating condition finally selected as being optimum should provide the lowest reliable instrument detection limits and method detection limits. Refer to Tables 1 and 4 for comparison of IDLs and MDLs, respectively. 10.2.4 If either the instrument operating conditions, such as incident power and/or nebulizer gas flow rate are changed, or a new torch injector tube having a different orifice i.d. is installed, the plasma and plasma viewing height should be reoptimized. 10.2.5 Before daily calibration and after the instrument warmup period, the nebulizer gas flow must be reset to the determined optimized flow. If a mass flow controller is being used, it should be reset t o t h ( i recorded optimized flow rat,e. In order Revision 1 . 2 May1994

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t o m a i n t a i n Val i d s p e c t r d l i n t e r e l e m e n t c o r r e c t i o n r o u t i n e s t h e n e b u l i z e r gas f l o w r a t e s h o u l d be t h e same f r o m d a y - t o - d a y (<2% change).

1 0 . 3 B e f o r e u s i n g t h e p r o c e d u r e ( S e c t i o n 1 1 . 0 ) t o a n a l y z e samples, t h e r e must be d a t a a v a i l a b l e d o c u m e n t i n g i n i t i a l d e m o n s t r a t i o n o f p e r f o r m a n c e . The r e q u i r e d d a t a and p r o c e d u r e i s d e s c r i b e d i n S e c t i o n 9 . 2 . T h i s d a t a must be g e n e r a t e d u s i n g t h e same i n s t r u m e n t o p e r a t i n g c o n d i t i o n s and c a l i b r a t i o n r o u t i n e ( S e c t . 1 1 . 3 ) t o be used f o r sample a n a l y s i s . These documented d a t a must be k e p t on f i l e and be a v a i l a b l e f o r r e v i e w by t h e d a t a u s e r .

1 0 . 4 A f t e r c o m p l e t i n g t h e i n i t i a l demonstration o f performance, b u t b e f o r e a n a l y z i n g samples, t h e l a b o r a t o r y must e s t a b l i s h and i n i t i a l l y v e r i f y an i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e c o r r e c t i o n r o u t i n e t o be used A general description concerning spectral d u r i n g sample a n a l y s i s . i n t e r f e r e n c e and t h e a n a l y t i c a l r e q u i r e m e n t s f o r b a c k g r o u n d c o r r e c t i o n and f o r c o r r e c t i o n o f i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e i n p a r t i c u l a r To d e t e r m i n e t h e a p p r o p r i a t e l o c a t i o n f o r a r e g i v e n i n S e c t i o n 4.1. b a c k g r o u n d c o r r e c t i o n and t o e s t a b l i s h t h e i n t e r e l e m e n t i n t e r f e r e n c e c o r r e c t i o n r o u t i n e , r e p e a t e d s p e c t r a l scan a b o u t t h e a n a l y t e w a v e l e n g t h and r e p e a t e d a n a l y s e s o f t h e s i n g l e e l e m e n t s o l u t i o n s may be r e q u i r e d . C r i t e r i a f o r d e t e r m i n i n g an i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e i s an a p p a r e n t p o s i t i v e o r n e g a t i v e c o n c e n t r a t i o n on t h e a n a l y t e t h a t i s o u t s i d e t h e 3-sigma c o n t r o l l i m i t s o f t h e c a l i b r a t i o n b l a n k f o r t h e a n a l y t e . (The u p p e r - c o n t r o l l i m i t i s t h e a n a l y t e I D L . ) Once e s t a b l i s h e d , t h e e n t i r e r o u t i n e must be i n i t i a l l y and p e r i o d i c a l l y v e r i f i e d a n n u a l l y o r whenever t h e r e i s a change i n instrument o p e r a t i n g c o n d i t i o n s (Sect 10.2.5). Only a p o r t i o n o f t h e c o r r e c t i o n r o u t i n e must be v e r i f i e d more f r e q u e n t l y o r on a d a i l y b a s i s . T e s t c r i t e r i a and r e q u i r e d s o l u t i o n s a r e d e s c r i b e d i n S e c t i o n 7 . 1 4 . I n i t i a l and p e r i o d i c v e r i f i c a t i o n d a t a o f t h e r o u t i n e s h o u l d be k e p t on f i l e . S p e c i a l c a s e s where o n - g o i n g v e r i f i c a t i o n a r e r e q u i r e d i s described i n Section 7.15.

11 0 PROCEDURE

1 1 . 1 Aqueous Sample P r e p a r a t i o n - D i s s o l v e d A n a l y t e s

1 1 . 1 . 1 F o r t h e d e t e r m i n a t i o n o f d i s s o l v e d a n a l y t e s i n g r o u n d w a t e r and s u r f a c e w a t e r s p i p e t o r a c c u r a t e l y t r a n s f e r an a l i q u o t ( 2 20 mL) o f t h e f i l t e r e d , a c i d p r e s e r v e d sample i n t o a 50-mL p o l y p r o p y l e n e c e n t r i f u g e t u b e . Add t h e a p p r o p r i a t e volumes o f ( l t l ) n i t r i c a c i d and ( l t l ) h y d r o c h l o r i c a c i d and 30% h y d r o g e n peroxide (not-stabilized) t o adjust the reagent concentration o f t h e a l i q u o t t o a p p r o x i m a t e a 2% ( v / v ) n i t r i c a c i d , 1% ( v / v ) h y d r o c h l o r i c a c i d , 3nd 0.4% ( v / v ) 30% h y d r o g e n p e r o x i d e s o l u t i o n ( e . g . , add 1 . 0 mL ( l t l ) HNO , 0 . 5 mL ( l t l ) HC1, and 0 . 1 mL 30% H 0, t o a 25 mL a l i q u o t o f sample). Cap t h e t u b e and m i x . h e sample i s r e a d y f o r a n a l y s i s ( S e c t . 1 . 3 ) . A l l o w a n c e f o r sample d i l u t i o n f r o m t h e a d d i t i o n o f a c i d s and h y d r o g e n p e r o x i d e s h o u l d be made i n d a t a c a l c u l a t i o n s .

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I f a p r e c i p i t a t e i s formed d u r i n g a c i d i f i c a t i o n , t r a n s p o r t , or s t o r a g e , t h e sample a1 i q u o t must be t r e a t e d using t h e procedure i n S e c t i o n 1 1 . 2 p r i o r t o analysis.

1 1 . 2 Aqueous Sample P r e p a r a t i o n

-

T o t a l Recoverable Analytes

1 1 . 2 . 1 For t h e " d i r e c t a n a l y s i s " of t o t a l r e c o v e r a b l e a n a l y t e s i n d r i n k i n g w a t e r samples c o n t a i n i n g t u r b i d i t y < 1 NTU, t r e a t an u n f i l t e r e d a c i d preserved sample a l i q u o t using t h e sample p r e p a r a t i o n procedure d e s c r i b e d i n S e c t i o n 1 1 . 1 . 1 w h i l e making allowance f o r sample d i l u t i o n i n t h e d a t a c a l c u l a t i o n ( S e c t . 1 . 2 ) . For t h e d e t e r m i n a t i o n of t o t a l r e c o v e r a b l e a n a l y t e s i n a l l o t h e r samples f o l l o w t h e procedure given i n S e c t i o n s 1 1 . 2 . 2 through 1 1 . 2 . 7 . 11.2.2 For t h e d e t e r m i n a t i o n of t o t a l r e c o v e r a b l e a n a l y t e s i n aqueous samples ( o t h e r t h a n d r i n k i n g w a t e r with < 1 NTU t u r b i d i t y , and aqueous samples c o n t a i n i n g undissolved s o l i d s > I % , S e c t . 1 . 4 ) , t r a n s f e r a 100-mL ( + 1 m L ) a l i q u o t from a well mixed, a c i d p r e s e r v e d sample t o a 250-mL G r i f f i n beaker ( S e c t s . 1 . 2 , 1 . 3 , 1 . 6 , 1 . 7 , 1 . 8 , & 1 . 9 ) . (When n e c e s s a r y , s m a l l e r sample a l i q u o t volumes may be u s e d . ) 1 1 . 2 . 3 Add 2.0 mL ( l t l ) n i t r i c a c i d and 1 . 0 mL o f ( l t l ) h y d r o c h l o r i c a c i d t o t h e beaker c o n t a i n i n g t h e measured volume of sample. P l a c e t h e beaker on t h e hot p l a t e f o r s o l u t i o n e v a p o r a t i o n . The hot p l a t e should be l o c a t e d in a fume hood and p r e v i o u s l y a d j u s t e d t o provide e v a p o r a t i o n a t a t e m p e r a t u r e of approximately b u t no h i g h e r t h a n 85'C. (See the f o l l o w i n g n o t e . ) The beaker should be covered w i t h an e l e v a t e d watch g l a s s o r o t h e r n e c e s s a r y s t e p s should be t a k e n t o p r e v e n t sample contamination from the fume hood environment. NOTE:

For p r o p e r h e a t i n g a d j u s t t h e t e m p e r a t u r e c o n t r o l o f the hot p l a t e such t h a t an uncovered G r i f f i n beaker c o n t a i n i n g 50 mL of w a t e r placed i n the c e n t e r o f the hot p l a t e can be maintained a t a t e m p e r a t u r e approximately b u t no h i g h e r than 85'C. (Once t h e beaker i s covered with a watch g l a s s t h e t e m p e r a t u r e o f the w a t e r w i l l r i s e t o approximately 95'C.)

11.2.4 Reduce t h e volume of the sample a l i q u o t t o about 20 mL by g e n t l e h e a t i n g a t 85°C. DO NOT BOIL. This s t e p t a k e s about 1 h f o r a 50 mL a l i q u o t w i t h t h e r a t e of e v a p o r a t i o n r a p i d l y i n c r e a s i n g a s t h e sample volume approaches 20 m L . (A s p a r e beaker c o n t a i n i n g 20 mL o f w a t e r can be used as a gauge.) 1 1 . 2 . 5 Cover t h e l i p of t h e beaker with a watch g l a s s t o reduce a d d i t i o n a l e v a p o r a t i o n and g e n t l y r e f l u x t h e sample f o r 30 minutes. ( S l i g h t b o i l i n g may o c c u r , b u t vigorous b o i l i n g must be avoided t o p r e v e n t l o s s of t h e HC1-H,O a z e o t r o p e . )

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11.2.6 Allow the beaker t.o cool. Quantitatively transfer the sample solution to a 50-in1 volumetric flask, add 0.2 rnL of 30% hydrogen peroxide (Sect.7.7), make t o vol m e with reagent water, stopper and mix. 11.2.7 Allow any undissolved material to settle overnight, or centrifuge a portion of the prepared sample until clear. (If after centrifuging or standing Overnight the sample contains suspended solids that would clog the uptake system to the nebulizer, a portion of the sample may be filtered for their removal prior to analysis. However, care should be exercised to avoid potential contamination from filtration.) The sample is now ready for analysis. Because the effects of various matrices on the stability of diluted samples cannot be characterized, all analyses should be performed as soon as possible after the completed preparation. 11.3 Sample Analysis 11.3.1 Prior to daily calibration of the instrument inspect the sample introduction system including the nebulizer, torch, injector tube and uptake tubing for salt deposits, dirt and debris that would restrict solution flow and affect instrument performance. Clean the system when needed or on a daily basis. 11.3.2 Configure the instrument system to the selected power and operating conditions as determined in Sections 10.1 and 10.2. 11.3.3 The instrument and nebulizer system must be allowed to become thermally stable before calibration and analyses. This usually requires at least 60 minutes of operation. After instrument warmup, complete any required optical profiling or alignment particular to the instrument. 11.3.4 For initial and daily operation calibrate the instrument according to the instrument manufacturer’s recommended procedures, using mixed calibration standard solutions (Sect. 7.10) and the calibration blank (Sect. 7.11.1). A peristaltic pump must be used to introduce all solutions to the nebulizer. To allow equilibrium to be reached in the plasma, nebulize all solutions for 30 sec after reaching the plasma before beginning integration of the background corrected signal to accumulate data. When possible, use the average value of replicate integration periods of the signal to be correlated to the analyte concentration. Flush the system with the rinse blank (Sect. 7.11.4) for a minimum o f 60 seconds (Sect. 4.4) between each standard. The calibration line should consist of a minimum of a calibration blank and a high standard. Replicates of the blank and highest standard provide an optimal distribution of calibration standards to minimize the confidence band for a straight-line calibration in a response region with uniform variance. 15

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11.3.5 After completion of the initial requirements of this method (Sects. 1 0 . 3 and 10.4), samples should be analyzed in the same operational manner used in the calibration routine with the rinse blank also being used between all sample solutions, LFBs, LFMs, and check solutions. 11.3.6 During the analysis of samples, the laboratory must comply with the required quality control described in Sections 9.3 and 9.4. 11.3.7 Determined sample analyte concentrations that are 90% or more of the upper limit of the analyte LDR must be diluted with reagent water that has been acidified in the same manner as calibration blank and reanalyzed (see Sect.11.3.8). Also, for the interelement spectral interference correction routines to remain valid during sample analysis, the interferant concentration must not exceed its LDR. If the interferant LDR is exceeded, sample dilution with acidified reagent water and In these circumstances analyte reanalysis is required. detection 1 imits are raised and determination by another approved test procedure (Sect. 1.2) that is either more sensitive and/or interference free is recommended. 11.3.8 When it is necessary to assess an operative matrix interference (e.g., signal reduction due to high dissolved solids), the tests described in Section 9.5 are recommended. 11.3.9 Report data as directed in Section 12. 11.4 If the method of standard additions (MSA) is used, standards are added at one or more levels to portions of a prepared sample. This technique16 compensates for enhancement or depression o f an analyte signal by a matrix. It will not correct for additive interferences such as contamination, interelement interferences, or baseline shifts. This technique is valid in the linear range when the interference effect is constant over the range, the added analyte responds the same as the endogenous analyte, and the signal is corrected for additive interferences. The simplest version of this technique is the singleaddition method. This procedure calls for two identical aliquots of t h e sample solution to be taken. To the first aliquot, a small volume of standard is added; while to the second aliquot, a volume of acid blank is added equal to the standard addition. The sample concentration is calculated by the following:

v, x c (S,-S,) x v, s, x

Sample Conc = (mg/L or mg/kg) where: C

=

S, = S, =

V, V,

= =

Concentration of the standard solution (mg/L) Signal for fortified aliquot Signal for unfortified aliquot Volume of the standard addition ( L ) Volume of the sample aliquot ( L ) used for MSA

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For more t h a n one f o r t i f i e d p o r t i o n o f t h e prepared sample, l i n e a r r e g r e s s i o n a n a l y s i s can be a p p l i e d u s i n g a computer o r c a l c u l a t o r program t o o b t a i n t h e c o n c e n t r a t i o n o f t h e sample s o l u t i o n . An a l t e r n a t i v e t o u s i n g t h e method o f s t a n d a r d a d d i t i o n s i s use o f t h e i n t e r n a l s t a n d a r d t e c h n i q u e by adding one o r m o r e elements ( n o t i n t h e samples and v e r i f i e d n o t t o cause an u n c o r r e c t e d i n t e r e l e m e n t s p e c t r a l i n t e r f e r e n c e ) a t t h e same c o n c e n t r a t i o n (which i s s u f f i c i e n t f o r optimum p r e c i s i o n ) t o t h e p r e p a r e d samples ( b l a n k s and s t a n d a r d s ) t h a t a r e a f f e c t e d t h e same a s t h e a n a l y t e s by t h e sample m a t r i x . Use t h e r a t i o o f analyte signal t o the i n t e r n a l standard signal f o r c a l i b r a t i o n and q u a n t i t a t i o n . 12.0 DATA ANALYSIS AND CALCULATIONS

1 2 . 1 Sample d a t a s h o u l d be r e p o r t e d i n u n i t s o f p g / L f o r a l l elements e x c e p t Ca, K, Mg, Na, and SiO, w h i c h s h o u l d be r e p o r t e d i n mg/L. 1 2 . 2 F o r p g / L d a t a v a l u e s l e s s t h a n t e n , two s i g n i f i c a n t f i g u r e s s h o u l d be used f o r r e p o r t i n g element c o n c e n t r a t i o n s . For d a t a v a l u e s g r e a t e r t h a n o r equal t o t e n , t h r e e s i g n i f i c a n t f i g u r e s should be used. For t h e a n a l y t e s Ca, K, Mg, Na, and SiO, w i t h MDLs < 0 . 0 1 mg/L, round t h e d a t a v a l u e s t o t h e thousandth p l a c e and r e p o r t a n a l y t e c o n c e n t r a t i o n s up t o t h r e e s i g n i f i c a n t f i g u r e s . When t h e MDLs f o r those a n a l y t e s a r e 2 0 . 0 1 mg/L, round t h e d a t a v a l u e s t o t h e hundredth p l a c e and r e p o r t a n a l y t e c o n c e n t r a t i o n s up t o t h r e e s i g n i f i c a n t f i g u r e s . 1 2 . 3 F o r d i s s o l v e d a n a l y t e s ( S e c t . 11.1) and t o t a l r e c o v e r a b l e analyses o f d r i n k i n g water w i t h t u r b i d i t y < lNTU (Sect. 11.2.1), r e p o r t the data g e n e r a t e d d i r e c t l y f r o m t h e i n s t r u m e n t w i t h allowance f o r sample d i l u t i o n . Do n o t r e p o r t a n a l y t e c o n c e n t r a t i o n s below t h e l a b o r a t o r y d e t e r m i n e d " d i r e c t a n a l y s i s " 1X MDL c o n c e n t r a t i o n . 1 2 . 4 F o r t o t a l r e c o v e r a b l e aqueous a n a l y t e s ( S e c t s . 11.2.2 - 1 1 . 2 . 7 ) r e p o r t I f a d i f f e r e n t a l i q u o t volume d a t a as i n s t r u c t e d i n S e c t i o n 1 2 . 2 . o t h e r t h a n 100 mL i s used f o r sample p r e p a r a t i o n , a d j u s t t h e d a t a accordingly using the appropriate d i l u t i o n factor. Also, account f o r any a d d i t i o n a l d i l u t i o n o f t h e p r e p a r e d sample s o l u t i o n needed t o complete t h e d e t e r m i n a t i o n o f a n a l y t e s exceeding 90% o r more o f t h e LDR upper l i m i t . Do n o t r e p o r t d a t a below t h e l a b o r a t o r y determined a n a l y t e 2X MDL c o n c e n t r a t i o n o r below an a d j u s t e d d e t e c t i o n l i m i t r e f l e c t i n g s m a l l e r sample a l i q u o t s used i n p r o c e s s i n g o r a d d i t i o n a l d i l u t i o n s r e q u i r e d t o complete t h e a n a l y s i s . 1 2 . 5 The QC d a t a o b t a i n e d d u r i n g t h e analyses p r o v i d e an i n d i c a t i o n o f t h e q u a l i t y o f t h e sample d a t a and s h o u l d be p r o v i d e d w i t h t h e sample results. 13.0 METHOD PERFORMANCE

1 3 . 1 L i s t e d i n Table 4 a r e t y p i c a l s i n g l e l a b o r a t o r y " d i r e c t a n a l y s i s " 1X MDLs and t o t a l r e c o v e r a b l e p r e c o n c e n t r a t e d 2 X MDLs determined f o r t h e recommended wavelengths u s i n g simultaneous ICP-AES and t h e i n s t r u m e n t c o n d i t i o n s l i s t e d i n Table 5. The MDLs were determined i n reagent b l a n k m a t r i x ( b e s t case s i t u a t i o n ) . PTFE beakers were used i n t h e R e v i s i o n 1.2 May1994

276

Methods for the Determination t o t a l recoverable determinations t o a v o i d boron and s i l i c a c o n t a m i n a t i o n f r o m glassware w i t h t h e f i n a l d i l u t i o n t o 50 mL completed i n p o l y p r o p y l e n e c e n t r i f u g e d t u b e s . Theoretically the p r e c o n c e n t r a t e d 2X MDLs s h o u l d be l o w e r t h a n t h e " d i r e c t a n a l y s i s " 1 X MDLs, however, f o r t h o s e a n a l y t e s where t h e 2X MDLs v a l u e s a r e s i g n i f i c a n t l y h i g h e r (2X MDL > 2 t i m e s t h e 1X MDL) e n v i r o n m e n t a l c o n t a m i n a t i o n i s suspected. 13.2 Data o b t a i n e d f r o m s i n g l e l a b o r a t o r y t e s t i n g o f t h e method a r e summarized i n Table 6 f o r f o u r d i f f e r e n t d r i n k i n g w a t e r s u p p l i e s ( t w o ground w a t e r s and two s u r f a c e w a t e r s ) and an ambient s u r f a c e w a t e r . The p r e c i s i o n and r e c o v e r y d a t a were c o l l e c t e d by simultaneous ICP-AES u t i l i z i n g t h e recommended wavelengths g i v e n i n Table 1 and t h e i n s t r u m e n t c o n d i t i o n s l i s t e d i n T a b l e 5. The u n f i l t e r e d d r i n k i n g w a t e r s were p r e p a r e d u s i n g t h e procedure d e s c r i b e d i n S e c t i o n 11.1 w h i l e t h e t o t a l r e c o v e r a b l e procedure ( S e c t s . 11.2.2 -11.2.7) was used t o p r e p a r e t h e ambient s u r f a c e w a t e r . F o r each m a t r i x , f i v e r e p l i c a t e a l i q u o t s were prepared, analyzed and t h e average o f t h e f i v e d e t e r m i n a t i o n s used t o d e f i n e t h e sample background c o n c e n t r a t i o n o f each a n a l y t e . I n a d d i t i o n , two f u r t h e r p a i r s o f d u p l i c a t e s were f o r t i f i e d a t d i f f e r e n t c o n c e n t r a t i o n l e v e l s . F o r each method a n a l y t e , t h e sample background c o n c e n t r a t i o n , mean p e r c e n t r e c o v e r y , t h e s t a n d a r d d e v i a t i o n o f t h e p e r c e n t r e c o v e r y and t h e r e 1 a t i v e p e r c e n t d i f f e r e n c e between t h e d u p l i c a t e f o r t i f i e d samples a r e l i s t e d i n T a b l e 6. The v a r i a n c e o f t h e f i v e r e p l i c a t e sample background d e t e r m i n a t i o n s i s included i n t h e c a l c u l a t e d standard d e v i a t i o n o f the percent r e c o v e r y when t h e a n a l y t e c o n c e n t r a t i o n i n t h e sample was g r e a t e r t h a n t h e MDL. F o r t i f i e d sample d a t a f o r t h e m a t r i x a n a l y t e s Cay K, Mg, Na, S r , and SiO, a r e n o t i n c l u d e d . However, t h e p r e c i s i o n and mean sample background c o n c e n t r a t i o n s f o r t h e s e s i x a n a l y t e s a r e 1 i s t e d s e p a r a t e l y i n Table 7 .

14.0 POLLUTION PREVENTION

1 4 . 1 P o l l u t i o n p r e v e n t i o n encompasses any t e c h n i q u e t h a t reduces o r e l i m i n a t e s t h e q u a n t i t y o r t o x i c i t y o f waste a t t h e p o i n t o f g e n e r a t i o n . Numerous o p p o r t u n i t i e s f o r p o l l u t i o n p r e v e n t i o n e x i s t i n l a b o r a t o r y o p e r a t i o n . The EPA has e s t a b l i s h e d a p r e f e r r e d h i e r a r c h y o f e n v i r o n m e n t a l management t e c h n i q u e s t h a t p l a c e s p o l l u t i o n p r e v e n t i o n as t h e management o p t i o n o f f i r s t c h o i c e . Whenever f e a s i b l e , 1 a b o r a t o r y personnel s h o u l d use p o l l u t i o n p r e v e n t i o n t e c h n i q u e s t o address t h e i r waste g e n e r a t i o n (e.g., S e c t . 7.9). When wastes cannot be f e a s i b l y reduced a t t h e source, t h e Agency recommends r e c y c l i n g as t h e n e x t b e s t o p t i o n . 14.2 F o r i n f o r m a t i o n about p o l l u t i o n p r e v e n t i o n t h a t may be a p p l i c a b l e t o l a b o r a t o r i e s and r e s e a r c h i n s t i t u t i o n s , c o n s u l t l e s s i s B e t t e r : L a b o r a t o r y Chemical Management f o r I l a s t e R e d u c t i o n , a v a i l a b l e f r o m t h e American Chemical S o c i e t y ' s Department o f Government R e l a t i o n s and Science P o l i c y , 1155 1 6 t h S t r e e t N . W . , Washington D.C. 20036, (202)872-4477.

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15.0 WASTE MANAGEMENT 15.1 The Environmental P r o t e c t i o n Agency r e q u i r e s t h a t l a b o r a t o r y waste management p r a c t i c e s be conducted c o n s i s t e n t w i t h a l l a p p l i c a b l e r u l e s and r e g u l a t i o n s . The Agency urges l a b o r a t o r i e s t o p r o t e c t t h e a i r , w a t e r , and l a n d by m i n i m i z i n g and c o n t r o l l i n g a l l r e l e a s e s f r o m hoods and bench o p e r a t i o n s , complying w i t h t h e l e t t e r and s p i r i t o f any sewer d i s c h a r g e p e r m i t s and r e g u l a t i o n s , and by complying w i t h a l l s o l i d and hazardous waste r e g u l a t i o n s , p a r t i c u l a r l y t h e hazardous waste i d e n t i f i c a t i o n r u l e s and l a n d d i s p o s a l r e s t r i c t i o n s . For f u r t h e r i n f o r m a t i o n on waste management c o n s u l t The Waste Management Manual f o r l a b o r a t o r y P e r s o n n e l , a v a i l a b l e f r o m t h e American Chemical S o c i e t y a t t h e address l i s t e d i n t h e S e c t i o n 1 4 . 2 . 16.0 REFERENCES 1.

U.S. Environmental P r o t e c t i o n Agency. I n d u c t i v e l y Coupled Plasma Atomic Emission S p e c t r o m e t r i c Method f o r Trace Element A n a l y s i s o f Water and Wastes - Method 200.7, V e r s i o n 3 . 3 , 1991.

2.

U.S. Environmental P r o t e c t i o n Agency. I n d u c t i v e l y Coupled Plasma Atomic Emission Spectrometry Method f o r t h e A n a l y s i s o f Waters and S o l i d s , EMMC, J u l y 1992.

3.

Boumans, P.W.J.M. L i n e Coincidence Tables f o r I n d u c t i v e l y Coupled Plasma Atomic Emission Spectrometry, 2nd e d i t i o n . Pergamon Press, Oxford, U n i t e d Kingdom, 1984.

4.

e t a l . I n d u c t i v e l y Coupled Plasma-Atomic Emission Winge, R.K. Spectroscopy: An A t l a s o f S p e c t r a l I n f o r m a t i o n , P h y s i c a l Science Data 20. E l s e v i e r Science P u b l i s h i n g , New York, New York, 1985.

5.

M a r t i n , T.D., C.A. B r o c k h o f f and J.T. Creed. Trace Metal Valence S t a t e C o n s i d e r a t i o n i n U t i l i z i n g an U l t r a s o n i c N e b u l i z e r f o r Metal Determination by ICP-AES. Winter Conference on Plasma S p e c t r o c h e m i s t r y , San Diego, CA, January, 10-15, 1994.

6.

Carcinogens - Working W i t h Carcinogens, Department o f H e a l t h , E d u c a t i o n , and W e l f a r e , P u b l i c H e a l t h S e r v i c e , Center f o r Disease C o n t r o l , N a t i o n a l I n s t i t u t e f o r O c c u p a t i o n a l S a f e t y and H e a l t h , P u b l i c a t i o n No. 77-206, Aug. 1977.

7.

OSHA S a f e t y and H e a l t h Standards, General I n d u s t r y , (29 CFR 1910), O c c u p a t i o n a l S a f e t y and H e a l t h A d m i n i s t r a t i o n , OSHA 2206, (Revised, January 1976).

8.

S a f e t y i n Academic Chemistry L a b o r a t o r i e s , American Chemical S o c i e t y Pub1 i c a t i o n , Committee on Chemical S a f e t y , 3 r d E d i t i o n , 1979.

9.

Proposed OSHA S a f e t y and H e a l t h Standards, L a b o r a t o r i e s , Occupational S a f e t y and H e a l t h A d m i n i s t r a t i o n , Federal R e g i s t e r , J u l y 24, 1986.

R e v i s i o n 1 . 2 May1994

278

Methods for the Determination 10.

Rohrbough, W.G. e t a l . Reagent Chemicals, American Chemical S o c i e t y S p e c i f i c a t i o n s , 7 t h e d i t i o n . American Chemical S o c i e t y , Washington, DC, 1986.

11.

American S o c i e t y f o r T e s t i n g and M a t e r i a l s . Standard S p e c i f i c a t i o n f o r Reagent Water, 01193-77. Annual Book o f ASTM Standards, Vol. 11.01. P h i l a d e l p h i a , PA, 1991.

12.

Code o f Federal R e g u l a t i o n s 40, Ch. 1, P t . 136 Appendix B.

13.

Wallace, G.F., Some F a c t o r s A f f e c t i n g t h e Performance o f an I C P Sample I n t r o d u c t i o n System. Atomic Spectroscopy, V o l . 4, p . 188-192, 1983.

14.

K o i r t y o h a n n , S.R. e t a l . Nomenclature System f o r t h e Low-Power Argon I n d u c t i v e l y Coupled Plasma, Anal. Chem. 2 : 1 9 6 5 , 1980

15.

Deming, S.N. and S . L . Morgan. Experimental Design f o r Q u a l i t y and P r o d u c t i v i t y i n Research, Development, and M a n u f a c t u r i n g , P a r t 111, pp 119-123. S h o r t c o u r s e pub1 i c a t i o n by S t a t i s t i c a l Designs, 9941 R o w l e t t , S u i t e 6, Houston, TX 77075, 1989.

16.

Winefordner, J.D., Trace A n a l y s i s : Spectroscopic Elements, Chemical A n a l y s i s , V o l . 46, pp. 41-42.

Methods

for

R e v i s i o n 1.2 May1994

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279

17.0 TABLES, DIAGRAMS. FLOWCHARTS, AND VALIDATION DATA TABLE 1.

Anal y t e

WAVELENGTHS, ESTIMATED INSTRUMENT DETECTION LIMITS, AND RECOMMENDED CALIBRATION Wave1 engtha (nm)

Detection Lirni tb (P9/L)

C a l i brate' to (mg/L)

~

A1 urni nurn Ant imony Arsenic B a r i urn B e r y l 1 iurn Boron Cadrni urn Calcium Cer iurn Chromium Cobalt Copper Iron Lead Lithium Magnesi urn Manganese Mercury Mol ybdenurn Nickel Pot ass iurn Sel en iurn S i l i c a (SiO,) S i 1v e r Sodi urn S t r o n t i urn Thal 1 iurn Tin Titanium Vanadi urn Zinc

308.215 206.833 193.759 493.409 313.042 249.678 226.502 315.887 413.765 205.552 228.616 324.754 259.940 220.353 670.784 279.079 257.610 194.227 203.844 231.604 766.491 196.090 251.611 328.068 588.995 421.552 190.864 189.980 334.941 292.402 213.856

1 1

3 0.2 0.05 2 0.2 1 20 0.9 0.4 0.3 0.3 2 0.4 2 0.2 3 1 0.8 40 8 10 (SiO,)

2 1 2 0.2 0.2 0.5 0.5 40 0.5 1 0.5 0.5 2 2 1 10 0.5 0.5 2 0.5 10 2 2

0.3

0.1

3 0.1 5 4 0.1 0.6 0.4

20 0.2 1 1 2 0.5 1

a The wavelengths l i s t e d a r e recommended because o f t h e i r s e n s i t i v i t y and

o v e r a l l a c c e p t a b i l i t y . O t h e r wavelengths may be s u b s t i t u t e d i f t h e y can p r o v i d e t h e needed s e n s i t i v i t y and a r e t r e a t e d w i t h t h e same c o r r e c t i v e t e c h n i q u e s f o r s p e c t r a l i n t e r f e r e n c e (see S e c t i o n 4.1). The 1i s t e d EMSL-Cincinnati e s t i m a t e d 3-sigma i n s t r u m e n t a l d e t e c t i o n l i m i t s a r e p r o v i d e d o n l y as a g u i d e t o i n s t r u m e n t a l l i m i t s . C

Suggested c o n c e n t r a t i o n f o r i n s t r u m e n t c a l i b r a t i o n .

Other c a l i b r a t i o n

l i m i t s i n t h e l i n e a r ranges may be used.

R e v i s i o n 1 . 2 May1994

280

Methods for the Determination TABLE 2. ON-LINE METHOD INTERELEMENT SPECTRAL INTERFERENCES ARISING FROM INTERFERANTS AT THE 20-mg/L LEVEL

Analyte Ag A1 As B Ba Be Ca Cd Ce co Cr cu Fe Hg K Li Mg Mn Mo Na Ni Pb

Sb Se SiO, Sn Sr T1

Ti V Zn

Wavelength (nm) 328.068 308.215 193.759 249.678 493.409 313.042 315.887 226.502 413.765 228.616 205.552 324.754 259.940 194.227 766.491 670.784 279.079 257.610 203.844 588.995 231.604 220.353 206.833 196.099 251.611 189.980 421.552 190.864 334.941 292.402 213.856

I n t e rferant* Ce,Ti ,Mn V,Mo,Ce,Mn V,A1 ,Co,Fe,Ni None None V,Ce Co,Mo, Ce Ni,Ti,Fe,Ce None Ti,Ba,Cd,Ni,Cr,Mo,Ce Be,Mo,Ni, Mo,Ti None V,Mo None None Ce Ce Ce None Co, T1 Co,A1 ,Ce,Cu,Ni , T i ,Fe Cr,Mo,Sn,Ti,Ce,Fe Fe None Mo,Ti,Fe,Mn,Si None Ti,Mo,Co,Ce,Al,V,Mn None Mo,Ti,Cr,Fe,Ce N i ,Cu,Fe

* These o n - l i n e i n t e r f e r e n c e s from method a n a l y t e s and t i t a n i u m o n l y were observed u s i n g an i n s t r u m e n t w i t h 0.035-nm r e s o l u t i o n (see Sect. 4.1.2). I n t e r f e r a n t ranked by magnitude o f i n t e n s i t y w i t h t h e most severe i n t e r f e r a n t l i s t e d f i r s t i n t h e row.

R e v i s i o n 1 . 2 May1994

Metals

281

TABLE 3. NIXED STANDARD SOLUTIONS' Sol ut 1 on

I I1 I11

IV V VI

Anal ytes Ag, As, B y Ba, Cd, Cu, Mn, and Sb K , Li, Mo, Sr, and Ti C o y V, and Ce Al, Cry Hg, SiO,, Sn, and Zn Be, F e y Ni, Pb, and T1 Se, C a y Mg,and Na

'

See Table 1 for recommended calibration concentrations. See Sections 1.10 and 4.3 for discussion on desolvation affects on A s , Cr, and Se. See Section 7.10 and 7.11 for preparation o f calibration standard and blank solutions.

Revision 1.2 Hay 1994

282

Methods for the Determination

TABLE 4 .

Analyte

METHOD DETECTION

1X MDL D i r e c t Analysis, pg/L

(MDL)")

LIMITS

2X MDL Total Recoverable Digestion, pg/L'*'

Ag A1

0.6

As

3

2

B Ba

2

4 0.2

0.6

4

20

0.2

Be Cd Ce co

Cr cu

0.05

0.02

0.4

0.2

5 0.6 2

0.4

5 0.4

2 2 3

Fe Hg Li Mn

0.7 10 2

0.7 0.09

0.9 0.08

Mo Ni

2

1

0.7

Pb

4

0.8 2

Sb* Se

3

3 3

5

Sn Sr

2 0.2

5

0.08

Ti T1

0.2

V

6 2

Zn

0.5

1X MDL. mq/L

Ca K

Mg Na SiO,

0.3 2 0.5 0.7 2x

MDL. mq/LC2'

0,005 0.09 0.005

0.03 0.05

0.04

0.05 0.03

0.002

0.01

(1)

Method detection limits are sample dependent and may vary as the sample matrix varies.

(2)

MDL concentrations are computed for original matrix with allowance for 2x sample preconcentration during preparation. Samples were processed in PTFE and diluted in 50-mL plastic centrifuge tubes.

*

Se MDL determined in tap water due to common matrix enhancement (Sect. 1.10) Revision1.2 May1994

Metals TABLE 5.

283

INDUCTIVELY COUPLED PLASMA AND ULTRASONIC NEBULIZER INSTRUMENT OPERATING CONDITIONS

ICP SPECTROMETER I n c i d e n t r f power

1400 w a t t s

R e f l e c t e d r f power

< 5 watts

Viewing h e i g h t above work c o i l I n j e c t o r tube o r i f i c e i.d. Argon s u p p l y

15 mm 1 mm

l i q u i d argon

Argon p r e s s u r e

40 p s i

C o o l a n t argon f l o w r a t e

19 L/min

Auxi 1 ia r y ( p l asma) argon f l o w r a t e

300 mL/min

ULTRASONIC NEBULIZER Aerosol c a r r i e r argon flow rate

570 mL/min

Sample u p t a k e r a t e c o n t r o l 1 ed t o

1.8 mL/min

Transducer power 1.4 MHz auto-tuned Desolvation temperature Condenser t e m p e r a t u r e

35 w a t t s 14OoC 5OC

R e v i s i o n 1.2 May 1994

284

Methods for the Determination

TABLE 6.

P R E C I S I O N AND RECOVERY DATA

IN

AQUEOUS MATRICES

REGION 2 - TAP WATER

SAMPLE CONC pG/L

HIGH SPIKE pG/L

AVERAGE RECOVERY R(%)

100 400 300 200

104 105 112 95 101

0.3 0.8 0.9 0.6 0.4

0.6 1.2 1.6

0.3 0.4

500 200 200

103 105 103 104 106

0.2

0.6 0.7 0.9 0.7 0.3

4.1 2.7 2.3

200 200 300 200 100

103 105 107 102 104

0.7 0.7 0.3 0.4 0.5

0.6 0.8 0.6 0.6 0.9

3.3 0.4 8.8 0.3 1.9

6.8 0.6 4.9 0.6 4.0

200 100 400 300 500

101 105 109 110 107

0.3 0.2 0.4 0.5 1.2

0.5 0.4 0.6 1.0 2.3

1.2 1.3 1.6 2.0 1.2

2.4 2.5 2.7 3.9 0.5

400 200 400 200 200

107 104 109 102 110

0.1 0.4 0.1 1 :2 0.6

0.2 0.7 0.2 2.3 1 .o

pG/L

AVERAGE RECOVERY R(%)

S(R)

RPD

t0.6 10.4 t3 5.3 5.8

10.0 40.0 30.0 20.0 20.0

114 115 118 94 100

2.0 3.8 0.7 3.8 1.6

3.5 0.4 1.1 0.8 2.4

Be Cd Ce co Cr

to.05

t0.4 <5. t0.6 t2

4.0 4.0 50.0 20.0 20.0

101 110 107 102 101

0.9 0.4 0.1 1.4 1.0

1.8 0.7 0.2 2.6 2.0

cu Fe Hg Li Mn

152. 106. t3 0.72 5.9

20.0 20.0 30.0 20.0 10.0

*

*

*

* *

106 100 101

2.2 1.9 1.9

Mo Ni Pb Sb Se

t2 t0.7 12.4 <3 <5

20.0 10.0 15.0 30.0 50.0

96 111 107 112 94

Sn Ti T1 V Zn

<5 <0.2 t6 <2 5.6

40.0 20.0 40.0 20.0 20.0

106 102 119 103 108

ANALYTE Ag A1 As

B Ba

S(R) RPD t

*

LOW

SPIKE

*

200

40 40

S(R)

0.5 0.3

RPD

0.9

0.7

Standard d e v i a t i o n o f percent recovery R e l a t i v e percent d i f f e r e n c e between d u p l i c a t e spike determinations Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t . Spike c o n c e n t r a t i o n <25% o f sample background concentration.

R e v i s i o n 1 . 2 May1994

Metals

TABLE 6.

285

PRECISION AND RECOVERY DATA I N AQUEOUS MATRICES (Cont.)

REGION 5 - TAP WATER

ANALYTE

SAMPLE CONC pG/L

LOW SPlKE fiG/L

AVERAGE RECOVERY R(%)

S(R)

RPD

pG/L

AVERAGE RECOVERY R(%)

10.0 40.0 30.0 20.0 20.0

114 108 110 104 105

0.7 5.1 1.5 2.6 1.4

1.1 1.0 2.7 0.2 1.0

100 400 300 200 200

109 111 114 99 104

0.2 0.7 0.7 0.4 0.4

0.4 0.7 I .2 0.6 0.6

HIGH

SPIKE

S(R)

RPD

Ag A1 As B Ba

t0.6 98.3

Be Cd Ce Co Cr

to.05

t0.4 t5 t0.6 t2

4.0 4.0 50.0 20.0 20.0

110 106 108 108 105

0.1 2.3 4.7 0.5 0.2

0.3 4.3 8.7 1.0 0.5

40 40 500 200 200

108 106 106 107 108

0.5 0.6 0.4 0.5 0.2

0.9 1.2 0.7 1 .o 0.4

cu Fe Hg Li Mn

3.9 7.3 <3 4.4 0.26

20.0 20.0 30.0 20.0 10.0

92 98 103 108 108

0.8 0.7 4.3 1.5 0.3

0.9 0.0 8.4 0.3 0.1

200 200 300 200 100

104 108 104 106 107

0.2 0.6 0.0 0.4 0.5

0.4 1.1 0.1 0.6 0.8

Mo Ni Pb Sb Se

<2 1.o t4 t3 t5

20.0 10.0 15.0 30.0 50.0

107 108 98 117 101

0.8 4.6 5.7 1.7 6.4

1.4 5.6 11.6 2.8 12.7

200 100 400 300 500

105 106 112 114 114

0.7 0.3 0.3 0.5 0.4

1.3 0.1 0.6 0.8 0.7

Sn Ti T1 V Zn

<5 0.23 t6 t2 4.5

40.0 20.0 40.0 20.0 20.0

119 109 108 105 111

1.1 0.1 2.9 3.0

1.9 0.0 5.3 5.7 0.2

400 200 400 200 200

114 108 110 105 113

0.7 0.5 1.o 1.5 0.1

1.3 0.8 1.7 2.9 0.2

S(R) RPD t

<3

26.8 30.2

0.8

Standard d e v i a t i o n o f percent recovery. R e l a t i v e percent d i f f e r e n c e between d u p l i c a t e s p i k e determinations. Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t .

Revision 1.2 May 1994

286

Methods for the Determination

TABLE 6 .

PRECISION AND RECOVERY DATA I N AQUEOUS MATRICES ( C o n t . )

REGION 6

SAMPLE CONC pG/L

-

TAP WATER

AVERAGE RECOVERY R(%)

S(R)

RPD

10.0 40.0 30.0 20.0 20.0

102 111 110

1 .o

3.8 8.6

2.0 6.8 10.7

102

1 .o

0.7

<5 t0.6 <2

4.0 4.0 50.0 20.0 20.0

102 95 93 95 97

0.7 2.9 3.0 1.6 1 .o

cu Fe Hg Li Mn

2.1 <2 t3 34.4 1.5

20.0 20.0 30.0 20.0 10.0

98 97 105 116 97

Mo Ni Pb Sb Se

52.7 t0.7 t4 t3 t5

20.0 10.0 15.0 30.0 50.0

Sn

6.1 2.5 t6 t2 3.6

40.0 20.0 40.0 20.0 20.0

ANALYTE Ag

A1

As B Ba Be Cd Ce co Cr

Ti T1 V Zn

S(R ) RPD t

*

t0.6 t4 5.2 98.7 18.0 0.07 tO.4

LOW SPIKE pG/L

HIGH SPIKE pG/L

AVERAGE RECOVERY R(%)

100 400 300 200 200

103 106 107 97 99

0.3 0.3 1.4 0.5 0.1

0.6 0.5 2.5 0.3 0.1

1.3 6.1 6.5 3.3 2.1

40 40 500 200

99 89 98 92 94

0.3 0.6 0.4 0.4 0.4

0.6 1.3 0.9 0.9 0.8

1.8 2.0 1.2 2.4 1.1

2.3 3.3 2.2 0.7 1.9

200 200 300 200 100

101 96 103 108 95

0.4 0.6 0.8 0.3 0.3

0.7 1.3 1.6 0.3 0.7

102 101 89 115 119

7.6 2.0 8.7 0.3 0.3

2.1 4.1 19.5 0.6 0.5

200 100 400 300 500

95 92 97 105 117

0.9 0.8 0.1 0.7

1.1

0.9 1.8 0.2 1.4 1.9

110 104 106 100 103

7.9 0.9 3.8 3.3 1.2

6.6 1.4 7.1 6.5 1.7

400 200 400 200 200

100 102 101 98 100

2.3 0.2 0.5 0.5 0.2

4.4 0.3 0.9 1.1 0.3

*

*

*

200

S(R)

RPD

Standard d e v i a t i o n o f percent recovery. R e l a t i v e percent d i f f e r e n c e between d u p l i c a t e spike determinations. Sample concentration below e s t a b l i s h e d method d e t e c t i o n l i m i t . Spike concentration t10% o f sample background concentration.

R e v i s i o n 1 . 2 May1994

Metals

TABLE 6 .

287

PRECISION AND RECOVERY DATA I N AQUEOUS MATRICES ( C o n t . )

REGION 10 - TAP WATER

ANALYTE

SAMPLE CONC pG/L

LOW SPIKE pG/L

AVERAGE RECOVERY R(%)

S(R)

RPD

0.5 3.7 5.5 1.9 0.8

0.9 4.4 9.0

~0.6 4.8 <3 24.4 10.7

10.0 40.0 30.0 20.0 20.0

115

Be Cd Ce co Cr

4.0

t0.4 <5 t0.6 (2

4.0

108 109 115 106 106

0.7 1.9 1.1

cu

<2 11.0 <3 1.2 9.8

20.0 20.0

Ni Pb Sb Se Sn Ti T1 V 2n

Ag

A1

As B Ba

Fe Hg Li Mn

Mo

S(R) RPD

<

101 122 90 104

1.4 1 .o

t i I GH SPIKE pG/L

AVERAGE RECOVERY R(%)

100 400 200

109 108 115 86 105

0.6 0.5 0.4 1 .o 0.4

1.1 0.7 0.6 2.1 0.8

108 105 107 105 107

0.2 0.4 0.I 0.3 0.3

0.4 0.7 0.2 0.5 0.5

300 200

S(R)

RPO

0.6

1.1

0.2

0.5

40 40 500 200 200

20.0 10.9

115 130 111 107 52

0.5 1.6 3.3 1.7 0.8

0.9 1.6 6.0 1.8 1.6

200 200 300 200 100

106 106 107 107 106

0.4 0.1 1.1 0.9 0.1

0.7 0.0 2.0 1.7 0.2

<2 t0.7 <4 <3 <5

20.0 10.0 15.0 30.0 50.0

109 113 95 118 100

1.2 2.0 1.7 3.3 2.7

2.3 3.5 3.5 5.6

200 100 400 300 500

104 105 109 114 112

0.2 0.4 0.9 0.1 1.2

0.4 0.8

7.3 0.39 8.2 <2 t0.5

40.0 20.0 40.0 20.0 20.0

114 108 105 106 110

3.5 0.7 6.4 2.5 0.0

2.7 1.2

400

7.2

400

4.7 0.0

200 200

110 108 110 104 110

1.4 0.1 1.4 0.4 0.3

2.4 0.1 2.4 0.9 0.5

50.0 20.0 20.0

30.0

1.2 3.4

1.9

5.4

200

1.7 0.1 2.1

Standard d e v i a t i o n o f p e r c e n t r e c o v e r y . R e l a t i v e p e r c e n t d i f f e r e n c e between d u p l i c a t e s p i k e d e t e r m i n a t i o n s . Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t .

R e v i s i o n 1.2 May1994

288

Methods for the Determination

TABLE 6.

PRECISION AND RECOVERY DATA I N AQUEOUS MATRICES (Cont.)

REGION 5

ANALYTE Ag A1 As

B Ba Be Cd Ce co Cr

SAMPLE CONC bG/L

t0.6 780 t3 38.8 51.7 0.12 t0.4 t5 1.8 t2

- R I V E R WATER

HlGH SPIKE pG/L

AVERAGE RECOVERY R(%)

102

*

0.8

*

1.6

* *

6.8

* *

50 200 150 100 100

105 104 100

1.0 3.6 1.3

2.0 1.5 0.9

100 98 118 96 101

0.8 1.3 3.0 1.8 0.5

0.5 2.5 5.1 1.8 1.o

20 20 250 100 100

107 94 105 100 103

2.0 1.5 0.9 0.8 0.8

3.7 3.2 1.8 1.6 1.6

98

2.6

*

1.5

101

0.8

1.4

102 93

0.7 14.9

1.3 4.9

*

100 100 150 100 50

107 106 93

1.5 1.7 10.4

2.8 1.5 3.7

LOW SPIKE pG/L

AVERAGE RECOVERY -R(%)

S(R)

RPD

5.0 20.0 15.0 10.0 10.0

98

2.0

*

4.1

108

*

3.7

*

2.0 2.0 25.0 10.0 10.0

*

S(R)

RPD

*

cu Fe Hg Li Mn

3.8 1240 <3 7.0 191

10.0 10.0 15.0 10.0 5.0

Mo Ni Pb Sb Se

t2 5.5 8.0 3.5 t5

10.0 5.0 7.5 15.0 25.0

109 79 91 84 97

3.0 13.5 45.8 5.3 1.4

5.5 7.4 9.4 0.6 2.9

100 50 200 150 250

102 105 104 107 107

1.2 1.7 2.1 0.9 2.7

2.3 2.2 2.4 1.4 5.1

Sn Ti T1 V Zn

t5 3.9 t6 t2 16.8

20.0 10.0 20.0 10.0 10.0

120 79 87 102 62

3.5 13.4 0.5 0.0 3.5

5.9 2.6 1.2 0.0 2.2

200 100 200 100 100

94 96 105 97 102

2.5 1.4 0.7 0.8 0.4

5.4 1.0 1.2 1.5 0.6

S(R) RPD t

*

*

*

*

*

*

*

Standard d e v i a t i o n o f percent recovery. R e l a t i v e percent d i f f e r e n c e between d u p l i c a t e spike determinations. Sample c o n c e n t r a t i o n below e s t a b l i s h e d method d e t e c t i o n l i m i t . Spike c o n c e n t r a t i o n (25% o f sample background c o n c e n t r a t i o n .

Revision1.2 Ray1994

Metals TABLE 7 .

AQUEOUS MATRIX

289

ELEMENT CONCENTRATIONS")

DRINKING WATER REGION 2 MATRIX ELEMENTS Ca K Mg Na SiO,

Sr

REGION 5

SAMPLE CONC mg/L

%RSD

4.08 0.786 0.626 7.83 3.09 0.029

0.8 5.4 1.4 0.6 0.5 0.6

SAMPLE MATRIX ELEMENTS

Ca K Mg

Na SiO, Sr

REGION 6 MATRIX ELEMENTS Ca K Mg Na SiO,

Sr

CONC mg/L

%RSD

27.4 1.62 7.18 9.97 6.22 0.146

0.9 1.8 0.9 0.4 1.0 0.6

REGION 10

SAMPLE CONC mg/L

%RSD

253 4.60 36.3 39.9 32.6 4.06

n.a. 0.9 1.0 0.9 0.9 1.4

MATRIX ELEMENTS

Ca K Mg

Na SiO,

Sr

SAMPLE CONC mg/L

19.9 1.84 1.43 19.4 37.3 0.063

%RSD

0.6 1.4 0.4 0.4

0.4 0.4

RIVER WATER REGION 5 MATRIX ELEMENTS Ca

K Mg Na SiO, Sr

SAMPLE CONC mg/L

31.5 2.27 9.38 12.1 1.54 0.220

%RSD

1.1 1.2 1.6 0.9 18.4 1.5

(1) Mean sample concentration and relative standard deviation were determined from 5 replicate aliquots o f each sample. Revision1.2 M a y 1 9 9 4

290

Methods for the Determination METHOD 218.6 DETERMINATION OF DISSOLVED HEXAVALENT CHROMIUM I N DRINKING WATER, GROUNDWATER, AND INDUSTRIAL WASTEWATER EFFLUENTS BY ION CHROMATOGRAPHY

R e v i s i o n 3.3 EMMC V e r s i o n

E.J. Arar, S.E. Long (Technology A p p l i c a t i o n s , I n c . ) , and Method 218.6, R e v i s i o n 3.2 (1991) E.J. Arar, J.D. P f a f f , and

T.D. M a r t i n -

Method 218.6,

J.D. P f a f f -

R e v i s i o n 3.3 (1994)

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U . S . ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

Metals

291

METHOD 218.6 DETERMINATION OF DISSOLVED HEXAVALENT CHROMIUM I N DRINKING WATER, GROUNDWATER, AND INDUSTRIAL WASTEWATER EFFLUENTS BY ION CHROMATOGRAPHY

1.0

SCOPE AND APPLICATION

1.1 T h i s method p r o v i d e s procedures f o r d e t e r m i n a t i o n o f d i s s o l v e d h e x a v a l e n t chromium (as CrO;-) i n d r i n k i n g water, groundwater, and in d u s t r i a1 wastewater e f f l u e n t s .

Anal y t e Hexaval e n t Chromi um (as CrO,*-)

Chemical A b s t r a c t s S e r v i c e R e g i s t r y Number (CASRN) 11104-59-9

1.2

For r e f e r e n c e where t h i s method i s approved f o r use i n compliance m o n i t o r i n g programs [e.g., Clean Water A c t (NPDES) o r Safe D r i n k i n g Water A c t (SDWA)] c o n s u l t b o t h t h e a p p r o p r i a t e s e c t i o n s o f t h e Code o f Federal R e g u l a t i o n (40 CFR P a r t 136 T a b l e 18 f o r NPDES, and P a r t 141 § 141.23 f o r d r i n k i n g w a t e r ) , and t h e l a t e s t Federal R e g i s t e r announcements.

1.3

The method d e t e c t i o n l i m i t s (MDL) o b t a i n e d by a s i n g l e l a b o r a t o r y f o r h e x a v a l e n t chromium (Cr(V1)) i n t h e above m a t r i c e s a r e l i s t e d i n Table 1. The MDL o b t a i n e d by an i n d i v i d u a l l a b o r a t o r y f o r a s p e c i f i c m a t r i x may d i f f e r f r o m t h o s e l i s t e d depending on t h e n a t u r e o f t h e sample and t h e i n s t r u m e n t a t i o n used. A m u l t i l a b o r a t o r y method d e t e c t i o n l i m i t (MMDL) i n r e a g e n t w a t e r was determined t o be 0 . 4 pg/L. The IMDL was based upon t h e w i t h i n - l a b o r a t o r y s t a n d a r d d e v i a t i o n (s,) o f t h i r t e e n p a i r e d analyses o f samples by t h i r t e e n 1 a b o r a t o r i e s a t an average a n a l y t e c o n c e n t r a t i o n o f 1.4 pg/L.

1.4

Samples c o n t a i n i n g h i g h l e v e l s o f a n i o n i c s p e c i e s such as s u l p h a t e and c h l o r i d e may cause column o v e r l o a d . Samples c o n t a i n i n g h i g h l e v e l s o f o r g a n i c s o r s u l f i d e s cause r a p i d r e d u c t i o n o f s o l u b l e Cr(V1) t o C r ( 1 I I ) . Samples must be s t o r e d a t 4°C and analyzed w i t h i n 24 h o f c o l 1e c t i o n .

1.5

T h i s method s h o u l d be used by a n a l y s t s e x p e r i e n c e d i n t h e use o f i o n chromatography. R e v i s i o n 3.3 May 1994

292

Methods for the Determination

2.0

SUMMARY OF METHOD 2.1

3.0

An aqueous sample i s f i l t e r e d through a 0.45-pm f i l t e r and t h e f i l t r a t e i s a d j u s t e d t o a pH of 9 t o 9 . 5 with a c o n c e n t r a t e d b u f f e r s o l u t i o n . A measured volume of t h e sample (50-250 pL) i s introduced i n t o t h e ion chromatograph. A guard column removes o r g a n i c s from t h e sample before t h e C r ( V I ) , a s CrO,’., i s s e p a r a t e d on a high c a p a c i t y anion exchange s e p a r a t o r column. Post-column d e r i v a t i z a t i o n of t h e Cr(V1) with diphenylcarbazide i s followed by d e t e c t i o n of t h e colored complex a t 530 nm.

DEFINITIONS 3.1

C a l i b r a t i o n Standard (CAL) - A s o l u t i o n prepared from the d i l u t i o n of s t o c k s t a n d a r d s o l u t i b n s . The CAL s o l u t i o n s a r e used t o c a l i b r a t e the instrument response with r e s p e c t t o a n a l y t e c o n c e n t r a t i o n ( S e c t . 7 . 9 ) .

3.2

Dissolved Analyte - The c o n c e n t r a t i o n o f a n a l y t e i n an aqueous sample t h a t w i l l pass through a 0.45-pm membrane f i l t e r assembly p r i o r t o sample a c i d i f i c a t i o n .

3.3

Instrument Performance Check (IPC) S o l u t i o n - A s o l u t i o n of the method a n a l y t e , used t o e v a l u a t e t h e performance of the instrument system with r e s p e c t t o a d e f i n e d s e t o f method c r i t e r i a .

3.4

Laboratory D u p l i c a t e s (LDI and LD2) - Two a l i q u o t s of t h e same sample taken i n the l a b o r a t o r y and analyzed s e p a r a t e l y with i d e n t i c a l procedures. Analyses o f LD1 and LO2 i n d i c a t e s p r e c i s i o n a s s o c i a t e d with l a b o r a t o r y procedures, but not with sample c o l l e c t i o n , p r e s e r v a t i o n , o r s t o r a g e procedures.

3.5

Laboratory F o r t i f i e d Blank (LFB) - An a l i q u o t of LRB t o which known q u a n t i t i e s of the method a n a l y t e s a r e added i n the l a b o r a t o r y . The LFB i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o determine whether the methodology i s i n c o n t r o l and whether t h e l a b o r a t o r y i s capable of making a c c u r a t e and p r e c i s e measurements.

3.6

Laboratory F o r t i f i e d Sample Matrix (LFM) - An a l i q u o t of an environmental sample t o which a known q u a n t i t y of the method a n a l y t e The LFM i s analyzed e x a c t l y l i k e a i s added i n the l a b o r a t o r y . sample, and i t s purpose i s t o determine whether t h e sample matrix contributes bias t o the analytical r e s u l t s . The background c o n c e n t r a t i o n of the a n a l y t e i n t h e sample matrix must be determined i n a s e p a r a t e a l i q u o t and t h e measured value i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n .

3.7

Laboratory Reagent Blank (LRB) - An a l i q u o t of reagent water o r o t h e r blank m a t r i c e s t h a t a r e t r e a t e d e x a c t l y a s a sample including exposure t o a l l glassware, equipment, s o l v e n t s , r e a g e n t s , and i n t e r n a l st.andards t h a t a r e used with o t h e r samples. The L R B i s used t o determine i f t h e method a n a l y t e o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t in t h e l a b o r a t o r y environment, r e a g e n t s , o r a p p a r a t u s . R e v i s i o n 3 . 3 May1994

Metals

293

3.8

Linear Dynamic Range (LDR) - The concentration range over which the instrument response to an analyte is linear.

3.9

Method Detection Limit (MDL) - The minimum concentration of an analyte that can be identified, measured, and reported with 99% confidence that the analyte concentration is greater than zero.

3 . 1 0 Quality Control Sample (QCS) - A solution of the method analyte of known concentration which is used to fortify an aliquot of LRB or

sample matrix. The QCS is obtained from a source external to the laboratory and different from the source of calibration standards. It is used to check either laboratory or instrument performance. 3 . 1 1 Stock Standard Solution -

A concentrated solution containing one or more method analytes prepared in the laboratory using assayed reference materials or purchased from a reputable commercial source.

4.0

INTERFERENCES 4.1

5.0

Interferences which affect the accurate determination of Cr(V1) may come from several sources. 4.1.1

Contamination - A trace amount of Cr is sometimes found in reagent grade salts. Since a concentrated buffer solution is used in this method to adjust the pH of samples, reagent blanks should be analyzed to assess for potential Cr(V1) contamination. Contamination can also come from improperly cleaned glassware or contact of caustic or acidic reagents or samples with stainless steel or pigmented material.

4.1.2

Reduction of Cr(V1) to Cr(II1) can occur in the presence of reducing species in an acidic medium. At pH 6.5 or greater, however, Cr0,2' which is less reactive than HCr0,-is the predominant species

4.1.3

Overloading of the analytical column capacity with high concentrations of anionic species, especially chloride and sulphate, will cause a loss of Cr(V1). The column specified in this method can handle samples containing up to 5% sodium sulphate or 2% sodium chloride2. Poor recoveries from fortified samples and tailing peaks are typical manifestations o f column overload.

SAFETY 5.1

Hexavalent chromium is toxic and a suspected carcinogen and should be handled with appropriate precautions. Extreme care should be exercised when weighing the salt for preparation of the stock standard. Each laboratory is responsible for maintaining a current awareness file o f OSHA regulations regarding the safe hand1 ing of chemicals specified in this method. A reference file of material Revision3.3 May1994

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Methods for the Determination s a f e t y d a t a sheets should a l s o be a v a i l a b l e t o a l l personnel i n v o l v e d i n t h e chemical

6.0

EOUIPMENT AND SUPPLIES 6.1

6. 2

I o n Chromatograph 6.1.1

I n s t r u m e n t equipped w i t h a pump capable o f w i t h s t a n d i n g a minimum backpressure o f 2000 p s i and o f d e l i v e r i n g a c o n s t a n t f l o w i n t h e range o f 1-5 mL/min and c o n t a i n i n g no m e t a l p a r t s i n t h e sample, e l u e n t o r r e a g e n t f l o w p a t h .

6.1.2

H e l i u m gas s u p p l y ( H i g h p u r i t y , 99.995%).

6.1.3

P r e s s u r i z e d e l u e n t c o n t a i n e r , p l a s t i c , 1- o r 2-L s i z e .

6.1.4

Sample l o o p s o f v a r i o u s s i z e s (50-25OpL).

6.1.5

A p r e s s u r i z e d r e a g e n t d e l i v e r y module w i t h a m i x i n g t e e and beaded m i x i n g c o i l .

6.1.6

Guard Column - A column p l a c e d b e f o r e t h e s e p a r a t o r column and c o n t a i n i n g a s o r b e n t capable o f removing s t r o n g l y a b s o r b i n g o r g a n i c s and p a r t i c l e s t h a t would o t h e r w i s e damage t h e s e p a r a t o r column (Dionex IonPac NG1 o r e q u i v a l e n t ) .

6.1.7

S e p a r a t o r Column - A column packed w i t h a h i g h c a p a c i t y a n i o n exchange r e s i n capable o f s e p a r a t i n g Cr0,'- from o t h e r sample c o n s t i t u e n t s (Dionex IonPac AS7 o r e q u i v a l e n t ) .

6.1.8

A low-volume f l o w - t h r o u g h c e l l , v i s i b l e lamp d e t e c t o r c o n t a i n i n g no m e t a l p a r t s i n c o n t a c t w i t h t h e e l u e n t f l o w p a t h . D e t e c t i o n wavelength i s a t 530 nm.

6.1.9

Recorder, i n t e g r a t o r o r computer f o r r e c e i v i n g analog o r d i g i t a l s i g n a l s f o r r e c o r d i n g d e t e c t o r response (peak h e i g h t o r a r e a ) as a f u n c t i o n o f t i m e .

Labware - A l l r e u s a b l e labware ( g l a s s , e t c . ) , i n c l u d i n g t h e sample c o n t a i n e r s , l a b o r a t o r y grade d e t e r g e n t and w a t e r , f o r 4 h i n a mixture o f d i l u t e n i t r i c f o l l o w e d by r i n s i n g w i t h t a p w a t e r and NOTE:

quartz, polyethylene, Teflon, s h o u l d be soaked o v e r n i g h t i n r i n s e d w i t h w a t e r , and soaked and h y d r o c h l o r i c a c i d (1+2+9) ASTM t y p e I w a t e r .

Chromic a c i d must n o t be used f o r c l e a p i n g glassware.

6.2.1

Glassware - Class A v o l u m e t r i c f l a s k s and a g r a d u a t e d c y l inder .

6.2.2

A s s o r t e d Class A c a l b r a t e d p p e t t e s .

6.2.3

10-mL ma1e 1u e r - l ock d i sposab e s y r i n g e s . R e v i s i o n 3 . 3 May1994

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6.2.4

0.45-pm s y r i n g e f i l t e r s .

6.2.5

Storage b o t t l e

-

295

ene, l - L c a p a c i t y .

H i g h dens

Sample P r o c e s s i n g Equipment High

density

6.3.1

L i a u i d samDle t r a n s D o r t c o n t a i n e r s p o i y p r o p y l ene, 125-mL c a p a c i t y

6.3.2

Supply o f dry i c e o r r e f r i g e r a n t p a c k i n g and Styrofoam shipment boxes.

6.3.3

pH m e t e r - To r e a d pH range 0-14 w i t h accuracy units.

6.3.4

0.45-pm f i l t e r d i s c s , 7.3-cm d i a m e t e r (Gelman Acro 50A, M f r . No. 4262 o r e q u i v a l e n t ) .

6.3.5

P l a s t i c s y r i n g e f i l t r a t i o n u n i t ( B a x t e r S c i e n t i f i c , Cat. No. 1240 I N o r e q u i v a l e n t ) .

.

-

0.03 pH

7 . 0 REAGENTS AND STANDARDS 7.1

Reagents - A l l c h e m i c a l s a r e ACS grade u n l e s s o t h e r w i s e i n d i c a t e d . 7.1.1

Ammonium h y d r o x i d e , NH,OH, (CASRN 1336-21-6).

(sp.gr.

7.1.2

Ammonium s u l p h a t e , (NH,);O,

7.1.3

1,5-Diphenylcarbazide,

7.1.4

Methanol , HPLC grade.

7.1.5

S u l f u r i c a c i d , c o n c e n t r a t e d (sp.gr.

0.902),

(CASRN 7783-20-2). (CASRN 140-22-7).

1.84).

7.2

Reagent Water - F o r a l l sample p r e p a r a t i o n s and d i l u t i o n s , ASTM Type I w a t e r (ASTM 01193) i s r e q u i r e d . S u i t a b l e w a t e r may be o b t a i n e d by p a s s i n g d i s t i l l e d w a t e r t h r o u g h a mixed bed o f a n i o n and c a t i o n exchange r e s i n s .

7.3

C r ( V 1 ) S t o c k Standard S o l u t i o n - To p r e p a r e a 1000 mg/L s o l u t i o n , d i s s o l v e 4.501 g o f Na,Cr0,'4H,O i n ASTM Type I w a t e r and d i l u t e t o 1 L. T r a n s f e r t o a p o l y p r o p y l e n e s t o r a g e c o n t a i n e r .

7.4

L a b o r a t o r y Reagent B l a n k (LRB) - Aqueous LREs can be prepared by a d j u s t i n g t h e pH o f ASTM Type I w a t e r t o 9-9.5 w i t h t h e same volume o f b u f f e r as i s used for samples.

7.5

L a b o r a t o r y F o r t i f i e d B l a n k (LFB) - To an a l i q u o t o f LRB add an a l i q u o t o f s t o c k s t a n d a r d (Sect. 7 . 3 ) t o produce a f i n a l c o n c e n t r a t i o n o f 100 R e v i s i o n 3 . 3 May1994

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Methods for the Determination p g / L o f C r ( V 1 ) . The LFB must be c a r r i e d t h r o u g h t h e e n t i r e sample p r e p a r a t i o n and a n a l y s i s scheme.

8.0

9.0

7.6

Q u a l i t y C o n t r o l Sample (QCS) - A q u a l i t y c o n t r o l sample must be o b t a i n e d from an o u t s i d e l a b o r a t o r y . D i l u t e an a l i q u o t a c c o r d i n g t o i n s t r u c t i o n s and a n a l y z e w i t h samples. A recommended minimum c o n c e n t r a t i o n f o r t h e QCS i s 10 p g / L .

7.7

E l u e n t - D i s s o l v e 33 g o f ammonium s u l p h a t e i n 500 mL o f ASTM t y p e I w a t e r and add 6.5 mL o f ammonium h y d r o x i d e . D i l u t e t o 1 L w i t h ASTM type I water.

7.8

Post-Column Reagent - D i s s o l v e 0.5 g o f l J 5 - d i p h e n y l c a r b a z i d e i n 100 mL o f HPLC grade methanol. Add t o about 500 mL o f ASTM t y p e I w a t e r c o n t a i n i n g 28 mL o f 98% s u l f u r i c a c i d w h i l e s t i r r i n g . D i l u t e w i t h ASTM t y p e I w a t e r t o 1 L i n a v o l u m e t r i c f l a s k . Reagent i s s t a b l e f o r f o u r o r f i v e days b u t s n o u l d be p r e p a r e d o n l y as needed.

7.9

B u f f e r S o l u t i o n - D i s s o l v e 33 g o f ammonium s u l p h a t e i n 75 mL o f ASTM t y p e I w a t e r and add 6 . 5 mL o f ammonium h y d r o x i d e . D i l u t e t o 100 mL w i t h ASTM t y p e I w a t e r .

SAMPLE COLLECTION, PRESERVATION, AND STORAGE

8.1

P r i o r t o sample c o l l e c t i o n , c o n s i d e r a t i o n s h o u l d be g i v e n t o t h e t y p e o f d a t a r e q u i r e d so t h a t a p p r o p r i a t e p r e s e r v a t i o n and p r e t r e a t m e n t s t e p s can be taken. F i l t r a t i o n and pH adjustment should be performed a t t h e t i m e o f sample c o l l e c t i o n o r as soon t h e r e a f t e r as p r a c t i c a l l y poss ib l e .

8.2

F o r d e t e r m i n a t i o n o f d i s s o l v e d C r ( V I ) , t h e sample s h o u l d be f i l t e r e d t h r o u g h a 0.45-pm f i l t e r . Use a p o r t i o n o f t h e sample t o r i n s e t h e s y r i n g e f i l t r a t i o n u n i t and f i l t e r and t h e n c o l l e c t t h e r e q u i r e d volume o f f i l t r a t e . A d j u s t t h e pH o f t h e sample t o 9-9.5 by adding d r o p w i s e a s o l u t i o n of t h e b u f f e r , p e r i o d i c a l l y c h e c k i n g t h e pH w i t h t h e pH m e t e r . A p p r o x i m a t e l y 10 mL o f sample a r e s u f f i c i e n t f o r t h r e e IC analyses.

8.3

S h i p and s t o r e t h e samples a t 4OC. B r i n g t o ambient t e m p e r a t u r e p r i o r t o a n a l y s i s . Samples must be analyzed w i t h i n 24 h o f c o l l e c t i o n .

QUALITY CONTROL 9.1

Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a f o r m a l q u a l i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f t h i s program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n of l a b o r a t o r y c a p a b i l i t y , and t h e a n a l y s i s o f l a b o r a t o r y r e a g e n t b l a n k s , and f o r t i f i e d b l a n k s and samples as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n performance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f the data thus generated.

9.2

I n i t i a l Demonstration o f Performance (mandatory) R e v i s i o n 3 . 3 May1994

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9.2.1

The initial demonstration of performance is used to characterize instrument performance (MDLs and linear dynamic range) and laboratory performance prior to sample analyses.

9.2.2

Method detection limit (MDL) - - A MDL should be established using reagent water fortified at a concentration of two-five times the estimated detection limit. To determine the MDL value, take seven rep1 icate a1 iquots of the fortified reagent water and process through the entire analytical method. Perform all calculations defined in the method and report the concentration values in the appropriate units. Calculate the MDL as follows:

MDL

=

where:

(t) X ( s ) t = Student’s t value for n-1 degrees of freedom at the 99% confidence level ; t = 3.143 for six degrees of freedom.

s = standard deviation o f the replicate analyses. The MDL must be sufficient to detect Cr (VI) at the required level according to compliance monitoring regulation (Sect. 1.2). The MDL should be determined annually, when a new operator begins work or whenever there is a change i n instrument analytical hardware or operating conditions. 9.2.3

9.3

Linear dynamic range (LDR) -- The LDR should be determined by analyzing a minimum of 7 calibration standards ranging in concentration from 1 pg/L to 5,000 pg/L across all sensitivity settings of the spectrophotometer. Normalize responses by dividing the response by the sensitivity setting multiplier. Perform the 1 inear regression o f normalized response vs. concentration and obtain the constants m and b , where m is the slope of the line and b is the y-intercept. Incrementally analyze standards of higher Concentration until the measured absorbance response, R , of a standard no longer yields a calculated concentration, C,, that is & 10% of the known concentration, C, where C, = ( R b ) / m . That concentration defines the upper limit of the LDR for your instrument and analytical operating conditions. Samples having a concentration that is 2 90% of the upper limit of the LDR must be diluted to fall within the bounds of the current calibration curve concentration range and reanalyzed.

Assessing Laboratory Performance (mandatory) 9.3.1

The laboratory must analyze at least one LRB (Sect. 7 . 4 ) with each set of samples. Reagent blank data are used to assess contamination from a laboratory environment. If the Revision3.3 May1994

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Cr(V1) v a l u e i n t h e r e a g e n t b l a n k exceeds t h e determined M D L , then l a b o r a t o r y o r r e a g e n t contamination should be s u s p e c t e d . Any determined source of contamination should be c o r r e c t e d and t h e samples r e a n a l y z e d .

9.3.2

The l a b o r a t o r y must analyze a t l e a s t one LFB ( S e c t . 7 . 5 ) w i t h each s e t of samples. C a l c u l a t e accuracy a s p e r c e n t recovery ( S e c t . 9 . 4 . 2 ) . I f t h e recovery of Cr(V1) f a l l s o u t s i d e t h e c o n t r o l l i m i t s ( S e c t . 9 . 3 . 3 ) , then t h e procedure i s judged o u t o f c o n t r o l , a n d t h e source of t h e problem should be i d e n t i f i e d and r e s o l v e d b e f o r e c o n t i n u i n g t h e analysis.

9.3.3

U n t i l s u f f i c i e n t d a t a become a v a i l a b l e ( u s u a l l y a minimum o f 20 t o 30 a n a l y s e s ) , a s s e s s 1 a b o r a t o r y performance a g a i n s t r e c o v e r y 1 i m i t s o f 90-110%. When s u f f i c i e n t i n t e r n a l performance d a t a becomes a v a i l a b l e , develop c o n t r o l l i m i t s from t h e p e r c e n t mean r e c o v e r y ( x ) and the s t a n d a r d d e v i a t i o n ( s ) of t h e mean r e c o v e r y . These d a t a a r e used t o e s t a b l i s h upper and lower c o n t r o l l i m i t s a s f o l l o w s :

UPPER CONTROL LIMIT LOWER CONTROL LIMIT

9.4

= =

x t 3s x - 3s

9.3.4

To v e r i f y t h a t t h e instrument i s p r o p e r l y c a l i b r a t e d on a c o n t i n u i n g b a s i s , r u n a L R B and a I P C ( S e c t . 3 . 3 ) a f t e r every t e n a n a l y s e s . The r e s u l t s of a n a l y s e s of s t a n d a r d s w i l l i n d i c a t e whether t h e c a l i b r a t i o n remains v a l i d . I f t h e measured c o n c e n t r a t i o n of t h e I P C ( a midpoint c a l i b r a t i o n s t a n d a r d ) d e v i a t e s from t h e t r u e c o n c e n t r a t i o n by more than t5%, perform a n o t h e r a n a l y s i s of t h e LPC. I f the d i s c r e p a n c y i s s t i l l +5% of the known c o n c e n t r a t i o n then the i n s t r u m e n t must be r e c a l i b r a t e d and t h e p r e v i o u s t e n samples r e a n a l y z e d . The i n s t r u m e n t response from t h e c a l i b r a t i o n check may be used f o r r e c a l i b r a t i o n purposes.

9.3.5

Q u a l i t y c o n t r o l sample (QCS) - Each q u a r t e r , t h e l a b o r a t o r y should a n a l y z e one o r more QCS. I f c r i t e r i a provided with t h e QCS a r e not w i t h i n +lo% of t h e s t a t e d v a l u e , c o r r e c t i v e a c t i o n must be taken and documented.

Assessing Analyte Recovery and Data Q u a l i t y 9.4.1

The l a b o r a t o r y must add a known amount o f Cr(V1) t o a minimum of 10% o f samples. The c o n c e n t r a t i o n l e v e l can be t h e same a s t h a t of t h e l a b o r a t o r y f o r t i f i e d blank (Sect. 7.5).

9.4.2

C a l c u l a t e t h e p e r c e n t recovery f o r Cr(V1) c o r r e c t e d f o r background c o n c e n t r a t i o n measured i n t h e u n f o r t i f i e d sample, and compare t h i s v a l u e t o t h e c o n t r o l l i m i t s e s t a b l i s h e d in S e c t . 9 . 3 . 3 f o r t h e a n a l y s i s o f LF6s. F o r t i f i e d recovery R e v i s i o n 3 . 3 May1994

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calculations are not required if the concentration of Cr(V1) added is less than 2X the sample background concentration. Percent recovery may be calculated in units appropriate to the matrix, using the following equation:

c, - c R =

x

100

F

where : R = percent recovery C,= fortified sample concentration C = sample background concentration F = concentration equivalent of Cr(V1) added to sample 9.4.3

If the recovery of Cr(V1) falls outside control limits established in Section 9.3.3 and the recovery obtained for the LFB was shown to be in control (Sect. 9 . 3 ) ’ the recovery problem encountered with the fortified sample is judged to be matrix related, not system related. The result for Cr(V1) in the unfortified sample must be labelled ’suspect matrix’.

10 0 CALIBRATION AND STANDARDIZATION

10.1 Establish IC operating conditions as indicated in Table 2. The flow rate of the eluent pump is set at 1 . 5 mL/min and the pressure of the

reagent delivery module adjusted so that the final flow rate of the post column reagent (Sect. 7.8) from the detector is 2.0 mL/min. This requires manual adjustment and measurement of the final flow rate using a graduated cylinder and a stop watch. A warm up period of approximately 30 min after the flow rate has been adjusted is recommended and the flow rate should be checked prior to calibration and sample analysis . 10.2 Injection sample loop size should be chosen based on anticipated

sample concentrations and the selected sensitivity setting of the spectrophotometer. A 250-pL loop was used to establish the method detection limits in Table 1. A 50-pL loop is normally sufficient for higher concentrations. The sample volume used to load the sample loop should be at least 10 times the loop size so that all tubing in contact with sample is thoroughly flushed with new sample to minimize cross-contamination. 10.3 Before using the procedure (Section 11.0) to analyze samples, there

must be data available documenting initial demonstration of performance. The required data and procedure is described in Section 9.2. This data must be generated using the same instrument operating conditions and calibration routine to be used for sample analysis. Revision3.3 May1994

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These documented data must be kept on file and be available for review by the data user. 1 0 . 4 The recommended calibration routine is given in Section 1 1 . 3 . 11.0 PROCEDURE

11.1 Filtered, pH adjusted samples at 4OC should be brought to

ambient temperature prior to analysis. 1 1 . 2 Initiate instrument operating configuration described in Section 1 0 and Table 2. 11.3 Calibration - Before samples are analyzed a calibration should be

performed using a minimum of three calibration solutions that bracket the anticipated concentration range of the samples. Calibration standards should be prepared from the stock standard (Sect. 7 . 3 ) by appropriate dilution with ASTM type I water (Sect. 7 . 2 ) in volumetric flasks. The solution should be adjusted to pH 9-9.5 with the buffer solution (Sect. 7 . 9 ) prior to final dilution.

or area) versus analyte concentration over a concentration range of one or two orders of magnitude. The calibration range should bracket the anticipated concentration range of samples. The coefficient o f correlation (r) for the curve should be 0 . 9 9 9 or greater.

1 1 . 4 Construct a calibration curve of analyte response (peak height

11.5 Draw into a new, unused syringe (Sect. 6 . 2 . 3 ) approximately 3 mL of sample. Inject 1OX the volume of the sample loop into the injection

valve of the IC. Sample concentrations that exceed the calibration range must be diluted and reanalyzed.

of samples, the laboratory must comply with the required quality control described in Sections 9 . 3 and 9.4.

1 1 . 6 During the analysis 12.0

DATA ANALYSIS AND CALCULATIONS 1 2 . 1 The sample concentration can be calculated from the calibration curve.

Report values in pg/L. Sample concentrations must be corrected for any Cr(V1) contamination found in the LRB. 12.2 The QC data obtained during sample analyses provide an indication of

the quality of sample data and should be reported with sample results. 13.0 METHOD PERFORMANCE

1 3 . 1 Instrumental operating conditions used for single-laboratory testing of the method are summarized in Table 2 . MDLs for dissolved Cr(V1) in

five matrix waters are listed in Table 1. 1 3 . 2 Single-analyst precision and accuracy data for five matrix waters,

drinking water, deionized water, groundwater, treated municipal sewage Revision3.3 May1994

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wastewater, and treated electroplating wastewater are listed in Table 3.

13.3 Pooled Precision and Accuracy: This method was tested by 21 volunteer laboratories in a joint study by the USEPA and the American Society for Testing and Materials (ASTM). Mean recovery and accuracy for Cr(V1) (as CrOb2.) was determined from the retained data of 13 laboratories in reagent water, drinking water, ground water, and various industrial wastewaters. For reagent water, the mean recovery and the overall, and single-analyst relative standard deviations were 105%, 7.8% and 3.9% respectively. For the other matrices combined, the same values were 96.7%, 11.9% and 6.3%, respectively. Table 4 contains the linear equations that describe the single-analyst standard deviation, overall standard deviation and mean recovery o f Cr(Y1) in reagent water and matrix water. 14.0 POLLUTION PREVENTION

14.1 Pollution prevention encompasses any technique that reduces or eliminates the quantity or toxicity of waste at the point of generation. Numerous opportunities for pollution prevention exist in laboratory operation. The EPA has established a preferred hierarchy of environmental management techniques that places pollution prevention as the management option of first choice. Whenever feasible, laboratory personnel should use pollution prevention techniques to address their waste generation. When wastes cannot be feasibly reduced at the source, the Agency recommends recycling as the next best option. 14.2 For information about pollution prevention that may be applicable to laboratories and research institutions, consult Less i s B e t t e r : L a b o r a t o r y Chemical Management f o r Waste R e d u c t i o n , available from the American Chemical Society’s Department of Government Relations and Science Policy, 1155 16th Street N.W., Washington D.C. 20036, (202)872-4477. 15.0

WASTE MANAGEMENT 15.1 The Environmental Protection Agency requires that laboratory waste

management practices be conducted consistent with all applicable rule and regulations. The Agency urges laboratories to protect the air, water, and land by minimizing and controlling all releases from hoods and bench operations, complying with the letter and spirit of any sewer discharge permits and regulations, and by complying with all solid and hazardous waste regulations, particularly the hazardous waste identification rules and land disposal restrictions. For further information on waste management consult The I a s t e Management Manual f o r L a b o r a t o r y P e r s o n n e l , available from the American Chemical Society at the address listed in the Sect. 14.2. Revision3.3 May1994

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16.0 REFERENCES

1.

G l a s e r , J.A., F o e r s t , D . L . , McKee, G . D . , Quave, S . A . and Budde, W . L . , and Technol., Vol.15, "Trace Analyses f o r Wastewaters", E n v i r o n . N0.12, 1981, pp.1426-1435.

2.

Dionex T e c h n i c a l Note No. 26, May 1990.

3.

Laboratories," "Proposed OSHA S a f e t y and H e a l t h Standards, O c c u p a t i o n a l S a f e t y and H e a l t h A d m i n i s t r a t i o n , Federal R e g i s t e r , J u l y 24, 1986.

4.

"OSHA S a f e t y and H e a l t h Standards, General I n d u s t r y , " (29 CFR 1910), O c c u p a t i o n a l S a f e t y and H e a l t h A d m i n i s t r a t i o n , OSHA 2206, r e v i s e d January 1976.

m.

R e v i s i o n 3 . 3 May1994

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17.0 TABLES. DIAGRAMS, FLOWCHARTS AND VALIDATION DATA

TABLE 1.

METHOD DETECTION LIMIT FOR C R ( V 1 )

Conc. Used t o Compute MDL uqlL

M a t r i x TvDe

MDL uq/L

Reagent Water

0.4

D r i n k i n g Water

0.3

Ground Water

0.3

Primary Sewage wastewater

0.3

Electroplating wastewater

2

0.3

TABLE 2. ION CHROMATOGRAPHIC CONDITIONS Columns: Eluent:

Guard Column - Dionex IonPac NG1 Separator Column - Dionex IonPac AS7

250 mM (NH,),SO, 100 mM NH,OH Flow r a t e = 1.5 mL/min

Post-Column Reagent:

Detector:

2mM Diphenylcarbohydrazide 10% v / v CH,OH 1 N H,SO, Flow r a t e = 0.5 mL/min

V i s i b l e 530 nm

R e t e n t i o n Time:

3 . 8 min

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304

Methods for the Determination TABLE 3 . SINGLE ANALYST PRECISION AND ACCURACY

Cr(V1)

Sample Type

(bCg/L) (a)

RPD ( b )

Mean Recovery (%)

100

100

0.8

1000

100

0.0

100

105

6.7

1000

98

1.5

100

98

0.0

1000

96

0.8

Primary sewage wastewater eff1 uent

100

100

0.7

1000

104

2.7

El ectropl ating wastewater eff1 uent

100

99

0.4

1000

101

0.4

Reagent Water Drinking Water Groundwater

(a) Sample fortified at this concentration level. ( b ) RPD - relative percent difference between duplicates. TABLE 4 .

SINGLE-ANALYST PRECISION, OVERALL PRECISION AND RECOVERY FROM MULTILABORATORY STUDY

Reagent Water (6-960 bCg/L)

Matrix Water (6-960 bCg/L)

Mean Recovery

X

X

Overall Standard Deviation

sR

=

0.035X t 0.893

sR

=

0.059X t 1.055

Single-Analyst Standard Devi at ion

S, =

0.021X t 0.375

S, =

0.041X t 0.393

=

1.020C t 0.592

=

0.989C - 0.411

Mean concentration, pg/L, exclusive of outliers. True value, p g / L . sR Overall standard deviation. s, Single-analyst standard deviation.

X C

Revision3.3 M a y 1 9 9 4

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METHOD 245.1 DETERMINATION OF MERCURY I N WATER BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY

R e v i s i o n 3.0 EMMC V e r s i o n

J.F. Kopp, M.C. tongbottom, and L.B. L o b r i n g - Mercury i n Water (Cold Vapor Technique), R e v i s i o n 1.0, (1972) J.F.

Kopp and L.B. L o b r i n g - Method 245.1,

L.B.

L o b r i n g and B.B. P o t t e r - Method 245.1,

J.W. O ’ D e l l , B.B. P o t t e r , L.B. R e v i s i o n 3.0 (1994)

R e v i s i o n 2.0 (1979)

Revision 2.3 (1991)

L o b r i n g , and T.D. M a r t i n

-

Method 245.1,

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

306

Methods for the Determination METHOD 245.1 DETERMINATION OF MERCURY I N WATER BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY

1.0

SCOPE AND APPLICATION

1.1 T h i s procedure’ measures t o t a l mercury d r i n k i n g , s u r f a c e , ground, domestic wastewater.

Analyte Mercury

2.0

sea,

(organic brackish waters,

t

inorganic) i n i n d u s t r i a l and

Chemical A b s t r a c t s S e r v i c e R e g i s t r y Number (CASRN) 7439-97-6

1.2

The range o f t h e method i s 0.2 t o 10 p g Hg/L. The range may be extended above o r below t h e normal range by i n c r e a s i n g o r d e c r e a s i n g sample s i z e . However, t h e a c t u a l method d e t e c t i o n l i m i t and l i n e a r w o r k i n g range w i l l be dependent on t h e sample m a t r i x , t y p e o f i n s t r u m e n t a t i o n c o n f i g u r a t i o n , and s e l e c t e d o p e r a t i n g c o n d i t i o n s .

1.3

Reduced volume o r semi-automated v e r s i o n s o f t h i s method, t h a t use B same r e a g e n t s and m o l a r r a t i o s , a r e a c c e p t a b l e p r o v i d e d t h e y meet the qua1 i t y c o n t r o l and performance r e q u i r e m e n t s s t a t e d i n t h e m e t h o d (Sect. 9.0).

1.4

F o r r e f e r e n c e where t h i s method i s approved f o r use i n compliance m o n i t o r i n g programs [e.g., Clean Water A c t (NPDES) o r Safe D r i n k i n g Water A c t (SDWA)] c o n s u l t b o t h t h e a p p r o p r i a t e s e c t i o n s o f t h e Code o f Federal R e g u l a t i o n (40 CFR P a r t 136 Table 1B f o r NPDES, and P a r t 141 § 141.23 f o r d r i n k i n g w a t e r ) , and t h e l a t e s t Federal R e g i s t e r announcements.

SUMMARY OF METHOD 2.1

A known p o r t i o n o f a w a t e r sample i s t r a n s f e r r e d t o a BOD b o t t l e , e q u i v a l e n t ground g l a s s s t o p p e r e d f l a s k o r o t h e r s u i t a b l e c l o s e d c o n t a i n e r . I t i s d i g e s t e d i n d i l u t e d p o t a s s i u m permanganate-potassium p e r s u l f a t e s o l u t i o n s and o x i d i z e d f o r 2 h a t 95°C. Mercury i n t h e d i g e s t e d w a t e r sample i s reduced w i t h stannous c h l o r i d e t o elemental mercury and measured by t h e c o n v e n t i o n a l c o l d vapor a t o m i c a b s o r p t i o n technique.

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307

DEFINITIONS

3.1

C a l i b r a t i o n B l a n k - A volume o f r e a g e n t w a t e r a c i d i f i e d w i t h t h e same a c i d m a t r i x as i n t h e c a l i b r a t i o n s t a n d a r d s . The c a l i b r a t i o n b l a n k i s a z e r o s t a n d a r d and i s used t o a u t o - z e r o t h e i n s t r u m e n t .

3.2

C a l i b r a t i o n Standard (CAL) - A s o l u t i o n p r e p a r e d f r o m t h e d i l u t i o n o f s t o c k s t a n d a r d s o l u t i o n s . The CAL s o l u t i o n s a r e used t o c a l i b r a t e t h e i n s t r u m e n t response w i t h r e s p e c t t o a n a l y t e c o n c e n t r a t i o n .

3.3

F i e l d Reagent B l a n k (FRB) - An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i x t h a t i s p l a c e d i n a sample c o n t a i n e r i n t h e l a b o r a t o r y and t r e a t e d as a sample i n a l l r e s p e c t s , i n c l u d i n g shipment t o t h e sampling s i t e , exposure t o t h e sampling s i t e c o n d i t i o n s , storage, p r e s e r v a t i o n , and a l l a n a l y t i c a l procedures. The purpose o f t h e FRB i s t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e f i e l d environment.

3.4

I n s t r u m e n t Performance Check ( I P C ) S o l u t i o n - A s o l u t i o n o f t h e method a n a l y t e , used t o e v a l u a t e t h e performance o f t h e i n s t r u m e n t system w i t h r e s p e c t t o a d e f i n e d s e t o f method c r i t e r i a .

3.5

L a b o r a t o r y D u p l i c a t e s (LD1 and LD2) - Two a l i q u o t s o f t h e same sample t a k e n i n t h e l a b o r a t o r y and analyzed s e p a r a t e l y w i t h i d e n t i c a l procedures. Analyses o f LD1 and LD2 i n d i c a t e s p r e c i s i o n a s s o c i a t e d w i t h l a b o r a t o r y procedures, b u t n o t w i t h sample c o l l e c t i o n , p r e s e r v a t i o n , o r s t o r a g e procedures.

3.6

L a b o r a t o r y F o r t i f i e d B l a n k (LFB) - An a l i q u o t o f LRB t o which a known q u a n t i t y o f t h e method a n a l y t e i s added i n t h e l a b o r a t o r y . The LFB i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o determine whether t h e methodology i s i n c o n t r o l and whether t h e l a b o r a t o r y i s capable o f making a c c u r a t e and p r e c i s e measurements.

3.7

L a b o r a t o r y F o r t i f i e d Sample M a t r i x (LFM) - An a l i q u o t o f an e n v i r o n m e n t a l sample t o w h i c h a known q u a n t i t y o f t h e method a n a l y t e i s added i n t h e l a b o r a t o r y . The LFM i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e sample m a t r i x contributes bias t o the analytical results. The background c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be determined i n a s e p a r a t e a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s .

3.8

L a b o r a t o r y Reagent B l a n k (LRB) - An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a l l glassware, equipment, s o l v e n t s , r e a g e n t s , and i n t e r n a l s t a n d a r d s t h a t a r e used w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f t h e method a n a l y t e o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e l a b o r a t o r y environment, r e a g e n t s , o r apparatus.

3.9 L i n e a r Dynamic Range (LOR) - The c o n c e n t r a t i o n range o v e r which t h e i n s t r u m e n t response t o an a n a l y t e i s l i n e a r . Revision 3 . 0

May 1994

308

Methods for the Determination 3.10 Method D e t e c t i o n L i m i t (MDL) - The minimum C o n c e n t r a t i o n o f an a n a l y t e t h a t can be i d e n t i f i e d , measured, and r e p o r t e d w i t h 99% c o n f i d e n c e t h a t the analyte concentration i s g r e a t e r than zero.

3 . 1 1 Q u a l i t y C o n t r o l Sample (QCS) - A s o l u t i o n o f t h e method a n a l y t e o f known c o n c e n t r a t i o n which i s used t o f o r t i f y an a l i q u o t o f LRB o r sample m a t r i x . The QCS i s o b t a i n e d f r o m a source e x t e r n a l t o t h e 1 a b o r a t o r y and d i f f e r e n t f r o m t h e source o f c a l ib r a t i o n s t a n d a r d s . I t i s used t o check e i t h e r l a b o r a t o r y o r i n s t r u m e n t performance. 3.12 Standard A d d i t i o n - The a d d i t i o n o f a known amount o f a n a l y t e t o t h e sample i n o r d e r t o d e t e r m i n e t h e r e l a t i v e response o f t h e d e t e c t o r t o an a n a l y t e w i t h i n t h e sample m a t r i x . The r e l a t i v e response i s t h e n used t o assess e i t h e r an o p e r a t i v e m a t r i x e f f e c t o r t h e sample a n a l y t e concentration. 3.13 S t o c k Standard S o l u t i o n - A c o n c e n t r a t e d s o l u t i o n c o n t a i n i n g one o r more method a n a l y t e s p r e p a r e d i n t h e l a b o r a t o r y u s i n g assayed r e f e r e n c e m a t e r i a l s o r purchased f r o m a r e p u t a b l e commercial source.

4.0

INTERFERENCES 4.1

I n t e r f e r e n c e s have been r e p o r t e d f o r w a t e r s c o n t a i n i n g s u l f i d e , c h l o r i d e , copper and t e l l u r i u m . O r g a n i c compounds which have broad band UV absorbance (around 253.7 nm) a r e c o n f i r m e d i n t e r f e r e n c e s The concentration l e v e l s f o r interferants are d i f f i c u l t t o define. This suggests t h a t q u a l i t y c o n t r o l procedures ( S e c t . 9) must be s t r i c t l y f o l 1owed.

.

5.0

4.2

V o l a t i l e m a t e r i a l s ( e . g . c h l o r i n e ) w h i c h absorb a t 253.7 nm w i l l cause a p o s i t i v e i n t e r f e r e n c e . I n o r d e r t o remove any i n t e r f e r i n g v o l a t i l e m a t e r i a l s , t h e dead a i r space i n t h e d i g e s t i o n vessel (BOD b o t t l e ) s h o u l d be purged b e f o r e a d d i t i o n o f stannous c h l o r i d e s o l u t i o n .

4.3

Low l e v e l mercury sample p r e p a r a t i o n , d i g e s t i o n , and a n a l y s i s may be s u b j e c t t o e n v i r o n m e n t a l c o n t a m i n a t i o n i f preformed i n areas w i t h I@ ambient backgrounds where mercury was p r e v i o u s l y employed as an a n a l y t i c a l r e a g e n t i n analyses such as t o t a l K j e l d a h l n i t r o g e n (TKN) o r chemical oxygen demand (COO).

SAFETY 5.1

The t o x i c i t y and c a r c i n o g e n i c i t y o f each r e a g e n t used i n t h i s method has n o t been f u l l y e s t a b l i s h e d . Each chemical s h o u l d be r e g a r d e d as a p o t e n t i a l h e a l t h hazard and exposure $0 t h e s e compounds s h o u l d be m i n i m i z e d by good l a b o r a t o r y p r a c t i c e s . Normal accepted l a b o r a t o r y s a f e t y p r a c t i c e s s h o u l d be f o l l o w e d d u r i n g r e a g e n t p r e p a r a t i o n and i n s t r u m e n t o p e r a t i o n . Always wear s a f e t y g l a s s e s o r f u l l - f a c e s h i e l d f o r eye p r o t e c t i o n when w o r k i n g w i t h t h e s e r e a g e n t s . Each l a b o r a t o r y i s responsible f o r maintaining a current safety plan, a current awareness f i l e o f OSHA r e g u l a t i o n s r e g a r d i n g t h e s a f e h a n d l i n g o f t h e chemicals s p e c i f i e d i n t h i s m e t h ~ d . ~ ' R e v i s i o n 3.0

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5.2

Mercury compounds a r e h i g h l y t o x i c i f swallowed, i n h a l e d , o r absorbed through t h e s k i n . Analyses s h o u l d be conducted i n a l a b o r a t o r y exhaust hood. The a n a l y s t should use chemical r e s i s t a n t g l o v e s when h a n d l i n g c o n c e n t r a t e d mercury s t a n d a r d s .

5.3

The a c i d i f i c a t i o n o f samples c o n t a i n i n g r e a c t i v e m a t e r i a l s may r e s u l t i n t h e r e l e a s e o f t o x i c gases, such as c y a n i d e s o r s u l f i d e s . A c i d i f i c a t i o n o f samples should be done i n a fume hood.

5.4

A l l p e r s o n n e l h a n d l i n g e n v i r o n m e n t a l samples known t o c o n t a i n o r t o have been i n c o n t a c t w i t h human waste s h o u l d be immunized a g a i n s t known d i s e a s e c a u s a t i v e agents.

EQUIPMENT AND SUPPLIES 6.1

Atomic A b s o r p t i o n C o l d Vapor System 6.1.1

Atomic A b s o r p t i o n Spectrophotometer - Any atomic a b s o r p t i o n u n i t h a v i n g an open sample p r e s e n t a t i o n area i n which t o mount t h e a b s o r p t i o n c e l l i s s u i t a b l e . I n s t r u m e n t s e t t i n g s recommended by t h e p a r t i c u l a r m a n u f a c t u r e r s h o u l d be f o l l o w e d . The use o f background c o r r e c t i o n i s recommended, b u t i s n o t mandatory.

6.1.2

Mercury H o l l o w Cathode Lamp - S i n g l e element h o l l o w cathode 1amp o r e l e c t r o d e l e s s d i s c h a r g e 1 amp and a s s o c i a t e d power supply.

6.1.3

A b s o r p t i o n C e l l - Standard spectrophotometer c e l l s 10-cm l o n g , h a v i n g q u a r t z windows may be used. S u i t a b l e c e l l s may be c o n s t r u c t e d f r o m p l e x i g l a s s t u b i n g , 1 - i n . 0.0. by 4 1/2in. long. The ends a r e ground p e r p e n d i c u l a r t o t h e l o n g i t u d i n a l a x i s and q u a r t z windows (1-in. d i a m e t e r by 1 / 1 6 - i n . t h i c k n e s s ) a r e cemented i n p l a c e . Gas i n l e t and o u t l e t p o r t s ( a l s o o f p l e x i g l a s s b u t 1 / 4 - i n . O.D.) a r e a t t a c h e d a p p r o x i m a t e l y 1 / 2 - i n . from each end. The c e l l i s s t r a p p e d t o a b u r n e r f o r s u p p o r t and a l i g n e d i n t h e f i g h t beam t o g i v e t h e maximum t r a n s m i t t a n c e .

6.1.4

A e r a t i o n Tubing - I n e r t m e r c u r y - f r e e t u b i n g i s used f o r passage o f mercury vapor from t h e sample b o t t l e t o t h e absorption c e l l . I n some systems, mercury vapor i s recycled. S t r a i g h t g l a s s t u b i n g t e r m i n a t i n g i n a coarse porous g l a s s a s p i r a t o r i s used f o r p u r g i n g mercury r e l e a s e d f r o m t h e w a t e r sample i n t h e BOD b o t t l e .

6.1.5

A i r Pump - Any pump ( p r e s s u r e o r vacuum system) capable o f p a s s i n g a i r 1 L/min i s used. Regulated compressed a i r can be used i n an open one-pass system.

6.1.6

D r y i n g Tube - Tube ( 6 - i n . x 3 / 4 - i n . OD) c o n t a i n i n g 20 g o f magnesium p e r c h l o r a t e . The f i l l e d t u b e i s i n s e r t e d ( i n R e v i s i o n 3.0

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Methods for the Determination l i n e ) between t h e BOD b o t t l e and t h e a b s o r p t i o n t u b e . In p l a c e o f t h e magnesium p e r c h l o r a t e d r y i n g tube, a small r e a d i n g lamp i s p o s i t i o n e d t o r a d i a t e h e a t ( a b o u t 10°C above ambient) on t h e a b s o r p t i o n c e l l . Heat f r o m t h e lamp prevents water condensation i n the c e l l . 6.1.7

Recorder - Any r n u l t i - r a n g e v a r i a b l e speed r e c o r d e r o r d a t a system t h a t i s c o m p a t i b l e w i t h t h e UV d e t e c t i o n system i s suitable.

Note:

I n s t r u m e n t s designed s p e c i f i c a l l y f o r mercury measurement u s i n g t h e c o l d vapor t e c h n i q u e a r e c o m m e r c i a l l y a v a i l a b l e and may be s u b s t i t u t e d f o r t h e a t o m i c a b s o r p t i o n c o l d vapor system d e s c r i b e d above.

6.2

Flowmeter, capable o f measuring an a i r f l o w o f 1 L/min.

6.3

A w a t e r b a t h w i t h a covered t o p and c a p a c i t y t o m a i n t a i n a w a t e r d e p t h o f 2 t o 3 i n c h e s a t 95°C.

6.4

A n a l y t i c a l balance, w i t h c a p a b i l i t y t o measure t o 0.1 mg, f o r use i n w e i g h i n g r e a g e n t s and p r e p a r i n g s t a n d a r d s .

6.5

Labware - A l l r e u s a b l e labware s h o u l d be s u f f i c i e n t l y c l e a n f o r t h e t a s k o b j e c t i v e s . P a r t i c u l a r a t t e n t i o n s h o u l d be g i v e n t o a l l ground g l a s s s u r f a c e s d u r i n g c l e a n i n g . R o u t i n e l y a l l i t e m s s h o u l d be soaked i n 30% HNO, and r i n s e d t h r e e t i m e s i n r e a g e n t w a t e r . Digestion c o n t a i n e r s used i n sample p r e p a r a t i o n t h a t do n o t r i n s e c l e a n o f t h e p r e v i o u s sample s h o u l d be washed w i t h a d e t e r g e n t s o l u t i o n p r i o r t o acid cleaning. 6.5.1

Glassware - V o l u m e t r i c f l a s k s and g r a d u a t e d c y l i n d e r s .

6.5.2

BOD b o t t l e s containers).

6.5.3

Assorted c a l i b r a t e d p i p e t t e s .

(or

other

equivalent

suitable

closed

7.. O REAGENTS AND STANDARDS 7.1

Reagents may c o n t a i n e l e m e n t a l i m p u r i t i e s which b i a s a n a l y t i c a l results. A l l r e a g e n t s s h o u l d be assayed by t h e chemical m a n u f a c t u r e r f o r mercury and meet ACS s p e c i f i c a t i o n s . The assayed mercury l e v e l o f a l l s o l i d r e a g e n t s used i n t h i s method s h o u l d n o t exceed 0.05 ppm. I t i s recommended t h a t t h e l a b o r a t o r y a n a l y s t assay a l l r e a g e n t s f o r mercury.

7.2

Reagent Water, ASTM t y p e I15.

7.3

N i t r i c A c i d (HNO,), c o n c e n t r a t e d ( s p . g r . i s n o t t o exceed 1 p g / L .

1 . 4 1 ) , assayed mercury l e v e l

R e v i s i o n 3.0

May 1994

Metals 7.3.1 7.4

N i t r i c a c i d (1+1) - Add 500 mL c o n c e n t r a t e d HNO, r e a g e n t w a t e r and d i l u t e t o 1 L .

S u l f u r i c A c i d (H,SO,), concentrated (sp.gr. l e v e l i s n o t t o exceed 1 pg/L. 7.4.1

311

t o 400 mL

1 . 8 4 ) , assayed mercury

to S u l f u r i c a c i d , 0 . 5 N - S l o w l y add 14.0 mL o f conc. H,SO, 500 mL o f r e a g e n t w a t e r and d i l u t e t o 1 L w i t h r e a g e n t w a t e r .

7.5

Mercury standard, s t o c k , 1 mL = 100 p g Hg: DO NOT DRY. CAUTION: h i g h l y t o x i c element. D i s s o l v e 0.1354 g HgCl i n 75 mL r e a g e n t water. Add 50.0 mL c o n c e n t r a t e d HNO, ( S e c t . 7.3) a n t d i l u t e t o volume i n l - L volumetric f l a s k w i t h reagent water,

7.6

Mercury c a l i b r a t i o n s t a n d a r d (CAL) - To each v o l u m e t r i c f l a s k used f o r s e r i a l d i l u t i o n s , a c i d i f y w i t h (0.1 t o 0.2% by volume) HNO, (Sect. 7.3). U s i n g mercury s t o c k s t a n d a r d ( S e c t . 7 . 5 ) , make s e r i a l d i l u t i o n s t o o b t a i n a c o n c e n t r a t i o n o f 0 . 1 p g Hg/mL.

7.7

Potassium permanganate s o l u t i o n - D i s s o l v e 5 g o f KMnO, reagent water.

i n 100 mL o f

7.8

Potassium p e r s u l f a t e s o l u t i o n - D i s s o l v e 5 g o f K,SO ,, reagent water.

i n 100 mL o f

7.9

Sodium chloride-hydroxylammonium c h l o r i d e s o l u t i o n - D i s s o l v e 12 g o f NaCl and 12 g o f h y d r o x y l a m i n e h y d r o c h l o r i d e (NH,OH'HCl) i n 100 mL r e a g e n t water. (Hydroxylamine s u l f a t e (NH20H),'H2S0, may be used i n p l a c e o f hydroxylamine hydrochloride.)

7.10 Stannous c h l o r i d e s o l u t i o n - Add 25 g o f SnC1;2H20 t o 250 mL o f 0.5 N H,SO,. ( S e c t . 7.4.1). T h i s m i x t u r e i s a suspension and should be s t i r r e d c o n t i n u o u s l y d u r i n g use. 7.11 B l a n k s - Three t y p e s o f b l a n k s a r e r e q u i r e d f o r t h e a n a l y s i s . The c a l i b r a t i o n b l a n k i s used i n e s t a b l i s h i n g t h e a n a l y t i c a l curve, t h e l a b o r a t o r y r e a g e n t b l a n k i s used t o assess p o s s i b l e c o n t a m i n a t i o n from t h e sample p r e p a r a t i o n procedure, and t h e l a b o r a t o r y f o r t i f i e d b l a n k i s used t o assess r o u t i n e l a b o r a t o r y performance. 7.11.1

The c a l i b r a t i o n b l a n k must c o n t a i n a l l r e a g e n t s i n t h e same c o n c e n t r a t i o n s and i n t h e same volume as used i n p r e p a r i n g t h e c a l ib r a t i o n s o l u t i o n s .

7.11.2

The l a b o r a t o r y r e a g e n t b l a n k (LRB) i s prepared i n t h e manner as t h e c a l i b r a t i o n b l a n k e x c e p t t h e LRB must be c a r r i e d t h r o u g h t h e e n t i r e sample p r e p a r a t i o n scheme.

7.11.3

The l a b o r a t o r y f o r t i f i e d b l a n k (LFB) i s prepared by f o r t i f y i n g a sample s i z e volume o f l a b o r a t o r y r e a g e n t b l a n k s o l u t i o n w i t h mercury t o a s u i t a b l e c o n c e n t r a t i o n o f > 1 O X t h e MDL, b u t < R e v i s i o n 3.0

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312

Methods for the Determination t h e m i d p o i n t c o n c e n t r a t i o n o f t h e c a l i b r a t i o n c u r v e . The LFB must be c a r r i e d t h r o u g h t h e e n t i r e sample p r e p a r a t i o n scheme. 7 . 1 2 I n s t r u m e n t Performance Check (IPC) S o l u t i o n - The I P C s o l u t i o n i s used It t o p e r i o d i c a l l y v e r i f y i n s t r u m e n t performance d u r i n g a n a l y s i s . must c o n t a i n a l l r e a g e n t s i n t h e same c o n c e n t r a t i o n a s t h e c a l i b r a t i o n s o l u t i o n s and mercury a t an a p p r o p r i a t e c o n c e n t r a t i o n t o approximate the midpoint o f t h e c a l i b r a t i o n curve. The I P C s o l u t i o n should be p r e p a r e d f r o m t h e same CAL s t a n d a r d ( S e c t . 7.6) as used t o p r e p a r e t h e c a l i b r a t i o n s o l u t i o n s . Agency programs may s p e c i f y o r r e q u e s t t h a t a d d i t i o n a l i n s t r u m e n t performance check s o l u t i o n s be p r e p a r e d a t s p e c i f i e d c o n c e n t r a t i o n s i n o r d e r t o meet p a r t i c u l a r program needs.

7.13 Q u a l i t y C o n t r o l Sample (QCS)

- For i n i t i a l and p e r i o d i c v e r i f i c a t i o n o f c a l i b r a t i o n s t a n d a r d s and i n s t r u m e n t performance, a n a l y s i s o f a QCS i s required. The QCS must be o b t a i n e d f r o m an o u t s i d e source d i f f e r e n t from t h e s t a n d a r d s t o c k s o l u t i o n , b u t p r e p a r e d i n t h e same manner as t h e c a l i b r a t i o n s o l u t i o n s . The c o n c e n t r a t i o n o f t h e mercury i n t h e QCS s o l u t i o n s h o u l d be such t h a t t h e r e s u l t i n g s o l u t i o n w i l l p r o v i d e an absorbance r e a d i n g near t h e m i d p o i n t o f t h e c a l i b r a t i o n curve. The QCS s h o u l d be analyzed q u a r t e r l y o r more f r e q u e n t l y as needed t o meet d a t a - q u a l i t y needs.

8.0

SAMPLE COLLECTION, PRESERVATION, AND STORAGE

8.1 Because o f t h e extreme s e n s i t i v i t y o f t h e a n a l y t i c a l procedure and t h e presence o f mercury i n a l a b o r a t o r y environment, c a r e must be taken t o a v o i d e x t r a n e o u s c o n t a m i n a t i o n . Sampling d e v i c e s , sample c o n t a i n e r s and p l a s t i c i t e m s s h o u l d be determined t o be f r e e o f mercury; t h e sample s h o u l d n o t be exposed t o any c o n d i t i o n i n t h e l a b o r a t o r y t h a t may r e s u l t i n c o n t a m i n a t i o n f r o m a i r b o r n e mercury vapor.

8.2

F o r t h e d e t e r m i n a t i o n o f t o t a l mercury ( i n o r g a n i c t o r g a n i c ) i n aqueous samples, samples a r e not f i l t e r e d , b u t a c i d i f i e d w i t h (ltl) n i t r i c a c i d ( S e c t . 7.3.1) t o pH < 2 ( n o r m a l l y , 3 mL o f (1i-1) a c i d p e r l i t e r o f sample i s s u f f i c i e n t f o r most ambient and d r i n k i n g water samples). P r e s e r v a t i o n may be done a t t h e t i m e o f c o l l e c t i o n , however, t o a v o i d t h e hazards o f s t r o n g a c i d s i n t h e f i e l d , t r a n s p o r t r e s t r i c t i o n s , and p o s s i b l e c o n t a m i n a t i o n i t i s recommended t h a t t h e samples be r e t u r n e d t o t h e l a b o r a t o r y as soon as p o s s i b l e a f t e r c o l l e c t i o n and a c i d p r e s e r v e d upon r e c e i p t i n t h e l a b o r a t o r y . F o l l o w i n g a c i d i f i c a t i o n , t h e sample s h o u l d be mixed, h e l d f o r s i x t e e n hours, and t h e n v e r i f i e d t o be pH < 2 j u s t p r i o r w i t h d r a w i n g an a l i q u o t f o r p r o c e s s i n g . I f f o r some reason such as h i g h a l k a l i n i t y t h e sample pH i s v e r i f i e d t o be > 2, more a c i d must be added and t h e sample h e l d f o r a d d i t i o n a l s i x t e e n hours u n t i l v e r i f i e d t o be pH < 2. The p r e s e r v e d sample s h o u l d be analyzed w i t h i n 28 days o f c o l l e c t i o n . NOTE:

When t h e n a t u r e o f t h e sample i s e i t h e r unknown o r i s known t o be hazardous, a c i d i f i c a t i o n s h o u l d be done i n a fume hood. See S e c t i o n 5 . 2 . Revision 3.0

May 1994

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8 . 3 A f i e l d b l a n k s h o u l d be p r e p a r e d and analyzed a s r e q u i r e d by t h e d a t a user. 9.0

Use t h e same c o n t a i n e r and a c i d as used i n sample c o l l e c t i o n .

QUALITY CONTROL 9.1

Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a formal The minimum r e q u i r e m e n t s o f t h i s q u a l i t y c o n t r o l ( Q C ) program. program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y by a n a l y s i s o f l a b o r a t o r y r e a g e n t b l a n k s , f o r t i f i e d b l a n k s and samples used f o r c o n t i n u i n g check on method performance. Commercially a v a i l a b l e w a t e r q u a l i t y c o n t r o l samples a r e a c c e p t a b l e f o r r o u t i n e l a b o r a t o r y use. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n performance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f t h e d a t a generated.

9.2

I n i t i a l D e m o n s t r a t i o n o f Performance (mandatory). 9.2.1

The i n i t i a l d e m o n s t r a t i o n o f performance i s used t o c h a r a c t e r i z e i n s t r u m e n t performance ( d e t e r m i n a t i o n o f l i n e a r dynamic ranges and a n a l y s i s o f q u a l i t y c o n t r o l samples) and l a b o r a t o r y performance ( d e t e r m i n a t i o n of method d e t e c t i o n l i m i t s ) p r i o r t o analyses conducted by t h i s method.

9.2.2

L i n e a r dynamic range (LDR) - The upper l i m i t o f t h e LDR must I t must be determined from a l i n e a r be e s t a b l i s h e d . c a l i b r a t i o n p r e p a r e d f r o m a minimum o f t h r e e d i f f e r e n t c o n c e n t r a t i o n standards, one o f which i s c l o s e t o t h e upper l i m i t o f t h e l i n e a r range. The LDR should be determined by analyzing succeedingly higher standard concentrations o f mercury u n t i l t h e observed a n a l y t e c o n c e n t r a t i o n i s no more t h a n 10% below t h e s t a t e d c o n c e n t r a t i o n o f t h e standard. The d e t e r m i n e d LDR must be documented and k e p t on f i l e . The LDR which may be used f o r t h e a n a l y s i s o f samples s h o u l d be judged by t h e a n a l y s t f r o m t h e r e s u l t i n g d a t a . Determined sample a n a l y t e c o n c e n t r a t i o n s t h a t a r e g r e a t e r t h a n 90% o f t h e d e t e r m i n e d upper LDR l i m i t must be d i l u t e d and reanalyzed. The LDR s h o u l d be v e r i f i e d a n n u a l l y o r whenever, i n t h e judgement o f t h e a n a l y s t , a change i n a n a l y t i c a l performance caused b y e i t h e r a change i n i n s t r u m e n t hardware o r o p e r a t i n g c o n d i t i o n s would d i c t a t e t h e y be r e d e t e r m i n e d .

9.2.3

Q u a l i t y c o n t r o l sample (QCS) - When b e g i n n i n g t h e use o f t h i s method, on a q u a r t e r l y b a s i s , a f t e r t h e p r e p a r a t i o n o f s t o c k or c a l i b r a t i o n s t a n d a r d s o l u t i o n s o r as r e q u i r e d t o meet d a t a qual i t y needs, v e r i f y t h e c a l i b r a t i o n standards and a c c e p t a b l e i n s t r u m e n t performance w i t h t h e p r e p a r a t i o n and analyses o f a QCS ( S e c t . 7.13). To v e r i f y t h e c a l i b r a t i o n standards, t h e d e t e r m i n e d c o n c e n t r a t i o n o f t h e QCS must be w i t h i n ? 10%o f t h e s t a t e d v a l u e . I f t h e c a l i b r a t i o n s t a n d a r d cannot be v e r i f i e d , performance o f t h e d e t e r m i n a t i v e s t e p o f t h e method i s u n a c c e p t a b l e . The source o f t h e problem must be i d e n t i f i e d and c o r r e c t e d b e f o r e e i t h e r p r o c e e d i n g on w i t h t h e i n i t i a l R e v i s i o n 3.0

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314

Methods for the Determination d e t e r m i n a t i o n o f method d e t e c t i o n 1 i m i t s o r c o n t i n u i n g w i t h ongoing analyses. 9.2.4

Method d e t e c t i o n l i m i t (MDL) - A mercury MDL must be e s t a b l i s h e d u s i n g an LRB s o l u t i o n f o r t i f i e d a t a concent;ation o f two t o t h r e e t i m e s t h e e s t i m a t e d d e t e c t i o n l i m i t . To d e t e r m i n e MDL v a l u e s , t a k e seven r e p l i c a t e a l i q u o t s o f t h e f o r t i f i e d LRB and process t h r o u g h t h e e n t i r e a n a l y t i c a l method. P e r f o r m a l l c a l c u l a t i o n s d e f i n e d i n t h e method and r e p o r t t h e concentration values i n the appropriate u n i t s . Calculate the MDL as f o l l o w s : MDL = ( t ) x ( S ) where:

Note:

t

=

s t u d e n t s ’ t v a l u e f o r a 99% c o n f i d e n c e l e v e l and a s t a n d a r d d e v i a t i o n e s t i m a t e w i t h n-1 degrees o f freedom [ t = 3.14 f o r seven r e p l i c a t e s ] .

S

=

s t a n d a r d d e v i a t i o n o f t h e r e p l i c a t e analyses.

I f t h e r e l a t i v e s t a n d a r d d e v i a t i o n (RSD) f r o m t h e analyses o f t h e seven a l i q u o t s i s < lo%, t h e c o n c e n t r a t i o n used t o d e t e r m i n e t h e mercury MDL may have been i n a p p r o p r i a t e l y h i g h f o r t h e d e t e r m i n a t i o n . I f so, t h i s c o u l d r e s u l t i n t h e c a l c u l a t i o n o f an u n r e a l i s t i c a l l y l o w MDL. C o n c u r r e n t l y , d e t e r m i n a t i o n o f MDL i n an LRB s o l u t i o n r e p r e s e n t s a b e s t case s i t u a t i o n and does n o t r e f l e c t p o s s i b l e m a t r i x e f f e c t s o f r e a l w o r l d samples. However, s u c c e s s f u l analyses o f LFMs (Sect. 9 . 4 ) can g i v e c o n f i d e n c e t o t h e MDL v a l u e d e t e r m i n e d i n LRB s o l u t i o n .

The MDL must be s u f f i c i e n t t o d e t e c t mercury a t t h e r e q u i r e d l e v e l a c c o r d i n g t o compliance m o n i t o r i n g r e g u l a t i o n ( S e c t . 1.2). The mercury MDL s h o u l d be d e t e r m i n e d a n n u a l l y , when a new o p e r a t o r b e g i n s work o r whenever, i n t h e judgement o f t h e a n a l y s t , a change i n a n a l y t i c a l performance caused by e i t h e r a change i n i n s t r u m e n t hardware o r o p e r a t i n g c o n d i t i o n s would d i c t a t e t h e y be r e d e t e r m i n e d . 9.3

Assessing L a b o r a t o r y Performance (mandatory) 9.3.1

L a b o r a t o r y r e a g e n t b l a n k (LRB) - The l a b o r a t o r y must analyze a t l e a s t one LRB ( S e c t . 7.11.2) w i t h each b a t c h o f 20 o r fewer samples o f t h e same m a t r i x . LRB d a t a a r e used t o assess c o n t a m i n a t i o n f r o m t h e l a b o r a t o r y environment. LRB v a l u e s t h a t exceed t h e MDL i n d i c a t e l a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n s h o u l d be suspected. When LRB v a l u e s c o n s t i t u t e 10% o r more o f t h e a n a l y t e l e v e l determined f o r a sample o r i s 2 . 2 t i m e s t h e a n a l y t e MDL whichever i s g r e a t e r , f r e s h a l i q u o t s o f t h e samples must be p r e p a r e d and analyzed a g a i n f o r t h e a f f e c t e d a n a l y t e s R e v i s i o n 3.0

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a f t e r t h e source o f c o n t a m i n a t i o n has been c o r r e c t e d and a c c e p t a b l e LRB v a l u e s have been o b t a i n e d . 9.3.2

L a b o r a t o r y f o r t i f i e d b l a n k (LFB) - The l a b o r a t o r y must analyze a t l e a s t one LFB ( S e c t . 7.11.3) w i t h each b a t c h o f samples. C a l c u l a t e accuracy as p e r c e n t r e c o v e r y u s i n g t h e f o l l o w i n g equation: LFB - LRB R =

x

100

S

where:

R LFB LRB s

= = = =

percent recovery. laboratory f o r t i f i e d blank. l a b o r a t o r y reagent blank. c o n c e n t r a t i o n e q u i v a l e n t o f mercury added t o f o r t i f y t h e LRB s o l u t i o n .

I f t h e r e c o v e r y o f mercury f a l l s o u t s i d e t h e r e q u i r e d c o n t r o l l i m i t s o f 85-115%, t h e a n a l y s i s i s j u d g e d o u t o f c o n t r o l , and t h e source o f t h e problem s h o u l d be i d e n t i f i e d and r e s o l v e d before c o n t i n u i n g analyses. 9.3.3

The l a b o r a t o r y must use LFB analyses d a t a t o assess l a b o r a t o r y performance a g a i n s t t h e r e q u i r e d c o n t r o l l i m i t s o f 85-115% (Sect.9.3.2). When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e ( u s u a l l y a minimum o f t w e n t y t o t h i r t y a n a l y s e s ) , o p t i o n a l c o n t r o l l i m i t s can be developed f r o m t h e mean p e r c e n t r e c o v e r y ( x ) and t h e s t a n d a r d d e v i a t i o n ( S ) o f t h e mean p e r c e n t r e c o v e r y . These d a t a can be used t o e s t a b l i s h t h e upper and l o w e r c o n t r o l l i m i t s as f o l l o w s : UPPER CONTROL LIMIT = x t 3s LOWER CONTROL LIMIT = x - 3s The o p t i o n a l c o n t r o l l i m i t s must be equal t o o r b e t t e r t h a n t h e r e q u i r e d c o n t r o l l i m i t s o f 85-115%. A f t e r each f i v e t o t e n new r e c o v e r y measurements, new c o n t r o l 1i m i t s can be c a l c u l a t e d u s i n g o n l y t h e most r e c e n t t w e n t y t o t h i r t y d a t a p o i n t s . Also, t h e s t a n d a r d d e v i a t i o n ( S ) d a t a s h o u l d be used t o e s t a b l i s h an on-going p r e c i s i o n s t a t e m e n t f o r t h e l e v e l o f c o n c e n t r a t i o n s i n c l u d e d i n t h e LFB. These d a t a must be k e p t on f i l e and be a v a i l a b l e f o r review.

9.3.4

I n s t r u m e n t performance check (IPC) s o l u t i o n - For a l l d e t e r m i n a t i o n s t h e l a b o r a t o r y must a n a l y z e t h e I P C s o l u t i o n ( S e c t . 7.12) and a c a l i b r a t i o n b l a n k i m m e d i a t e l y f o l l o w i n g each c a l i b r a t i o n , a f t e r e v e r y t e n t h sample ( o r more f r e q u e n t l y , i f r e q u i r e d ) and a t t h e end o f t h e sample r u n . A n a l y s i s o f t h e c a l i b r a t i o n b l a n k s h o u l d always be < t h e MDL. A n a l y s i s o f t h e I P C s o l u t i o n i m m e d i a t e l y f o l l o w i n g c a l i b r a t i o n must v e r i f y t h a t t h e i n s t r u m e n t i s w i t h i n f 5% o f c a l i b r a t i o n . Subsequent R e v i s i o n 3.0

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a n a l y s e s o f t h e IPC s o l u t i o n must be w i t h i n f 10 % of c a l i b r a t i o n . I f t h e c a l i b r a t i o n cannot be v e r i f i e d w i t h i n t h e s p e c i f i e d l i m i t s , a n a l y s i s must be d i s c o n t i n u e d , t h e c a u s e determined a n d / o r in t h e c a s e o f d r i f t the i n s t r u m e n t r e c a l i b r a t e d . All samples f o l l o w i n g t h e l a s t a c c e p t a b l e I P C s o l u t i o n must be r e a n a l y z e d . The a n a l y s i s d a t a o f the c a l i b r a t i o n blank a n d I P C s o l u t i o n must be k e p t on f i l e w i t h t h e sample a n a l y s e s d a t a . 9.4

Assessing Analyte Recovery and Data Q u a l i t y 9.4.1

Sample homogeneity and t h e chemical nature of t h e sample m a t r i x can a f f e c t mercury recovery and t h e q u a l i t y o f t h e d a t a . Taking s e p a r a t e a l i q u o t s from t h e sample f o r r e p l i c a t e and f o r t i f i e d a n a l y s e s can i n some c a s e s a s s e s s t h e e f f e c t . Unless o t h e r w i s e s p e c i f i e d by t h e d a t a u s e r , l a b o r a t o r y o r program, t h e f o l l o w i n g l a b o r a t o r y f o r t i f i e d m a t r i x (LFM) procedure ( S e c t 9.4.2) i s required.

9.4.2

The l a b o r a t o r y must add a known amount of mercury t o a minimum o f 10% o f samples o r one sample p e r sample s e t , whichever i s g r e a t e r . In each c a s e t h e LFM a l i q u o t must be a d u p l i c a t e o f t h e a l i q u o t used f o r sample a n a l y s i s . S e l e c t a sample w i t h a low mercury background t h a t i s r e p r e s e n t a t i v e of the t y p e o f I t i s recommended t h a t t h i s w a t e r samples being a n a l y z e d . sample be analyzed p r i o r t o f o r t i f i c a t i o n . The c o n c e n t r a t i o n of mercury added may vary based on t h e n a t u r e of samples being a n a l y z e d . When p o s s i b l e , t h e c o n c e n t r a t i o n should be t h e same a s t h a t added t o t h e L R B , b u t should not exceed the midpoint c o n c e n t r a t i o n of t h e c a l i b r a t i o n c u r v e . Over t i m e , samples from a l l r o u t i n e sample s o u r c e s should be f o r t i f i e d .

9.4.3

C a l c u l a t e the p e r c e n t r e c o v e r y , c o r r e c t e d f o r background c o n c e n t r a t i o n measured i n the u n f o r t i f i e d sample a l i q u o t , and compare t h e s e v a l u e s t o t h e c o n t r o l l i m i t s t o t h e d e s i g n a t e d LFM r e c o v e r y range of 70-130%. Percent r e c o v e r y may be calculated using the following equation:

R =

cs - c

x 100

S

where:

R

=

C,

= = =

C

s 9.4.4

p e r c e n t recovery f o r t i f i e d sample c o n c e n t r a t i o n sample background c o n c e n t r a t i o n c o n c e n t r a t i o n e q u i v a l e n t o f mercury added w a t e r sarnpl e .

to

I f mercury recovery f a l l s o u t s i d e t h e d e s i g n a t e d r a n g e , and t h e l a b o r a t o r y performance i s shown t o be i n c o n t r o l ( S e c t . 9 . 3 ) , Revision 3.0

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the recovery problem encountered with the fortified water sample is judged to be matrix related, not system related. The result for mercury in the unfortified sample must be labelled to inform the data user that the results are suspect due to matrix effects. 10.0 CALIBRATION

AND STANDARDIZATION

10.1 Conveniently arrange and connect the various components of the instrument system using one of the options shown in Figure 1. If adjustable, the monochromator should be set to 253.65 nm. Prior to

the use of this method the air flow should be optimized. (The recommended air flow rate through the system is 1 liter per minute.) For all determinations allow an instrument and hollow cathode lamp warm up period of not less than 15 min. When an instrument designed specifically for the determination o f mercury by the cold vapor technique is being utilized, the analyst should follow the instructions provided by the manufacturer. 10.2 Before using the procedure (Section 11.0) to analyze samples, there

must be data available documenting initial demonstration of performance. The required data and procedure is described in Section 9.2. This data must be generated using the same instrument operating conditions and calibration routine used for sample analysis. These documented data must be kept on file and be available for review by the data user. 10.3 The recommended calibration routine is given

in Section 11.2.

11.0 PROCEDURE 11.1 Sample Preparation 11.1.1 Transfer 100 mL of the water sample [or an aliquot diluted with reagent water (Sect. 7.2) to 100 mL] into a sample container.

NOTE:

For reduced volume analysis, adjust sample and reagent volumes to maintain the required sample to reagent ratios.

11.1.2 Add 5 mL of H,SO,

(Sect. 7.4) and 2 . 5 mL of HNO, (Sect. 7.3) to

the container. 11.1.3 To each container add 15 mL KMnO, solution (Sect. 7.7).

For sewage or industry wastewaters, additional KMnO, may be required. Shake and add additional portions of KMnO, solution, if necessary, until the purple color persists for at least 15 min. Add 8 mL of K,S,O, solution (Sect. 7.8) to each container. Mix thoroughly, cap and cover the top of the sample container (if required) with aluminum foil or other appropriate cover. Heat for 2 h in a water bath at 95°C. Revision 3.0 Hay 1994

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Methods for the Determination 11.1.4 Remove t h e sample c o n t a i n e r s from t h e w a t e r b a t h and c o o l t o room t e m p e r a t u r e . ( D u r i n g t h e c o o l down p e r i o d proceed w i t h i n s t r u m e n t warm up and c a l i b r a t i o n . ) 11.1.5 When t h e samples a r e a t room temperature, t o each c o n t a i n e r , add 6 mL o f NaC1-(NH20H)2-H2S0, s o l u t i o n ( S e c t . 7 . 9 ) t o reduce t h e excess permanganate. 11.2 Sample A n a l y s i s 11.2.1 B e f o r e b e g i n n i n g d a i l y c a l i b r a t i o n t h e i n s t r u m e n t s h o u l d be reconfigured t o the optimized conditions. Turn on t h e i n s t r u m e n t and c i r c u l a t i n g pump. A d j u s t pump r a t e t o 1 L/min o r as r e q u i r e d . A l l o w system t o s t a b i l i z e . 11.2.2 Prepare c a l i b r a t i o n standards by t r a n s f e r r i n g 0.5, 1.0, 2.0, 5.0 and 10 mL a l i q u o t s o f t h e 0.1 pg/mL CAL ( S e c t . 7 . 6 ) t o a s e r i e s o f sample c o n t a i n e r s ( S e c t . 6 . 5 . 2 ) . D i l u t e t h e s t a n d a r d a l i q u o t s t o 100 mL w i t h r e a g e n t w a t e r ( S e c t . 7.2) and process as d e s c r i b e d i n S e c t s . 11.1.2, 11.1.3 ( w i t h o u t h e a t i n g ) , and 11.1.5. These s o l u t i o n s c o n t a i n 0.05 t o 1.0 p g o f Hg. (Other a p p r o p r i a t e c a l i b r a t i o n standards, volumes, and ranges may a l s o be used.) 11.2.3 T r e a t i n g each s t a n d a r d s o l u t i o n c o n t a i n e r i n d i v i d u a l l - y , add 5 mL o f SnC1, s o l u t i o n ( S e c t . 7.10) and i m m e d i a t e l y a t t a c h t h e c o n t a i n e r t o t h e a e r a t i o n apparatus. The absorbance, as e x h i b i t e d e i t h e r on t h e i n s t r u m e n t o r r e c o r d i n g d e v i c e , w i l l i n c r e a s e and r e a c h maximum w i t h i n 30 sec. As soon as t h e maximum response i s o b t a i n e d , a p p r o x i m a t e l y 1 min, open t h e bypass v a l u e ( o r o p t i o n a l l y remove a s p i r a t o r f r o m t h e sample c o n t a i n e r i f i t i s vented under t h e hood) and c o n t i n u e a e r a t i o n u n t i l t h e absorbance r e t u r n s t o i t s minimum v a l u e . 11.2.4 Close t h e by-pass v a l u e , remove t h e a s p i r a t o r f r o m t h e s t a n d a r d s o l u t i o n c o n t a i n e r and c o n t i n u e a e r a t i o n . Repeat (Sect. 11.2.3) u n t i l d a t a f r o m a l l s t a n d a r d s have been c o l l e c t e d . 11.2.5 C o n s t r u c t a s t a n d a r d c u r v e by p l o t t i n g peak h e i g h t , area o r maximum response o b t a i n e d f r o m each s t a n d a r d s o l u t i o n , v e r s u s micrograms o f mercury i n t h e c o n t a i n e r . The s t a n d a r d c u r v e must comply w i t h Sect. 9.2.2. C a l i b r a t i o n u s i n g computer o r c a l c u l a t o r based r e g r e s s i o n c u r v e f i t t i n g t e c h n i q u e s on concentration/response data i s acceptable. 11.2.6 F o l l o w i n g c a l i b r a t i o n t h e d i g e s t e d samples a r e analyzed i n t h e same manner as t h e s t a n d a r d s o l u t i o n s d e s c r i b e d i n S e c t i o n 11.2.3. However, p r i o r t o t h e a d d i t i o n of t h e SnCl s o l u t i o n , p l a c e t h e a s p i r a t o r i n s i d e t h e c o n t a i n e r above t h e f i q u i d , and purge t h e head space ( 2 0 t o 30 sec) t o remove p o s s i b l e gaseous interference. R e v i s i o n 3.0

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1 1 . 2 . 7 During the analysis o f samples, the laboratory must comply with the required quality control described in Sections 9 . 3 and 9.4. 12.0

DATA ANALYSIS AND CALCULATIONS 1 2 . 1 From the prepared calibration curve (Sect. 1 1 . 2 . 4 ) compute sample

values by comparing response with the standard curve. 12.2 Calculate the mercury concentration in the sample +y the formula:

12.3 Report mercury concentrations to the proper significant figures in

mg/L, pg/L or ng/L as required. 13.0 METHOD PERFORMANCE

13.1

In a single laboratory (EMSL), using an Ohio River composite sample with a background mercury concentration of 0 . 3 5 pg/L Hg and fortified with concentration o f 1.0, 3.0, and 4 . 0 pg/L Hg, the standard deviations were ? 0.14, f 0.10 and f 0.08 pg/L Hg, respectively. Standard deviation at the 0 . 3 5 pg/L Hg level was f 0.16 pg/L Hg. Percent recoveries at the three levels were 89%, 87%, and 87%, respectively .

13.2

In a joint EPA/ASTM interlaboratory study of the cold vapor technique for total mercury in water, increments of organic and inorganic mercury were added to natural waters. Recoveries were determined by difference. A statistical summary of this study is found in Table 1.

14.0 POLLUTION PREVENTION 1 4 . 1 Pollution

prevention encompasses any technique that reduces or eliminates the quantity or toxicity of waste at the point of generation. Numerous opportunities for pollution prevention exist in laboratory operation. The EPA has established a preferred hierarchy of environmental management techniques that places pollution prevention as the management option of first choice. Whenever feasible, laboratory personnel should use pollution prevention techniques to address their waste generation. When wastes cannot be feasibly reduced at the source, the Agency recommends recycling as the next best option.

1 4 . 2 For information about pollution prevention that may be applicable to laboratories and research institutions, consult Less i s Better:

Laboratory Chemical Management f o r Waste Reduction, available from the American Chemical Society’s Department of Government Relations and Science Policy, 1155 16th Street N.W., Washington D . C . 20036, (202)872-4477.

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Methods for the Determination

15.0 WASTE MANAGEMENT

15.1 The Environmental Protection Agency requires that laboratory waste management practices be conducted consistent with all applicable rule and regulations. The Agency urges laboratories to protect the air, water, and land by minimizing and controlling all releases from hoods and bench operations, complying with the letter and spirit o f any sewer discharge permits and regulations, and by complying with all solid and hazardous waste regulations, particularly the hazardous waste identification rules and land disposal restrictions. For further information on waste management consult The Waste Management Manual f o r l a b o r a t o r y P e r s o n n e l , available from the American Chemical Society at the address listed in the Sect. 14.2. 16.0 REFERENCES

1.

Kopp, J . F . , Longbottom, M.C., and Lobring, L.B., 'Cold Vapor' Method for Determining Mercury"; J. Am. Water Works ASSOC., Vol. 6 4 , No. 1 , January 1972.

2.

"Safety in Academic Chemistry Laboratories", American Chemical Society Publication, Committee on Chemical Safety, 3rd Edition, 1979.

3.

"OSHA Safety and Health Standards, General Industry", (29CFR 1910), Occupational Safety and Health Administration, OSHA 2206, revised January 1976.

4.

"Proposed OSHA Safety and Health Standards, Laboratories", Occupational Safety and Health Administration, Federal Register, July 24, 1986.

5.

"Specification for Reagent Water", 01193, Annual Book o f ASTM Standards, Vol. 11.01, 1990.

6.

Code of Federal Regulations 40, Ch. 1 , Pt. 136 Appendix B.

'I

Revision 3.0 May 1994

Metals 17.0

TABLES, DIAGRAMS, FLOWCHARTS, AND VALIDATION DATA

TABLE 1.

Number o f Labs

76 a0 a2 77 a2 79 79 7a

321

INTERLABORATORY PRECISION AND ACCURACY DATA FOR FLAMELESS ATOMIC ABSORPTION

True Values uq/L

0.21 0.27 0.51 0.60 3.4 4.1 8.8 9.6

Mean Value USIL

0.349 0.414 0.674 0.709 3.41 3 .a1 8.77 9.10

Standard Deviation uq/L

0.276 0.279 0.541 0.390 1.49 1.12 3.69 3.57

RSD %

89 67

ao

55 44 29 42 39

Mean Accuracy as % Bias 66 53 32 18 0.34 -7.1 -0.4 -5.2

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Methods for the Determination

Sunplc Soludon In R0.D. Botde

Optlon 1

Figure 1. Apparatus for Flameless Mercury Determination Because of the toxic nature of mercury vapor, inhalation must be avoided. Therefore, a bypass has been included in the system to either vent the mercury vapor into an exhaust hood or pass the vapor through some absorbing media, such as: a) equal volumes of 0.1 N KMnO, and 1 0 % H,SO, b ) 0.25% iodine in a 3% KI solution. A specially treated charcoal that will absorb mercury vapor is also available from Barnebey and Cheney, P.O. Box 2526, Columbus, OH 43216, Catalog No. 580-13 O r 580-22.

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METHOD 245.3 DETERMINATION OF INORGANIC MERCURY (11) AND SELECTED ORGANOMERCURIALS I N DRINKING AND GROUND WATER BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (HPLC) WITH ELECTROCHEMICAL DETECTION (ECD)

O t i s Evans and B e t t y Jacobs I n o r g a n i c C h e m i s t r y Branch C h e m i s t r y Research D i v i s i o n

R e v i s i o n 1.1 A p r i l 1991

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

324

Methods for the Determination METHOD 245.3 DETERMINATION OF INORGANIC MERCURY (11) AND SELECTED ORGANOMERCURIALS I N DRINKING AND GROUND WATER BY H I G H PERFORMANCE L I Q U I D CHROMATOGRAPHY (HPLC) WITH ELECTROCHEMICAL DETECTION (ECD)

1.

2.

SCOPE AND APPLICATION

1.1

T h i s method i s a p p l i c a b l e t o t h e d e t e r m i n a t i o n o f c e r t a i n d i s s o l v e d mercury s p e c i e s i n d r i n k i n g and ground w a t e r .

1.2

The a n a l y t i c a l range i s a p p r o x i m a t e l y 2 p g / L t o 10 mg/L i n o r g a n i c mercury (11) and o r g a n o m e t a l l i c mercury compounds.

1.3

The method d e t e c t i o n l i m i t s (MDLs) a r e 1 . 8 p g / L f o r mercury ( 1 1 ) , 1.9 p g / L f o r methylmercury, 1 . 7 p g / L f o r e t h y l m e r c u r y , and 0 . 8 p g / L f o r phenylmercury.

1.4

T h i s method s h o u l d be used by a n a l y s t s e x p e r i e n c e d i n l i q u i d chromatography w i t h e l e c t r o c h e m i c a l d e t e c t i o n (LCEC).

SUMMARY OF METHOD

2.1

3.

T h i s method d e s c r i b e s a p r o c e d u r e f o r t h e s p e c i a t i o n o f c e r t a i n d i s s o l v e d mercury i o n i c a n a l y t e s i n d r i n k i n g and ground w a t e r . I n o r g a n i c mercury ( 1 1 ) , methylmercury, e t h y l m e r c u r y , and phenylmercury a r e d e t e r m i n e d by reversed-phase HPLC w i t h r e d u c t i v e amperornetric e l e c t r o c h e m i c a l d e t e c t i o n ' - 6 . The mercury a n a l y t e s a r e complexed o n - c o l u n w i t h 2-mercaptoethanol (2-ME) t o f o r m chargen e u t r a l species'-' The mercury complexes a r e e l u t e d w i t h 60% (w/w) methanol ( i s o c r a t c e l u t i o n c o n d i t i o n s ) b u f f e r e d a t pH 5.5. The maximum r e t e n t i o n t i m e i s l e s s t h a n 10 min a t a f l o w r a t e o f 0.6 mL/min ( F i g u r e 1)

DEFINITIONS

3.1

FIELD DUPLICATES (FD1 and FD2) - Two s e p a r a t e samples c o l l e c t e d a t t h e same t i m e and p l a c e d under i d e n t i c a l c i r c u m s t a n c e s and t r e a t e d e x a c t l y t h e same t h r o u g h f i e l d and l a b o r a t o r y procedures. Analyses o f FD1 and FD2 g i v e a measure o f t h e p r e c i s i o n a s s o c i a t e d w i t h sample c o l l e c t i o n , p r e s e r v a t i o n and s t o r a g e , as w e l l as w i t h l a b o r a t o r y procedures.

3.2

F I E L D REAGENT BLANK (FRB) - Reagent w a t e r p l a c e d i n a sample c o n t a i n e r i n t h e l a b o r a t o r y and t r e a t e d as a sample i n a l l r e s p e c t s , i n c l u d i n g exposure t o sampling s i t e c o n d i t i o n s , s t o r a g e , p r e s e r v a t i o n and a l l a n a l y t i c a l p r o c e d u r e s . The,purpose o f t h e FRB i s t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e f i e l d environment.

Metals

3.3 LABORATORY DUPLICATES ( L D l and LD2)

- Two sample a1 t h e a n a l y t i c a l l a b o r a t o r y and a n a l y z e d s e p a r a t e l y w p r o c e d u r e s . Analyses of LD1 and LD2 g i v e a measure a s s o c i a t e d w i t h l a b o r a t o r y procedures, b u t n o t w i t h c o l l e c t i o n preservation, o r storage procedures.

3.4

325

quots t a k e n i n t h identica o f the prec sion sample

LABORATORY FORTIFIED BLANK (LFB) - An a l i q u o t o f r e a g e n t w a t e r t o w h i c h known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e methodology i s i n c o n t r o l , and whether t h e l a b o r a t o r y i s c a p a b l e o f making a c c u r a t e and p r e c i s e measurements a t t h e r e q u i r e d d e t e c t i o n l i m i t .

3.5 LABORATORY PERFORMANCE CHECK SOLUTION (LPCS) - A s o l u t i o n o f method a n a l y t e s used t o e v a l u a t e t h e performance o f t h e LCEC system w i t h r e s p e c t t o a d e f i n e d s e t o f method c r i t e r i a .

3.6 LABORATORY REAGENT BLANK (LRB)

- An a l i q u o t o f r e a g e n t w a t e r t h a t i s t r e a t e d e x a c t l y as a sample. I t i s exposed t o a l l t h e glassware, method s o l v e n t s , and r e a g e n t s t h a t a r e used w i t h o t h e r samples. The purpose o f t h e LRB i s t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e l a b o r a t o r y environment, t h e r e a g e n t s , o r t h e apparatus.

3.7 METHOD DETECTION LIMIT (MDL)

- The minimum c o n c e n t r a t i o n o f an a n a l y t e t h a t can be i d e n t i f i e d , measured and r e p o r t e d w i t h 99% confidence t h a t t h e analyte concentration i s g r e a t e r than zero.

3.8

ORGANOMETALLIC COMPOUNDS - Compounds i n w h i c h t h e carbon atoms o f o r g a n i c groups a r e bound t o m e t a l atoms.

3.9

PRIMARY DILUTION STANDARD SOLUTION - A s o l u t i o n o f s e v e r a l a n a l y t e s p r e p a r e d i n t h e l a b o r a t o r y f r o m s t o c k s t a n d a r d s o l u t i o n s and d i l u t e d as needed t o p r e p a r e c a l i b r a t i o n s o l u t i o n s and f o r t i f i e d b l a n k s .

3.10 SPECIATION - The d e t e r m i n a t i o n o f c e r t a i n i n d i v i d u a l p h y s i c o chemical forms o f an element.

3.11 STOCK STANDARD SOLUTION - A c o n c e n t r a t e d s o l u t i o n c o n t a i n i n g a s i n g l e c e r t i f i e d s t a n d a r d t h a t i s a method a n a l y t e , o r a concentrated s o l u t i o n o f a s i n g l e a n a l y t e prepared i n t h e l a b o r a t o r y w i t h an assayed r e f e r e n c e compound. S t o c k s t a n d a r d s o l u t i o n s a r e used t o p r e p a r e p r i m a r y d i l u t i o n s t a n d a r d s .

3.12 QUALITY CONTROL SAMPLE ( Q C S ) l - A sample m a t r i x c o n t a i n i n g method a n a l y t e s o r a s o l u t i o n o f method a n a l y t e s i n a w a t e r m i s c i b l e s o l v e n t w h i c h i s used t o f o r t i f y r e a g e n t w a t e r o r e n v i r o n m e n t a l samples. The QCS i s o b t a i n e d f r o m a source e x t e r n a l t o t h e l a b o r a t o r y , and i s used t o check l a b o r a t o r y performance w i t h e x t e r n a l l y prepared t e s t m a t e r i a l s .

326

Methods for the Determination 3.13 C A L I B R A T I O N STANDARD (CAL) - A s o l u t i o n prepared from t h e p r i m a r y d i l u t i o n standard s o l u t i o n and stock standard s o l u t i o n s . The CAL s o l u t i o n s a r e use t o c a l i b r a t e t h e instrument response w i t h r e s p e c t t o an a l y te c o n c e n tra ti o n . 3 . 1 4 AMPEROMETRIC DETECTOR - An e l e c t r o c h e m i c a l d e t e c t o r employing a working e l e c tro d e , which i s kept a t a c o n s t a n t p o t e n t i a l versus a ref ere n c e e l e c tro d e . A small p o r t i o n of t h e e l e c t r o a c t i v e species passing th e e l e c t r o d e i s e l e c t r o l y z e d (reduced o r o x i d i z e d ) and t h e e l e c t r o l y s i s current i s a function o f the concentration o f the eluted electroactive material. 3 . 1 5 GOLD AMALGAMATED MERCURY ELECTRODE (GAME) - A mercury coated g o l d elect ro d e .

4.

INTERFERENCES 4.1

I nt erfe re n c e s i n t h i s method may be caused by contaminants i n solven ts , reagents, glassware, T e f l o n b o t t l e s (metals s t o r a g e ) , and o t h e r sample processing apparatus. These i n t e r f e r e n c e s may l e a d t o a r t i f a c t s o r e l e v a te d b a s e l i n e s i n l i q u i d chromatograms. A l l reagents and apparatus must be r o u t i n e l y demonstrated t o be f r e e from i n t e r f e r e n c e s under t h e c o n d i t i o n s o f t h e a n a l y s i s by r u n n i n g a l a b o r a t o r y reagent b l a n k (Sect. 1 0 . 6 ) .

4.1.1

4.1.2

Glassware and T e f l o n b o t t l e s must be s c r u p u l o u s l y cleaned. Soak i n concentrated n i t r i c a c i d andqrinse t h o r o u g h l y w i t h organic f r e e deionized, d i s t i l l e d water. I f these c o n ta i n e rs a re used f o r f r e e metal and organometal s o l u t i o n p r e p a r a t i o n and storage they should be soaked and f i l l e d w i t h a 5 t o 10% (v /v ) s o l u t i o n o f n i t r i c a c i d f o r one week, ri n s e d , sealed and s to r e d c o n t a i n i n g deionized, d i s t i l l e d water. The use o f h i g h p u r i t y reagents and s o l v e n t s helps t o minimize i n t e r f e r e n c e problems. P u r i f i c a t i o n o f s o l v e n t s by d i s t i l l a t i o n i n a l l - g l a s s systems may be r e q u i r e d .

4.2

I n t e r f e r i n g contamination may occur when a sample c o n t a i n i n g l o w conce n tra ti o n s o f a n a l y te s i s analyzed immediately f o l l o w i n g a sample c o n t a i n i n g r e l a t i v e l y h i g h c o n c e n t r a t i o n s o f a n a l y t e s . A preve n ti v e technique i s between-sample r i n s i n g o f t h e sample s y r i n g e and sample l o o p w i t h methanol and/or water. A f t e r a n a l y s i s o f a sample c o n t a i n i n g h i g h c o n c e n t r a t i o n s o f analytes, one o r more 1aboratory reagent blanks should be analyzed.

4.3

M a t r i x i n t e r f e r e n c e s may be caused by contaminants t h a t are present i n t h e sample. The e x t e n t o f m a t r i x i n t e r f e r e n c e w i l l v a r y consi d e ra b l y from source t o source, depending upon t h e sample type.

4.4

Electrochemical i n t e r f e r e n c e s a r e caused by species which are e l e c t r o c h e m i c a l l y a c t i v e ( i . e . , r e d u c i b l e a t t h e surface o f t h e

Metals

327

GAME) and have r e t e n t i o n times which a r e t h e same o r v e r y 5 i m i l a r t o t h e a n a l y t e s ( o r because o f t h e t y p e o f r e d u c t i o n process can produce broad chromatographic responses which obscure l a r g e p o r t i o n s o f t h e r e s u l t a n t chromatograms). Amperometric ( r e d u c t i v e ) e l e c t r o c h e m i c a l d e t e c t i o n o f mercury a n a l y t e s r e q u i r e s t h e complete removal o f oxygen from t h e e l u e n t and sample (1,2,10,11,13-25). (-So1u t i o n s i n atmospheric equi 1 ib r i u m t y p i c a l l y c o n t a i n 10- t o 10 M oxygen. The s p e c i f i c r e a c t i o n ( s ) depends on e l e c t r o d e m a t e r i a l , p o t e n t i a l , and e l e c t r o l y t e c o m p o s i t i o n ) . The presence o f oxygen r e s u l t s i n two d i s t i n c t y e t c l o s e l y r e l a t e d problems: m o b i l e phase oxygen and sample oxygen. M o b i l e phase oxygen c o n t r i b u t e s t o onerous r e s i d u a l c u r r e n t s t h a t make t r a c e measurements v i r t u a l l y i m p o s s i b l e . To l o w e r m o b i l e phase oxygen t o a c c e p t a b l e l e v e l s , deoxygenation can be f a c i l i t a t e d by a c o m b i n a t i o n o f s p a r g i n g w i t h i n e r t gas ( i n s u f f i c i e n t a l o n e ) and warming o f t h e e l u e n t s o l u t i o n .

4.4.1

Sample oxygen i s r e t a i n e d on reversed-phase columns ( n o t e l u t e d i n t h e v o i d volume) and e l u t e s as a broad, t a i l i n g band. I t s r e t e n t i o n t i m e i s independent o f t h e c o n c e n t r a t i o n s o f t h e m o b i l e phase c o n s t i t u e n t s ; t h e r e f o r e , m a n i p u l a t i o n o f t h e e l u t i o n p o s i t i o n i s d i f f i c u l t . Oxygen i s d e t e c t e d as a peak when o n l y t h e m o b i l e phase i s purged (sparged) w i t h i n e r t gas. E l i m i n a t i o n o f t h e sample oxygen i n t e r f e r e n c e can be accomplished by p u r g i n g w i t h an i n e r t gas p r i o r t o i n j e c t i o n . The sample i s p l a c e d i n a 3 t o 5 mL v i a l , as shown i n F i g u r e 2b, and purged w i t h a stream o f i n e r t gas f o r =: 5 min. The sample a l i q u o t i s i n t r o d u c e d i n t o t h e sample i n j e c t i o n , J o o p v i a a c l o s e d system t o p r e v e n t r e e n t r y o f oxygen

.

4.4.2

5.

M o b i l e phase oxygen. B o t h p o s i t i v e and n e g a t i v e oxygen peaks can a r i s e i n LCEC. The f o r m e r occurs when t h e sample s o l u t i o n i s n o t purged w i t h an i n e r t gas. A n e g a t i v e oxygen peak o c c u r s when t h e m o b i l e phase c o n t a i n s more oxygen t h a n t h e sample. The n e g a t i v e peak has t h e same r e t e n t i o n t i m e and shape b u t may be l o w e r i n magnitude t h e n t h e p o s i t i v e oxygen peak.

SAFETY

5.1

The t o x i c i t y o r c a r c i n o g e n i c i t y o f each r e a g e n t used i n t h i s method has n o t been p r e c i s e l y d e f i n e d ; however, each chemical compound must be t r e a t e d as a p o t e n t i a l h e e l t h hazard. The l a b o r a t o r y i s r e s p o n s i b l e f o r m a i n t a i n i n g a c u r r e n t awareness f i l e o f OSHA r e g u l a t i o n s r e g a r d i n g t h e s a f e hand1 i n g o f t h e chemicals s p e c i f i e d i n t h i s method. A r e f e r e n c e f i l e o f m a t e r i a l s a f e t y d a t a sheets should a l s o be made a v a i l a b l e t o a l l personnel i n v o l v e d i n t h e chemical a n a l y s i s . A d d i t i o n a l r e f e r e n c e s t o l a b o r a t o r y s a f e t y should be i d e n t i f i e d and made a v a i l a b l e f o r t h e i n f o r m a t i o n o f t h e personnel u s i n g t h i s method.

328

Methods for the Determination The c u r r e n t OSHA standard f o r organo ( a l k y l ) mercury i s 0.01 mg o f organo ( a l k y l ) mercury per cubic meter o f a i r (mg/m ) avergged over Organo an eight-hour work s h i f t w i t h a c e i l i n g l e v e l o f 0.04 mg/m ( a l k y l ) mercury can a f f e c t the body i f i t i s inhaled, comes i n contact w i t h t h e eyes o r skin, o r i s swallowed. I t may e n t e r t h e body through t h e s k i n . Skin t h a t becomes contaminated w i t h organo ( a l k y l ) mercury should be immediately washed o r showered w i t h soap o r m i l d detergent and water.

.

I f organo ( a l k y l ) mercury compounds are s p i l l e d o r leaked:

6.

1.

Remove i g n i t i o n sources.

2.

V e n t i l a t e area o f s p i l l o r l e a k .

3.

I f i n t h e s o l i d form, c o l l e c t f o r reclamation or disposal .

4.

I f i n t h e l i q u i d form, absorb on paper towels. Evaporate i n a safe place (such as a fume hood).

5.1.1

The a d d i t i o n o f t h e complexing agent, 2-Mercaptoethanol (2ME), should be performed i n a hood.

5.1.2

The e l u e n t pH should be adjusted i n a hood.

5.1.3

Precautions must be taken i n t h e p r e p a r a t i o n o f t h e GAME t o prevent aerosols and s p i l l s .

5.1.4

Disposal o f waste (solvents, analytes, etc.) from t h e system must be according t o l o c a l r e g u l a t i o n s .

APPARATUS AND EQUIPMENT (Some s p e c i f i c a t i o n s are suggested)

6.1

HIGH PERFORMANCE LIQUID CHROMATOGRAPH 6.1.1

An HPLC system designed f o r pumping solvents a t p r e c i s e l y c o n t r o l l e d f l o w r a t e s and pressures. The system should be capable o f i n j e c t i n g 10- t o 200- p L a l i q u o t s . NOTE: Amperometric r e d u c t i v e electrochemical d e t e c t i o n o f t h e mercury analytes r e q u i r e s t h e complete removal o f oxygen from t h e e l u e n t and samples. Copper t u b i n g (1/8 i n . ) may be used f o r l i n e s from t h e purge gas ( A r ) tank t o t h e mobile phase f l a s k . F i t t i n g s and t u b i n g (1/16 i n . 0.d.) constructed from type 346 s t a i n l e s s s t e e l should be used f o r a l l o t h e r connections’*’ @ 1 1 0 1 4 * 1 5 .

6.1.2

A n a l y t i c a l column--25 cm x 4.6 mm I . D . s t a i n l e s s s t e e l packed w i t h LiChrosorb RP-18 ( 5 p m i r r e g u l a r l y shaped

Metals

329

p a r t i c l e s ) hydrocarbon phase (C-18 (00s)) bonded s i l i c a (EM Science) o r e q u i v a l e n t . 6.1.3

Guard column--70 mm x 4.6 mm I . D . s t a i n l e s s s t e e l packed w i t h P e r i s o r b RP-18 (30-40 pm) (EM Science) o r e q u i v a l e n t .

6.1.4

Pre-column ( s a t u r a t o r column)--70 mm x 4.6 mm I . D . s t a i n l e s s s t e e l packed w i t h s p h e r i c a l s i l i c a (18 pm) (EM Science) o r equivalent.

6.1.5

E l e c t r o c h e m i c a l d e t e c t o r ( p o t e n t i o s t a t / c u r r e n t amp1 i f i e r ) .

6.1.6

6.1.5.1

Working e l e c t r o d e . - GAME.

6.1.5.2

Reference e l e c t r o d e - Ag/AgCl 3M NaC1).

O t h e r columns o r d e t e c t o r s may be used i f t h e requirements o f Sect. 10.5 can be met.

6.2

S t r i p C h a r t Recorder - V a r i a b l e speed.

6.3

Balance--Analytical, 0.01 mg.

6.4

General purpose l a b o r a t o r y , t o p - l o a d i n g , m e t r i c , a u t o m a t r i c c a l i b r a t i o n , f u l l r a n g e - t a r i n g r e a d i b i l i t y t o 0.01 g.

6.5

F i l t r a t i o n Apparatus--To f i l t e r samples and m o b i l e phases used i n HPLC, use 250 mL g l a s s r e s e r v o i r (connects t o 1 L b o t t l e o r vacuum f l a s k ) , f u n n e l base and stopper, clamp, s t a i n l e s s s t e e l h o l d e r , screen and T e f l o n g a s k e t s ( F i g u r e 3). Recommended a r e 47-mm f i l t e r s ( M i l l i p o r e Type HA, 0.45 pm, f o r w a t e r and M i l l i p o r e Type FH, 0.5pm, f o r o r g a n i c s o r e q u i v a l e n t ) .

6.6

GLASSWARE

6.7

capable o f accurately weighing t o t h e nearest

6.6.1

Three-neck d i s t i l l a t i o n f l a s k w i t h a l l e q u i v a l e n t h e i g h t necks o f f 24/40 j o i n t s .

6.6.2

Condenser, Graham, D r i p T i p I n n e r (bottom) and Outer ( t o p ) f 24/40 J o i n t s .

6.6.3

R e a c t i o n vials--S-mL c a p a c i t y s e r v e as sample c e l l s and purge gas s a t u r a t i o n chambers.

6.6.4

Bubbler--3 29/42 j o i n t s (frit n o t r e q u i r e d ) .

6.6.5

Connecting Adapter, f 24/40 j o i n t (condenser end).

Standard l - L h e a t i n g m a n t l e .

330

Methods for the Determination

6.8 Temperature Controller--Capab e of maintaining temperatures within 2OC of desired point. 6.9 Thermistor probe--Heavy duty

aboratory style ('20

cm long).

6.10 Septa--White rubber for 3 2 4 / 4 0 joints.

6.11 Refrigerated Recirculating Cooler--With sealable reservoir, temperature controller, recirculating pump, air cooled refrigeration ( + l.O°C). Circulation is in a closed loop configuration (system).

6.12 SYRINGES 6.12.1 Hypodermic syringe--5 mL glass (gas tight). 6.12.2

7.

Microliter gas tight syringe--50 pL an 100 pL needle: 90' blunt tip, 2" long, 0.028" OD (22s gauge), no electrotaper.

REAGENTS AND CONSUMABLE HATERIALS 7.1 Acetonitrile (CAsRN-75-05-8)--HPLC grade. 7.2

Deionized, distilled water (CASRN-7732-18-5): Prepared by passing distilled water through mixed bed cation and anion exchange resins. Use deionized, distilled water for all reagents, eluent solutions, calibration standards and dilutions. In this method, the term deionized distilled water will be used interchangeably with reagent water (i.e., water in which an interferent is not observed at the method detection limit of the compounds of interest).

7.3

Inert Gas--High purity argon or helium for degassing eluents and samples.

7.4 HPLC MOBILE PHASE 7.4.1

Acetic acid, G1 acial (CASRN-64-19-7)--Ul trex grade (for eluent pH adjustment).

7.4.2

Ammonium hydroxide (CASRN-1336-21-6)--Ultrex grade, 20% (for eluent pH adjustment).

7.4.3

Eluent: Mix 600 g of methanol (Sect. 7.4.5) and 400 g water (Sect. 7.2.), pH 5.5, add 200 p L of 2-mercaptoethanol to 1L of solution. (The total volume is c 1.125 L.) Allow to cool, adjust the pH, transfer to a 1-L volumetric flask (refrigerate the remainder) and add the complexing agent (Sect. 7.4.4)).

7.4.4

2-Mercaptoethanol (CASRN-60-24-2)--CAUTION: stench, harmful vapor; store in hood.

Combustible,

Metals

7.4.5 7.5

331

Methanol (CASRN-67-56-1)--High purity solvent, HPLC grade.

Ethylmercury chloride (CASRN-107-27-7).

7.6 Mercuric chloride (CASRN-7487-94-7).

7.7 Mercury, metal (CASRN-7439-97-6)--Triple

distilled.

7.8 Methylmercury chloride (CASRN-115-09-3).

7.9 Nitric acid, conc. (CASRN-7697-37-2)--sp gr 1.41. 7.10 Nitric acid, 1:l: Add 50 mL conc. HNO (Sect. 7.9) to 40 mL of distilled, deionized water (Sect. 7.2j, cool, and dilute to 100 mL.

7.11 Phenylmercury acetate (CASRN-62-38-4). 7.12 Sodium chloride (CASRN-7647-14-5)--Crystal, ACS grade, 3M. Dissolve 43.8 g of sodium chloride in deionized, distilled water (Sect. 7.2) and dilute to 250 mL. 7.13 Stock standard solutions (1000 pg/mL) of the mercury analytes may be prepared from reagent grade chemicals. Typical metal stock solution preparation procedures follow. The amount of organic solvent, acetonitrile, (Sect. 7.1) is added as needed in order to dissolve the particular mercury organometal. 7.13.1

Mercury (11) solution, stock, 1 mg/mL: Dissolve 0.1354 g of mercuric chloride (Sect. 7.6) in deionized, distilled water with stirring until completely dissolved. Transfer to a 100 mL volumetric flask and dilute to volume. Transfer to a 125-mL Teflon bottle and refrigerate. This solution can be stored and used for at least six months.

7.13.2

Methylmercury solution, stock, 1 mg/mL methylmercury: Dissolve 0.5822 g of methylmercuric chloride (Sect. 7.8) in deionized, distilled water (minimum volume of water added initially) with constant stirring. Add acetonitrile (Sect. 7.1) slowly until dissolution is complete. In 500 mL total volume, approximately 10% ( V / V ) CH,CN is sufficient to dissolve this amount of material. Dilute to 500 mL total volume and transfer to a Teflon bottle for refrigeration and storage. This solution can be stored and used for at least six months.

7.13.3

Ethylmercury solution, stock, 1 mg/mL ethylmercury: Dissolve 0.5771 g of ethylmercuric chloride (Sect. 7.5) in deionized distilled water with constant stirring. Because Ethylmercuric chloride is difficult to dissolve in water, add acetonitrile (Sect. 7.1) until there is complete dissolution. Approximately 200 mL of 40% ( V / V ) acetonitrile

332

Methods for the Determination (Sect. 7 .1 ), i s needed. D i l u t e t o 500 mL w i t h d i s t i l l e d , d e i o n i z e d water (Sect. 7 . 2 ) , t r a n s f e r t o a T e f l o n b o t t l e f o r r e f r i g e r a t i o n and storage. This s o l u t i o n can be s t o r e d and used f o r a t l e a s t s i x months.

8.

7.13.4

Phenylmercury s o l u t i o n , stock, 1 mg/mL phenylmercury: D i s s o l v e 0.6063 g o f phenylmercuric a c e t a t e (Sect. 7.11). Add approximately 10% ( V / V ) a c e t o n i t r i l e (Sect. 7.1) t o a i d i n d i s s o l u t i o n . D i l u t e t o 500 mL w i t h deionized, d i s t i l l e d w a t e r (Sect. 7.2) and r e f r i g e r a t e i n a T e f l o n b o t t l e . This s o l u t i o n can be s to re d and used f o r a t l e a s t s i x months.

NOTE :

For a n a l y s ts who do n o t r o u t i n e l y perform mercury analyses o r do n o t wish t o generate excessive amounts o f mercury waste, t h e s t a t e d volumes and/or amounts o f organometal s a l t s should be reduced p r o p o r t i o n a t e l y . Primary and secondary d i l u t i o n standards may be d i l u t e d t o 10 mL o r 25 mL o f s o l u t i o n t o avoid t h i s problem.

SAMPLE COLLECTION, PRESERVATION AND HANDLING 8.1

Sample Collection--Samples should be c o l l e c t e d i n d u p l i c a t e i n amber colore d g l a s s c o n ta i n e rs o r g l a s s c o n t a i n e r s wrapped i n aluminum f o i l . The c o n ta i n e rs should n o t be p r e r i n s e d w i t h sample p r i o r t o collection. 8.1.1

When sampling from a water tap, open t h e t a p and a l l o w t h e system t o f l u s h u n t i l t h e water temperature has s t a b i l i z e d . A d j u s t t h e f l o w t o about 500 mL/min and c o l l e c t d u p l i c a t e samples from t h e f l o w i n g stream.

8.1.2

When sampling from an open body o f water, f i l l t h e sample c o n t a i n e r w i t h water from a r e p r e s e n t a t i v e area. Sampling equipment, i n c l u d i n g automatic samplers, must be f r e e o f p l a s t i c t u b i n g and o t h e r components t h a t may l e a c h i n t e r f e r e n t s i n t o t h e water. Automatic samplers t h a t composite samplers over t i m e must use r e f r i g e r a t e d g l a s s / T e f l o n sample c o n t a i n e r s .

8.2

Sample Pre s e rv a ti o n --Al l samples should be i c e d o r r e f r i g e r a t e d a t 4 ° C from t h e ti m e o f c o l l e c t i o n u n t i l f i l t r a t i o n . The samples should be f i l t e r e d as soon as p o s s i b l e ( Fi g u r e 3) a f t e r r e c e i v e d i n the laboratory.

8.3

Holding Time--Samples should be analyzed immediately a f t e r f i l t r a t i o n . I f t h i s i s n o t p o s s i b l e , samples should be r e f r i g e r a t e d a t 4 ° C . Maximum sample h o l d i n g t i m e i s one week.

Metals 8.4

9.

333

FIELD BLANKS 8.4.1

Processing a f i e l d r e a g e n t b l a n k (FRB) i s recommended a l o n g w i t h each sample s e t , which i s composed o f t h e samples c o l l e c t e d f r o m t h e same g e n e r a l sample s i t e a t a p p r o x i m a t e l y t h e same t i m e . A t t h e l a b o r a t o r y , f i l l a sample c o n t a i n e r w i t h r e a g e n t w a t e r , s e a l , and s h i p t o t h e sampling s i t e along w i t h t h e empty sample c o n t a i n e r s . R e t u r n t h e FRB t o t h e l a b o r a t o r y w i t h f i l l e d sample b o t t l e s .

NOTE:

The p r e v e n t i o n o f c o n t a m i n a t i o n and l o s s e s i s o f paramount importance i n organomercury s p e c i a t i o n and a n a l y s i s . P o t e n t i a l sources o f c o n t a m i n a t i o n i n t h e l a b o r a t o r y environment a r e d u s t , r e a g e n t i m p u r i t i e s , and sample c o n t a c t w i t h l a b o r a t o r y apparatus ( r e s u l t i n g i n c o n t a m i n a t i o n by l e a c h i n g o r s u r f a c e d e s o r p t i o n ) . D e p l e t i o n o f mercury v i a a d s o r p t i o n o n t o c o n t a i n e r s u r f a c e s must a l s o be c o n s i d e r e d .

CALIBRATION AND STANDARDIZATION 9.1

E s t a b l i s h LCEC o p e r a t i n g c o n d i t i o n s e q u i v a l e n t t o t h o s e i n d i c a t e d i n Table 1. C a l i b r a t e t h e HPLC system u s i n g t h e e x t e r n a l s t a n d a r d technique.

9.2

EXTERNAL STANDARD CALIBRATION PROCEDURE 9.2.1

An e x t e r n a l s t a n d a r d i s a s o l u t i o n c o n t a i n i n g a known amount o f a p u r e compound t h a t i s analyzed w i t h t h e same procedures and c o n d i t i o n s t h a t a r e used t o analyze samples c o n t a i n i n g t h a t compound. From measured d e t e c t o r responses t o known amounts o f t h e e x t e r n a l standard, a sample c o n c e n t r a t i o n o f t h a t compound can be c a l c u l a t e d f r o m measured d e t e c t o r response t o t h a t compound i n a sample analyzed w i t h t h e same procedures.

9.2.2

A t l e a s t t h r e e c a l i b r a t i o n standards a r e needed. One should c o n t a i n each a n a l y t e a t a c o n c e n t r a t i o n near t o b u t g r e a t e r t h a n i t s method d e t e c t i o n l i m i t (MDL) ( T a b l e 2); t h e o t h e r two s h o u l d b r a c k e t t h e c o n c e n t r a t i o n range expected i n t h e samples o r d e f i n e t h e w o r k i n g range o f t h e d e t e c t o r . For example, i f t h e MDL i s 1.0 p g / L and a sample i s expected t o c o n t a i n a p p r o x i m a t e l y 5.0 p g / L , aqueous standards s h o u l d be p r e p a r e d a t c o n c e n t r a t i o n s o f 2.0 p g / L , 5.0 p g / L , and 10.0 p g / L .

9.2.3

I n j e c t 0 . 1 mL o f each c a l i b r a t i o n s t a n d a r d and t a b u l a t e peak h e i g h t o r area response v e r s u s t h e c o n c e n t r a t i o n o f t h e standard. The r e s u l t s a r e t o be used t o p r e p a r e a c a l i b r a t i o n c u r v e f o r each a n a l y t e by p l o t t i n g t h e peak h e i g h t o r area v e r s u s t h e c o n c e n t r a t i o n .

334

Methods for the Determination

9.2.4

The working c a l i b r a t i o n curve must be v e r i f i e d on each working day by th e measurement o f one o r more c a l i b r a t i o n standards (and when/if t h e working e l e c t r o d e i s changed between analyses). I f t h e response f o r an a n a l y t e v a r i e s from t h e response p r e d i c t e d by t h e c a l i b r a t i o n curve (Sect. 9.2.2) by more than f lo%, t h e t e s t must be repeated u s i n g a f r e s h c a l i b r a t i o n standard. I f t h e r e s u l t s s t i l l do n o t agree ( i . e . , t h e response i s o f f by more than lo%), generate a new c a l i b r a t i o n curve f o r each a n a l y t e . (Assuming t h a t th e e l e c t r o d e surface i s " f a t i g u e d " , t h e a n a l y s t should change t h e GAME b e f o r e proceeding f u r t h e r ) . Ge n e ra l l y t h e e l e c t r o d e can be used 3 t o 4 days b e f o r e t h e o l d amalgam surface has t o be removed.

+

9.2.5

10.

S i n g l e p o i n t c a l i b r a t i o n i s sometimes an acceptable a l t e r n a t i v e t o a c a l i b r a t i o n curve. S i n g l e p o i n t standards should be prepared from t h e p r i m a r y d i l u t i o n standard s o l u t i o n s . The s i n g l e p o i n t c a l i b r a t i o n standard(s) should be prepared a t a c o n c e n t r a t i o n t h a t produces a response c l o s e ( + 10%) t o t h a t o f t h e unknowns.

OUALITY CONTROL 10.1 Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o operate a q u a l i t y c o n t r o l (QC) program. The minimum requirements o f t h i s program c o n s i s t o f t h e f o l l o w i n g : an i n i t i a l demonstration o f l a b o r a t o r y c a p a b i l i t y and r e g u l a r analyses o f l a b o r a t o r y reagent blanks ( i n c l u d i n g s o l v e n t / e l u e n t blanks) and l a b o r a t o r y f o r t i f i e d blanks ( l a b o r a t o r y QC samples). The l a b o r a t o r y must m a i n t a i n records t o document t h e q u a l i t y o f t h e data generated.

10.2 I n i t i a l demonstration o f low system ( d e t e c t o r ) background response (i.e., minimum r e s i d u a l (background) c u r r e n t and low n o i s e o u t p u t ) .

10.2.1

The system must operate w i t h t h e minimum absolute background c u r r e n t i n o rd e r t o o p t i m i z e s e n s i t i v i t y . D e t e c t i o n o f a n a l y te s a t low c o n c e n t r a t i o n s (e.g., 20 p g / L ) can r e s u l t i n chromatograms being superimposed on a background c u r r e n t which may exceed t h e peak h e i g h t s o f t h e analytes. High background c u r r e n t s may increase i n s t r u m e n t a l s u s c e p t i b i l i t y t o f l o w v a r i a t i o n n o i s e and p o s s i b l y l e a d t o n o n l i n e a r d e v i a t i o n s i n t h e c a l i b r a t i o n c u r v e ( s ) . The Faradaic response, which may a r i s e from an electrochemical r e a c t i o n o f t h e e l e c t r o a c t i v e i m p u r i t i e s i n t h e mobile phase ( e l u e n t ) i s t h e p r i n c i p a l component o f t h e c u r r e n t produced a t a constant p o t e n t i a l d e t e c t o r . The most common sources o f background c u r r e n t are t h e o x i d a t i o n / r e d u c t i o n o f t h e e l u e n t o r b u f f e r s a l t s , oxygen ( e i t h e r e l u e n t o r sample), f e r r o u s and/or f e r r i c i r o n and o t h e r metals i o n s .

Metals 10.2.2

335

The n o i s e a s s o c i a t e d w i t h an e l e c t r o c h e m i c a l d e t e c t o r i s dependent on t h e magnitude o f t h e background s i g n a l . I n g e n e r a l , t h e h i g h e r t h e background, t h e h i g h e r t h e n o i s e . The r a t i o o f t h e n o i s e t o t h e background c u r r e n t s t a y s about t h e same. Noise can be random o r p e r i o d i c and superimposed on t h e s t e a d y s t a t e background s i g n a l . The n o i s e r e p r e s e n t s t h e c o l l e c t i v e c o n t r i b u t i o n s f r o m pump p u l s a t i o n s , f l o w c e l l hydrodynamics, s u r f a c e r e a c t i o n s , s t a t i c e l e c t r i c i t y , power l i n e n o i s e , and e l e c t r o n i c s i g n a l a m p l i f i c a t i o n . N o i s e can be m i n i m i z e d by ( a ) o b t a i n i n g p u l s e l e s s f l o w , ( b ) f r e q u e n t system p a s s i v a t i o n , ( c ) p r o p e r maintenance o f pump s e a l s and check v a l u e s i n o r d e r t o m i n i m i z e f l o w f l u c t u a t i o n s , ( d ) p r o p e r system g r o u n d i n g , and ( e ) c a r e f u l s c r u t i n y o f t h e w o r k i n g e l e c t r o d e s u r f a c e - - a smooth, s h i n y m i r r o r - l i k e f i n i s h i s desirable.

10.3 Another p o s s i b l e source o f n o i s e i s t h e r e f e r e n c e e l e c t r o d e w h i c h provides a stable, reproducible voltage t o which t h e working e l e c t r o d e p o t e n t i a l maybe r e f e r e n c e d . The p o t e n t i a l v a l u e s h o u l d n o t v a r y w i t h t i m e and s h o u l d be r e p r o d u c i b l e f r o m e l e c t r o d e t o e l e c t r o d e . Leaks can o c c u r due t o d r y i n g and c r a c k i n g o f t h e porous p l u g . A s a consequence, t h e i n t e r n a l e l e c t r o l y t e c o n c e n t r a t i o n changes and s u b s e q u e n t l y t h e r e f e r e n c e p o t e n t i a l . 10.4 A i r bubbles t r a p p e d around and/or between t h e w o r k i n g and r e f e r e n c e e l e c t r o d e can cause n o i s e , random as w e l l as p e r i o d i c w i t h c o n s t a n t a m p l i t u d e and f r e q u e n c y . 10.5 I n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y accuracy and p r e c i s i o n . Analyze seven r e p l i c a t e s o f a l a b o r a t o r y f o r t i f i e d b l a n k s o l u t i o n ( l a b o r a t o r y QC samples) c o n t a i n i n g each a n a l y t e a t c o n c e n t r a t i o n l e v e l s n e a r t h e low c a l i b r a t i o n s t a n d a r d . (See r e g u l a t i o n s and maximum c o n t a m i n a n t l e v e l s f o r guidance on a p p r o p r i a t e concentrations.) 10.5.1

Prepare each r e p l i c a t e b y a d d i n g an a p p r o p r i a t e a l i q u o t o f the primarylsecondary d i l u t i o n standard solution, o r other c e r t i f i e d q u a l i t y c o n t r o l sample, t o r e a g e n t w a t e r . Analyze each r e p l i c a t e a c c o r d i n g t o t h e p r o c e d u r e d e s c r i b e d i n Sect. 11.

10.5.2

C a l c u l a t e t h e measured c o n c e n t r a t i o n o f each a n a l y t e i n each r e p l i c a t e and t h e mean accuracy ( a s mean percentage o f t r u e v a l u e ) and p r e c i s i o n (as r e l a t i v e s t a n d a r d d e v i a t i o n , RSD) o f t h e seven measurements o f each a n a l y t e .

10.5.3

F o r each a n a l y t e a t 50 k g / L , t h e mean accuracy expressed as a percentage o f t h e t r u e v a l u e i s a p p r o x i m a t e l y 93% and t h e RSD i s 5 11%.

336

Methods for the Determination 10.5.4

A n a l y s t s s h o u l d d e v e l o i l and m a i n t a i n a system o f c o n t r o l c h a r t s t o p l o t t h e p r e c i s i o n and accuracy o f a n a l y t e measurements o v e r t i m e .

10.5.5

I t i s recommended t h a t t h e l a b o r a t o r y p e r i o d i c a l l y document and d e t e r m i n e i t s d e t e c t i o n l i m i t c a p a b i l i t i e s f o r t h e a n a l y t e s o f i n t e r e s t . NOTE: The d e t e r m i n a t i o n o f t h e method d e t e c t i o n l i m i t (MDL) f o r t h i s method was p e r f o r m e d under s p e c i a l ( i d e a l ) e x p e r i m e n t a l c o n d i t i o n s i n o r d e r t o a c h i e v e t h e d e s i r e d l e v e l . The GAME was s p e c i a l l y p r e p a r e d and t h e system was a l l o w e d t o e q u i l i b r a t e o v e r a 4 day p e r i o d . E l u e n t f l o w was m a i n t a i n e d a t a p p r o x i m a t e l y 0.30.4 mL/min. The c u r r e n t s e n s i t i v i t y was i n c r e a s e d u n t i l t h e l o w e s t s e t t i n g was a c h i e v a b l e . The MDL o f each a n a l y t e was c a l c u l a t e d ( T a b l e 2 ) u s i n g procedures d e s c r i b e d in1*. The l i s t e d MDLs s h o u l d be a c h i e v a b l e o r l o w e r w i t h c o m m e r c i a l l y a v a i l a b l e i n s t r u m e n t a t i o n , which i n c l u d e improved s o l v e n t d e l i v e r y systems, new t r a n s d u c e r c e l l d e s i g n s , and i n s t a l l a b l e i n - l i n e deoxygenators t h a t remove a t l e a s t 99% o f t h e oxygen i n t h e sample and m o b i l e phase w i t h o u t affecting t h e i r i n t e g r i t y . Analyte detection a t regulatory l e v e l s s h o u l d be a c h i e v a b l e .

10.6 L a b o r a t o r y Reagent Blanks (LRB) B e f o r e p r o c e s s i n g any samples, t h e a n a l y s t must demonstrate t h a t a l l g l a s s w a r e and r e a g e n t i n t e r f e r e n c e s a r e under c o n t r o l . Each t i m e a s e t o f r e a g e n t s i s changed ( f r e s h e l u e n t added) o r a new w o r k i n g o r r e f e r e n c e e l e c t r o d e i n s t a l l e d , a LRB must be analyzed. I f w i t h i n t h e r e t e n t i o n t i m e window o f any a n a l y t e o f i n t e r e s t t h e LRB produces a peak t h a t would p r e v e n t t h e d e t e r m i n a t i o n o f t h a t a n a l y t e , d e t e r m i n e t h e source o f c o n t a m i n a t i o n and e l i m i n a t e t h e i n t e r f e r e n c e b e f o r e p r o c e s s i n g samples .

10.7 A s i n g l e l a b o r a t o r y f o r t i f i e d b l a n k c o n t a i n i n g each mercury a n a l y t e a t a c o n c e n t r a t i o n as s p e c i f i e d i n S e c t . 10.5 must be a n a l y z e d w i t h each s e t o f samples. E v a l u a t e t h e accuracy o f t h e measurements. Any problems must be l o c a t e d and c o r r e c t e d b e f o r e f u r t h e r analyses a r e performed. 10.8 A f i e l d r e a g e n t b l a n k s h o u l d be analyzed w i t h each s e t o f f i e l d samples. D a t a / i n f o r m a t i o n from t h e s e analyses w i l l be used t o h e l p d e f i n e and d e t e r m i n e c o n t a m i n a t i o n r e l a t e d t o f i e l d sampling and transportation activities. 10.9 Each q u a r t e r , rep1 i c a t e l a b o r a t o r y f o r t i f i e d b l a n k s must be analyzed t o d e t e r m i n e t h e p r e c i s i o n o f t h e l a b o r a t o r y measurements. These d a t a w i l l be used i n documenting d a t a q u a l i t y . 10.10 Each q u a r t e r , t h e l a b o r a t o r y must a n a l y z e a q u a l i t y c o n t r o l sample o b t a i n e d from an e x t e r n a l source. A q u a l i t y c o n t r o l sample s h o u l d be a n a l y z e d each t i m e a new s e t o f standards a r e used. The e n t i r e

Metals

337

a n a l y t i c a l p r o c e d u r e must be checked, i f u n a c c e p t a b l e accuracy d a t a i s obtained. 10.11 The l a b o r a t o r y must a n a l y z e an unknown performance e v a l u a t i o n sample ( i f a v a i l a b l e ) a t l e a s t once p e r y e a r . R e s u l t s f o r each a n a l y t e must be w i t h i n e s t a b l i s h e d acceptance l i m i t s . 11.

PROCEDURE-LIQUID CHROMATOGRAPHY WITH ELECTROCHEMICAL DETECTION (LCEC1

11.1

T a b l e 1 summarizes t h e recommended o p e r a t i n g c o n d i t i o n s f o r LCEC and p r e s e n t s a n a l y t e r e t e n t i o n t i m e s observed u s i n g t h i s method. The o p e r a t i n g c o n d i t i o n s may be changed ( e . g . , f l o w r a t e , m o d i f i e r p e r c e n t , e l e c t r o d e p o t e n t i a l , e t c . ) i n o r d e r t o enhance t h e separation o r detection.

11.2

CHROMATOGRAPHIC PROCEDURES 11.2.1

E l e c t r o d e c e l l p r e p a r a t i o n : The c e l l s h o u l d be p o l i s h e d b e f o r e use'. F)rom b e g i n n i n g use, and r e g u l a r l y d u r i n g i t s use, a new mercury f i l m must be d e p o s i t e d on t h e g o l d d i s k . F o l l o w t h e p r o c e d u r e f o r e l e c t r o d e p r e p a r a t i o n as s t a t e d i n t h e o p e r a t o r ' s manual. Mercury a p p l i c a t i o n - - T h i s process s h o u l d be c a r r i e d o u t i n a t r a y i n t h e e v e n t o f an a c c i d e n t a l s p i l l . F o l l o w t h e p r e c a u t i o n s f o r h a n d l i n g mercury. NOTE: Mercury has a h i g h vapor p r e s s u r e and s h o u l d always be s t o r e d i n a c l o s e d c o n t a i n e r o r under w a t e r . P r i o r t o mercury a p p l i c a t i o n r i n s e t h e e l e c t r o d e surface w i t h a small amount o f methanol and a i r - d r y b e f o r e p r o c e e d i n g . D e p o s i t i o n o f t h e mercury f i l m on t h e g o l d d i s k i s accomplished by p l a c i n g a small d r o p o f mercury on t h e g o l d s u r f a c e . Cover t h e e n t i r e s u r f a c e w i t h mercury u s i n g a d i s p o s a b l e p i p e t . Wait = 3-5 m i n u t e s , t h e n remove t h e excess mercury g e n t l y w i t h t h e sharp edge o f an i n d e x c a r d . ( T h i s s t e p may be r e p e a t e d 2 t o 4 t i m e s ) . The mercury s u r f a c e can be smoothed w i t h a s o f t t i s s u e ( l e n s t i s s u e works b e s t ) t o o b t a i n a s h i n y , m i r r o r f i n i s h . (DISPOSE OF WASTE MERCURY CAREFULLY.) I f excess mercury i s l e f t on t h e e l e c t r o d e , t h e r e i s a p o s s i b i l i t y o f a short c i r c u i t w i t h the a u x i l i a r y electrode (stainless s t e e l t o p ) . I n some i n s t a n c e s , t h e i n s e r t i o n o f a second g a s k e t between t h e e l e c t r o d e cube h a l v e s can remedy t h e problem. Sometimes i t i s n o t necessary t o remove t h e o l d amalgam s u r f a c e b e f o r e a f r e s h mercury s u r f a c e can be a p p l i e d . The new mercury s u r f a c e can be formed on t o p o f t h e o l d amalgam. F o l l o w t h e same p r o c e d u r e as f o r a f r e s h gold surface.

338

Methods for the Determination The amalgam r e q u i r e s a p e r i o d o f e q u i l i b r a t i o n f o l l o w i n g i t s formation. U s u a l l y a l l o w i n g t h e amalgam t o r e s t o v e rn i g h t i s s u f f i c i e n t .

11.3 SYSTEM OPERATION 11.3.1

The i n s tru m e n ta ti o n should be t u r n e d on and allowed t o become s t a b l e b e fo re beginning.

11.3.2

The f o l l o w i n g chromatographic s t a r t - u p przocedure i s recommended f o r r e d u c t i v e LCEC a n a l y s i s . DEOXYGENATION: Before i n i t i a t i n g f l o w through t h e LC system, t h e e l u e n t, which i s placed i n a 2-L d i s t i l l a t i o n f l a s k , i s r e f l u x e d a t 40 k 5°C w h i l e being purged v i g o r o u s l y w i t h i n e r t gas (argon o r helium) f o r approximately 1-2 hours ( Fi g u r e 2 A ) . Then t h e degassed mobile phase i s pumped through t h e LCEC system t o f o r c e o u t any oxygen e n t r a i n e d i n t h e s t a t i o n a r y phase pores (column i n t e r s t i c e s ) . Degassing t h e system may r e q u i r e 100-150 mL o f mobile phase. The system must be f l u s h e d th o ro u g h l y . Next, t h e working e l e c t r o d e i s t u r n e d on ( a f t e r flushing) using the l e a s t sensitive gain setting. The c u r r e n t i s monitored u n t i l t h e background c u r r e n t has s t a b i l i z e d i n t h e d e s i r e d range, u s u a l l y 80 t o 100 nA.

11.3.3

Sample degassing i s n e c e s s i t a t e d when working a t p o t e n t i a l s more n e g a t i v e than -0.1 V f o r t h e Care must be taken i n o r d e r t o preserve t h e sample’s o r i g i n a l composition. The purge gas should be p re s a tu ra te d w i t h mobile phase o r water and flowed g e n t l y through t h e sample t o minimize i t s evaporation. Degassing a 3.5-4 mL sample r e q u i r e s approximately 5 min.

11.3.4

The Sample i n j e c t i o n r e q u i r e s a closed system. i n j e c t i o n v a l v e i n l e t i s immersed i n t h e f i l t e r e d and degassed sample s o l u t i o n and t h e sample a l i q u o t i s s l o w l y drawn i n t o t h e i n @ c t i o n l o o p by g e n t l e s u c t i o n (F i g u re 2C)1a11s141 Exposure t o oxygen i s avoided and t h e i n t e g r i t y o f t h e closed system i s preserved.

.

12.

CALCULATIONS

12.1 Calcu l a te a n a l y te c o n c e n tra ti o n s i n t h e sample by u t i l i z i n g t h e c a l i b r a t i o n c u rv e (s ) generated from t h e responses o f a n a l y t e s i n standard sol u t ions

.

12.2 Data should be rounded t o t h e t e n t h s p l a c e and r e p o r t e d i n micrograms p e r l i t e r .

Metals 13.

14.

339

PREC I S I O N AND ACCURACY 13.1

I n a s i n g l e l a b o r a t o r y t h e MDL” was d e t e r m i n e d f o r each a n a l y t e . Seven a l i q u o t s o f t h e f o r t i f i e d d i s t i l l e d w a t e r sample were measured and t h e r e s u l t s used t o c a l c u l a t e t h e MDL a t t h e 99% c o n f i d e n c e l e v e l . The c a l c u l a t e d MDLs ( T a b l e 2) ranged f r o m 0.8 t o 1.9 p g / L .

13.2

I n a s i n g l e laboratory, analyte recoveries from l a b o r a t o r y d i s t i l l e d w a t e r , t a p w a t e r , and two groundwaters were determined a t a n a l y t e c o n c e n t r a t i o n s r a n g i n g from 50 t o 200 p g / L (Tables 3-5). Recoveries averaged 90 f 7% RSD w i t h comparable v a l u e s o b t a i n e d o v e r t h e e n t i r e range o f c o n c e n t r a t i o n s . The s t a n d a r d d e v i a t i o n o f t h e measurements on a l l w a t e r s was a p p r o x i m a t e l y 1.52 p g / L w i t h an RSD o f a p p r o x i m a t e l y 0.64%.

REFERENCES

1.

Evans, 0. and McKee, G.D.,

Analyst,

1987, 112, 983.

2.

Evans, 0. and McKee, G.D.,

Analyst,

1988, 113, 243.

3.

MacCrehan, W.A., 10, 1175.

4.

MacCrehan, W.A., D u r s t , R.A., and Bellama, J.M., Nat. Bur. Stand. (U.S.), Spec. Publ., 1977, No.519, 57.

5.

MacCrehan, W.A.

6.

MacCrehan, W.A.,

7.

Holak, W.,

J. L i a . Chromatoar.

8.

Holak, W.,

Analyst,

9.

K r u l l , I.S., Bushee, D.S., Analyst, 1986, 111, 345.

D u r s t , R.A.,

and Bellama, J.M., Anal. L e t t .

and D u r s t , R.A., Anal. Chem.,

Anal. Chem.

1977,

1978, 50, 2108.

1981, 53, 74. 1985, 8, 563.

1982, 107, 1457. S c h l e i c h e r , R.G.,

and Smith, S.B.,

Jr.,

10.

” I n s t a l l a t i o n / O p e r a t i o n s Manual f o r Amperometric C o n t r o l l e r and Transducer Package,” B i o a n a l y t i c a l Systems, West L a f a y e t t e , IN, 1984.

11.

Jacobs, W. Curr. Sep. 1982, 4, 45.

12.

Glaser, J.A., F o e r s t , D.L., McKee, G.D., Quave, S.A., W.L., E n v i r o n . Sci. Technol., 1981, 15, 1426.

13.

Lewis, J.Y., Zodda, J.P., Chem., 1983, 55, 708.

Deutsch, E.,

and Budde,

and Heineman, W.R.,

Anal.

340

Methods for the Determination

14.

Bratin, K . , and Kissinger, P . T . , J a l a n t g 1982, 29, 365.

15.

Bratin, K . , and Kissinger, P . T . , (Suppl.2), 321.

-oar.,

1981, 4 ,

Metals TABLE 1.

PRIMARY CHROMATOGRAPHIC CONDITIONS Absolute Retention l i m e , Min (a) (b)

Analyte Mercury ( I I ) Methyl mercury Et hy 1mercury Phenyl mercury

(a) (b)

341

3.3 3.5 4.2 5.3

5.4 5.9 6.9 9.2

Flow r a t e - 1.0 mL/min. Flow r a t e - 0.6 mL/min. Primary Conditions: A n a l y t i c a l Column: 25 cm x 4.6 mm i . d . , EM Science LiChrosorb RP-18 (5pm) S a t u r a t o r Column, 70 mm x 4.6 mm i . d . Science

Pre-Column:

(18 pm) EM

Guard Column:

70 mm X 4.6 mm i.d., EM Science P e r i s o r b RP-18 (30-40 pm)

Mobi e Phase:

I s o c r a t i c e l u t i o n - 60% (w/w) methanol, 0.01% ( V / V ) 2-mercaptoethanol, pH 5.5 acetate buffered

F1ow Rate:

1.0 mL/min o r 0.6 mL/min*

I n j e c t i o n volume:

100 p L

Detector: Electrochemical (GAME);

- 0.800 V vs. Ag/AgCl

*The optimum f l o w r a t e i s = 1.0 mL/min. However, i n some instances i t i s d e s i r a b l e t o use a lower f l o w r a t e . A f l o w r a t e o f 0.6 mL/min allows a s l i g h t l y b e t t e r separation between Hg(I1) and CH Hg' than a f l o w r a t e o f 1.0 mL/min. The lower f l o w r a t e does, however, r e s u l t i n approximately a 6-12% decrease i n t h e a n a l y t i c a l s i g n a l s .

342

Methods for the Determination TABLE 2.

METHOD DETECTION L I M I T (MDL) (a)

Hg ( I I )

Parameter

CH,Hg'

CH ,H , g'

CH ,H , g'

Retention time, min

=5.3

-5.8

-6.9

z9.5

MDL*, pg/L

~1.8

z1.9

=1.7

z0.8

(a)

Experimental c o n d i t i o n s :

60% (W/W)

o f 2-mercaptoethanol (ME). 0.6

mL min-

lb in

-2;

1

.

CH,OH,

pH 5.5 acetate b u f f e r , 200 pL

P o t e n t i a l , - 0.800V vs. Ag/AgCl; f l o w r a t e

Other c o n d i t i o n s : 100 p L sample loop;

c u r r e n t o f f s e t ca.

(25cm x 4.6mm i.d.).

-

= 45.5OC, =

2250

20 nA; GAME; and LiChrosorb RP-18 (5 pm)

*For t h e MDL determination seven r e p l i c a t e

measurements were made on s o l u t i o n s c o n t a i n i n g each a n a l y t e (12). f o r t i f i e d value ( t r u e concentration) o f each analyte i s 10 pgfL.

The

Metals TABLE 3. RECOVERY OF ANALYTES FROH REAGENT WATER (a)

Mixture

(a)

Hg Analytes

Hg determ] ned CLQ L (mean f s.d.)

Recovery, % (mean f s.d.)

120

113.2 f 2.1

94.4 f 1.8

120

117.1 f 1.4

97.6 f 1.2

120

118.4 f 1.5

98.7 f 1.3

120

123.2 f 0.8

102.6 f 0.6

150

153.0 f 1.3

102.0 f 0.9

150

154.6 f 1.4

103.1 f 1.0

150

154.4 f 1.4

103.0 f 0.9

150

143.3 f 0.3

95.5 f 0.2

250

249.0 f 0.8

99.6 f 0.3

250

255.7 f 1.6

102.3 f 0.6

2 50

255.2 f 2.2

102.1 f 0.9

250

250.5 f 0.8

100.2 f 0.3

Hg addef c(9 L'

Three determinations per s o l u t i o n ; 40% ( W / W ) f l o w r a t e = 1.0 mL/min.

methanol;

343

344

Methods for the Determination TABLE 4. RECOVERY OF ANALYTES FROM GROUNDWATER (LAKOTA HILLS) ( a )

Hg d e t e r m i r e d Mixture

(a)

Hg A n a l y t e s

Hg addef ccg L-

Crg L (mean f s . d . )

50 50 50 50

38.5 45.8 51.9 41.2

f f f f

70 70 70 70

58.1 65.0 64.5 68.5

f 0.1 f 3.5 f 2.4

90 90 90 90

72.9 84.2 85.8 98.0

120 120 120 120

0.3 0.0 0.2 0.4

Recovery, % (mean f s.d.)

77.0 91.6 103.8 82.4

f

0.6

k 0.0 f 0.4 f 0.9 f 0.2 f 5.0 f 3.5

f 0.8

83.0 92.9 92.1 97.9

f f f f

0.3 3.0 1.2 1.8

81.0 93.6 95.3 100.0

f 0.3 f 3.4

99.8 114.5 115.4 118.5

f f f f

0.0 1.9 1.0 1.0

83.2 95.4 96.1 98.8

f 0.0

150 150 150 150

143.9 143.3 144.9 145.9

f f f f

0.4 0.9 0.2 0.7

95.9 95.5 96.6 97.3

f 0.2

200 200 200 200

200.1 192.8 190.1 185.1

f 2.3 f 1.3 f 1.6

100.0 96.4 95.1 92.6

f 1.1 f 0.7

k

1.2

Two d e t e r m i n a t i o n s p e r s o l u t i o n ; 40% ( W / W ) f l o w r a t e = 1.0 mL/min.

methanol;

f 1.1

f 1.3 f 2.0

f 1.6 f 0.8 f 0.9

f 0.6 f 0.1 f

0.5

f 0.8 f 0.6

Metals

TABLE

5.

RECOVERY OF ANALYTES FROM GROUND WATER (CLERMONT COUNTY, OH) AND TAP WATER (CINCINNATI, OH) ( A )

Hg added

Mixture

Hg Analytes

p9L.l

Hg measured i n groundwater Pg L-l (mean f s . d .

50 50 50 50

52.3 43.6 42.1 49.0

f 2.0 f 2.0 f 3.9 f 2.3

100 100 100 100

98.6 93.3 97.0 94.9

f 4.0 f 3.5 f 2.6 f 3.0

120 120 120 120

120.1 111.5 109.4 120.6

f f f f

Hg measured i n t a p water Recovery, % Recovery, % P9L.l (mean f s . d . ) (mean f s . d . )

(mean f s . d . )

49.5 51.1 44.8 47.6

4.5 3.3 5.4 4.6

104.6 87.2 85.4 96.8

f 4.0 f 4.3 f 1.9 f 4.5

99.0 103.4 89.6 95.2

100.7 f 0.9 103.1 f 1.9 88.0 f 6.5 99.3 f 0.8

98.6 93.3 91.0 94.9

f 4.0 f 3.5 f 2.6 f 3.0

101.9 f 0.9 103.1 f 1.9 88.0 f 6.5 99.3 & 0.8

100.1 92.9 91.2 100.5

f 0.4 f 4.1 f 3.5

f f f f

0.5 1.3 4.0 0.4

150 150 150 150 (a)

345

Three d e t e r m i n a t i o n s p e r s o l u t i o n ; 60% (W/W)

150.5 153.3 129.5 138.9

f f f f

3.6 2.4 3.8 2.0

f 9.0 f 6.7 f11.0 f 9.1

f 0.3 100.3 102.2 86.3 92.6

methanol, f l o w r a t e = 1.0 mL/min.

f 2.4 f 1.6 f 2.6 f 1.3

346

Methods for the Determination

1

0

2

4

6

8

Retention Time (min.) F i g u r e 1 , Separation o f f o u r charge-neutral mercury a n a l y t e s . Conditions: e l u e n t , 60% ( W / W ) methanol, column, LiChrosorb RP-18 ( 5 pm),, 25 x 0 . 4 6 cm; pH 5.5 a c e t a t e buffer; 0.01% ( V / V ) 2-ME; f l o w r a t e , 1.0 mL min- ; standard m i x t u r e , 10 pg mL- each a n a l y t e ; sample loop, 100 pL. (1) H g I I ; (2) methylmercury; ( 3 ) ethylmercury; and ( 4 ) phenylmercury.

0

Figure 2 . (a) (b)

=I-

""o'='

""'

(c)

D e o x y g e n a c i o n .Appara:as

M o b i l e Phase Degassing S a m p l e Degassing I n j e c c o r in Load ?ss;:isr..i

Water In

To Pump Argon In

118" Stainless Steel Tubing Temperature Probe To Heat Control Unit

6" Stainless Steel

INJECTOR 1

Heating Mantle Argon In

o Injector 'Load" Position 6

To Sample

i Sample Loop

Argon Saturation Chamber

Sample

Solution

LOAD POSITION

z2

c m w

P 4

348

Methods for the Determination

Stainless Steel

Figure

5.

Sample and Mobile Phase Filtration A p p a r a t u s

Metals METHOD 245.5 DETERMINATION OF MERCURY I N SEDIMENTS BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY

Edited by L a r r y B. Lobring and B i l l y B. P o t t e r Inorganic Chemistry Branch Chemistry Research D i v i s i o n

Revision 2.3 A p r i l 1991

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

349

350

Methods for the Determination METHOD 245.5 DETERMINATION OF MERCURY I N SEDIMENTS BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY

1.

SCOPE AND APPLICATION

1.1 T h i s procedure'*2 measures t o t a l mercury ( o r g a n i c + i n o r g a n i c ) i n s o i l s , sediments, bottom d e p o s i t s and sludge t y p e m a t e r i a l s . 1.2

2.

3.

The range o f t h e method i s 0.2 t o 5 k g / g . The range may be extended above o r below t h e normal range by i n c r e a s i n g or d e c r e a s i n g sample s i z e o r by o p t i m i z i n g i n s t r u m e n t s e n s i t i v i t y .

SUMMARY OF METHOD

2.1

A weighed p o r t i o n o f t h e sediment sample i s t r a n s f e r r e d t o a BOD b o t t l e ( o r e q u i v a l e n t f l a s k f i t t e d w i t h a ground g l a s s s t o p p e r ) and d i g e s t e d i n aqua r e g i a f o r 2 min a t 950C. The d i g e s t e d sediment sample i s d i l u t e d . Potassium permanganate i s added t o t h e sediment sample. The BOD b o t t l e i s t r a n s f e r r e d t o t h e w a t e r b a t h where t h e sediment sample i s o x i d i z e d f o r 30 min a t 95°C. Mercury i n t h e d i g e s t e d sediment sample i s reduced w i t h stannous c h l o r i d e t o elemental mercury and measured by t h e c o n v e n t i o n a l c o l d vapor atomic absorption technique.

2.2

An a l t e r n a t e d i g e s t i o n 3 i n v o l v i n g t h e use o f an a u t o c l a v e i s described i n (Sect. 11.3).

DEFINITIONS

3.1

BIOCHEMICAL OXYGEN DEMAND (BOD) BOTTLE - BOD b o t t l e , 300 f 2 mL w i t h a ground g l a s s s t o p p e r o r an e q u i v a l e n t f l a s k , f i t t e d w i t h a ground glass stopper.

3.2

C A L I BRAT ION BLANK - A volume o f ASTM t y p e I 1 r e a g e n t w a t e r prepared i n t h e same manner ( a c i d i f i e d ) as t h e c a l i b r a t i o n standard.

3.3

CALIBRATION STANDARD (CAL) - A s o l u t i o n p r e p a r e d from t h e mercury s t o c k standard s o l u t i o n used t o c a l i b r a t e t h e i n s t r u m e n t response w i t h respect t o analyte concentration.

3.4

INSTRUMENT DETECTION LIMIT (IDL) - The mercury c o n c e n t r a t i o n t h a b produces a s i g n a l equal t o t h r e e t i m e s t h e s t a n d a r d d e v i a t i o n o f t h e blank signal.

3.5

LABORATORY F O R T I F I E D BLANK (LFB) - An a l i q u o t o f ASTM t y p e I 1 reagent water t o which known q u a n t i t i e s o f i n o r g a n i c and/or o r g a n i c mercury a r e added i n t h e l a b o r a t o r y . The LFB i s analyzed e x a c t l y

Metals

351

l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether method performance i s w i t h i n accepted c o n t r o l l i m i t s .

3.6

LABORATORY F O R T I F I E D SAMPLE MATRIX (LFM) - An a l i q u o t o f a sediment sample t o which known q u a n t i t i e s o f c a l i b r a t i o n standard a r e added i n t h e l a b o r a t o r y . The LFM i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o determine whether t h e sample m a t r i x c o n t r i b u t e s b i a s t o t h e a n a l y t i c a l r e s u l t s . The background c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be determined i n a separate a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r t h e c o n c e n t r a t i o n s found.

3.7

LABORATORY REAGENT BLANK (LRB) - An a l i q u o t o f ASTM t y p e I 1 r e a g e n t w a t e r t h a t i s t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a l l glassware, equipment, and r e a g e n t s used i n analyses. The LRB i s used t o determine i f method a n a l y t e o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e l a b o r a t o r y environment, r e a g e n t s , o r apparatus.

3.8

LINEAR DYNAMIC RANGE (LDR) - The c o n c e n t r a t i o n range o v e r which t h e a n a l y t i c a l w o r k i n g c u r v e remains l i n e a r .

3.9

METHOD DETECTION LIMIT (MDL) - The minimum c o n c e n t r a t i o n o f mercury t h a t can be i d e n t i f i e d , measured and r e p o r t e d w i t h 99% c o n f i d e n c e t h a t t h e a n a l y t e c o n c e n t r a t i o n i s g r e a t e r t h a n z e r o and determined from a n a l y s i s o f seven LFMs.

3 . 1 0 QUALITY CONTROL SAMPLE (QCS) - A sediment sample c o n t a i n i n g known c o n c e n t r a t i o n o f mercury d e r i v e d f r o m e x t e r n a l l y prepared t e s t m a t e r i a l s . The QCS i s o b t a i n e d f r o m a source e x t e r n a l t o t h e 1 a b o r a t o r y and is used t o check 1a b o r a t o r y performance. 3 . 1 1 SEDIMENT SAMPLE - A f l u v i a l , sand and/or humic sample m a t r i x exposed t o a marine, b r a c k i s h o r f r e s h w a t e r environment. I t i s l i m i t e d by t h i s method t o t h a t p o r t i o n which may be passed t h r o u g h a number 10 s i e v e o r a 2 mm mesh s i e v e . 3.12 STOCK STANDARD SOLUTION - A c o n c e n t r a t e d mercury s o l u t i o n prepared i n t h e l a b o r a t o r y u s i n g assayed m e r c u r i c c h l o r i d e o r s t o c k standard s o l u t i o n purchased f r o m a r e p u t a b l e commercial source.

4.

INTERFERENCES

4.1

I n t e r f e r e n c e s have been r e p o r t e d f o r w a t e r s c o n t a i n i n g s u l f i d e , c h l o r i d e , copper and t e l l u r i u m . Organic compounds which have broad band UV absorbance (around 253.7 nm) a r e c o n f i r m e d i n t e r f e r e n c e s . The c o n c e n t r a t i o n l e v e l s f o r i n t e r f e r a n t s a r e d i f f i c u l t t o d e f i n e . T h i s suggests t h a t q u a l i t y c o n t r o l procedures ( S e c t . 10) must be s t r ic t 1y f o l 1owed.

4.2

V o l a t i l e m a t e r i a l s which absorb a t 253.7 nm w i l l cause a p o s i t i v e i n t e r f e r e n c e . I n o r d e r t o remove any i n t e r f e r i n g v o l a t i l e

352

Methods for the Determination m a t e r i a l s , t h e dead a i r space i n t h e BOD b o t t l e s h o u l d be purged b e f o r e a d d i t i o n o f stannous c h l o r i d e s o l u t i o n .

5.

SAFETY 5.1

The t o x i c i t y and c a r c i n o g e n i c i t y o f each r e a g e n t used i n t h i s method has n o t been f u l l y e s t a b l i s h e d . Each chemical s h o u l d be r e g a r d e d as a p o t e n t i a l h e a l t h hazard and exposure4 t o t h e s e compounds s h o u l d be m i n i m i z e d by good l a b o r a t o r y p r a c t i c e s . Normal accepted 1 a b o r a t o r y s a f e t y p r a c t i c e s s h o u l d be f o l l o w e d d u r i n g r e a g e n t p r e p a r a t i o n and i n s t r u m e n t o p e r a t i o n . Always wear s a f e t y g l a s s e s o r f u l l - f a c e s h i e l d f o r eye p r o t e c t i o n when w o r k i n g w i t h t h e s e r e a g e n t s . Each l a b o r a t o r y i s r e s p o n s i b l e f o r m a i n t a i n i n g a c u r r e n t s a f e t y p l a n , a c u r r e n t awareness f i l e o f OSHA r e g u l a t i o n s r e a r d i n g t h e s a f e h a n d l i n g o f t h e c h e m i c a l s s p e c i f i e d i n t h i s method 6

.

5.2

6.

Mercury compounds a r e h i g h l y t o x i c i f swallowed, i n h a l e d , o r absorbed t h r o u g h t h e s k i n . Analyses s h o u l d be conducted i n a l a b o r a t o r y exhaust hood. The a n a l y s t s h o u l d use chemical r e s i s t a n t g l o v e s when h a n d l i n g c o n c e n t r a t e d mercury s t a n d a r d s .

APPARATUS AND EQUIPMENT 6.1

ABSORPTION CELL - Standard s p e c t r o p h o t o m e t e r c e l l s 10-cm l o n g , h a v i n g q u a r t z windows may be used. S u i t a b l e c e l l s may be c o n s t r u c t e d f r o m p l e x i g l a s s t u b i n g , l - i n . O.D. by 4 1 / 2 - i n . l o n g . The ends a r e ground p e r p e n d i c u l a r t o t h e l o n g i t u d i n a l a x i s and q u a r t z windows ( 1 - i n . d i a m e t e r by 1 / 1 6 - i n . t h i c k n e s s ) a r e cemented i n p l a c e . Gas i n l e t and o u t l e t p o r t s ( a l s o o f p l e x i g l a s s b u t 1 / 4 - i n . O.D.) a r e a t t a c h e d a p p r o x i m a t e l y 1 / 2 - i n . f r o m each end. The c e l l i s s t r a p p e d t o a b u r n e r f o r s u p p o r t and a l i g n e d i n t h e l i g h t beam t o g i v e t h e maximum t r a n s m i t t a n c e .

6.2

AERATION TUBING - I n e r t m e r c u r y - f r e e t u b i n g i s used f o r passage o f mercury vapor f r o m t h e sample b o t t l e t o t h e a b s o r p t i o n c e l l . I n some systems, mercury vapor i s r e c y c l e d . S t r a i g h t g l a s s t u b i n g t e r m i n a t i n g i n a c o a r s e porous g l a s s a s p i r a t o r i s used f o r p u r g i n g mercury r e l e a s e d f r o m t h e sediment sample i n t h e BOD b o t t l e .

6.3

A I R PUMP - Any pump ( p r e s s u r e o r vacuum system) c a p a b l e o f p a s s i n g a i r 1 L/min i s used. Regulated compressed a i r can be used i n an open one-pass system.

6.4

ATOMIC ABSORPTION SPECTROPHOTOMETER - Any a t o m i c a b s o r p t i o n u n i t h a v i n g an open sample p r e s e n t a t i o n area i n which t o mount t h e a b s o r p t i o n c e l l i s s u i t a b l e . I n s t r u m e n t s e t t i n g s recommended by t h e p a r t i c u l a r m a n u f a c t u r e r s h o u l d be f o l l o w e d . I n s t r u m e n t s d e s i g n e d s p e c i f i c a l l y f o r mercury measurement u s i n g t h e c o l d vapor t e c h n i q u e a r e c o m m e r c i a l l y a v a i l a b l e and may be s u b s t i t u t e d f o r t h e a t o m i c absorption spectrophotometer.

6.5

B I O C H E M I C A L OXYGFN IEMAND

(BOD) BOTTLE

- See S e c t . 3 . 1 .

Metals

353

6.6

D R Y I N G TUBE - Tube ( 6 - i n . x 3 / 4 - i n . OD) c o n t a i n i n g 20 g o f magnesium p e r c h l o r a t e . The f i l l e d t u b e i s i n s e r t e d ( i n - l i n e ) between t h e BOD b o t t l e and t h e a b s o r p t i o n t u b e . I n p l a c e o f t h e magnesium p e r c h l o r a t e d r y i n g tube, a small r e a d i n g lamp i s p o s i t i o n e d 0 r a d i a t e heat (about 10°C above ambient) on t h e a b s o r p t i o n c e 1 . Heat from t h e lamp p r e v e n t s w a t e r c o n d e n s a t i o n i n t h e c e l l .

6.7

FLOWMETER

6.8

MERCURY HOLLOW CATHODE LAMP - S i n g l e element h o l l o w cathode e l e c t r o d e l e s s d i s c h a r g e lamp and a s s o c i a t e d power s u p p l y .

6.9

PYREX D I S H - Any a p p r o p r i a t e s i z e , (8-in. x 8-in.) o r (8-in. x 12in.).

-

Capable o f measuring an a i r f l o w o f 1 L/min. amp o r

6.10 RECORDER - Any mu1t i - r a n g e v a r i a b l e speed r e c o r d e r t h a t is c o m p a t i b l e w i t h t h e UV d e t e c t i o n system i s s u i t a b l e . 6.11 S I E V E - H i g h - d e n s i t y p o l y e t h y l e n e ; p o l y e s t e r mesh, no. 10 mesh, 12i n . 0.D and 3 1 / 2 - i n . depth. 6.12 WATER BATH - The w a t e r b a t h s h o u l d have a covered t o p and c a p a c i t y t o s u s t a i n a w a t e r d e p t h o f 2 - i n . t o 3 - i n . a t 95°C f 1 ° C . The dimensions o f t h e w a t e r b a t h should be l a r g e enough t o accommodate BOD b o t t l e s c o n t a i n i n g CAL, LFB, LFM, LRB, QCS and sediment samples w i t h t h e l i d on.

7.

REAGENTS AND CONSUMABLE MATERIALS

7.1

Reagents may c o n t a i n elemental i m p u r i t i e s which b i a s a n a l y i c a l r e s u l t s . A l l r e a g e n t s should be assayed by t h e chemical m a n u f a c t u r e r f o r mercury and meet ACS s p e c i f i c a t i o n s . I t S recommended t h a t t h e l a b o r a t o r y a n a l y s t assay a l l r e a g e n t s f o r mercury. 7.1.1

H y d r o c h l o r i c A c i d (HCL), c o n c e n t r a t e d ( s p . g r . 1. 9 ) 9 (CASRN 7647-01-0); assayed mercury l e v e l i s n o t o exceed 1 PPb.

7.1.2

Hydroxylamine H y d r o c h l o r i d e (NH OH'HCl), (CASRN 5470-11-1) may be used i n p l a c e o f hydroxytamine s u l f a t e (Sect. 7.6); assayed mercury l e v e l o f compound i s n o t t o exceed 0.05 ppm.

7.1.3

Hydroxylamine S u l f a t e [ (NH,OH);H SO,] (CASRN 10039-54-0); assayed mercury l e v e l o f compoun6 i s n o t t o exceed 0.05 ppm.

7.1.4

M e r c u r i c C h l o r i d e (tigcl,),

(CASRN 7487-94-7).

354

Methods for the Determination

7.1.5

N i t r i c Acid (HNO,), concentrated ( s p . g r . 1 . 4 1 ) , (CASRN 7697-37-2); assayed mercury l e v e l i s n o t t o exceed 1 ppb.

7.1.6

Potassium Permanganate (KMnO,), (CASRN 7722-64-7); mercury l e v e l i s n o t t o exceed 0 . 0 5 ppm.

7.1.7

Reagent Water, ASTM type II.7

7.1.8

Sodium C h l o ri d e (NaCl), (CASRN 7647-14-5); l e v e l i s n o t t o exceed 0.05 ppm.

7.1.9

Stannous C h l o ri d e (SnC1;2H2O) , (CASRN 10025-69-1); assayed mercury l e v e l i s n o t t o exceed 0 . 0 5 ppm.

7.1.10

Stannous S u l f a t e (SnSO,) , (CASRN 7488-55-3) ; assayed mercury l e v e l i s n o t t o exceed 0 . 0 5 ppm.

7.1.11

S u l f u r i c Acid (H,SO,), concentrated (sp.gr. 1 . 8 4 ) , (CASRN 7664-93-9); assayed mercury l e v e l i s n o t t o exceed 1 ppb.

assayed

assayed mercury

7.2

AQUA R E G I A - Prepare immediately b e f o r e use by c a r e f u l l y adding t h r e e volumes o f conc. HC1 (Sect. 7 . 1 . 1 ) t o one volume o f conc. HNO, (Sect. 7 . 1 . 5 ) .

7.3

MERCURY CALIBRATION STANDARD - To each v o l u m e t r i c f l a s k used f o r s e r i a l d i l u t i o n s , a c i d i f y w i t h ( 0 . 1 t o 0.2% by volume) HNO, (Sect. 7 . 1 . 5 ) . Using mercury stock standard (Sect. 7 . 4 ) , make s e r i a l d i l u t i o n s t o o b t a i n a c o n c e n t r a t i o n o f 0 . 1 pg Hg/mL. Th i s standard should be prepared j u s t b e f o r e analyses.

7.4

MERCURY STOCK STANDARD - D i s s o l v e i n a 100-mL v o l u m e t r i c f l a s k 0.1354 g HgCl (Sect. 7 . 1 . 4 ) w i t h 75 mL o f reagent water (Sect. 7 . 1 . 7 ) . Add $0 mL o f conc. HNO, (Sect. 7 . 1 . 5 ) and d i l u t e t o mark. Concentration i s 1 . 0 mg Hg/mL. '

7.5

POTASSIUM PERMANGANATE SOLUTION- D i s s o l v e 5 g o f KMnO, (Sect. 7 . 1 . 6 ) i n 100 mL o f reagent water (Sect. 7 . 1 . 7 ) .

7.6

SODIUM CHLORIDE-HYDROXYLAMINE SULFATE SOLUTION - D i s s o l v e 12 g o f NaCl (Sect. 7 . 1 . 8 ) and 12 g o f (NH,OH) H ' ,SO, (Sect. 7 . 1 . 3 ) or 12 g o f NH OH-HCl (Sect. 7 . 1 . 2 ) ] d i l u t e w i t 6 reagent water (Sect. 7 . 1 . 7 ) t o 105 mL.

7.7

STANNOUS CHLORIDE SOLUTION - Add 25 g o f SnC1;2HO (Sect. 7 . 1 . 9 ) o r 25 g o f SnSO, (Sect. 7 . 1 . 1 0 ) t o 250 mL o f 0 . 5 N d2S0, (Sect. 7 . 8 ) . T his m i x t u r e i s a suspension and should be s t i r r e d c o n t i n u o u s l y d u r i n g use.

7.8

SULFURIC ACID, 0.5 N - Slowly add 1 4 . 0 mL o f conc. H SO, 7 . 1 . 1 1 ) d i l u t e t o 1 L w i t h reagent water (Sect. 7 . 1 . 5 ) .

(Sect.

Metals 8.

9.

355

SAMPLE COLLECTION, PRESERVATION AND STORAGE 8. 1

Because o f t h e extreme s e n s i t i v i t y o f t h e a n a l y t i c a l procedure and t he presence o f mercury i n a l a b o r a t o r y environment, c a r e must be taken t o avoid extraneous contamination. Sampling devices, sample cont a i n e rs , and p l a s t i c items should be determined t o be f r e e o f mercury; t h e sample should n o t be exposed t o any c o n d i t i o n i n t h e l a b o r a t o r y t h a t may r e s u l t i n contamination from a i r b o r n e mercury contamination. A l l items used i n t h e sample p r e p a r a t i o n should be soaked i n 30% HNO (Sect. 7.1.5) and r i n s e d t h r e e times i n reagent water (Sect. 7 . 1 . j ) .

8.2

The sediment sample should be preserved w i t h n i t r i c a c i d t o an approximate pH o f 2.

8.3

Slowly decant t h e water from t h e s e t t l e d sediment sample. Transfer t h e sediment sample i n t o a Pyrex t r a y and mix thoroughly w i t h a Teflon spatula. D i s c a rd s t i c k s , stones, s h e l l s , l i v i n g o r dead t i s s u e s and o t h e r f o r e i g n o b j e c t s from t h e sediment sample.

8.4

T ransfe r t h e sediment from t h e Pyrex t r a y t o a 10-mesh (approximately 2-mm) s i e v e c o l l e c t i n g t h e sediment sample i n an appro p ri a te c o n ta i n e r. I f enough sample has been c o l l e c t e d , a second c o n ta i n e r may be used f o r t h e percent wet weight det er m i n a ti o n .

8.5

While t h e sample may be analyzed w i t h o u t d r y i n g , i t has been found t o be more convenient t o analyze a d r y sample. M o i s t u r e may be d r i v e n o f f i n a d r y i n g oven a t a temperature o f 60°C. No mercury losses have been observed by u s i n g t h i s d r y i n g step. The d r y sample should be p u l v e r i z e d and th o ro u g h l y mixed b e f o r e t h e a l i q u o t i s weighed.

CALIBRATION AND STANDARDIZATION 9.1

T rans fe r 0.5, 1.0, 2.0, 5.0 and 10 mL a l i q u o t s o f t h e 0.1 pg/mL CAL (Sect. 7.3) t o a s e r i e s o f 300-mL BOD b o t t l e s . These BOD b o t t l e s w i l l c o n t a i n 0.5 t o 1.0 pg o f Hg and a r e used t o c a l i b r a t e t h e instrument.

9.2

To each o f t h e BOD b o t t l e s add enough reagent water (Sect. 7.1.7) t o make a t o t a l volume o f 10 mL. Add 5 mL o f aqua r e g i a (Sect. 7.2) immediately cap and cover t h e t o p o f t h e BOD b o t t l e w i t h aluminum f o i l o r o t h e r a p p ro p ri a te cover.

9.3

Construct a standard curve by p l o t t i n g peak h e i g h t o r maximum response o f t h e standards (obtained i n Sect. 11.7) versus micrograms o f mercury contained i n t h e b o t t l e s . The standard curve should comply w i t h Sect. 10.2.3. C a l i b r a t i o n u s i n g computer o r c a l c u l a t o r based re g re s s i o n curve f i t t i n g techniques on concentration/response data i s acceptable.

356 10.

Methods for the Determination

gUALITY CONTROL 10.1 Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a f o r m a l q u a l i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f t h i s program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y capab i l i t y by analyses o f l a b o r a t o r y r e a g e n t b l a n k s , f o r t i f i e d b l a n k s and samples used f o r c o n t i n u i n g check on method performance. Standard Reference M a t e r i a l s (SRMS)', 9i l o a r e a v a i l a b l e and should be used t o Val i d a t e l a b o r a t o r y performance. Commercially a v a i l a b l e sediment r e f e r e n c e m a t e r i a l s a r e a c c e p t a b l e f o r r o u t i n e l a b o r a t o r y use. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n performance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f t h e d a t a generated. 10.2 I N I T I A L DEMONSTRATION OF PERFORMANCE. 10.2.1

The i n i t i a l d e m o n s t r a t i o n o f performance i s used t o c h a r a c t e r i z e i n s t r u m e n t performance (MDLs and l i n e a r c a l i b r a t i o n ranges) f o r analyses conducted by t h i s method.

10.2.2

A mercury MDL should be e s t a b l i s h e d u s i n g LFM a t a conce7,tration o f two t o f i v e t i m e s t h e e s t i m a t e d d e t e c t i o n limit To determine MDL v a l u e s , t a k e seven r e p l i c a t e a l i q u o t s o f t h e LFM and process t h r o u g h t h e e n t i r e a n a l y t i c a l method. Perform a l l c a l c u l a t i o n s d e f i n e d i n t h e method and r e p o r t t h e c o n c e n t r a t i o n v a l u e s i n t h e a p p r o p r i a t e u n i t s . C a l c u l a t e t h e MDL as f o l l o w s :

.

MDL = ( t ) x (S) where: t = S t u d e n t ' s t v a l u e f o r a 99% c o n f i d e n c e l e v e l and a s t a n d a r d d e v i a t i o n e s t i m a t e w i t h n-1 degrees o f freedom i s , t = 3.14 f o r seven replicates.

S

=

s t a n d a r d d e v i a t i o n o f t h e r e p l i c a t e analyses.

A MDL s h o u l d be determined e v e r y s i x months o r whenever a s i g n i f i c a n t change i n background o r i n s t r u m e n t response i s expected (e.g. , d e t e c t o r change).

10.2.3

L i n e a r c a l i b r a t i o n ranges - The upper l i m i t o f t h e l i n e a r c a l i b r a t i o n range should be e s t a b l i s h e d f o r mercury by d e t e r m i n i n g t h e s i g n a l responses f r o m a minimum o f t h r e e d i f f e r e n t c o n c e n t r a t i o n standards, one o f which i s c l o s e t o t h e upper l i m i t o f t h e l i n e a r range. L i n e a r c a l i b r a t i o n ranges should be determined e v e r y s i x months o r whenever a s i g n i f i c a n t change i n i n s t r u m e n t response i s observed.

10.3 ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS

Metals

357

10.3.1

The l a b o r a t o r y must analyze a t l e a s t one LRB ( S e c t . 3.7) w i t h each s e t o f samples. LRB d a t a a r e used t o assess c o n t a m i n a t i o n from t h e l a b o r a t o r y environment and t o c h a r a c t e r i z e s p e c t r a l background from t h e reagents used i n sample p r o c e s s i n g . I f a mercury v a l u e i n a LRB exceeds i t s determined MDL, t h e n l a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n i s suspect, Any determined source o f c o n t a m i n a t i o n should be e l i m i n a t e d and t h e samples reanalyzed.

10.3.2

The l a b o r a t o r y must analyze a t l e a s t one LFB (Sect. 3.5) w i t h each b a t c h o f samples. C a l c u l a t e accuracy as p e r c e n t I f r e c o v e r y o f mercury f a l l s r e c o v e r y (Sect. 10.4.2). o u t s i d e c o n t r o l l i m i t s (Sect. 10.3.3), t h e method i s judged o u t o f c o n t r o l . The source o f t h e problem should be i d e n t i f i e d and r e s o l v e d b e f o r e c o n t i n u i n g analyses.

10.3.3

U n t i l s u f f i c i e n t d a t a ( u s u a l l y a minimum o f 20 t o 30 analyses) become a v a i l a b l e , each l a b o r a t o r y should assess i t s performance a g a i n s t r e c o v e r y 1i m i t s o f 85-115%. When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e , develop c o n t r o l l i m i t s from t h e p e r c e n t mean r e c o v e r y ( x ) and t h e standard d e v i a t i o n (S) o f t h e mean r e c o v e r y . These d a t a a r e used t o e s t a b l i s h upper and l o w e r c o n t r o l l i m i t s as f o l l o w s :

UPPER CONTROL LIMIT LOWER CONTROL LIMIT

= =

x t 3s x - 3s

A f t e r each f i v e t o t e n new r e c o v e r y measurements, new c o n t r o l l i m i t s should be c a l c u l a t e d u s i n g o n l y t h e most r e c e n t 20 t o 30 d a t a p o i n t s . 10.4 ASSESSING ANALYTE RECOVERY - LABORATORY F O R T I F I E D SAMPLE MATRIX 10.4.1

The l a b o r a t o r y must add a known amount o f mercury t o a minimum o f 10% o f samples o r one sample p e r sample s e t , whichever i s g r e a t e r . S e l e c t a sediment sample t h a t is r e p r e s e n t a t i v e o f t h e t y p e o f sediment b e i n g analyzed and has a l o w mercury background. I t i s recommended t h a t t h i s sample be analyzed p r i o r t o f o r t i f i c a t i o n . The f o r t i f i c a t i o n should be 20% t o 50% h i g h e r t h a n t h e analyzed v a l u e . Over time, samples f r o m a l l r o u t i n e sample sources should be f o r t i f i e d .

10.4.2

C a l c u l a t e t h e p e r c e n t r e c o v e r y , c o r r e c t e d f o r background c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o t h e c o n t r o l l i m i t s e s t a b l i s h e d i n Sect. 10.3.3 f o r t h e analyses o f LFBs. A r e c o v e r y calculation i s not required i f the concentration o f the a n a l y t e added i s l e s s t h a n 10% o f t h e sample background c o n c e n t r a t i o n . Percent r e c o v e r y may be c a l c u l a t e d i n

358

Methods for the Determination u n i t s a p p ro p ri a te t o the m a t r i x , u s i n g t h e f o l l o w i n g equation:

c,

-

c x 100

R = S

where, R

C, C s

10.4.3

11.

percent recovery f o r t i f i e d sample c o n c e n t r a t i o n = sample background c o n c e n t r a t i o n = c o n c e n tra t i o n e q u i v a l e n t o f f o r t i f i e r added t o sediment sample.

= =

I f mercury recovery f a l l s o u t s i d e t h e designated range, and t h e l a b o r a t o r y performance i s shown t o be i n c o n t r o l (Sect. 10.3), t h e recovery problem encountered w i t h t h e f o r t i f i e d sediment sample i s judged t o be m a t r i x r e l a t e d , n o t system r e l a t e d . The r e s u l t f o r mercury i n t h e u n f o r t i f i e d sample must be l a b e l l e d t o i n f o r m t h e d a t a user t h a t t h e r e s u l t s are suspect due t o m a t r i x e f f e c t s .

PROCEDURE

11.1 Weigh 0.2-9 p o r t i o n s o f d r y sample and p l a c e i n bottom o f a BOD b o t t l e . Add 5 mL o f reagent water (Sect. 7 . 1 . 7 ) and 5 mL o f aqua r e g i a (Sect. 7.2) immediately cap and cover t h e t o p o f t h e BOD b o t t l e w i t h aluminum f o i l o r o t h e r a p p r o p r i a t e cover. O p t i o n a l l y a range f r o m 0.033 g t o 3.4 g may be used t o a d j u s t t h e response t o st ay w i t h i n t h e l i n e a r range o f t h e standards.

11.2 Mix thoroughly, and p l a c e i n t h e water b a t h f o r 2 min a t 95°C. 11.3 Remove t h e BOD b o t t l e s and a l l o w t o c o o l . Add 50 mL reagent water (Sect. 7.1.7) and 15 mL potassium permanganate s o l u t i o n (Sect. 7.5) t o each sample b o t t l e . Cap and cover t h e t o p o f t h e BOD b o t t l e w i t h aluminum f o i l o r o t h e r a p p ro p ri a t e cover. Mix thoroughly, and p l a c e i n t h e water b a th f o r 30 rnin a t 95°C. An a l t e r n a t e d i g e s t i o n procedure employing an autoclave may a l s o be used. I n t h i s method 5 mL o f conc. H,SO (Sect. 7.1.11) and 2 mL o f conc. HNO, (Sect. 7.1.5) are added t o 0.) g sediment sample. Then 5 mL o f s a tu ra te d potassium permanganate s o l u t i o n i s added and t h e BOD b o t t l e i s capped w i t h a piece o f aluminum f o i l . The samples are then autoclaved a t 12loC/15 p s i . f o r 15 min.

11.4 Turn on t h e spectrophotometer and c i r c u l a t irig pump. pump r a t e t o 1 L/min. stabilize.

Adjust the Allow t h e spectrophotometer and pump t o

11.5 Cool t h e BOD b o t t l e s t o r o o m t r ,i p ~ ~ r a t u raen d d i l u t e i n t h e f o l l o w i n g manner:

Metals

359

11.5.1

To BOD b o t t l e s c o n t a i n i n g t h e i n s t r u m e n t c a l i b r a t i o n standards l a b o r a t o r y f o r t i f i e d b l a n k (LFB) and l a b o r a t o r y r e a g e n t b l a n k (LRB) add 50 mL o f r e a g e n t w a t e r (Sect. 7 . 1 . 7 ) .

11.5.2

To BOD b o t t l e s c o n t a i n i n g t h e sediment samples, q u a l i t y c o n t r o l sample (QCS) and l a b o r a t o r y f o r t i f i e d sample m a t r i x (LFM) add 55 mL o f r e a g e n t w a t e r ( S e c t . 7.1.7).

11.6 To each BOD b o t t l e , add 6 mL o f NaCl-(NH20H),’H,S0, reduce t h e excess permanganate.

(Sect. 7.6) t o

11.7 T r e a t i n g each b o t t l e i n d i v i d u a l l y : 11.7.1

P l a c i n g t h e a s p i r a t o r i n s i d e t h e BOD b o t t l e and above t h e l i q u i d , purge t h e head space (20 t o 30 sec) t o remove p o s s i b l e gaseous i n t e r f e r e n t s .

11.7.2

Add 5 mL o f SnC1, s o l u t i o n ( S e c t . 7.7) and i m m e d i a t e l y a t t a c h t h e b o t t l e t o t h e a e r a t i o n apparatus.

11.7.3

The absorbance, as e x h i b i t e d e i t h e r on t h e spectrophotometer o r t h e r e c o r d e r , w i l l i n c r e a s e and reach maximum w i t h i n 30 sec. As soon as t h e r e c o r d e r pen l e v e l s o f f , a p p r o x i m a t e l y 1 min, open t h e bypass v a l u e ( o r o p t i o n a l l y remove a s p i r a t o r f r o m t h e BOD b o t t l e i f i t i s vented under t h e hood) and c o n t i n u e t h e a e r a t i o n u n t i l t h e absorbance r e t u r n s t o i t s minimum v a l u e .

11.8 Close t h e bypass v a l u e , remove t h e a s p i r a t o r from t h e BOD b o t t l e and c o n t i n u e t h e a e r a t i o n . Repeat s t e p (Sect. 11.7) u n t i l a l l BOD b o t t l e s have been a e r a t e d and recorded. 12.

CALCULATIONS 12.1 Measure t h e peak h e i g h t o f t h e unknown f r o m t h e c h a r t and r e a d t h e mercury v a l u e f r o m t h e s t a n d a r d c u r v e . 12.2 C a l c u l a t e t h e mercury c o n c e n t r a t i o n i n t h e sample by t h e formula:

” Hg’g

=

g Hg i n the a l i q u o t w t . ‘of the aliquot in grams

12.3 Report mercury c o n c e n t r a t i o n s as f o l l o w s : Below 0 . 1 p g / g , < 0.1 pg/g; between 0 . 1 and 1 p g / g , t o t h e n e a r e s t 0.01 p g ; between 1 and 10 1.1919, t o n e a r e s t 0.1 pg; above 10 p g / g , t o n e a r e s t p g .

360 13.

Methods for the Determination PRECISION AND ACCURACY 13.1 The standard d e v i a t i o n f o r mercury n sed ment samp es a r e r e p o r t e d a s 0.29 f 0.02 jig Hg/g and 0.82 f 0.03 jig Hg/g w i t h r e c o v e r i e s f o r LFM b e i n g 97% and 94% r e s p e c t i v e l y . Thes sediment samples were f o r t if i e d w i t h methyl m e r c u r i c c h l o r i d e . Qua1it y assurance d a t a f o r t h e sediment survey was c o n t r i b u t e d by U.S. EPA, Environmental Research l a b o r a t o r y - D u l u t h . See T a b l e 1.

14.

REFERENCES

1.

Bishop, J.N., "Mercury i n Sediments", O n t a r i o Water Resources Comm., Toronto, O n t a r i o , Canada, 1971.

2.

Glass, G.E.; Sorensen, J.A.; Schmidt, K.W.; Rapp Jr., G.R.; "New Source I d e n t i f i c a t i o n o f Mercury Contamination i n t h e Great Lakes", ~ Envion. S c i . and Technol., Vol.3,No. 7, 1990.

3.

Salma, M., p r i v a t e communication, EPA Cal/Nev B a s i n O f f i c e , Almeda, C a l if o r n i a .

4.

" S a f e t y i n Academic Chemistry L a b o r a t o r i e s " , American Chemical S o c i e t y P u b l i c a t i o n , Committee on Chemical S a f e t y , 3 r d E d i t i o n , 1979.

5.

"OSHA S a f e t y and H e a l t h Standards, General I n d u s t r y " , (29CFR 1910), Occupational S a f e t y and H e a l t h A d m i n i s t r a t i o n , OSHA 2206, r e v i s e d January, 1976.

6.

"Proposed OSHA S a f e t y and H e a l t h Standards, L a b o r a t o r i e s " , Occupational S a f e t y and H e a l t h A d m i n i s t r a t i o n , Federal R e g i s t e r , J u l y 24, 1986.

7.

" S p e c i f i c a t i o n f o r Reagent Water", D1193, Annual Book o f ASTM Standards, Vol. 11.01, 1990.

8.

N a t i o n a l I n s t i t u t e o f Standards and Technology, O f f i c e o f Standards Reference M a t e r i a l s , G a i t h e r s b u r g , MD 20899: E s t u a r i n e Sediment (SRM 1646), Trace Elements i n a Calcerous Loam S o i l (CRM 8032), Trace Elements i n L i g h t l y Sandy S o i l (CRM 8033), Trace Elements i n Sewer Sludge-Domestic (CRM 8034), Trace Elements i n Sewer SludgeI n d u s t r i a l (CRM 8035).

9.

Branch o f Geochemistry, US G e o l o g i c a l Survey, 12201 S u n r i s e V a l l e y D r i v e , Reston, VA 22092: Marine Mud (MAG-1).

10.

N a t i o n a l Research C o u n c i l o f Canada, M a r i n e A n a l y t i c a l Chemistry Standards Proqram, D i v i s i o n o f Chemistry. M o n t r e a l Road. Ottawa. O n t a r i o KIA OR9, Canada: M a r i n e Sediments (SCSS-1, MESS-1, andPACS-1).

11.

Code o f Federal R e g u l a t i o n s 40, Ch. 1, P t . 136 Appendix B.

Metals TABLE 1. QUALITY ASSURANCE SUMMARY FQR 15 SEDIMENT ANALYSES 1988 SURVEY OF MINNESOTA LAKES"

.

Parameter Detection L i m i t i n Flask3 (ns Hg/L)

Value 6.6

-

Number o f Samples o r SamDle P a i r s 47 1

P r e c i s i o n (ng Hg/L) Lab Field

27 26

29 96

Bias (%) Spike Recovery (%) Loss on Drying (%)

-2 100 & 7 5.3 1.0

30 27 72

*

361

'

Data were furnished by Gary Glass, U.S. EPA, Environmental Research Laboratory - Duluth, Minnesota 55804, and John A. Sorensen, College o f Science and Engineering, U n i v e r s i t y o f Minnesota, Duluth, Minnesota 55812.

'

The a n a l y t i c a l instrument used t o achieve t h e p r e c i s i o n and accuracy included: Perkin Elmer atomic absorption spectrophotometers (Model 403 and 5000) equipped w i t h deuterium background c o r r e c t o r s , e l e c t r o d e l e s s discharge lamp (ME-782) and power supply (APR), and Heath Schlumberger (SR-206) c h a r t recorder. A s l i t w i d t h o f 1 mm ( s p e c t r a l band w i t h 0.07 nm) was used a t a wavelength o f 253.7 nm. The instruments were operated i n t h e concentration mode (10 x) w i t h t h e i n t e g r a t i o n s e t a t 10 average ( t e n samples o f t h e signal are averaged as one value per second). The concentration readout o f t h e s i g n a l was recorded on t h e s t r i p c h a r t a t 20 mv/25 cm c h a r t width. The elemental mercury analyte was c i r c u l a t e d (1 L/min) through a (18 x 1.8 cm) c y l i n d r i c a l absorption c e l l using a Neptune Dyna Pump. A f t e r t h e atomic absorption r e s u l t i n g from t h e presence o f mercury vapor reached a maximum i n about 0.5-1.0 min, t h e pump was turned o f f and t h e absorption peak climbed t o i t s f i n a l value. 3

Long, G.L.; Winefordner, J.D.; Anal. Chem. 1983, Vol. 55: 712A-724A.

362

Methods for the Determination

& AIR PUMP

SCRUBBER CONTAlNIN0 A MERCURY SAMPLE SOCVrlON IN BOO BOTTLE

A8SoRBhJO MEW

Flguro 1. Apparatus for f l ~ t o t rNercury Dettnhation

Because o f the toxic nature o f mercury vapor, inhalation must be avoided. Therefore, a bypass has been Included in the system to either vent the mercury vapor into a exhaust hood or pass the vapor through some absorbing media, such as: a) equal volumes o f 0.1 N KMnO, and 10% H,SO, b) 0.25% iodtne in a 3% KI solution. A specially treated charcoal that will absorb mercury vapor i s also available from Barnebey and Cheney, P . O . Box 2526, Columbus, OH 43216, Catalog No. 58013 or 580-22.

Metals METHOD 245.6 DETERMINATION OF MERCURY I N TISSUES BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY

E d i t e d by L a r r y B. Lobring and B i l l y B. P o t t e r I n o r g a n i c Chemistry Branch Chemi s t r y Research D i v i s i on

Revision 2 . 3 A p r i l 1991

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

363

364

Methods for the Determination METHOD 2 4 5 . 6 DETERMINATION OF MERCURY I N TISSUES BY COLD VAPOR ATOMIC ABSORPTION SPECTROMETRY

1.

2.

SCOPE AND APPLICATION 1.1

T h i s procedure measures t o t a l mercury ( o r g a n i c t i n o r g a n i c ) i n b i o l o g i c a l t i s s u e samples.

1.2

The range o f t h e method i s 0 . 2 t o 5 p g / g . The r a n g e may be extended above o r below t h e normal range by i n c r e a s i n g o r d e c r e a s i n g sample s i z e o r by o p t i m i z i n g i n s t r u m e n t s e n s i t i v i t y .

SUMMARY OF METHOD

2.1

3.

A weighed p o r t i o n o f t h e t i s s u e sample i s d i g e s t e d w i t h s u l f u r i c and n i t r i c a c i d a t 58°C f o l l o w e d by o v e r n i g h t o x i d a t i o n w i t h p o t a s s i u m permanganate and p o t a s s i u m p e r s u l f a t e a t room t e m p e r a t u r e . Mercury i n t h e d i g e s t e d sample i s reduced w i t h stannous c h l o r i d e t o e l e m e n t a l mercury and measured b y t h e c o n v e n t i o n a l c o l d v a p o r a t o m i c absorption technique.

DEFINITIONS

3.1

BIOCHEMICAL OXYGEN DEMAND (BOD) BOTTLE - BOD b o t t l e , 300 k 2 mL w i t h a ground g l a s s s t o p p e r o r an e q u i v a l e n t f l a s k , f i t t e d w i t h a ground glass stopper.

3.2

CALIBRATION BLANK - A volume o f ASTM t y p e I 1 r e a g e n t w a t e r p r e p a r e d i n t h e same manner ( a c i d i f i e d ) as t h e c a l i b r a t i o n s t a n d a r d .

3.3

CALIBRATION STANDARD (CAL) - A s o l u t i o n p r e p a r e d f r o m t h e mercury s t o c k s t a n d a r d s o l u t i o n used t o c a l i b r a t e t h e i n s t r u m e n t response w i t h respect t o analyte concentration.

3.4

INSTRUMENT DETECTION L I M I T ( I D L ) - The mercury c o n c e n t r a t i o n t h a t produces a s i g n a l e q u a l t o t h r e e t i m e s t h e s t a n d a r d d e v i a t i o n o f t h e blank signal.

3.5

LABORATORY F O R T I F I E D BLANK (LFB) - A n a l i q u o t o f ASTM t y p e I 1 r e a g e n t w a t e r t o w h i c h known q u a n t i t i e s o f i n o r g a n i c a n d / o r o r g a n i c mercury a r e added i n t h e l a b o r a t o r y . The LFB i s a n a l y z e d e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether method performance i s w i t h i n accepted c o n t r o l l i m i t s .

3.6

LABORATORY F O R T I F I E D SAMPLE MATRIX (LFM) - A p o r t i o n o f a t i s s u e sample t o w h i c h known q u a n t i t i e s o f c a l i b r a t i o n s t a n d a r d a r e added i n t h e l a b o r a t o r y . The LFM i s a n a l y z e d e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e sample m a t r i x c o n t r i b u t e s

Metals

365

bias to the analytical results.

The background concentrations of the analytes in the sample matrix must be determined in a separate aliquot and the measured values in the LFM corrected for the concentrations found. - An aliquot of ASTM type I 1 reagent water that is treated exactly as a sample including exposure to all glassware, equipment, and reagents used in analyses. The LRB is used to determine if method analyte or other interferences are present in the laboratory environment, the reagents or apparatus.

3.7 LABORATORY REAGENT BLANK (LRB)

3.8 LINEAR DYNAMIC RANGE (LDR)

- The concentration range over which the analytical working curve remains linear.

- The minimum concentration of mercury that can be identified, measured and reported with 99% confidence that the analyte concentration is greater than zero and determined from analysis of laboratory fortified tissue sample matrix (LFM).

3.9 METHOD DETECTION LIMIT (MDL)

- A tissue sample containing known concentration of mercury derived from externally prepared test materials. The QCS is obtained from a source external to the laboratory and is used to check laboratory performance.

3.10 QUALITY CONTROL SAMPLE (QCS)

3.11 TISSUE SAMPLE - A biological sample matrix exposed to a marine,

brackish or fresh water environment. to the edible tissue portion.

It is limited by this method

3.12 STOCK STANDARD SOLUTION - A concentrated solution containing mercury

prepared in the laboratory using assayed mercuric chloride or stock standard solution purchased from a reputable commercial source. 4.

INTERFERENCES 4.1

Interferences have been reported for waters containing sulfide, chloride, copper and tellurium. Organic compounds which have broad band UV absorbance (around 253.7 nm) are confirmed interferences. The concentration levels for interferants are difficult to define. This suggests that quality control procedures (Sect. 10) must be s tri ct 1 y fol 1 owed.

4.2

Volatile materials which absorb at 253.7 nm will cause a positive interference. In order to remove any interfering volatile materials, the dead air space in the BOD bottle should be purged before the addition of stannous chloride solution.

4.3

Interferences associated with the tissue matrix are corrected for in calibration procedure (Sect. 9).

366

Methods for the Determination

5.

SAFETY 5.1

The t o x i c i t y and c a r c i n o g e n i c i t y o f each reagent used i n t h i s method has not been f u l l y e s ta b l i s h e d . Each chemical should be regarded as a p o t e n t i a l h e a l t h hazard and exposure, t o these compounds should be minimized by good l a b o r a t o r y p r a c t i c e s . Normal accepted l a b o r a t o r y s a f e t y p r a c t i c e s should be f o l l o w e d d u r i n g reagent p r e p a r a t i o n and instrument o p e r a t i o n . A l w a y s wear s a f e t y glasses o r f u l l - f a c e s h i e l d f o r eye p r o t e c t i o n when working w i t h these reagents. Each l a b o r a t o r y i s r e s p o n s i b l e f o r m a i n t a i n i n g a c u r r e n t s a f e t y plan, a c u r r e n t awareness f i l e o f OSHA r e g u l a t i o n s r e a5ding t h e s a f e h a n d l i n g o f t h e chemicals s p e c i f i e d i n t h i s method

9. .

5.2

Mercury compounds are h i g h l y t o x i c i f swallowed, i n h a l e d , o r absorbed through t h e s k i n . Analyses should be conducted i n a l a b o r a t o r y exhaust hood, The a n a l y s t should use chemical r e s i s t a n t gloves when h a n d l i n g concentrated mercury standards.

5.3

A l l personnel hand1 i n g t i s s u e samples should beware o f b i o l o g i c a l

hazards associated w i t h t i s s u e samples. B i v a l v e m o l l u s k may concentrate t o x i n s and pathogenic organisms. Tissue d i s s e c t i o n should be conducted i n a bio-hazard hood and personnel should wear s u r g i c a l mask and gloves. 6.

APPARATUS AND EQUIPMENT

6.1

ABSORPTION CELL - Standard spectrophotometer c e l l s 10-cm long, having q u a rtz windows may be used. S u i t a b l e c e l l s may be constru c te d from p l e x i g l a s s tubing, l - i n . O.D. by 4-1/2-in. long. The ends are ground p e rp e n d i c u l a r t o t h e l o n g i t u d i n a l a x i s and quartz windows ( 1 - i n . diameter by 1/16-in. t h i c k n e s s ) are cemefited i n place. Gas i n l e t and o u t l e t p o r t s ( a l s o o f p l e x i g l a s s b u t 1/4i n . O.D.) are a tta c h e d approximately 1 / 2 - i n . from each end. The c e l l i s strapped t o a burner f o r support and a l i g n e d i n t h e l i g h t beam t o g i v e t h e maximum tra n s m i t t a n c e .

6.2

AERATION TUBING - I n e r t mercury-free t u b i n g i s used f o r passage o f mercury vapor from t h e sample b o t t l e t o t h e a b s o r p t i o n c e l l . I n some systems, mercury vapor i s r e c y c l e d . S t r a i g h t g l a s s t u b i n g t e r m i n a t i n g i n a coarse porous g l a s s a s p i r a t o r i s used f o r p u r g i n g mercury released from t h e t i s s u e sample i n t h e BOD b o t t l e .

6.3 A I R PUMP

- Any pump (pressure o r vacuum system) capable o f passing a i r a t 1 L/min i s used. Regulated compressed a i r can be used i n an open one-pass system.

6.4

ATOMIC ABSORPTION SPECTROPHOTOMETER - Any atomic a b s o r p t i o n u n i t having an open sample p r e s e n t a t i o n area i n which t o mount t h e abso rp ti o n c e l l i s s u i t a b l e . Instrument s e t t i n g s recommended by t h e p a r t i c u l a r manufacturer should be f o l l o w e d . Instruments designed s p e c i f i c a l l y f o r mercury measurement u s i n g t h e c o l d vapor technique

Metals

367

a r e c o m m e r c i a l l y a v a i l a b l e and may be s u b s t i t u t e d f o r t h e atomic a b s o r p t i o n spectrophotometer. 6.5

BIOCHEMICAL OXYGEN DEMAND (BOD) BOTTLE - See S e c t . 3.1.

6.6

DRYING TUBE - Tube ( 6 - i n . x 3 / 4 - i n . OD) c o n t a i n i n g 20 g o f magnesium p e r c h l o r a t e . The f i l l e d t u b e i s i n s e r t e d ( i n - l i n e ) between t h e 80D b o t t l e and t h e a b s o r p t i o n tube. I n p l a c e o f t h e magnesium p e r c h l o r a t e d r y i n g tube, a small r e a d i n g lamp i s p o s i t i o n e d t o r a d i a t e h e a t (about 10°C above ambient) on t h e a b s o r p t i o n c e l l . T h i s a v o i d s w a t e r condensation i n t h e c e l l .

6.7

FLOWMETER - Capable o f measuring an a i r f l o w o f 1 L/min.

6.8

MERCURY HOLLOY CATHODE LAMP - S i n g l e element h o l l o w cathode lamp o r e l e c t r o d e l e s s d i s c h a r g e lamp and a s s o c i a t e d power supply.

6.9

RECORDER - Any mu1t i -range v a r i a b l e speed r e c o r d e r t h a t is c o m p a t i b l e w i t h t h e UV d e t e c t i o n system i s s u i t a b l e .

6.10 WATER BATH .- The w a t e r b a t h should have a covered t o p and c a p a c i t y t o s u s t a i n a w a t e r depth o f 2 - i n . t o 3 - i n . a t 95°C k 1°C. The dimensions o f t h e w a t e r b a t h should be l a r g e enough t o accommodate BOD b o t t l e s c o n t a i n i n g CAL, LFB, LFM, LRB, QCS and t i s s u e samples w i t h t h e l i d on.

7.

REAGENTS AND CONSUNABLE MATERIALS 7.1

Reagents may c o n t a i n elemental i m p u r i t i e s which b i a s a n a l y t i c a l r e s u l t s . A l l r e a g e n t s should be assayed by t h e chemical m a n u f a c t u r e r f o r mercury and meet ACS s p e c i f i c a t i o n s . 7.1.1

Hydroxylamine H y d r o c h l o r i d e (NH OH’HCl), (CASRN 5470-11-1) may be used i n p l a c e o f hydroxyjamine s u l f a t e i n Sect. 7.6. The assayed mercury l e v e l o f e i t h e r compound i s n o t t o exceed 0.05 ppm.

7.1.2

Hydroxyl amine S u l f a t e [ (NH,OH),’H,SO,] (CASRN 10039-54-0) ; assayed mercury l e v e l i s n o t t o exceed 1 ppb.

7.1.3

M e r c u r i c C h l o r i d e (HgCl,),

7.1.4

c o n c e n t r a t e d ( s p . g r . 1.41), (CASRN N i t r i c A c i d (HNO,), 7697-37-2); assayed mercury l e v e l i s n o t t o exceed 1 ppb.

7.1.5

(CASRN 7722-64-7); Potassium Permanganate (KMnO,), mercury l e v e l i s n o t t o exceed 0.05 ppm.

7.1.6

, (CASRN 7727-21-1); Potassium P e r s u l f a t e (K,S,O,) mercury l e v e l i s n o t t o exceed 0.05 ppm.

7.1.7

Reagent Water, ASTM t y p e I I . 4

(CASRN 7487-94-7).

assayed assayed

368

8.

Methods for the Determination 7.1.8

Sodium C h l o r i d e (NaC!), (CASRN 7647-14-5); l e v e l i s n o t t o exceed 0.05 ppm.

assayed mercury

7.1.9

Stannous C h l o r i d e (SnC1;2H20), (CASRN 10025-69-1); assayed mercury l e v e l i s n o t t o exceed 0.05 ppm.

7.1.10

Stannous S u l f a t e (SnSO,), (CASRN 7488-55-3); mercury l e v e l i s n o t t o exceed 0.05 ppm.

7.1.11

S u l f u r i c A c i d (H,SO,), c o n c e n t r a t e d ( s p . g r . 1.84), (CASRN 7664-93-9); assayed mercury l e v e l i s n o t t o exceed 1 ppb.

assayed

7.2

MERCURY CALIBRATION STANDARD - To each v o l u m e t r i c f l a s k used f o r s e r i a l d i l u t i o n s , a c i d i f y w i t h ( 0 . 1 t o 0.2% by volume) HNO, (Sect. 7.1.4). U s i n g mercury s t o c k s t a n d a r d ( S e c t . 7.3), make s e r i a l d i l u t i o n s t o o b t a i n a c o n c e n t r a t i o n o f 0.1 p g Hg/mL. T h i s standard s h o u l d be p r e p a r e d j u s t b e f o r e analyses.

7.3

MERCURY STOCK STANDARD - D i s s o l v e i n a 100-mL v o l u m e t r i c f l a s k 0.1354 g HgC1, ( S e c t . 7.1.3) w i t h 75 mL o f r e a g e n t w a t e r (Sect. 7 . 1 . 7 ) . Add 10 mL o f conc. HNO, ( S e c t . 7.1.4) and d i l u t e t o mark. C o n c e n t r a t i o n i s 1.0 mg Hg/mL.

7.4

POTASSIUM PERMANGANATE SOLUTION - D i s s o l v e 5 g o f KMnO, (Sect. 7.1.5) i n 100 mL o f r e a g e n t w a t e r ( S e c t . 7.1.7).

7.5

POTASSIUM PERSULFATE SOLUTION - D i s s o l v e 5 g o f KS, O ,, i n 100 mL o f r e a g e n t w a t e r (Sect. 7.1.7).

7.6

SODIUM CHLORIDE-HYDROXYLAMINE SULFATE SOLUTION - D i s s o l v e 12 g o f N a C l ( S e c t . 7.1.8) and 12 g o f (NH,OH);H,SO, (Sect. 7.1.2) o r 12 g o f NH OH'HC1 ( S e c t . 7.1.1) d i l u t e w i t h r e a g e n t w a t e r ( S e c t . 7.1.7) t o 106 mL.

7.7

STANNOUS CHLORIDE SOLUTION - Add 25 g SnCl '2H 0 ( S e c t . 7.1.9) o r 25 g o f SnSO, t o 250 mL o f 0.5 N H SO, ( S e c i . f . 8 ) . T h i s m i x t u r e i s a suspension and s h o u l d be s t i r r e d c o n t i n u o u s l y d u r i n g use.

7.8

SULFURIC ACID, 0.5 N - S l o w l y add 14.0 mL o f conc. H SO (Sect. 7.1.10) d i l u t e t o 1 L w i t h r e a g e n t w a t e r (Sect. 5 . 1 . 7 ) .

(Sect. 7.1.6)

SAMPLE COLLECTION. PRESERVATION AND STORAGE

8.1

Because o f t h e extreme s e n s i t i v i t y o f t h e a n a l y t i c a l procedure and t h e presence o f mercury i n a l a b o r a t o r y environment, c a r e must be t a k e n t o a v o i d extraneous c o n t a m i n a t i o n . Sampling d e v i c e s , sample c o n t a i n e r s and p l a s t i c items s h o u l d be determined t o be f r e e o f mercury; t h e sample should n o t be exposed t o any c o n d i t i o n i n t h e l a b o r a t o r y t h a t may r e s u l t i n c o n t a c t o r a i r b o r n e mercury contamination.

Metals

9.

10.

369

8.2

The t i s s u e samp w i t h Method 200 Determination o o n l y Sect. 8. I

8.3

Weigh 0.2- t o 0.3-9 p o r t i o n s o f each sample and place i n t h e bottom o f a d r y BOD b o t t l e . Care must be taken t h a t none o f t h e sample adheres t o t h e s i d e o f t h e b o t t l e . Immediately cap and cover t h e t o p o f th e BOD b o t t l e w i t h aluminum f o i l .

e should be preserved and d i s s e c t e d i n accordance 3 , "Sample Pre p a r a t i o n Procedure f o r Spectrochemical T o t a l Recoverable Elements i n B i o l o g i c a l Tissues", ssue D i s s e c ti o n , i s used i n t h i s method.

CALIBRATION AND STANDARDIZATION 9.1

The c a l i b r a t i o n curve i s prepared from values determined f o r p o r t i o n s o f f o r t i f i e d t i s s u e t r e a t e d i n t h e manner used f o r t h e t i s s u e samples being analyzed. For p r e p a r a t i o n o f t h e c a l i b r a t i o n standards, blend a p o r t i o n o f t i s s u e i n a Waring blender.

9.2

T rans fe r a c c u r a t e l y weighed p o r t i o n s t o each o f f i v e d r y BOD b o t t l e s , Each sample should weigh about 0.2 g. Add 4 mL o f conc. H,SO, and 1 mL o f conc. HNO, t o each b o t t l e and p l a c e i n a water bat h maintained a t 58°C u n t i l t h e t i s s u e i s completely d i s s o l v e d (30 t o 60 mi n u te s ).

9.3

Cool and t r a n s f e r 0.5, 2.0, 5.0 and 10.0 mL a l i q u o t s o f t h e CAL (Sect. 7.2) s o l u t i o n c o n t a i n i n g 0.5 t o 1.0 p g o f Hg t o t h e BOD b o t t l e s c o n t a i n i n g t i s s u e . Cool t o 4 ° C i n an i c e b a t h and c a u t i o u s l y add 15 mL o f potassium permanganate s o l u t i o n (Sect. 7.4) and 8 mL o f potassium p e r s u l f a t e (Sect. 7.5). A l l o w t o stand overn i g h t a t room temperature under o x i d i z i n g c o n d i t i o n s .

9.4

Construct a standard curve by p l o t t i n g peak h e i g h t o r maximum response o f t h e standard (obtained i n Sect. 11.7) versus micrograms o f mercury contained i n t h e b o t t l e s . The standard curve should comply w i t h Sect. 10.2.3. C a l i b r a t i o n u s i n g computer o r c a l c u l a t o r based re g re s s i o n curve f i t t i n g techniques on concentration/response data i s acceptable.

QUALITY CONTROL 10.1 Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o operate a formal q u a l i t y c o n t r o l (QC) program. The minimum requirements o f t h i s program c o n s i s t o f an i n i t i a l demonstration o f l a b o r a t o r y c a p a b i l i t y by analyses o f l a b o r a t o r y reagent blanks, f o r t i f i e d blanks and samples used f o r c o n t i n u i n %heck on method performance. Standard Reference M a t e r i a l s (SRMs)'. are a v a i l a b l e and should be used t o v a l i d a t e l a b o r a t o r y performance. Commercially a v a i l a b l e t i s s u e reference m a t e r i a l s are acceptable f o r r o u t i n e l a b o r a t o r y use. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n performance records t h a t d e f i n e t h e q u a l i t y o f d a ta generated.

370

Methods for the Determination 10.2 I N I T I A L DEMONSTRATION OF PERFORMANCE

10.2.1

The i n i t i a l d e m o n s t r a t i o n o f performance i s used t o c h a r a c t e r i z e i n s t r u m e n t performance (MDLs and l i n e a r c a l i b r a t i o n ranges) f o r analyses conducted by t h i s method.

10.2.2

A mercury MDL should be e s t a b l i s h e d u s i n g LFM a t a conce t r a t i o n o f two t o f i v e t i m e s t h e e s t i m a t e d d e t e c t i o n l i m i t 7 . To determine MDL values, t a k e seven r e p l i c a t e a l i q u o t s o f t h e LFM and process t h r o u g h t h e e n t i r e a n a l y t i c a l method. Perform a l l c a l c u l a t i o n s d e f i n e d i n t h e method and r e p o r t t h e c o n c e n t r a t i o n v a l u e s i n t h e a p p r o p r i a t e u n i t s . C a l c u l a t e t h e MDL as f o l l o w s :

MDL = ( t ) x (S) where, t =

S =

S t u d e n t ' s t v a l u e f o r a 99% c o n f i d e n c e l e v e l and a s t a n d a r d d e v i a t i o n e s t i m a t e w i t h n-1 degrees o f freedom [ t = 3.14 f o r seven rep1 i c a t e s ] . s t a n d a r d d e v i a t i o n o f t h e r e p l i c a t e analyses.

A MDL should be d e t e r m i n e d e v e r y s i x months o r whenever a s i g n i f i c a n t change i n background o r i n s t r u m e n t response i s expected (e.g., d e t e c t o r change). 10.2.3

L i n e a r c a l i b r a t i o n ranges - The upper l i m i t o f t h e l i n e a r c a l i b r a t i o n range s h o u l d be e s t a b l i s h e d f o r mercury by d e t e r m i n i n g t h e s i g n a l responses f r o m a minimum o f t h r e e d i f f e r e n t c o n c e n t r a t i o n standards, one o f which i s c l o s e t o t h e upper l i m i t o f t h e l i n e a r range. L i n e a r c a l i b r a t i o n ranges should be determined e v e r y s i x months o r whenever a s i g n i f i c a n t change i n i n s t r u m e n t response i s observed.

10.3 ASSESSING LABORATORY PERFORMANCE - REAGENT AND FORTIFIED BLANKS 10.3.1

The l a b o r a t o r y must a n a l y z e a t l e a s t one LRB (Sect. 3.7) w i t h each s e t o f samples. LRB d a t a a r e used t o assess c o n t a m i n a t i o n f r o m t h e l a b o r a t o r y environment and t o c h a r a c t e r i z e s p e c t r a l background f r o m t h e r e a g e n t s used i n sample p r o c e s s i n g . I f an mercury v a l u e i n a LRB exceeds i t s determined MDL, t h e n l a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n i s suspect. Any determined source o f c o n t a m i n a t i o n s h o u l d be c o r r e c t e d and t h e samples reanalyzed.

10.3.2

The l a b o r a t o r y must analyze a t l e a s t one LFB (Sect. 3.5) w i t h each b a t c h o f samples. C a l c u l a t e accuracy as p e r c e n t r e c o v e r y ( S e c t . 10.4.2). I f t h e r e c o v e r y o f mercury f a l l s o u t s i d e c o n t r o l l i m i t s ( S e c t . 10.3.3), t h e method i s

Metals

371

judged o u t o f c o n t r o l . The source o f t h e problem should be i d e n t i f i e d and r e s o l v e d b e f o r e c o n t i n u i n g analyses. 10.3.3

U n t i l s u f f i c i e n t d a t a ( u s u a l l y a minimum o f 20 t o 30 analyses) become a v a i l a b l e , each l a b o r a t o r y should assess i t s performance a g a i n s t r e c o v e r y l i m i t s o f 85-115%. When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e , develop c o n t r o l l i m i t s f r o m t h e p e r c e n t mean r e c o v e r y ( x ) and t h e s t a n d a r d d e v i a t i o n ( S ) o f t h e mean r e c o v e r y . These d a t a a r e used t o e s t a b l i s h upper and l o w e r c o n t r o l l i m i t s as f o l l o w s :

UPPER CONTROL LIMIT LOWER CONTROL LIMIT

= =

x t 3s x - 3s

A f t e r each f i v e t o t e n new r e c o v e r y measurements, new c o n t r o l l i m i t s s h o u l d be c a l c u l a t e d u s i n g o n l y t h e most r e c e n t 20 t o 30 d a t a p o i n t s . 10.4 ASSESSING ANALYTE RECOVERY - LABORATORY FORTIFIED SAMPLE MATRIX 10.4.1

The l a b o r a t o r y must add a known amount o f mercury t o a minimum o f 10% o f samples o r one sample p e r sample s e t , whichever i s g r e a t e r . S e l e c t a t i s s u e sample t h a t i s r e p r e s e n t a t i v e o f t h e t y p e o f t i s s u e b e i n g analyzed and has a l o w mercury background. I t i s recommended t h a t t h i s sample be analyzed p r i o r t o f o r t i f i c a t i o n . The f o r t i f i c a t i o n s h o u l d be 20% t o 50% h i g h e r t h a n t h e analyzed v a l u e . Over t i m e , samples f r o m a l l r o u t i n e sample sources s h o u l d be f o r t i f i e d .

10.4.2

C a l c u l a t e t h e p e r c e n t r e c o v e r y , c o r r e c t e d f o r background c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o t h e c o n t r o l l i m i t s e s t a b l i s h e d i n Sect. 10.3.3 f o r t h e analyses o f LFBs. A r e c o v e r y calculation i s not required i f the concentration o f the a n a l y t e added i s l e s s t h a n 10% o f t h e sample background c o n c e n t r a t ion. P e r c e n t r e c o v e r y may be c a l c u l a t e d i n u n i t s appropriate t o the matrix, using the following equation:

c, - c x 100

R = S

where, R = p e r c e n t r e c o v e r y C, = f o r t i f i e d sample c o n c e n t r a t i o n C = sample background c o n c e n t r a t i o n s = concentration equivalent o f f o r t i f i e r added t o t i s s u e sample.

372

Methods for the Determination 10.4.3

11.

I f mercury r e c o v e r y f a l l s o u t s i d e t h e d e s i g n a t e d range, and t h e l a b o r a t o r y performance i s shown t o be i n c o n t r o l ( S e c t . 1 0 . 3 ) , t h e r e c o v e r y problem encountered w i t h t h e f o r t i f i e d t i s s u e sample i s judged t o be m a t r i x r e l a t e d , n o t system r e l a t e d The r e s u l t f o r mercury i n t h e u n f o r t if ied sampl e must be l a b e l l e d t o i n f o r m t h e d a t a u s e r t h a t t h e r e s u t s a r e suspect due t o m a t r i x e f f e c t s .

PROCEDURE ( S e c t . 7.1.10) and 1 mL o f conc. HNO, 11.1 Add 4 mL o f conc. H,SO ( S e c t . 7.1.4) t o each b o t t l e and p l a c e i n a w a t e r b a t h m a i n t a i n e d a t 58°C u n t i l t h e t i s s u e i s c o m p l e t e l y d i s s o l v e d (30 t o 60 m i n ) . 11.2 Cool t o 4°C i n an i c e b a t h and c a u t i o u s l y add 5 mL o f p o t a s s i u m permanganate s o l u t i o n ( S e c t . 7.4) i n 1 mL i n c r e m e n t s . Add an a d d i t i o n a l 10 mL o r more o f permanganate, as necessary t o m a i n t a i n o x i d i z i n g c o n d i t i o n s . Add 8 mL o f p o t a s s i u m p e r s u l f a t e s o l u t i o n (Sect. 7 . 5 ) . A l l o w t o s t a n d o v e r n i g h t a t room t e m p e r a t u r e .

A s an a l t e r n a t i v e t o t h e o v e r n i g h t d i g e s t i o n , t i s s u e s o l u b i l i z a t i o n may be c a r r i e d o u t i n a w a t e r b a t h a t 80°C f o r 30 min. The sample i s c o o l e d and 15 mL o f p o t a s s i u m permanganate s o l u t i o n ( S e c t . 7.4) added c a u t i o u s l y f o l l o w e d by 8 mL o f p o t a s s i u m p e r s u l f a t e s o l u t i o n ( S e c t . 7 . 5 ) . A t t h i s p o i n t , t h e sample i s r e t u r n e d t o t h e w a t e r b a t h and d i g e s t e d f o r an a d d i t i o n a l 90 min a t 30°C. C a l i b r a t i o n s t a n d a r d s a r e t r e a t e d i n t h e same manner. 11.3 T u r n on t h e s p e c t r o p h o t o m e t e r and c i r c u l a t i n g pump. A d j u s t t h e pump r a t e t o 1 L/min. A l l o w t h e s p e c t r o p h o t o m e t e r and pump t o s t a b i l i z e . 11.4 Cool t h e BOD b o t t l e s t o room t e m p e r a t u r e and d i l u t e i n t h e f o 1owing manner: 11.4.1

To each BOD b o t t l e c o n t a i n i n g t h e CAL, LFB and LRB, add 50 mL o f r e a g e n t w a t e r ( S e c t . 7.1.7).

11.4.2

To each BOD b o t t l e c o n t a i n i n g a t i s s u e sample, QCS add 55 mL o f r e a g e n t w a t e r (Sect. 7.1.7).

r

LFM,

11.5 To each BOD b o t t l e , add 6 mL o f sodium c h l o r i d e - h y d r o x y l a m i n e s u l f a t e s o l u t i o n ( S e c t . 7.6) t o reduce t h e excess permanganate. 11.6 T r e a t i n g each b o t t l e i n d i v i d u a l l y : 11.6.1

P l a c i n g t h e a s p i r a t o r i n s i d e t h e BOD b o t t l e and above t h e l i q u i d , p u r g e t h e head space (20 t o 30 sec) t o remove p o s s i b l e gaseous i n t e r f e r e n t s .

11.6.2

Add 5 mL o f stannous c h l o r i d e s o l u t i o n ( S e c t . 7.7) and immediately a t t a c h t h e b o t t l e t o t h e a e r a t i o n apparatus.

Metals 11.6.3

373

The absorbance, as e x h i b i t e d e i t h e r on t h e s p e c t r o photometer o r t h e r e c o r d e r , w i l l i n c r e a s e and r e a c h maximum w i t h i n 30 sec. A s soon as t h e r e c o r d e r pen l e v e l s o f f , a p p r o x i m a t e l y 1 min, open t h e bypass v a l u e ( o r o p t i o n a l l y remove a s p i r a t o r f r o m t h e BOD b o t t l e i f i t i s vented under t h e hood) and c o n t i n u e t h e a e r a t i o n u n t i l t h e absorbance r e t u r n s t o i t s minimum v a l u e .

11.7 Close t h e bypass v a l u e , remove t h e a s p i r a t o r f r o m t h e BOD b o t t l e and c o n t i n u e t h e a e r a t i o n . Repeat s t e p ( S e c t . 11.6) u n t i l a l l BOD b o t t l e s have been a e r a t e d and r e c o r d e d .

12.

CALCULATIONS 12.1 Measure t h e peak h e i g h t o f t h e unknown f r o m t h e c h a r t and r e a d t h e mercury v a l u e f r o m t h e s t a n d a r d c u r v e .

12.2 C a l c u l a t e t h e mercury c o n c e n t r a t i o n i n t h e sample by t h e f o r m u l a :

" Hg'g

=

g Hg in t h e a l i q u o t wt. 'of the a l i q u o t in grams

12.3 Report mercury c o n c e n t r a t i o n s as f o l l o w s : Below 0.1 p g / g , < 0 . 1 p g / g ; between 0 . 1 and 1 p g / g , t o t h e n e a r e s t 0.01 p g ; between 1 and 10 p g / g , t o n e a r e s t 0 . 1 1-19; above 10 p g / g , t o n e a r e s t p g . 13.

PRECISION AND ACCURACY

13.1 The s t a n d a r d d e v i a t i o n f o r mercury i n f i s h t i s s u e samples a r e r e p o r t e d as 0.19 ? 0.02 pg Hgfg , 0.74 k 0.05 pg Hg/g and 0.74 f 0.05 pg Hg/g w i t h r e c o v e r i e s f o r LFM b e i n g 112%, 93%, and 86%, r e s p e c t i v e l y . These t i s s u e samples were f o r t i f i e d w i t h m e t h y l mercuric chloride.

14.

REFERENCES

1.

" S a f e t y i n Academic C h e m i s t r y L a b o r a t o r i e s " , American Chemical S o c i e t j Pub1 i c a t i o n , Committee on Chemical S a f e t y , 3 r d E d i t i o n , 1979.

2.

"OSHA S a f e t y and H e a l t h Standards, General I n d u s t r y " , (29CFR 1910), O c c u p a t i o n a l S a f e t y and H e a l t h A d m i n i s t r a t i o n , OSHA 2206, r e v i s e d January, 1976.

3.

"Proposed OSHA S a f e t y and H e a l t h Standards, L a b o r a t o r i e s " , O c c u p a t i o n a l S a f e t y and H e a l t h A d m i n i s t r a t i o n , Federal R e g i s t e r , J u l y 24, 1986.

4.

" S p e c i f i c a t i o n f o r Reagent Water," Annual Book o f ASTM Standards, 01193, V o l . 11.01, 1990.

374

Methods for the Determination 5.

N a t i o n a l I n s t i t u t e o f Standards and Technology, O f f i c e o f Standards Reference M a t e r i a l s , G a i t h e r s b u r g , MD 20899: A q u a t i c P l a n t Lagarosiphon m a j o r (CRM 8030), A q u a t i c P l a n t - P l a t i h y p n i d i u m r i p a r i o i d e s (CRM 8031). O y s t e r T i s s u e (SRM 1566a), A l b a c o r e Tuna (RM 5 0 ) .

6.

N a t i o n a l Research C o u n c i l o f Canada, Marine A n a l y t i c a l Chemistry Standards Program, D i v i s i o n o f Chemistry, M o n t r e a l Road, Ottawa, O n t a r i o K1A OR9, Canada: D o g f i s h L i v e r (DOLT-l), D o g f i s h Muscle (DORM-l), Non D e f a t t e d L o b s t e r Hepatopancreas (LUTS-I), L o b s t e r Hepatopancreas (TORT-1).

7.

Code o f Federal R e g u l a t i o n s 40, Ch. 1, P t . 136 Appendix B.

Metals

375

SCRUBBER C ONTAlNINQ A MERCUFN ABSORBNQ MEW

Flguro 1. Apparatus for Flaaelrtt Mercury Detcnhrtbn

Because of the toxic nature o f mercury vapor, inhalation must be avoided. Therefore, a bypass has been Included in the system to either vent the mercury vapor into a exhaust hood or pass the vapor through some absorbing media, such as: a) equal volumes of 0.1 N KMn0, and 10% H,SO, b) 0.25% iodine I n a 3% KI solutlon. A specially treated charcoal that will absorb mercury vapor is also available from Barnebey and Cheney, P.O. Box 2526, Columbus, OH 43216, Catalog No. 58013 or 580-22.

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PART I1 METHODS FOR THE DETERMINATION OF INORGANIC SUBSTANCES IN ENVIRONMENTAL SAMPLES

377

378

Methods for the Determination METHOD 180.1 DETERMINATION OF TURBIDITY BY NEPHELOMETRY

E d i t e d by James W . O ' D e l l Inorganic Chemistry Branch Chemistry Research D i v i s i o n

Revision 2.0 August 1993

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

Inorganic Substances

379

METHOD 180.1 DETERMINATION OF TURBIDITY BY NEPHELOMETRY 1.0

2.0

SCOPE AND APPLICATION 1.1

T h i s method c o v e r s t h e d e t e r m i n a t i o n o f t u r b i d i t y i n d r i n k i n g , ground, s u r f a c e , and s a l i n e w a t e r s , domestic and i n d u s t r i a l wastes.

1.2

The a p p l i c a b l e range i s 0 t o 40 n e p h e l o m e t r i c t u r b i d i t y u n i t s (NTU). H i g h e r v a l u e s may be o b t a i n e d w i t h d i l u t i o n o f t h e sample.

SUMMARY OF METHOD 2.1

3.0

The method i s based upon a comparison o f t h e i n t e n s i t y o f l i g h t s c a t t e r e d by t h e sample under d e f i n e d c o n d i t i o n s w i t h t h e i n t e n s i t y o f l i g h t s c a t t e r e d by a s t a n d a r d r e f e r e n c e suspension. The h i g h e r the i n t e n s i t y o f scattered l i g h t , the higher the t u r b i d i t y . Readings, i n NTU's, a r e made i n a nephelometer designed a c c o r d i n g t o s p e c i f i c a t i o n s g i v e n i n s e c t i o n s 6.1 and 6.2. A p r i m a r y standard suspension i s used t o c a l i b r a t e t h e i n s t r u m e n t . A secondary s t a n d a r d suspension i s used as a d a i l y c a l i b r a t i o n check and i s m o n i t o r e d p e r i o d i c a l l y f o r d e t e r i o r a t i o n u s i n g one o f t h e p r i m a r y standards. 2.1.1

Formazin polymer i s used as a p r i m a r y t u r b i d i t y suspension f o r w a t e r because i t i s more r e p r o d u c i b l e t h a n o t h e r t y p e s o f standards p r e v i o u s l y used f o r t u r b i d i t y a n a l y s i s .

2.1.2

A c o m m e r c i a l l y a v a i l a b l e polymer p r i m a r y s t a n d a r d i s a l s o approved f o r use f o r t h e N a t i o n a l I n t e r i m P r i m a r y D r i n k i n g Water R e g u l a t i o n s . T h i s s t a n d a r d i s i d e n t i f i e d as AMCO-AEPA1, a v a i 1a b l e f r o m Advanced Polymer Systems.

DEFINITIONS 3.1

CALIBRATION BLANK (CB) -- A volume o f r e a g e n t w a t e r f o r t i f i e d w i t h t h e same m a t r i x as t h e c a l i b r a t i o n standards, b u t w i t h o u t t h e a n a l y t e s , i n t e r n a l standards, o r s u r r o g a t e s a n a l y t e s .

3.2

INSTRUMENT PERFORMANCE CHECK SOLUTION (IPC) -- A s o l u t i o n o f one o r more method a n a l y t e s , s u r r o g a t e s , i n t e r n a l standards, o r o t h e r t e s t substances used t o e v a l u a t e t h e performance o f t h e i n s t r u m e n t system w i t h respect t o a defined set o f c r i t e r i a .

3.3

LABORATORY REAGENT BLANK (LRB) -- An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a l l glassware, equipment, s o l v e n t s , r e a g e n t s , i n t e r n a l s t a n d a r d s , and s u r r o g a t e s t h a t a r e used w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e

380

Methods for the Determination p r e s e n t i n t h e l a b o r a t o r y environment, t h e r e a g e n t s , o r t h e apparatus. 3.4

LINEAR C A L I B R A T I O N RANGE (LCR) -- The c o n c e n t r a t i o n range o v e r w h i c h t h e i n s t r u m e n t response i s l i n e a r .

3.5

MATERIAL SAFETY DATA SHEET (MSDS) -- W r i t t e n i n f o r m a t i o n p r o v i d e d b y vendors c o n c e r n i n g a chemical ' s t o x i c i t y , h e a l t h hazards, p h y s i c a l p r o p e r t i e s , f i r e , and r e a c t i v i t y d a t a i n c l u d i n g s t o r a g e , s p i l l , and handling precautions.

3.6

PRIMARY CALIBRATION STANDARD (PCAL) -- A suspension p r e p a r e d f r o m t h e p r i m a r y d i l u t i o n s t o c k s t a n d a r d suspension. The PCAL suspensions a r e used t o c a l i b r a t e t h e i n s t r u m e n t response w i t h respect t o analyte concentration.

3.7

QUALITY CONTROL SAMPLE (QCS) -- A s o l u t i o n o f t h e method a n a l y t e o f known c o n c e n t r a t i o n s t h a t i s used t o f o r t i f y an a l i q u o t o f LRB m a t r i x . The QCS i s o b t a i n e d f r o m a source e x t e r n a l t o t h e l a b o r a t o r y , and i s used t o check l a b o r a t o r y performance.

3.8

SECONDARY CALIBRATION STANDARDS (SCAL) -- Commercially prepared, s t a b i l i z e d s e a l e d l i q u i d o r g e l t u r b i d i t y standards c a l i b r a t e d a g a i n s t p r o p e r l y p r e p a r e d and d i l u t e d f o r m a z i n o r s t y r e n e d i v i n y l benzene polymers.

3.9

STOCK STANDARD SUSPENSION (SSS) -- A c o n c e n t r a t e d suspension c o n t a i n i n g t h e a n a l y t e p r e p a r e d i n t h e l a b o r a t o r y u s i n g assayed r e f e r e n c e m a t e r i a1 s o r purchased f r o m a r e p u t a b l e commercial source. S t o c k s t a n d a r d suspension i s used t o p r e p a r e c a l i b r a t i o n suspensions and o t h e r needed suspensions.

4.0 INTERFERENCES

5.0

4.1

The presence o f f l o a t i n g d e b r i s and coarse sediments w h i c h s e t t l e o u t r a p i d l y w i l l g i v e l o w r e a d i n g s . F i n e l y d i v i d e d a i r bubbles can cause h i g h r e a d i n g s .

4.2

The presence o f t r u e c o l o r , t h a t i s t h e c o l o r o f w a t e r which i s due t o d i s s o l v e d substances t h a t absorb l i g h t , w i l l cause t u r b i d t i e s t o be low, a l t h o u g h t h i s e f f e c t i s g e n e r a l l y n o t s i g n i f i c a n t w i h d r i n k i n g waters.

4.3

L i g h t a b s o r b i n g m a t e r i a l s such as a c t i v a t e d carbon i n s i g n i f c a n t c o n c e n t r a t i o n s can cause l o w r e a d i n g s .

SAFETY 5.1

The t o x i c i t y o r c a r c i n o g e n i c i t y o f each r e a g e n t used i n t h i s method has n o t been f u l l y e s t a b l i s h e d . Each chemical should be r e g a r d e d as a p o t e n t i a l h e a l t h hazard and exposure s h o u l d be as l o w as reasonably achievable.

Inorganic Substances

381

5.2 Each laboratory is responsible for maintaining a current awareness file o f OSHA regulations regarding the safe handling of the chemicals specified in this method. A reference file of Material Safety Data Sheets (MSDS) should be made available to all personnel involved in the chemical analysis. The preparation of a formal safety plan is also advisable. 5.3 Hydrazine Sulfate (7.2.1) is a carcinogen. It is highly toxic and may be fatal if inhaled, swallowed, or absorbed through the skin. Formazin can contain residual hydrazine sulfate. Proper protection should be employed. 6.0 EQUIPMENT AND SUPPLIES

6.1 The turbidimeter shall consist of a nephelometer, with light source for illuminating the sample, and one or more photo-electric detectors with a readout device to indicate the intensity of light scattered at right angles to the path o f the incident light. The turbidimeter should be designed so that little stray light reaches the detector in the absence of turbidity and should be free from significant drift after a short warm-up period.

6.2 Differences in physical design of turbidimeters will cause differences in measured values for turbidity, even though the same suspension is used for calibration. To minimize such differences, the following design criteria should be observed: 6.2.1 Light source: Tungsten lamp operated at a color temperature between 2200-3000°K. 6.2.2 Distance traversed by incident light and scattered light within the sample tube: Total not to exceed 10 cm. 6.2.3 Detector: Centered at 90" to the incident light path and not to exceed k 30" from 90". The detector, and filter system if used, shall have a spectral peak response between 400 and 600 nm. 6.3 The sensitivity o f the instrument should permit detection o f a turbidity difference of 0.02 NTU or less in waters having turbidities less than 1 unit. The instrument should measure from 0 to 40 units turbidity. Several ranges may be necessary to obtain both adequate coverage and sufficient sensitivity for l o w turbidi t ies.

6.4 The sample tubes to be used with the available instrument must be of clear, colorless glass or plastic. They should be kept scrupulously clean, both inside and out, and discarded when they become scratched or etched. A light coating o f silicon oil may be used to mask minor imperfections in glass tubes. They must not be handled at all where the light strikes them, but should be provided with sufficient extra length, or with a protective case, so that they may be handled.

382

Methods for the Determination

Tubes should be checked, indexed and read a t t h e o r i e n t a t i o n t h a t produces t h e lowest background blank v a l u e .

7.0

6.5

Balance -- A n a l y t i c a l , capable of a c c u r a t e l y weighing t o the n e a r e s t 0.0001 g .

6.6

Glassware -- Class A volumetric f l a s k s and p i p e t s as r e q u i r e d .

REAGENTS AND STANDARDS

7.1

Reagent w a t e r , t u r b i d i t y - f r e e : Pass deionized d i s t i l l e d w a t e r through a 0.451.1 pore s i z e membrane f i l t e r , i f such f i l t e r e d water shows a lower t u r b i d i t y than u n f i l t e r e d d i s t i l l e d water.

7.2

Stock s t a n d a r d suspension (Formazin):

7.3

7.2.1

(CASRN 10034Dissolve 1.00 g hydrazine s u l f a t e , (NH ),.H,SO,, 93-2) i n reagent water and d i l u t e t o 160 mL i n a volumetric f l a s k . CAUTION--CARCINOGEN

7.2.2

Dissolve 10.00 g hexamethylenetetramine (CASRN 100-97-0) i n r e a g e n t water and d i l u t e t o 100 mL i n a volumetric f l a s k . In a 100 mL volumetric f l a s k , mix 5 . 0 mL of each s o l u t i o n (7.2.1 t 7.2.2). Allow t o s t a n d 24 hours a t 25 k 3"C, then d i l u t e t o the mark with reagent water.

Primary c a l i b r a t i o n standards: Mix and d i l u t e 10.00 mL of s t o c k s t a n d a r d suspension ( 7 . 2 ) t o 100 mL with r e a g e n t water. The t u r b i d i t y of t h i s suspension i s d e f i n e d a s 40 NTU. For o t h e r v a l u e s , mix and d i l u t e p o r t i o n s of t h i s suspension a s r e q u i r e d . 7.3.1

8.0

A new s t o c k standard suspension (7.2) should be prepared each month. Primary c a l i b r a t i o n s t a n d a r d s (7.3) should be prepared d a i l y by d i l u t i o n o f the s t o c k s t a n d a r d suspension.

7.4

Formazin i n commercially prepared primary c o n c e n t r a t e d s t o c k s t a n d a r d suspension (SSS) may be d i l u t e d and used a s r e q u i r e d . Dilute t u r b i d i t y s t a n d a r d s should be prepared d a i l y .

7.5

AMCO-AEPA-1 S t y r e n e Divinylbenzene polymer primary s t a n d a r d s a r e a v a i l a b l e f o r s p e c i f i c instruments and r e q u i r e no p r e p a r a t i o n o r d i l u t i o n p r i o r t o use.

7.6

Secondary s t a n d a r d s may be a c c e p t a b l e a s a d a i l y c a l i b r a t i o n check, but must be monitored on a r o u t i n e b a s i s f o r d e t e r i o r a t i o n and rep1 aced a s r e q u i r e d .

SAMPLE COLLECTION, PRESERVATION AND STORAGE

8.1 Samples should be c o l l e c t e d i n p l a s t i c o r g l a s s b o t t l e s . All b o t t l e s must be thoroughly cleaned and r i n s e d with t u r b i d i t y f r e e water. Volume c o l l e c t e d should be s u f f i c i e n t t o i n s u r e a

Inorganic Substances

383

r e p r e s e n t a t i v e sample, a l l o w f o r r e p l i c a t e a n a l y s i s ( i f r e q u i r e d ) , and m i n i m i z e waste d i s p o s a l .

8.2

No chemical p r e s e r v a t i o n i s r e q u i r e d .

Cool sample t o 4°C.

8.3 Samples s h o u l d be analyzed as soon as p o s s i b l e a f t e r c o l l e c t i o n .

If s t o r a g e i s r e q u i r e d , samples m a i n t a i n e d a t 4°C may be h e l d f o r up t o 48 h.

9.0

QUALITY CONTROL

9.1

Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a formal q u a l i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f t h i s program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y and a n a l y s i s o f l a b o r a t o r y r e a g e n t b l a n k s and o t h e r s o l u t i o n s as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n performance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f d a t a generated.

9.2

I N I T I A L DEMONSTRATION OF PERFORMANCE.

9.3

9.2.1

The i n i t i a l d e m o n s t r a t i o n o f performance i s used t o c h a r a c t e r i z e i n s t r u m e n t performance ( d e t e r m i n a t i o n o f LCRs and a n a l y s i s o f QCS).

9.2.2

L i n e a r C a l i b r a t i o n Range (LCR) -- The LCR must be determined i n i t i a l l y and v e r i f i e d e v e r y 6 months o r whenever a s i g n i f i c a n t change i n i n s t r u m e n t response i s observed o r expected. The i n i t i a l d e m o n s t r a t i o n o f l i n e a r i t y must use s u f f i c i e n t standards t o i n s u r e t h a t t h e r e s u l t i n g curve i s l i n e a r . The v e r i f i c a t i o n o f l i n e a r i t y must use a minimum o f a b l a n k and t h r e e s t a n d a r d s . I f any v e r i f i c a t i o n d a t a exceeds t h e i n i t i a l v a l u e s b y k lo%, l i n e a r i t y must be r e e s t a b l i s h e d . I f any p o r t i o n o f t h e range i s shown t o be n o n l i n e a r , s u f f i c i e n t s t a n d a r d s must be used t o c l e a r l y d e f ine t h e n o n l in e a r p o r t i o n .

9.2.3

Q u a l i t y C o n t r o l Sample (QCS) -- When b e g i n n i n g t h e use o f t h i s method, on a q u a r t e r l y b a s i s o r as r e q u i r e d t o meet d a t a - q u a l i t y needs, v e r i f y t h e c a l i b r a t i o n standards and a c c e p t a b l e i n s t r u m e n t performance w i t h t h e p r e p a r a t i o n and a n a l y s i s o f a QCS. I f t h e determined c o n c e n t r a t i o n s a r e n o t w i t h i n & 10% o f t h e s t a t e d values, performance o f t h e d e t e r m i n a t i v e s t e p o f t h e method i s unacceptable. The source o f t h e problem must be i d e n t i f i e d and c o r r e c t e d b e f o r e c o n t i n u i n g w i t h on-going analyses.

ASSESSING LABORATORY PERFORMANCE

9.3.1

L a b o r a t o r y Reagent B l a n k (LRB) -- The l a b o r a t o r y must analyze a t l e a s t one LRB w i t h each b a t c h o f samples. Data produced

384

Methods for the Determination

are used to assess contamination from the laboratory env i ronmen t . 9.3.2

Instrument Performance Check Solution (IPC) - - For all determinations, the laboratory must analyze the IPC (a midrange check standard) and a calibration blank immediately following daily calibration, after every tenth sample (or more frequently, if required) and at the end of the sample run. Analysis of the IPC solution and calibration blank immediately following calibration must verify that the instrument is within f 10% of calibration. Subsequent analyses of the IPC solution must verify the calibration i s still within f 10%. If the calibration cannot be verified within the specified limits, reanalyze the IPC solution. If the second analysis of the IPC solution confirms calibration to be outside the limits, sample analysis must be discontinued, the cause determined and/or in the case of drift the instrument recalibrated. All samples following the last acceptable IPC solution must be reanalyzed. The analysis data of the calibration blank and IPC solution must be kept on file with the sample analyses data. NOTE: Secondary calibration standards (SS) may also be used as the IPC.

9.3.3

Where additional reference materials such as Performance Evaluation samples are available, they should be analyzed to provide additional performance data. The analysis of reference samples is a valuable tool for demonstrating the ability to perform the method acceptably.

10.0 CALIBRATION AND STANDARDIZATION

The manufacturer's operating instructions should be followed. Measure standards on the turbidimeter covering the range of interest. If the instrument is already calibrated in standard turbidity units, this procedure will check the accuracy of the calibration scales. At least one standard should be run in each instrument range to be used. Some instruments permit adjustments o f sensitivity so that scale values will correspond to turbidities. Solid standards, such as those made of lucite blocks, should never be used due to potential calibration changes caused by surface scratches. If a pre-calibrated scale is not supplied, calibration curves should be prepared for each range of the instrument.

10.1 Turbidimeter calibration:

11.0 PROCEDURE

11.1 Turbidities less than 40 units:

If possible, allow samples to come to room temperature before analysis. Mix the sample to thoroughly disperse the solids. Wait until air bubbles disappear then pour the sample into the turbidimeter tube. Read the turbidity directly from the instrument scale or from the appropriate calibration curve.

Inorganic Substances

385

Dilute the sample with one or more volumes o f turbidity-free water until the turbidity falls below 40 units. The turbidity of the original sample is then computed from the turbidity of the diluted sample and the dilution factor. For example, if 5 volumes of turbidity-free water were added to 1 volume of sample, and the diluted sample showed a turbidity of 30 units, then the turbidity o f the original sample was 180 units.

11.2 Turbidities exceeding 40 units:

11.2.1 Some turbidimeters are equipped with several separate scales.

The higher scales are to be used only as indicators of required dilution volumes to reduce readings to less than 40 NTU. NOTE 1: Comparative work performed in the Environmental Monitoring Systems Laboratory - Cincinnati (EMSL-Cincinnati) indicates a progressive error on sample turbidities in excess o f 40 units. 12.0 DATA ANALYSIS AND CALCULATIONS 12.1 Multiply sample readings by appropriate dilution to obtain final

reading. 12.2 Report results as follows:

NTU 0.0 - 1.0 1 - 10 10 - 40 40 - 100 100 - 400 400 - 1000 > 1000 13.0

Record to Nearest: 0.05 0.1 1 5 10 50 100

METHOD PERFORMANCE 13.1 In a single laboratory (EMSL-Cincinnati), using surface water samples at levels of 26, 41, 75 and 180 NTU, the standard deviations were & 0.60, f 0.94, f 1.2 and f 4.7 units, respectively. 13.2 The interlaboratory precision and accuracy data in Table 1 were

developed using a reagent water matrix. Values are in NTU. 14.0 POLLUTION PREVENTION 14.1 Pollution prevention encompasses any technique that reduces or

eliminates the quantity o r toxicity of waste at the point of generation. Numerous opportunities for pollution prevention exist in laboratory operation. The EPA has established a preferred hierarchy of environmental management techniques that places pollution prevention as the management option of first choice.

386

Methods for the Determination Whenever f e a s i b l e , l a b o r a t o r y personnel s h o u l d use p o l l u t i o n p r e v e n t i o n t e c h n i q u e s t o address t h e i r waste g e n e r a t i o n . When w a s t e s cannot be f e a s i b l y reduced a t t h e source, t h e Agency recommends r e c y c l i n g as t h e n e x t b e s t o p t i o n . 14.2 T h e q u a n t i t y o f chemicals purchased should be based on expected usage d u r i n g i t s s h e l f l i f e and d i s p o s a l c o s t o f unused m a t e r i a l . A c t u a l r e a g e n t p r e p a r a t i o n volumes should r e f l e c t a n t i c i p a t e d usage and r e a g e n t s t a b i l i t y . 14.3 For i n f o r m a t i o n about p o l l u t i o n p r e v e n t i o n t h a t may be a p p l i c a b l e t o l a b o r a t o r i e s and r e s e a r c h i n s t i t u t i o n s , c o n s u l t "Less i s B e t t e r : L a b o r a t o r y Chemical Management f o r Waste Reduction," a v a i l a b l e f r o m t h e American Chemical S o c i e t y ' s Department o f Government R e g u l a t i o n s and Science P o l i c y , 1155 1 6 t h S t r e e t N.W., Washington D.C. 20036, (202)872-4477.

15.0 WASTE MANAGEMENT

15.1 The U . S . Environmental P r o t e c t i o n Agency r e q u i r e s t h a t l a b o r a t o r y waste management p r a c t i c e s be conducted c o n s i s t e n t w i t h a l l a p p l i c a b l e r u l e s and r e g u l a t i o n s . Excess r e a g e n t s , samples and method process wastes s h o u l d be c h a r a c t e r i z e d and d i s p o s e d o f i n an a c c e p t a b l e manner. The Agency urges l a b o r a t o r i e s t o p r o t e c t t h e a i r , w a t e r and l a n d by m i n i m i z i n g and c o n t r o l l i n g a l l r e l e a s e s f r o m hoods, and bench o p e r a t i o n s , complying w i t h t h e l e t t e r and s p i r i t o f any waste d i s c h a r g e p e r m i t and r e g u l a t i o n s , and by c o m p l y i n g w i t h a l l s o l i d and hazardous waste r e g u l a t i o n s , p a r t i c u l a r l y t h e hazardous waste i d e n t i f i c a t i o n r u l e s and l a n d d i s p o s a l r e s t r i c t i o n s . F o r f u r t h e r i n f o r m a t i o n on waste management c o n s u l t t h e "Waste Management Manual f o r L a b o r a t o r y Personnel, 'I a v a i 1a b l e f r o m t h e American Chemical S o c i e t y a t t h e address l i s t e d i n S e c t . 14.3. 16.0 REFERENCES

1.

Annual Book o f ASTM Standards, Volume 11.01 Water (l), Standard D1889-88AY p. 359, (1993).

2.

Standard Methods f o r t h e Examination o f Water and Wastewater, 1 8 t h E d i t i o n , pp. 2-9, Method 21308, (1992).

Inorganic Substances

387

17.0 TABLES, DIAGRAMS, FLOWCHARTS AND VALIDATION DATA

TABLE 1.

INTERLABORATORY P R E C IS ION AND ACCURACY DATA

TRUE VALUE (TI

NUMBER OF VALUES RE PORT ED 373

0.450 ~

RESIDUAL FOR X

STANDARD D E V IA T ION (S)

RESIDUAi FOR S

0.4864

0.0027

0.1071

-0.0078

MEAN (X)

~~

3 74

0 600

0.6026

-0.0244

0.1048

-0.0211

289

0.65

0.6931

0.0183

0.1301

0.0005

482

0.910

0.9744

0.0013

0.2512

0.1024

484

0.910

0.9919

0.0688

0.1486

-0.0002

489

1 .oo

0.9405

-0.0686

0.1318

-0.0236

640

1.36

1.3456

-0.0074

0.1894

0.0075

487

3.40

3.2616

-0.0401

0.3219

-0.0103

288

4.8

4.5684

-0.0706

0.3776

-0.0577

5.60

5.6984

0.2952

0.4411

-0.0531

5.95

5.6026

-0.1350

0.4122

-0.1078

~ 714 _ _ _

64 1

REGRESSIONS: X

~

= 0.955T t 0.54,

S

7

"

"74T

+

0.082

388

Methods for the Determination METHOD 300.0 DETERMINATION OF INORGANIC ANIONS BY ION CHROMATOGRAPHY

John D. Pfaff Inorganic Chemistry Branch Chemistry Research Division

Revision 2.1 August 1993

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

Inorganic Substances

389

METHOD 300.0 DETERMINATION OF INORGANIC ANIONS BY ION CHROMATOGRAPHY 1.0 SCOPE AND APPLICATION

1.1

This method covers the determination of the following inorganic anions: PART A. Bromide Chloride Fluoride Nitrate

Nitrite Ortho-Phosphate-P Sulfate

PART B. Bromate Chl orate

Chlorite

1.2 The matrices applicable to each method are shown below: A.

Drinking water, surface water, mixed domestic and industrial wastewaters, groundwater, reagent waters, solids (after extraction 11.7), leachates (when no acetic acid is used).

6.

Drinking water and reagent waters

1.3 The single laboratory Method Detection Limit (MDL defined in Sect. 3.2) for the above analytes is listed in Tables 1A and 1B. The MDL for a specific matrix may differ from those listed, depending upon the nature of the sample. 1.4 Method A i s recommended for drinking and wastewaters. The multilaboratory ranges tested for each anion are as follows: Anal vte Bromide Chloride F1 uoride Ni trate-N Ni tri te-N Ortho-Phosphate-P Sulfate

!!KlLL

0.63 0.78 0.26 0.42 0.36 0.69 2.85 -

21.0 26.0 8.49 14.0 12.0 23.1 95.0

390

Methods for the Determination 1 . 5 This method i s recommended f o r use only by o r under t h e s u p e r v i s i o n of a n a l y s t s experienced in t h e use of ion chromatography and i n the i n t e r p r e t a t i o n of the r e s u l t i n g ion chromatograms. 1.6

When t h i s method i s used t o analyze u n f a m i l i a r samples f o r any of t h e above a n i o n s , anion i d e n t i f i c a t i o n should be supported by t h e use of a f o r t i f i e d sample matrix covering t h e anions of i n t e r e s t . The f o r t i f i c a t i o n procedure i s d e s c r i b e d i n S e c t . 1 1 . 6 .

1.7

Users of t h e method d a t a should s t a t e t h e d a t a - q u a l i t y o b j e c t i v e s p r i o r t o a n a l y s i s . Users of t h e method must demonstrate t h e a b i l i t y t o g e n e r a t e a c c e p t a b l e r e s u l t s w i t h t h i s method, using the procedures d e s c r i b e d i n S e c t . 9 . 0 .

2.0 SUMMARY OF METHOD 2.1

A small volume o f sample, t y p i c a l l y 2 t o 3 mL, i s introduced i n t o an ion chromatograph. The anions of interest a r e s e p a r a t e d and measured, using a system comprised of a guard column, a n a l y t i c a l column, suppressor d e v i c e , and c o n d u c t i v i t y d e t e c t o r .

2.2

The main d i f f e r e n c e s between P a r t s A and B a r e the s e p a r a t o r columns and guard columns. S e c t i o n s 6 . 0 and 7.0 w i l l e l i c i t t h e differences.

2.3

An e x t r a c t i o n procedure must be performed t o use t h i s method f o r s o l i d s (See 1 1 . 7 ) .

2.4

Limited performance-based method m o d i f i c a t i o n s may be a c c e p t a b l e provided they a r e f u l l y documented and meet o r exceed requirements expressed i n S e c t . 9 . 0 , Q u a l i t y Control.

3.0 DEFINITIONS 3.1

CALIBRATION BLANK (CB) -- A volume of reagent water f o r t i f i e d with t h e same matrix a s t h e c a l i b r a t i o n s t a n d a r d s , but without the a n a l y t e s , i n t e r n a l s t a n d a r d s , or s u r r o g a t e a n a l y t e s .

3.2

CALIBRATION STANDARD (CAL) -- A s o l u t i o n prepared from the primary d i l u t i o n s t a n d a r d s o l u t i o n o r s t o c k s t a n d a r d s o l u t i o n s and the i n t e r n a l s t a n d a r d s and s u r r o g a t e a n a l y t e s . The CAL s o l u t i o n s a r e used t o c a l i b r a t e the instrument response with r e s p e c t t o a n a l y t e concentration.

3.3

FIELD DUPLICATES (FD) -- Two s e p a r a t e samples c o l l e c t e d a t t h e same time and p l a c e under i d e n t i c a l circumstances and t r e a t e d e x a c t l y the same throughout f i e l d and l a b o r a t o r y procedures. Analyses of f i e l d d u p l i c a t e s i n d i c a t e t h e p r e c i s i o n a s s o c i a t e d with sample c o l l e c t i o n , p r e s e r v a t i o n and s t o r a g e , a s we1 1 a s w i t h 1aboratory procedures.

3.4

INSTRUMENT PERFORMANCE CHECK SOLUTION (IPC) -- A s o l u t i o n of one o r more method a n a l y t e s , s u r r o g a t e s , i n t e r n a l s t a n d a r d s , or o t h e r t e s t

Inorganic Substances

391

s u b s t a n c e s used t o e v a l u a t e t h e p e r f o r m a n c e o f t h e i n s t r u m e n t system with respect t o a defined set o f c r i t e r i a . 3.5

LABORATORY FORTIFIED BLANK (LFB) - - An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t o w h i c h known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB i s a n a l y z e d e x a c t l y l i k e a sample, and i t s p u r p o s e i s t o d e t e r m i n e w h e t h e r t h e m e t h o d o l o g y i s i n c o n t r o l , and w h e t h e r t h e l a b o r a t o r y i s c a p a b l e o f m a k i n g a c c u r a t e and p r e c i s e measurements.

3.6

LABORATORY FORTIFIED SAMPLE MATRIX (LFM) -- An a l i q u o t o f an e n v i r o n m e n t a l sample t o w h i c h known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFM i s a n a l y z e d e x a c t l y l i k e a sample, and i t s p u r p o s e i s t o d e t e r m i n e w h e t h e r t h e sample m a t r i x c o n t r i b u t e s b i a s t o t h e a n a l y t i c a l r e s u l t s . The b a c k g r o u n d c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be d e t e r m i n e d i n a s e p a r a t e a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s .

3.7

LABORATORY REAGENT BLANK (LRB) -- An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y as a sample i n c l u d i n g e x p o s u r e t o a l l g l a s s w a r e , equipment, s o l v e n t s , r e a g e n t s , i n t e r n a l s t a n d a r d s , and s u r r o g a t e s t h a t a r e used w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e present i n t h e l a b o r a t o r y environment, t h e reagents, o r t h e apparatus.

3.8

LINEAR CALIBRATION RANGE (LCR) -- The c o n c e n t r a t i o n r a n g e o v e r w h i c h t h e i n s t r u m e n t response i s l i n e a r .

3.9

MATERIAL SAFETY DATA SHEET (MSDS) -- W r i t t e n i n f o r m a t i o n p r o v i d e d by v e n d o r s c o n c e r n i n g a c h e m i c a l ' s t o x i c i t y , h e a l t h hazards, p h y s i c a l p r o p e r t i e s , f i r e , and r e a c t i v i t y d a t a i n c l u d i n g s t o r a g e , s p i l l , and handling precautions.

3.10 METHOD DETECTION L I M I T (MDL) -- The minimum c o n c e n t r a t i o n b f an a n a l y t e t h a t c a n b e i d e n t i f i e d , measured and r e p o r t e d w i t h 99% c o n f i d e w e t h a t t h e a n a l y t e c o n c e n t r a t i o n i s g r e a t e r than zero. 3.11 PERFORMANCE EVALUATION SAMPLE (PE) -- A s o l u t i o n o f method a n a l y t e s d i s t r i b u t e d b y t h e Q u a l i t y Assurance Research D i v i s i o n (QARD), E n v i r o n m e n t a l M o n i t o r i n g Systems L a b o r a t o r y ( E M S L - C i n c i n n a t i ) , U . S. E n v i r o n m e n t a l P r o t e c t i o n Agency, C i n c i n n a t i , O h i o , t o mu1t i p l e l a b o r a t o r i e s f o r a n a l y s i s . A volume o f t h e s o l u t i o n i s added t o a known volume o f r e a g e n t w a t e r and a n a l y z e d w i t h p r o c e d u r e s used f o r samples. R e s u l t s o f a n a l y s e s a r e used b y QARD t o d e t e r m i n e s t a t i s t i c a l l y t h e a c c u r a c y and p r e c i s i o n t h a t c a n be e x p e c t e d when a method i s p e r f o r m e d b y a competent a n a l y s t . A n a l y t e t r u e v a l u e s a r e unknown t o t h e a n a l y s t . 3.12 QUALITY CONTROL SAMPLE (QCS) - - A s o l u t i o n o f method a n a l y t e s o f known c o n c e n t r a t i o n s t h a t i s used t o f o r t i f y an a l i q u o t o f LRB o r

392

Methods for the Determination

sample matrix. The QCS is obtained from a source external to the laboratory and different from the source of calibration standards. It is used to check 1 aboratory performance with externally prepared test materials. 3 . 1 3 STOCK STANDARD SOLUTION (SSS) - - A concentrated solution containing

one or more method analytes prepared in the laboratory using assayed reference materials or purchased from a reputable commercial source. 4.0

INTERFERENCES

4.1

Interferences can be caused by substances with retention times that are similar to and overlap those of the anion of interest. large amounts of an anion can interfere with the peak resolution of an adjacent anion. Sample dilution and/or fortification can be used to solve most interference problems associated with retention times.

4.2 The water dip or negative peak that elutes near, and can interfere

with, the fluoride peak can usually be eliminated by the addition of the equivalent of 1 mL of concentrated eluent (7.3 1OOX) to 100 mL of each standard and sample. 4.3 Method interferences may be caused by contaminants in the reagent

water, reagents, glassware, and other sample processing apparatus that lead to discrete artifacts or elevated baseline in ion chromatograms. 4.4 Samples that contain particles larger than 0.45 microns and reagent solutions that contain particles larger than 0.20 microns require

filtration to prevent damage to instrument columns and flow systems. 4.5

Any anion that is not retained by the column or only slightly retained will elute in the area of fluoride and interfere. Known coelution is caused by carbonate and other small organic anions. At concentrations of fluoride above 1.5 mg/L, this interference may not be significant, however, it is the responsibility of the user to generate precision and accuracy information in each sample matrix.

4.6

The acetate anion elutes early during the chromatographic run. The retention times of the anions also seem to differ when large amounts of acetate are present. Therefore, this method is not recommended for leachates of solid samples when acetic acid is used for pH adjustment.

4.7

The quantitation of unretained peaks should be avoided, such as low molecular weight organic acids (formate, acetate, propionate etc.) which are conductive and coelute with or near fluoride and would bias the fluoride quantitation in some drinking and most waste waters.

4.8

Any residual chlorine dioxide present in the sample will result in the formation of additional chlorite prior to analysis. If any

Inorganic Substances

393

c o n c e n t r a t i o n of c h l o r i n e d i o x i d e i s suspected i n t h e sample purge t h e sample with a n i n e r t gas (argon o r n i t r o g e n ) f o r about f i v e minutes o r u n t i l no c h l o r i n e d i o x i d e remains. 5.0

SAFETY 5.1

The t o x i c i t y o r c a r c i n o g e n i c i t y of each reagent used i n t h i s method have not been f u l l y e s t a b l i s h e d . Each chemical should be regarded a s a p o t e n t i a l h e a l t h hazard and exposure should be a s low a s reasonablv a c h i e v a b l e . Cautions a r e included f o r known extremely hazardous" materi a1 s o r procedures,

5.2

Each l a b o r a t o r y i s r e s p o n s i b l e f o r maintaining a f i l e of OSHA r e g u l a t i o n s regarding t h e s a f e hand chemicals s p e c i f i e d i n t h i s method. A r e f e r e n c e S a f e t y Data Sheets (MSDS) should be made a v a i l a b involved i n t h e chemical a n a l y s i s . The p r e p a r a t s a f e t y plan i s a l s o a d v i s a b l e .

5.3

The following chemicals have t h e p o t e n t i a l t o be highly t o x i c o r hazardous, c o n s u l t MSDS. 5.3.1

6.0

c u r r e n t awareness ing of t h e f i l e of Material e t o a l l personnel on of a formal

S u l f u r i c a c i d (7.4)

Equipment and S u p p l i e s

6.1

Balance -- A n a l y t i c a l , capable of a c c u r a t e l y weighing t o t h e n e a r e s t 0.0001 g .

6.2

Ion chromatograph -- Analytical system complete with ion chromatograph and a l l r e q u i r e d a c c e s s o r i e s i n c l u d i n g s y r i n g e s , a n a l y t i c a l columns, compressed g a s s e s and d e t e c t o r s . 6.2.1

Anion guard column: A p r o t e c t o r of t h e s e p a r a t o r column. I f omitted from t h e system t h e r e t e n t i o n times will be s h o r t e r . Usually packed with a s u b s t r a t e t h e same a s t h a t i n the s e p a r a t o r COI umn.

6.2.2

Anion s e p a r a t o r column: This column produces t h e s e p a r a t i o n shown i n Figures 1 and 2. 6.2.2.1

Anion a n a l y t i c a l co umn (Method A): The s e p a r a t i o n shown i n Figure 1 was generated using a Dionex AS4A column P/N 37041). An optional column may be used f comparable r e s o l u t i o n of peaks i s o b t a i n e d , and t h e requirements of S e c t . 9.2 can be met.

6.2.2.2

Anion a n a l y t i c a l column (Method B). The s e p a r a t i o n shown i n Figure 2 was generated using a Dionex AS9 column ( P / N 42025). An optional column may be used i f comparable r e s o l u t i o n of peaks i s

394

Methods for the Determination

obtained and the requirements of Sect. 9.2 can be met. 6.2.3

Anion suppressor device: The data presented in this method were generated using a Dionex anion micro membrane suppressor (P/N 37106).

6.2.4

Detector - - Conductivity cell: approximately 1.25 pL internal volume, (Dionex, or equivalent) capable of providing data as required in Sect. 9.2.

6.3 The Dionex AI-450 Data Chromatography Software was used to generate all the data in the attached tables. Systems using a stripchart recorder and integrator or other computer based data system may achieve approximately the same MDL's but the user should demonstrate this by the procedure outlined in Sect. 9.2. 7.0

Reagents and Standards 7.1

Sample bottles: Glass or polyethylene of sufficient volume to allow replicate analyses o f anions of nterest.

7.2 Reagent water: Distilled or deionized water, free o f the anions of interest. Water should contain partic es no larger than 0.20 microns. 7.3 Eluent solution (Method A and Method B): Sodium bicarbonate (CASRN 144-55-8) 1.7 mM, sodium carbonate (CASRN 497-19-8) 1.8 mM. Dissolve 0.2856 g sodium bicarbonate (NaHCO,) and 0.3816 g o f sodium carbonate (Na,CO,) in reagent water (7.2) and dilute to 2 L.

7.4 Regeneration solution (micro membrane suppressor) : Sulfuric acid (CASRN-7664-93-9) 0.025N. Dilute 2.8 mL conc. sulfuric acid to 4 L with reagent water.

(H,SO,)

7.5 Stock standard solutions, 1000 mg/L (1 mg/mL): Stock standard solutions may be purchased as certified solutions or prepared from ACS reagent grade materials (dried at 105°C for 30 min) as listed be1 ow. 7.5.1

Bromide (Br-) 1000 mg/L: Dissolve 1.2876 g sodium bromide (NaBr, CASRN 7647-15-6) in reagent water and dilute to 1 1.

7.5.2

Bromate (BrO,-) 1000 mg/L: Dissolve 1.17989 of sodium bromate (NaBrB,, CASRN 7789-38-0) in reagent water and dilute to 1 L.

7.5.3

Chlorate (CIO - ) 1000 mg/L: Dissolve 1.27539 of sodium chlorate (NaCjO,, CASRN 7775-09-9) in reagent water and dilute to I L.

Inorganic Substances

395

7.5.4

C h l o r i d e (CL-) 1000 mg/L: D i s s o l v e 1.6485 g sodium c h l o r i d e (NaC1, CASRN 7647-14-5) i n r e a g e n t w a t e r and d i l u t e t o 1 L.

7.5.5

C h l o r i t e (C10 - ) 1000 mg/L: D i s s o l v e 1.34109 o f sodium c h l o r i t e (NaCjO,, CASRN 7758-19-2) i n r e a g e n t w a t e r and d i l u t e t o 1 L.

7.5.6

F l u o r i d e ( F - ) 1000 mg/L: D i s s o l v e 2.21009 sodium f l u o r i d e (NaF, CASRN 7681-49-4) i n r e a g e n t w a t e r and d i l u t e t o 1 L.

7.5.7

N i t r a t e (NO- -N) 1000 mg/L: D i s s o l v e 6.0679 g sodium n i t r a t e (Nab800,, CASRN 7631-99-4) i n r e a g e n t w a t e r and d i l u t e t o 1 L.

7.5.8

N i t r i t e (NO- -N) 1000 mg/L: D i s s o l v e 4.9257 g sodium n i t r i t e (Nah,, CASRN 7632-00-0) i n r e a g e n t w a t e r and d i l u t e t o 1 L.

7.5.9

Phosphate (PO' -P) 1000 mg/L: D i s s o l v e 4.3937 g potassium CASRN 7778-77-0) i n r e a g e n t w a t e r phosphate (KH,bO and d i l u t e t o 1

r.

7.5.10

S u l f a t e (SO,=) 1000 mg/L: D i s s o l v e 1.8141 g potassium s u l f a t e ( K SO,, CASRN 7778-80-5) i n r e a g e n t w a t e r and dilute to L. NOTE:

7.6

8.0

S t a b i l i t y o f standards: S t o c k standards (7.5) a r e s t a b l e f o r a t l e a s t 1 month when s t o r e d a t 4°C. Except f o r t h e c h l o r i t e s t a n d a r d which i s o n l y s t a b l e f o r two weeks. D i l u t e w o r k i n g standards s h o u l d be p r e p a r e d weekly, e x c e p t t h o s e t h a t c o n t a i n n i t r i t e and phosphate s h o u l d be p r e p a r e d f r e s h d a i l y .

E t h y l e n e d i a m i n e p r e s e r v a t i o n s o l u t i o n : D i l u t e 10 mL o f e t h y l e n e d i a m i n e (99%) (CASRN 107-15-3) t o 200 mL w i t h r e a g e n t w a t e r . Use 1 mL o f t h i s d i l u t i o n t o each 1 L o f sample taken.

Sample C o l l e c t i o n . P r e s e r v a t i o n and S t o r a q e

8.1

Samples s h o u l d be c o l l e c t e d i n p l a s t i c o r g l a s s b o t t l e s . A l l b o t t l e s must be t h o r o u g h l y cleaned and r i n s e d w i t h r e a g e n t w a t e r . Volume c o l l e c t e d s h o u l d be s u f f i c i e n t t o i n s u r e a r e p r e s e n t a t i v e sample, a l l o w f o r r e p l i c a t e a n a l y s i s , i f r e q u i r e d , and m i n i m i z e waste d i s p o s a l .

8.2

Sample p r e s e r v a t i o n and h o l d i n g t i m e s f o r t h e anions t h a t can be determined by t h i s method a r e as f o l l o w s : Anal v t e

Preservation

H o l d i n q Time

Bromate

None r e q u i r e d

28 days

396

Methods for the Determination

Bromide Chlorate Chloride Chlorite F1 uor i de Ni trate-N Combined (Nitrate/Nitrite) Ni tri te-N O-Phosphate-P Sulfate

None required None required None required Cool to 4°C None required Cool to 4°C conc. H,SO, to a pH < 2 Cool to 4°C Cool to 4°C Cool to 4°C

28 days 28 days

28 days immed i ate1 y 28 days 48 hours 28 days 48 hours 48 hours 28 days

NOTE: If the determined value for the combined nitrate/nitrite exceeds 0.5 mg/L as N', a resample must be analyzed for the individual concentrations o f nitrate and nitrite. 8.3

The method of preservation and the holding time for samples analyzed by this method are determined by the anions of interest. In a given sample, the anion that requires the most preservation treatment and the shortest holding time will determine the preservation treatment. It is recommended that all samples be cooled to 4°C and held for no longer than 28 days for Method A and analyzed immediately in Method B. NOTE:

9.0

If the sample cannot be analyzed for chlorite within < 10 minutes, the sample may be preserved by adding 1 mL of the ethylenediamine (EDA) preservation solution (7.6) to 1 L of sample. This will preserve the concentration of the chlorite for up to 14 days. This addition of EDA has no effect on bromate or chlorate, so they can also be determined in a sample preserved with EDA. Residual chlorine dioxide should be removed from the sample (per 4.8) prior to the addition of EDA.

DUALITY CONTROL 9.1

Each laboratory using this method is required to operate a formal quality control (QC) program. The minimum requirements o f t h i s program consist of an initial demonstration of laboratory capability, and the periodic analysis of laboratory reagent blanks, fortified blanks and other laboratory solutions as a continuing check on performance. The laboratory is required to maintain performance records that define the quality of the data that are generated.

9.2

INITIAL DEMONSTRATION OF PERFORMANCE 9.2.1

The initial demonstration o f performance is used to characterize instrument performance (determination of LCRs and analysis of QCS) and laboratory performance

Inorganic Substances

397

(determination of MDLs) prior to performing analyses by this method. 9.2.2

Linear Calibration Range (LCR) -- The LCR must be determined initially and verified every 6 months or whenever a significant change in instrument response is observed or expected. The initial demonstration of linearity must use sufficient standards to insure that the resulting curve is linear. The verification of linearity must use a minimum of a blank and three standards. If any verification data exceeds the initial values by f lo%, linearity must be reestablished. If any portion of the range is shown to be nonlinear, sufficient standards must be used to clearly define the nonlinear portion.

9.2.3

Quality Control Sample (QCS) -- When beginning the use of this method, on a quarterly basis or as required to meet data-quality needs, verify the calibration standards and acceptable instrument performance with the preparation and analyses of a QCS. If the determined concentrations are not within f 10% of the stated values, performance of the determinative step of the method is unacceptable. The source of the problem must be identified and corrected before either proceeding with the initial determination of MDLs or continuing with on-going analyses.

9.2.4

Method Detection Limit (MDL) -- MDLs must be established for all analytes, using reagent water (blank) fortified at a concentration of two to three times the estimated instrument detection 1 imit.'6' To determine MDL values, take seven replicate aliquots of the fortified reagent water and process through the entire analytical method. Perform all calculations defined in the method and report the concentration values in the appropriate units. Calculate the MDL as follows:

MDL where, t

=

=

(t) x (S)

Student's t value for a 99% confidence level and a standard deviation estimate with n-1 degrees of freedom [t = 3.14 for seven rep1 icates] .

S = standard deviation of the replicate analyses.

MDLs should be determined every 6 months, when a new operator begins work or whenever there is a significant change in the background or instrument response. 9.3 ASSESSING LABORATGRY PERFORMANCE

398

Methods for the Determination

9.3.1

Laboratory Reagent B l a n k ( L R B ) - - The l a b o r a t o r y must analyze a t l e a s t one L R B with each batch of samples. Data produced a r e used t o a s s e s s contamination from the l a b o r a t o r y environment. Values t h a t exceed t h e MDL i n d i c a t e l a b o r a t o r y o r reagent contamination should be suspected and correctiv-e a c t i o n s must be taken before continuing t h e analysis.

9.3.2

Laboratory F o r t i f i e d Blank ( L F B ) -- The l a b o r a t o r y must analyze a t l e a s t one LFB with each batch of samples. C a l c u l a t e accuracy a s p e r c e n t recovery ( S e c t . 9 . 4 . 2 ) . I f t h e recovery of any a n a l y t e f a l l s o u t s i d e t h e r e q u i r e d c o n t r o l l i m i t s of 90-110%, t h a t a n a l y t e i s judged o u t of c o n t r o l , and t h e source o f t h e problem should be i d e n t i f i e d and resolved before c o n t i n u i n g a n a l y s e s .

9.3.3

The l a b o r a t o r y must use LFB a n a l y s e s d a t a t o a s s e s s 1 a b o r a t o r y performance a g a i n s t t h e r e q u i r e d c o n t r o l 1 imi t s of 90-110%. When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e ( u s u a l l y a minimum of 20-30 a n a l y s e s ) , o p t i o n a l c o n t r o l l i m i t s can be developed from the p e r c e n t mean recovery (x) and t h e s t a n d a r d d e v i a t i o n (S) of t h e mean recovery. These d a t a can be used t o e s t a b l i s h t h e upper and lower c o n t r o l l i m i t s a s follows: UPPER CONTROL LIMIT LOWER CONTROL LIMIT

= =

x t 3s x - 3s

The o p t i o n a l c o n t r o l l i m i t s must be equal t o o r b e t t e r than t h e r e q u i r e d c o n t r o l l i m i t s of 90-110%. A f t e r each f i v e t o t e n new recovery measurements, new c o n t r o l l i m i t s can be c a l c u l a t e d using only t h e most r e c e n t 20-30 d a t a p o i n t s . Also, t h e standard d e v i a t i o n (S) d a t a should be used t o e s t a b l i s h an on-going p r e c i s i o n statement f o r the l e v e l o f c o n c e n t r a t i o n s included i n t h e LFB. These d a t a must be kept on f i l e and be a v a i l a b l e f o r review. 9.3.4

Instrument Performance Check S o l u t i o n (IPC) -- For a l l d e t e r m i n a t i o n s the l a b o r a t o r y must analyze the IPC ( a midrange check s t a n d a r d ) and a c a l i b r a t i o n blank immediately following d a i l y c a l i b r a t i o n , a f t e r every t e n t h sample ( o r more f r e q u e n t l y , i f r e q u i r e d ) and a t t h e end of the sample run. Analysis of the IPC s o l u t i o n and c a l i b r a t i o n blank immediately following c a l i b r a t i o n must v e r i f y t h a t t h e instrument i s within f 10% of c a l i b r a t i o n . Subsequent a n a l y s e s o f t h e I P C s o l u t i o n must v e r i f y the c a l i b r a t i o n i s s t i l l w i t h i n f 10%. I f t h e c a l i b r a t i o n cannot be v e r i f i e d w i t h i n t h e s p e c i f i e d l i m i t s , reanalyze the IPC s o l u t i o n . I f t h e second a n a l y s i s of t h e IPC s o l u t i o n confirms c a l i b r a t i o n t o be o u t s i d e t h e l i m i t s , sample a n a l y s i s must be d i s c o n t i n u e d , t h e cause determined and/or i n t h e c a s e of d r i f t , t h e instrument r e c a l i b r a t e d . All samples following

Inorganic Substances

399

t h e l a s t a c c e p t a b l e I P C s o l u t i o n must be reanalyzed. The a n a l y s i s d a t a of t h e c a l i b r a t i o n blank and IPC s o l u t i o n must be kept on f i l e with t h e sample a n a l y s e s d a t a . 9.4

ASSESSING ANALYTE RECOVERY AND DATA Q U A L I T Y 9.4.1

Laboratory F o r t i f i e d Sample Matri'x (LFM) -- The l a b o r a t o r y must add a known amount of a n a l y t e t o a minimum of 10% of t h e r o u t i n e samples. I n each c a s e t h e LFM a l i q u o t must be a d u p l i c a t e of t h e a l i q u o t used f o r sample a n a l y s i s . The a n a l y t e c o n c e n t r a t i o n must be high enough t o be d e t e c t e d above t h e o r i g i n a l sample and should not be l e s s than f o u r times the MDL. The added a n a l y t e c o n c e n t r a t i o n should be the same a s t h a t used i n t h e l a b o r a t o r y f o r t i f i e d blank. 9.4.1.1

9.4.2

I f t h e c o n c e n t r a t i o n of f o r t i f i c a t i o n i s l e s s than 25% of t h e background c o n c e n t r a t i o n of t h e matrix the matrix recovery should n o t be c a l c u l a t e d .

C a l c u l a t e the percent recovery f o r each a n a l y t e , c o r r e c t e d f o r c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare these v a l u e s t o t h e d e s i g n a t e d LFM recovery range 90-110%. Percent recovery may be c a l c u l a t e d using t h e following e q u a t i o n :

R =

c, - c

x 100

S

where,

R

p e r c e n t recovery. f o r t i f i e d sample c o n c e n t r a t i o n . C = sample background c o n c e n t r a t i o n . s = c o n c e n t r a t i o n e q u i v a l e n t of a n a l y t e added t o sample.

C,

= =

9.4.3

Until s u f f i c i e n t d a t a becomes a v a i l a b l e ( u s u a l l y a minimum of 20 t o 30 a n a l y s i s ) , a s s e s s l a b o r a t o r y performance a g a i n s t recovery l i m i t s f o r method A of 80 t o 120% and 75 t o 125% f o r method B. When s u f f i c i e n t i n t e r n a l performance d a t a becomes avai 1a b l e develop control 1 imi t s from p e r c e n t mean recovery and t h e standard d e v i a t i o n of the mean recovery.

9.4.4

I f the recovery of any a n a l y t e f a l l s o u t s i d e the designated LFM recovery range and t h e l a b o r a t o r y performance f o r t h a t a n a l y t e i s shown t o be i n c o n t r o l ( S e c t . 9 . 3 ) , t h e recovery problem encountered with t h e LFM i s judged t o be e i t h e r m a t r i x o r s o l u t i o n r e l a t e d , not system r e l a t e d .

9.4.5

Where r e f e r e n c e m a t e r i a l s a r e a v a i l a b l e , they should be analyzed t o provide a d d i t i o n a l performance d a t a . The

400

Methods for the Determination

a n a l y s i s of r e f e r e n c e samples i s a v a l u a b l e t o o l f o r d e m o n s t r a t i n g t h e a b i l i t y t o perform the method a c c e p t a b l y . 9 .4.6

I n r e c o g n i t i o n o f t h e r a p i d advances o c c u r r i n g i n chromatography, t h e a n a l y s t i s p e r m i t t e d c e r t a i n o p t i o n s , such a s t h e use o f d i f f e r e n t columns and/or e l u e n t s , t o improve t h e s e p a r a t i o n s o r lower t h e c o s t of measurements. Each time such m o d i f i c a t i o n s t o t h e method a r e made, t h e a n a l y s t i s r e q u i r e d t o r e p e a t t h e procedure i n S e c t . 9 . 2 .

9.4.7

I t i s recommended t h a t t h e l a b o r a t o r y adopt a d d i t i o n a l q u a l i t y a s s u r a n c e p r a c t i c e s f o r use with t h i s method. The s p e c i f i c p r a c t i c e s t h a t a r e most p r o d u c t i v e depend upon t h e needs o f t h e l a b o r a t o r y and t h e n a t u r e o f t h e samples. F i e l d d u p l i c a t e s may be analyzed t o monitor t h e p r e c i s i o n of t h e sampling t e c h n i q u e . When doubt e x i s t s over t h e i d e n t i f i c a t i o n of a peak i n t h e chromatogram, c o n f i r m a t o r y t e c h n i q u e s such a s sample d i l u t i o n and f o r t i f i c a t i o n , must be used. Whenever p o s s i b l e , t h e l a b o r a t o r y should perform a n a l y s i s of q u a l i t y c o n t r o l check samples and p a r t i c i p a t e i n r e l e v a n t performance e v a l u a t i o n sample s t u d i e s .

9.4.8

A t l e a s t q u a r t e r l y , r e p l i c a t e s of LFBs should be analyzed t o d e t e r m i n e t h e p r e c i s i o n of t h e l a b o r a t o r y measurements. Add t h e s e r e s u l t s t o t h e on-going c o n t r o l c h a r t s t o document d a t a qua1 i t y .

9.4.9

When using P a r t B, t h e a n a l y s t should be aware o f t h e p u r i t y o f t h e r e a g e n t s used t o p r e p a r e s t a n d a r d s . Allowances must be made when t h e s o l i d m a t e r i a l s a r e l e s s than 99% pure.

10 0 Calibration and Standardization 10.1 E s t a b l i s h ion chromatographic o p e r a t i n g parameters e q u i v a l e n t t o t h o s e i n d i c a t e d i n T a b l e s 1 A o r 1B. 10.2 For each a n a l y t e o f interest, p r e p a r e c a l i b r a t i o n s t a n d a r d s a t a minimum o f t h r e e c o n c e n t r a t i o n l e v e l s and a b l a n k by adding a c c u r a t e l y measured volumes o f one o r more s t o c k s t a n d a r d s ( 7 . 5 ) t o a v o l u m e t r i c f l a s k and d i l u t i n g t o volume with r e a g e n t w a t e r . I f a sample a n a l y t e c o n c e n t r a t i o n exceeds t h e c a l i b r a t i o n range t h e sample may be d i l u t e d t o f a l l w i t h i n t h e r a n g e . I f t h i s i s n o t p o s s i b l e t h e n t h r e e new c a l i b r a t i o n c o n c e n t r a t i o n s must be chosen, two o f which must b r a c k e t t h e c o n c e n t r a t i o n of t h e sample a n a l y t e o f i n t e r e s t . Each a t t e n u a t i o n range of t h e instrument used t o a n a l y z e a sample must be c a l i b r a t e d i n d i v i d u a l l y . 10.3 Using i n j e c t i o n s of 0 . 1 t o 1 . 0 m L (determined by i n j e c t i o n volume) o f each c a l i b r a t i o n s t a n d a r d , t a b u l a t e peak h e i g h t r e s p o n s e s a g a i n s t t h e c o n c e n t r a t i o n . The r e s u l t s a r e used p r e p a r e a c a l i b r a t i o n curve f o r each a n a l y t e . During t h i s c e d u r e , r e t e n t i o n t i m e s must be r e c o r d e d .

loop o r area to pro-

Inorganic Substances

401

10.4 The calibration curve must be verified on each working day, or

whenever the anion eluent is changed, and after every 20 samples. If the response or retention time for any analyte varies from the expected values by more than f lo%, the test must be repeated, using fresh calibration standards. If the results are still more than f lo%, a new calibration curve must be prepared for that analyte. 10.5 Nonlinear response can result when the separator column capacity is

exceeded (overloading). The response of the detector to the sample when diluted 1:1, and when not diluted, should be compared. I f the calculated responses are the same, samples o f this total anionic concentration need not be diluted. 0 Procedure 11.1 Tables 1A and 1B summarize the recommended operating conditions for

the ion chromatograph. Included in these tables are estimated retention times that can be achieved by this method. Other columns, chromatographic conditions, or detectors may be used if the requirements of Sect. 9.2 are met. 11.2 Check system calibration daily and, if required, recalibrate as described in Sect. 10.

Flush injection loop thoroughly, using each new sample. Use the same size loop for standards and samples. Record the resulting peak size in area or peak height units. An automated constant volume injection system may also be used.

11.3 Load and inject a fixed amount of well mixed sample.

11.4 The width of the retention time window used to make identifications

should be based upon measurements of actual retention time variations of standards over the course o f a day. Three times the standard deviation of a retention time can be used t o calculate a suggested window size for each analyte. However, the experience of the analyst should weigh heavily in the interpretation o f chromatograms. 11.5 If the response for the peak exceeds the working range of the

system, dilute the sample with an appropriate amount of reagent water and reanalyze. 11.6 If the resulting chromatogram fails to produce adequate resolution, or if identification of specific anions is questionable, fortify the

sample with an appropriate amount of standard and reanalyze. NOTE:

Retention time is inversely proportional to concentration. Nitrate and sulfate exhibit the greatest amount of change, although all anions are affected to some degree. In some cases this peak migration may produce poor resolution or identification.

402

Methods for the Determination 11.7 The f o l l o w i n g e x t r a c t i o n s h o u l d be used f o r s o l i d m a t e r i a l s . Add an amount o f r e a g e n t w a t e r equal t o t e n t i m e s t h e w e i g h t o f d r y s o l i d m a t e r i a l t a k e n as a sample. T h i s s l u r r y i s mixed f o r t e n m i n u t e s using a magnetic s t i r r i n g device. F i l t e r t h e r e s u l t i n g s l u r r y b e f o r e i n j e c t i n g u s i n g a 0 . 4 5 p membrane t y p e f i l t e r . T h i s can be t h e t y p e t h a t a t t a c h e s d i r e c t l y t o t h e end o f t h e s y r i n g e . Care s h o u l d be t a k e n t o show t h a t good r e c o v e r y and i d e n t i f i c a t i o n o f peaks i s o b t a i n e d w i t h t h e u s e r ' s m a t r i x t h r o u g h t h e use of f o r t if ied samples

.

11.8 I t has been r e p o r t e d t h a t l o w e r d e t e c t i o n l i m i t s f o r bromate (=7 p g / L ) can be o b t a i n e d u s i n g a b o r a t e based e l u e n t ' I . The use o f t h i s e l u e n t o r o t h e r e l u e n t s t h a t improve method performance may be c o n s i d e r e d as a m i n o r m o d i f i c a t i o n o f t h e method and as such s t i l l are acceptable. 11.9 Should more complete r e s o l u t i o n be needed between peaks t h e e l u e n t ( 7 . 3 ) can be d i l u t e d . T h i s w i l l spread o u t t h e r u n b u t w i l l a l s o cause t h e l a t e r e l u t i n g anions t o be r e t a i n e d l o n g e r . The a n a l y s t must d e t e r m i n e t o what e x t e n t t h e e l u e n t i s d i l u t e d . T h i s d i l u t i o n s h o u l d n o t be c o n s i d e r e d a d e v i a t i o n f r o m t h e method.

12.0 DATA ANALYSIS AND CALCULATIONS 12.1 Prepare a c a l i b r a t i o n c u r v e f o r each a n a l y t e by p l o t t ing in s t r u m e n t response a g a i n s t s t a n d a r d c o n c e n t r a t i o n . Compu e sample c o n c e n t r a t i o n b y comparing sample response w i t h t h e s t a n d a r d c u r v e . Mu1 t i p l y answer by a p p r o p r i a t e d i l u t i o n f a c t o r . 12.2 Report o n l y t h o s e v a l u e s t h a t f a l l between t h e owest and t h e h i g h e s t c a l i b r a t i o n standards. Samples exceedi g t h e h i g h e s t s t a n d a r d s h o u l d be d i l u t e d and r e a n a l y z e d .

12.3 Report r e s u l t s i n mg/L. 12.4 Report

NO:, NO HP~,'

as N as N as P

13.0 METHODS PERFORMANCE 13.1 T a b l e s 1A and 2A g i v e t h e s i n g l e l a b o r a t o r y (EMSL-Cincinnati) MDL f o r each a n i o n i n c l u d e d i n t h e method under t h e c o n d i t i o n s l i s t e d . 13.2 Tables 2 A and 2B g i v e t h e s i n g l e l a b o r a t o r y (EMSL-Cincinnati) s t a n d a r d d e v i a t i o n f o r each a n i o n i n c l u d e d i n t h e method i n a v a r i e t y o f waters f o r t h e l i s t e d conditions. 13.3 M u l t i p l e l a b o r a t o r y accuracy and b i a s d a t a ( S ) and e s t i m a t e d s i n g l e o p e r a t o r v a l u e s ( S o ) f o r r e a g e n t , d r i n k i n g and waste w a t e r u s i n g

Inorganic Substances

method A are given for each anion in Tables 3 through 9 . 19 laboratories were used for this data.

403

Data from

13.4 Some of the bias statements, for example chloride and sulfate, may

be misleading due to spiking small increments of the anion into large naturally occurring concentrations o f the same anion. 14.0 POLLUTION PREVENTION 14.1 Pollution prevention encompasses any technique that reduces or eliminates the quantity or toxicity of waste at the point o f

generation. Numerous opportunities for pollution prevention exist in laboratory operation. The EPA has established a preferred hierarchy of environmental management techniques that places pollution prevention as the management option of first choice. Whenever feasible, laboratory personnel should use pollution prevention techniques to address their waste generation. When wastes cannot be feasibly reduced at the source, the Agency recommends recycling as the next best option. 14.2 Quantity of the chemicals purchased should be based on expected

usage during its shelf life and disposal cost of unused material. Actual reagent preparation vol umes should reflect anticipated usage and reagent stability. 14.3 For information about pollution prevention that may be applicable to

laboratories and research institutions, consult "Less is Better: Laboratory Chemical Management for Waste Reduction," available from the American Chemical Society's Department of Government Regulations and Science Policy, 1155 16th Street N.W., Washington D.C.

20036, (202) 872-4477.

15.0 WASTE MANAGEMENT 15.1 The Environmental Protection Agency requires that laboratory waste

management practices be conducted consistent with all applicable rules and regulations. Excess reagents, samples and method process wastes should be characterized and disposed of in an acceptable manner. The Agency urges laboratories to protect the air, water, and land by minimizing and controlling all releases from hoods and bench operations, complying with the letter and spirit of any waste discharge permit and regulations, and by complying with all sol id and hazardous waste regulations, particularly the hazardous waste identification rules and land disposal restrictions. For further information on waste management consult the "Waste Management Manual for Laboratory Personnel, available from the American Chemical Society at the address listed in Sect. 'I

14.3.

404

Methods for the Determination

16.0 REFERENCES 1.

"Determination of Inorganic Disinfection By-products by Ion Chromatography", J . Pfaff, C. Brockhoff. J . Am. Water Works ASSOC., Vol 82, No. 4, pg 192.

2.

Standard Methods for the Examination of Water and Wastewater, Method 41106, "Anions by Ion Chromatography", 18th Edition o f Standard Methods ( 1 9 9 2 ) .

3.

Dionex, System 4000 Operation and Maintenance Manual, Dionex Corp., Sunnyvale, California 94086, 1988.

4.

Method Detection Limit (MDL) as described in "Trace Analyses for Wastewater," J . Glaser, D. Foerst, G. McKee, S. Quave, W . Budde, Environmental Science and Technology, Vol. 15, Number 12, page 1426, December, 1981.

5.

American Society for Testing and Materials. Test Method for Anions in Water by Chemically-Suppressed Ion Chromatography D4327-91. Annual Book of Standards, Vol 11.01 (1993).

6.

Code of Federal Regulations 40, Ch. 1, Pt. 136, Appendix B.

7.

Hautman, D.P. &. Bolyard, M. Analysis of Oxyhalide Disinfection Byproducts and other Anions of Interest in Drinking Water by Ion Chromatography. Jour. o f Chromatog., 602, (1992), 65-74.

Inorganic Substances 17.0 TABLES, DIAGRAMS, FLOWCHARTS AND VALIDATION DATA

TABLE 1A.

CHROMATOGRAPHIC CONDITIONS AND DETECTION L I M I T S I N REAGENT WATER (PART A)

ANALYTE

F1 u o r i de Chloride N i tri te-N Bromide N itrate-N o-Phosphate-P Sulfate

PEAK #

*

1 2 3 4 5 6 7

RETENTION TIME(M1N)

1.2

1.7 2.0 2.9 3.2 5.4 6.9

MDL mg/L

0.01 0.02 0.004 0.01 0.002 0.003 0.02

Standard C o n d i t i o n s : Columns: as s p e c i f i e d i n 6.2.2.1 D e t e c t o r : as s p e c i f i e d i n 6.2.4 E l u e n t : as s p e c i f i e d i n 7 . 3

Pump Rate: 2.0 mL/min Sample Loop: 50 pL

MDL c a l c u l a t e d f r o m d a t a system u s i n g a y - a x i s s e l e c t i o n o f 1000 ns and w i t h a s t r i p c h a r t r e c o r d e r w i t h an a t t e n u a t o r s e t t i n g o f 1 uMHO f u l l s c a l e .

*

See F i g u r e 1

405

406

Methods for the Determination TABLE 16.

CHROAATOGRAPHIC CONDITIONS AND DETECTION LIMITS I N REAGENT WATER (PART B )

* ANA LYTE

PEAK #

Chlorite Bromate Chlorate

1 2 4

RETENT ION TIME(M1N)

2.8 3.2 7.1

MDL mg/L

0.01 0.02 0.003

Standard Conditions: Column: as specified in 6.2.2.2 Detector: as specified in 6.2.4 Eluent: as specified in 7.3

*

See Figure 2

Pump Rate: 1.0 rnllrnin. Sample Loop: 50 pL Attentuation - 1 y-axis - 500 ns

Inorganic Substances TABLE 2A.

SINGLE-OPERATOR ACCURACY AND B I A S OF STANDARD ANIONS (METHOD A)

SAMPLE ANALYTE

TYPE

Bromide

RW DW

sw ww

GW SD

Chl or ide

RW DW

sw ww

GW

SD F1 uoride

RW DW

sw

ww

GW SD

Nitrate- N

RW DW

sw ww

GW

SD

Nitrite- N

RW DW

sw

ww

GW SD

o-Phosphate- P

RW DW

sw ww GW

KNOWN CONC. (mq/L)

NUMBER OF

MEAN RECOVERY

REPLICATES

%

STANDARD DEVIATION (mq/L1

0.08

2 .o

7 7 7 7

99 105 95 105 92 82

20.0 20.0 10.0 20.0 20.0 20.0

7 7 7 7 7 7

96 108 86 101 114 90

0.35 1.19 0.33 5.2 1.3 0.32

2.0 1.o 1.o 1.o 0.4 5.0

7 7 7 7 7 7

91 92 73 87 95 101

0.05 0.06 0.05 0.07 0.07 0.35

10.0 10.0 10.0 10.0 10.0 10.0

7 7 7 7 7 7

103 104 93 101 97 82

0.21 0.27 0.17 0.82 0.47 0.28

10.0 10.0 5.0 5.0 10.0 2.0

7 7 7 7 7 7

97 121 92 91 96 98

0.14 0.25 0.14 0.50 0.35 0.08

10.0 10.0 10.0 10.0 10.0

7 7 7 7 7

99 99 98 106 95

0.17 0.26 0.22 0.85 0.33

5.0 5.0 5.0 5.0 5.0

7 7

0.10

0.13 0.34 0.34 0.06

407

408

Methods for the Determination TABLE 2A (CONT'D)

Sulfate

RW DW

20.0 50.0

7 7

99

0.40

105

ww

40.0 40.0 40.0

7

95

7 7

102 112

3.35 1.7 6.4 3.2

sw

GW

RW DW

= = SW =

Reagent Water D r i n k i n g Water S u r f a c e Water

WW

= Mixed Domestic and I n d u s t r i a l Wastewater GW = Groundwater SD = USEPA QC S o l i d ( s h a l e )

Inorganic Substances T A B L E 28. SINGLE-OPERATOR

ACCURACY AND B I A S OF BY-PRODUCT (PART B ) NUMBER

MEAN STANDARD RECOVERY D E V I A T I O N REPLICATES % (mg/L)

ANALYTE

Bromate

RW

5.0 1 .o 0.1 0.05

103 98 155 122

0.07 0.04 0.005 0.01

DW

5.0 1 .o 0.1 0.05

95 85 98 98

0.04

5.0 1 .o 0.1 0.05

101 97 100 119

0.06

DW

5.0 1.o 0.1 0.05

101 115 121 110

0.04 0.01 0.005 0.01

RW

5.0 1.0 0.1 0.05

100 98 86 94

0.04 0.01 0.01 0.01

DW

5.0 1 .o 0.1 0.05

96 100 76 96

0.03 0.02 0.00 0.01

Chlorate

Chlorite

RW DW

= =

RW

Reagent Water Drinking Water

SPIKE (mg/L)

OF

SAMPLE TYPE

0.02 0.005

0.005 0.01 0.01 0.05

409

410

Methods for the Determination TABLE 3.

WATER Reagent

Drinking

Waste

AM'T ADDED mg/L

MULTIPLE LABORATORY (11-19) DETERMINATION OF BIAS FOR FLUORIDE

AM'T FOUND mg/L

S,

so

BIAS %

0.26 0.34 2.12 2.55 6.79 8.49

0.25 0.29 2.12 2.48 6.76 8.46

0.08 0.11 0.07 0.14 0.20 0.30

0.11

-3.8 -14.7

0.12

0.0 -2.7 -0.4 -0.4

0.26 0.34 2.12 2.55 6.79 8.49

0.24 0.34 2-09 2.55 6.84 8.37

0.08 0.11 0.18 0.16 0.54 0.75

0.05

0.26 0.34 2.12 2.55 6.79 8.49

0.25 0.32 2.13 2.48 6.65 8.27

0.15 0.08 0.22 0.16 0.41 0.36

0.06

0.19

0.06 0.25

0.15 0.20

-7.7 0.0 -1.4 0.0 t0.7 -1.4 -3.8 -5.9 t0.5 -2.7 -2.1 -2.6

Inorganic Substances TABLE 4 .

WATER Reagent

Drinking

Waste

M U L T I P L E LABORATORY (n=19) D E T E R M I N A T I O N O F B I A S FOR CHLORIDE

A M ' T ADDED mg/ L

A M ' T FOUND mg/ L

S,

so

0.29

0.78 1.04 6.50 7.80 20.8 26.0

0.79 1.12 6.31 7.76 20.7 25.9

0.17 0.46 0.27 0.39 0.54 0.58

0.78 1.04 6.50 7.80 20.8 26.0

0.54 0.51 5.24 6.02 20.0 24.0

0.35 0.38 1.35 1.90 2.26 2.65

0.20

0.78 1.04 6.50 7.80 20.8 26.0

0.43 0.65 4.59 5.45 18.3 23.0

0.32 0.48 1.82 2.02 2.41 2.50

0.39

0.14 0.62

1.48 1.14

0.83 1.57

BIAS %

t1.3 t7.7 -2.9 -0.5 -0.5 -0.4 -30.8 -51 .O -19.4 -22.8 -3.8 -7.7 -44.9 -37.5 -29.4 -30.1 -11.8 -11.5

411

412

Methods for the Determination TABLE 5 . MULTIPLE LABORATORY (n=19) DETERMINATION OF B I A S FOR N I T R I T E

WATER Reagent

Drinking

Waste

AM'T ADDED mg/L

AM'T FOUND mg/L

0.36 0.48 3.00 3.60 9.60 12.0

0.48 3.18 3.83 9.84 12.1

0.36 0.48 3.00 3.60 9.60 12.0 0.36 0.48 3.00 3.60 9.60 12.0

0.37

S, 0.04 0.06 0.12

-

so

NITROGEN

BIAS %

0.04

t2.8

0.06

4.0 t6.4 t2.5 t0.6

0.0

0.12

0.36 0.27

0.26

0.30 0.40 3.02 3.62 9.59 11.6

0.13 0.14 0.23 0.22 0.44 0.59

0.03

0.34 0.46 3.18 3.76 9.74 12.0

0.06 0.07 0.13 0.18 0.49 0.56

0.12

-16.7 -16.7 t0.7 t0.6

0.28

-0.1 -3.1

0.04

-5.6 -4.2 t6.0 t4.4 t1.5 t0.3

0.10 0.26

Inorganic Substances TABLE 6 . M U L T I P L E LABORATORY (n=19) D E T E R M I N A T I O N OF B I A S FOR BROMIDE

WATER Reagent

Drinking

Waste

A M ' T ADDED mg/L

A M ' T FOUND mg/L

S,

so

0.63 0.84 5.24 6.29 16.8 21 .o

0.69 0.85 5.21 6.17 17.1 21.3

0.11 0.12 0.22 0.35 0.70 0.93

0.05

0.63 0.84 5.24 6.29 16.8 21.0

0.63 0.81 5.11 6.18 17.0 20.9

0.13 0.13 0.23 0.30 0.55 0.65

0.04

0.63 0.84 5.24 6.29 16.8 21.0

0.63 0.85 5.23 6.27 16.6 21.1

0.15 0.15 0.36 0.46 0.69 0.63

0.21 0.36

BIAS

x

t9.5 t1.2 -0.6 -1.9 t1.6 t1.5

0.13 0.57 0.09 0.11 0.43

0.0 -3.6 -2.5 -1.7 t0.9 -0.4

0.0 t1.2 -0.2 -0.3 -1.0 t0.3

413

414

Methods for the Determination TABLE 7 .

WATER

Reagent

Drinking

Waste

MULTIPLE LABORATORY (n=19) DETERMINATION OF BIAS FOR NITRATE

AM'T ADDED mg/L

AM'T FOUND mg/L

S,

-

NITROGEN

so

0.42 0.56 3.51 4.21 11.2 14.0

0.42 0.56 3.34 4.05 11.1 14.4

0.04 0.06 0.15 0.28 0.47 0.61

0.02

0.42 0.56 3.51 4.21 11.2 14.0

0.46 0.58 3.45 4.21 11.5 14.2

0.08 0.09 0.27 0.38 0.50 0.70

0.03

0.42 0.56 3.51 4.21 11.2 14.0

0.36 0.40 3.19 3.84 10.9 14.1

0.07 0.16 0.31 0.28 0.35 0.74

0.06

0.08

0.34

0.10 0.48

0.07 0.51

BIAS %

0.0 0.0 -4.8 -3.8 -1.1 t2.6

t9.5 t3.6 -1.7 0.0 t2.3 t1.6 -14.6 -28.6 -9.1 -8.8 -3.0 t0.4

Inorganic Substances TABLE 8.

WATER

Reagent

Drinking

Waste

MULTIPLE LABORATORY (n=19) DETERMINATION OF B I A S FOR ORTHO-PHOSPHATE

AM'T ADDED mg/L

AM'T FOUND mg/L

S,

so

0.06

0.69 0.92 5.77 6.92 18.4 23.1

0.69 0.98 5.72 6.78 18.8 23.2

0.06 0.15 0.36 0.42 1.04 0.35

0.69 0.92 5.77 6.92 18.4 23.1

0.70 0.96 5.43 6.29 18.0 22.6

0.17 0.20 0.52 0.72 0.68 1.07

0.17

0.68 0.92 5.77 6.92 18.4 23.1

0.64 0.82 5.18 6.24 17.6 22.4

0.26 0.28 0.66 0.74 2.08 0.87

0.09

0.18 0.63

0.40 0.59

0.34 1.27

BIAS %

0.0 t6.5 -0.9 -2.0 t2.1 t0.4

t1.4 t4.3 -5.9 -9.1 -2.2 -2.0 -7.2 -10.9 -10.2 -9.8 -4.1 -3.0

415

416

Methods for the Determination TABLE 9 .

WATER

Reagent

Drinking

Waste

MULTIPLE LABORATORY (n=19) DETERMINATION OF BIAS FOR SULFATE

AM'T ADDED mg/L

AM'T FOUND mg/L

S,

so

BIAS %

2.85 3.80 23.8 28.5 76.0 95.0

2.83 3.83 24.0 28.5 76.8 95.7

0.32 0.92 1.67 1.56 3.42 3.59

0.52

2.85 3.80 23.8 28.5 76.0 95.0

1.12 2.26 21.8 25.9 74.5 92.3

0.37 0.97 1.26 2.48 4.63 5.19

0.41

2.85 3.80 23.8 28.5 76.0 95.0

1.89 2.10 20.3 24.5 71.4 90.3

0.37 1.25 3.19 3.24 5.65 6.80

0.24

0.68 2.33

0.51 2.70

0.58 3.39

-0.7 t0.8 t0.8 -0.1 tl.l +0.7 -60.7 -40.3 -8.4 -9.1 -2.0 -2.8 -33.7 -44.7 -14.7 -14.0 -6.1 -5.0

Inorganic Substances

417

Method A Peak 1 2 3 4 5 6 7

2

Ret. Tlme

Ion

1.17 1.73

Fc I-

2.02 2.95 3.20 5.38 6.92

NO,-

so,'-

mglL 2 20 2 2 10 2 60

3.23 3.63 7.08

BrO; ClCIO;

0.1 0.1 0.1

Br NO,HP0,'-

1

Minutes Qure 1. Chromatogram showing separatlon uslng the ASIA column

Method B I

' 2

2 3 4

4

418

Methods for the Determination METHOD 335.4 DETERMINATION OF TOTAL CYANIDE BY SEMI-AUTOMATED COLORIMETRY

E d i t e d by James W . O'Dell I n o r g a n i c Chemistry Branch Chemistry Research D i v i s i o n

R e v i s i o n 1.0 August 1993

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

Inorganic Substances

419

METHOD 3 3 5 . 4 DETERMINATION OF TOTAL CYANIDE BY SEMI-AUTOMATED COLORIMETRY

1.0

SCOPE AND APPLICATION

1.1 T h i s method c o v e r s t h e d e t e r m i n a t i o n o f c y a n i d e i n d r i n k i n g , ground, s u r f a c e , and s a l i n e w a t e r s , domestic and i n d u s t r i a l wastes. 1.2 2.0

3.0

The a p p l i c a b l e range i s 5 t o 500 ,ug/L.

SUMMARY OF METHOD

2.1

The c y a n i d e as h y d r o c y a n i c a c i d (HCN) i s r e l e a s e d f r o m c y a n i d e complexes by means o f a manual r e f l u x - d i s t i l l a t i o n o p e r a t i o n and absorbed i n a scrubber c o n t a i n i n g sodium h y d r o x i d e s o l u t i o n . The c y a n i d e i o n i n t h e a b s o r b i n g s o l u t i o n i s c o n v e r t e d t o cyanogen c h l o r i d e by r e a c t i o n s w i t h chloramine-T, t h a t subsequently r e a c t s w i t h p y r i d i n e and b a r b i t u r i c a c i d t o g i v e a r e d - c o l o r e d complex.

2.2

Reduced volume v e r s i o n s o f t h i s method t h a t use t h e same r e a g e n t s and m o l a r r a t i o s a r e a c c e p t a b l e p r o v i d e d t h e y meet t h e q u a l i t y c o n t r o l and performance r e q u i r e m e n t s s t a t e d i n t h e method.

2.2

L i m i t e d performance-based method m o d i f i c a t i o n s may be a c c e p t a b l e p r o v i d e d t h e y a r e f u l l y documented and meet o r exceed r e q u i r e m e n t s expressed i n S e c t . 9.0, Q u a l i t y C o n t r o l .

DEFINITIONS

3.1

CALIBRATION BLANK (CB) -- A volume o f r e a g e n t w a t e r f o r t i f i e d w i t h t h e same m a t r i x as t h e c a l i b r a t i o n standards, b u t w i t h o u t t h e a n a l y t e s , i n t e r n a l standards, o r s u r r o g a t e a n a l y t e s .

3.2

CALIBRATION STANDARD (CAL) -- A s o l u t i o n p r e p a r e d f r o m t h e p r i m a r y d i l u t i o n s t a n d a r d s o l u t i o n o r s t o c k s t a n d a r d s o l u t i o n s and t h e i n t e r n a l standards and s u r r o g a t e a n a l y t e s . The CAL s o l u t i o n s are used t o c a l i b r a t e t h e i n s t r u m e n t response w i t h r e s p e c t t o a n a l y t e concentration.

3.3

INSTRUMENT PERFORMANCE CHECK SOLUTION ( I P C ) -- A s o l u t i o n o f one o r more method a n a l y t e s , s u r r o g a t e s , i n t e r n a l standards, o r o t h e r t e s t substances used t o e v a l u a t e t h e performance o f t h e i n s t r u m e n t system w i t h respect t o a defined set o f c r i t e r i a .

3.4

LABORATORY FORTIFIED BLANK (LFB) -- An a l i q u o t o t h e r b l a n k m a t r i c e s t o which known q u a n t i t i e s a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB l i k e a sample, and i t s purpose i s t o d e t e r m i n e

o f reagent water o r o f t h e method i s analyzed e x a c t l y whether t h e

420

Methods for the Determination

methodology is in control, and whether the laboratory is capable o f making accurate and precise measurements. - - An aliquot of an environmental sample to which known quantities of the method analytes are added in the laboratory. The LFM is analyzed exactly like a sample, and its purpose is to determine whether the sample matrix contributes bias to the analytical results. The background concentrations of the analytes in the sample matrix must be determined in a separate aliquot and the measured values in the LFM corrected for background concentrations.

3.5 LABORATORY FORTIFIED SAMPLE MATRIX (LFM)

3.6 LABORATORY REAGENT BLANK (LRB) - - An aliquot of reagent water or other blank matrices that are treated exactly as a sample including exposure to all glassware, equipment, solvents, reagents, internal standards, and surrogates that are used with other samples. The LRB is used to determine if method analytes or other interferences are present in the laboratory environment, the reagents, or the apparatus. 3.7

LINEAR CALIBRATION RANGE (LCR) -- The concentration range over which the instrument response is linear.

3 . 8 MATERIAL SAFETY DATA SHEET (MSDS) -- Written information provided by

vendors concerning a chemical's toxicity, health hazards, physical properties, fire, and reactivity data including storage, spill, and handling precautions. 3.9 METHOD DETECTION LIMIT (MDL) -- The minimum concentration of an analyte that can be identified, measured and reported with 99%

confidence that the analyte concentration is greater than zero. 3.10 QUALITY CONTROL SAMPLE (QCS) -- A solution of method analytes of known concentrations that is used to fortify an aliquot o f LRB or sample matrix. The QCS is obtained from a source external t o the

laboratory and different from the source of calibration standards. It i s used to check laboratory performance with externally prepared test materi a1 s . 3.11 STOCK STANDARD SOLUTION (SSS) -- A concentrated solution containing

one or more method analytes prepared in the laboratory using assayed reference materials or purchased from a reputable commercial source. 4.0

INTERFERENCES 4.1

Several interferences are encountered with this method. Some of the known interferences are aldehydes, nitrate-nitrite, oxidizing agents, such as chlorine, thiocyanate, thiosulfate and sulfide. Multiple interferences may require the analysis of a series of laboratory fortified sample matrices (LFM) to verify the suitability of the chosen treatment. Some interferences are eliminated or reduced by the distillation.

Inorganic Substances

421

4.2 Sulfides adversely affect the procedure by producing hydrogen sulfide during distillation. If a drop of the sample on lead acetate test paper indicates the presence of sulfide, treat 25 mL more of the stabilized sample (pH 2 12) than that required for the cyanide determination with powdered cadmium carbonate. Yellow cadmium sulfide precipitates if the sample contains sulfide. Repeat this operation until a drop o f the treated sample solution does not darken the lead acetate test paper. Filter the solution through a dry filter paper into a dry beaker, and from the filtrate, measure the sample to be used for analysis. Avoid a large excess of cadmium and a long contact time in order to minimize a loss by complexation or occlusion of cyanide on the precipitated material. 4.3

High results may be obtained for samples that contain nitrate and/or nitrite. During the distillation nitrate and nitrite will form nitrous acid that will react with some organic compounds to form oximes. These oximes will decompose under test conditions to generate HCN. The interference of nitrate and nitrite is eliminated by pretreatment with sulfamic acid.

4.4 Oxidizing agents, such as chlorine, decompose most of the cyanides. Test a drop of the sample with potassium iodide-starch paper (KIstarch paper) at time of collection; a blue color indicates the need for treatment. Add ascorbic acid, a few crystals at a time, until a drop of sample produces no color on the indicator paper; then add an additional 0.06 g of ascorbic acid for each liter of sample volume. Sodium arsenite has also been employed to remove oxidizing agents. 4.5 Other compatible procedures for the removal or suppression o f interferences may be employed provided they do not adversely effect the overall performance of the method. 4.6

5.0

Method interferences may be caused by contaminants in the reagent water, reagents, glassware, and other sample processing apparatus that bias analyte response.

SAFETY

5.1 The toxicity or carcinogenicity of each reagent used in this method has not been fully established. Each chemical should be regarded as a potential health hazard and exposure should be as low as reasonably achievable. Cautions are included for known extremely hazardous materials or procedures. 5.2

Each laboratory is responsible for maintaining a current awareness file of OSHA regulations regarding the safe handling of the chemicals specified in this method. A reference file of Material Safety Data Sheets (MSDS) should be made available to all personnel involved in the chemical analysis. The preparation of a formal safety plan is also advisable.

422

Methods for the Determination 5.3 The following chemicals have the potential to be highly toxic or hazardous, consult MSDS. 5.3.1

Hydrochloric acid (7.5)

5.3.2

Silver nitrate (7.9)

5.3.3

Potass um cyanide (7.10)

5.3.4

Sulfur c acid (7.14)

5.4 Because of the toxicity o f evolved hydrogen cyanide (HCN), distillation should be performed in a well vented hood. 6.0

EQUIPMENT AND SUPPLIES

6.1 Balance -- Analytical, capable o f accurately weighing to the nearest 0.0001 g.

6.2 Glassware -- Class A volumetric flasks and pipets as required. 6.3 Midi reflux distillation apparatus including boiling flask condenser, and absorber as shown in Figure 1.

6.4 Heating mantel or heating block as required. 6.5 Automated continuous flow analysis equipment designed to deliver and react sample and reagents in the required order and ratios.

7.0

6.5.1

Sampling device (sampler)

6.5.2

Mu1 ti channel pump

6.5.3

Reaction unit or manifold

6.5.4

Colorimetric detector

6.5.5

Data recording device

REAGENTS AND STANDARDS

7.1

Reagent water: Distilled or deionized water, free o f the analyte o f interest. ASTM type I 1 or equivalent.

7.2 Ascorbic acid: Crystal (CASRN-50-81-7) 7.3 Chloramine-T: Dissolve 2.0 g of chloramine-T (CASRN-127-65-1) in 500 mL of reagent water.

7.4 Magnesium Chloride Solution: Weigh 510 g o f MgC1,.6H 0 (CASRN-778630-3) into a 1000 mL flask, dissolve and dilute to 1 with reagent water.

Inorganic Substances

423

7.5

P y r i d i n e B a r b i t u r i c A c i d Reagent: P l a c e 15 g o f b a r b i t u r i c a c i d (CASRN-67-52-7) i n a 1 L beaker. Wash t h e s i d e s o f t h e beaker w i t h about 100 mL o f r e a g e n t w a t e r . Add 75 mL o f p y r i d i n e (CASRN-110-861) and mix. Add 15 mL o f conc. HC1 (CASRN-7647-01-0) and mix. D i l u t e t o 900 mL w i t h r e a g e n t w a t e r and m i x u n t i l a l l t h e b a r b i t u r i c a c i d has d i s s o l v e d . T r a n s f e r t h e s o l u t i o n t o a 1-L f l a s k and d i l u t e t o t h e mark.

7.6

Sodium dihydrogenphosphate b u f f e r , 1 M: D i s s o l v e 138 g o f NaH,PO,.H,O (CASRN-10049-21-5) i n 1 L o f r e a g e n t w a t e r . R e f r i g e r a t e t h i s solution.

7.7

Sodium H y d r o x i d e S o l u t i o n , 1.25 N: D i s s o l v e 50 g o f NaOH (CASRN1310-73-2) i n r e a g e n t w a t e r , and d i l u t e t o 1 L w i t h r e a g e n t w a t e r .

7.8

Sodium Hydroxide, 0.25 N: D i l u t e 200 mL o f 1.25 N Sodium h y d r o x i d e s o l u t i o n (7.7) t o 1 L w i t h r e a g e n t w a t e r .

7.9

Standard S i l v e r N i t r a t e S o l u t i o n , 0.0192 N: Prepare b y c r u s h i n g a p p r o x i m a t e l y 5 g AgNO (CASRN-7761-88-8) c r y s t a l s and d r y i n g t o c o n s t a n t w e i g h t a t 40"E. Weigh o u t 3.2647 g o f d r i e d AgNO,, d i s s o l v e i n r e a g e n t water, and d i l u t e t o 1000 mL (1 mL = 1 mg CN).

7.10 S t o c k Cyanide S o l u t i o n : D i s s o l v e 2.51 g o f KCN (CASRN-151-50-8) and 2 g KOH (CASRN-1310-58-3) i n 900 mL o f r e a g e n t w a t e r . S t a n d a r d i z e w i t h 0.0192 N AgNO ( 7 . 9 ) . D i l u t e t o a p p r o p r i a t e c o n c e n t r a t i o n so t h a t 1 mL = 1 mg Ch. 7.11 Standard Cyanide S o l u t i o n , i n t e r m e d i a t e : D i l u t e 10.0 mL o f s t o c k ( 1 mL = 1 mg CN) (7.10) t o 100.0 w i t h r e a g e n t w a t e r (1 mL = 100.0 p g CN. 7.12 Working Standard Cyanide S o l u t i o n : Prepare f r e s h d a i l y by d i l u t i n g 20.0 mL o f i n t e r m e d i a t e c y a n i d e s o l u t i o n (7.11) t o 200.0 mL w i t h r e a g e n t w a t e r and s t o r e i n a g l a s s s t o p p e r e d b o t t l e . 1 mL = 10.0 pg CN. 7.13 S u l f a m i c A c i d :

(CASRN-212-57-3).

7.14 S u l f u r i c A c i d , 18N: S l o w l y add 500 mL o f c o n c e n t r a t e d H,SO, 5329-14-6) t o 500 mL o f r e a g e n t water. 8.6

(CASRN-

SAMPLE COLLECTION, PRESERVATION AND STORAGE 8.1

Samples s h o u l d be c o l l e c t e d i n p l a s t i c o r g l a s s b o t t l e s . A l l b o t t l e s must be t h o r o u g h l y cleaned and r i n s e d w i t h r e a g e n t w a t e r . Volume c o l l e c t e d s h o u l d be s u f f i c i e n t t o i n s u r e a r e p r e s e n t a t i v e sample, a l l o w f o r r e p l i c a t e a n a l y s i s ( i f r e q u i r e d ) , and m i n i m i z e waste d i s p o s a l .

424

Methods for the Determination 8.2

I f t h e sample c o n t a i n s c h l o r i n e o r hydrogen s u l f i d e , see Sect. 4.0 f o r treatment.

8.3

Samples must be p r e s e r v e d w i t h sodium h y d r o x i d e pH 2 12 and c o o l e d t o 4°C a t t h e t i m e o f c o l l e c t i o n .

8.4 Samples s h o u l d be analyzed as soon as p o s s i b l e a f t e r c o l l e c t i o n .

If

s t o r a g e i s r e q u i r e d , p r e s e r v e d samples a r e m a i n t a i n e d a t 4°C and may be h e l d f o r up t o 14 days. 9.0

QUALITY CONTROL 9.1

Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a f o r m a l q u a l i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f t h i s program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y , t h e p e r i o d i c analysis o f l a b o r a t o r y reagent blanks, f o r t i f i e d b l a n k s , and o t h e r l a b o r a t o r y s o l u t i o n s as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n p e r formance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f t h e d a t a t h a t a r e generated.

9.2

I N I T I A L DEMONSTRATION OF PERFORMANCE 9.2.1

The i n i t i a l d e m o n s t r a t i o n o f performance i s used t o c h a r a c t e r i z e i n s t r u m e n t performance ( d e t e r m i n a t i o n o f LCRs and a n a l y s i s o f QCS) and l a b o r a t o r y performance ( d e t e r m i n a t i o n o f MDLs) p r i o r t o p e r f o r m i n g analyses by t h i s method.

9.2.2

L i n e a r C a l i b r a t i o n Range (LCR) -- The LCR must be determined i n i t i a l l y and v e r i f i e d e v e r y 6 months o r whenever a s i g n i f i c a n t change i n i n s t r u m e n t response i s observed o r expected. The i n i t i a l d e m o n s t r a t i o n o f l i n e a r i t y must use s u f f i c i e n t standards t o i n s u r e t h a t t h e r e s u l t i n g curve i s l i n e a r . The v e r i f i c a t i o n o f l i n e a r i t y must use a minimum o f a b l a n k and t h r e e standards. If any v e r i f i c a t i o n d a t a exceeds t h e i n i t i a l v a l u e s by f lo%, l i n e a r i t y must be r e e s t a b l i s h e d . I f any p o r t i o n o f t h e range i s shown t o be n o n l i n e a r , s u f f i c i e n t standards must be used t o c l e a r l y define the nonlinear portion.

9.2.3

Q u a l i t y C o n t r o l Sample (QCS) -- When b e g i n n i n g t h e use of t h i s method, on a q u a r t e r l y b a s i s o r as r e q u i r e d t o meet data-qua1 i t y needs, v e r i f y t h e c a l i b r a t i o n standards and a c c e p t a b l e i n s t r u m e n t performance w i t h t h e p r e p a r a t i o n and analyses o f a QCS. I f t h e d e t e r m i n e d c o n c e n t r a t i o n s a r e n o t w i t h i n f 10% o f t h e s t a t e d v a l u e s , performance o f t h e d e t e r m i n a t i v e s t e p o f t h e method i s unacceptable. The source o f t h e problem must be i d e n t i f i e d and c o r r e c t e d b e f o r e e i t h e r p r o c e e d i n g on w i t h t h e i n i t i a l d e t e r m i n a t i o n o f MDLs o r c o n t i n u i n g w i t h on-going analyses.

Inorganic Substances 9.2.4

425

Method D e t e c t i o n L i m i t (MDL) - - MDLs must be e s t a b l i s h e d f o r a l l analytes, using reagent water (blank) f o r t i f i e d a t a c o n c e n t r a t i o n o f two t o t h r e e t i m e s t h e e s t i m a t e d i n s t r u m e n t detection l i m i t . ' " To d e t e r m i n e MDL v a l u e s , t a k e seven rep1 i c a t e a1 i q u o t s o f t h e f o r t i f i e d r e a g e n t w a t e r and process t h r o u g h t h e e n t i r e a n a l y t i c a l method. P e r f o r m a l l c a l c u l a t i o n s d e f i n e d i n t h e method and r e p o r t t h e concentration values i n the appropriate u n i t s . Calculate t h e MDL as f o l l o w s : MDL = ( t ) x ( S ) where, t

=

S t u d e n t ' s t v a l u e f o r a 99% c o n f i d e n c e l e v e l and a s t a n d a r d d e v i a t i o n e s t i m a t e w i t h n-1 degrees o f freedom [ t = 3.14 f o r seven r e p l i c a t e s ] .

S = s t a n d a r d d e v i a t i o n o f t h e r e p l i c a t e analyses.

MDLs s h o u l d be d e t e r m i n e d e v e r y 6 months, when a new o p e r a t o r b e g i n s work o r whenever t h e r e i s a s i g n i f i c a n t change i n t h e background o r i n s t r u m e n t response. 9.3

ASSESSING LABORATORY PERFORMANCE 9.3.1

L a b o r a t o r y Reagent B l a n k (LRB) -- The l a b o r a t o r y must a n a l y z e a t l e a s t one LRB w i t h each b a t c h o f samples. Data produced a r e used t o assess c o n t a m i n a t i o n f r o m t h e l a b o r a t o r y environment. Values t h a t exceed t h e MDL i n d i c a t e l a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n s h o u l d be suspected and c o r r e c t i v e a c t i o n s must be t a k e n b e f o r e c o n t i n u i n g t h e analysis,

9.3.2

L a b o r a t o r y F o r t i f i e d B l a n k (LFB) -- The l a b o r a t o r y must a n a l y z e a t l e a s t one LFB w i t h each b a t c h o f samples. C a l c u l a t e accuracy as p e r c e n t r e c o v e r y (Sect. 9.4.2). If t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e r e q u i r e d c o n t r o l l i m i t s of 90-110%, t h a t a n a l y t e i s judged o u t o f c o n t r o l , and t h e source o f t h e problem s h o u l d be i d e n t i f i e d and r e s o l v e d b e f o r e c o n t i n u i n g analyses.

9.3.3

The l a b o r a t o r y must use LFB analyses d a t a t o assess 1 a b o r a t o r y performance a g a i n s t t h e r e q u i r e d c o n t r o l 7 i m i t s o f 90-110%. When s u f f i c i e n t i n t e r n a l performance d a t a becomes a v a i l a b l e ( u s u a l l y a minimum o f 20-30 analyses), o p t i o n a l c o n t r o l l i m i t s can be developed f r o m t h e p e r c e n t mean r e c o v e r y ( x ) and t h e s t a n d a r d d e v i a t i o n ( S ) o f t h e mean r e c o v e r y . These d a t a can be used t o e s t a b l i s h t h e upper and l o w e r c o n t r o l l i m i t s as f o l l o w s : UPPER CONTROL LIMIT LOWER CONTROL LIMIT

= =

x t 3s x - 3s

426

Methods for the Determination The o p t i o n a l c o n t r o l l i m i t s must be equal t o o r b e t t e r t h a n t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%. A f t e r each f i v e t o t e n new r e c o v e r y measurements, new c o n t r o l l i m i t s can be c a l c u l a t e d u s i n g o n l y t h e most r e c e n t 20-30 d a t a p o i n t s . A l s o , t h e standard d e v i a t i o n ( S ) d a t a s h o u l d be used t o e s t a b l i s h an on-going p r e c i s i o n statement f o r t h e l e v e l o f c o n c e n t r a t i o n s i n c l u d e d i n t h e LFB. These d a t a must be k e p t on f i l e and be a v a i l a b l e f o r r e v i e w . 9.3.4

9.4

I n s t r u m e n t Performance Check S o l u t i o n (IPC) -- F o r a l l d e t e r m i n a t i o n s , t h e l a b o r a t o r y must analyze t h e I P C ( a midrange check s t a n d a r d ) and a c a l i b r a t i o n b l a n k i m m e d i a t e l y f o l l o w i n g d a i l y c a l i b r a t i o n , a f t e r e v e r y t e n t h sample ( o r more f r e q u e n t l y , i f r e q u i r e d ) , and a t t h e end o f t h e sample r u n . A n a l y s i s o f t h e I P C s o l u t i o n and c a l i b r a t i o n b l a n k i m m e d i a t e l y f o l l o w i n g c a l i b r a t i o n must v e r i f y t h a t t h e 10% o f c a l i b r a t i o n . Subsequent i n s t r u m e n t i s w i t h i n -i analyses o f t h e I P C s o l u t i o n must v e r i f y t h e c a l i b r a t i o n is s t i l l w i t h i n k 10%. I f t h e c a l i b r a t i o n cannot be v e r i f i e d w i t h i n the specified l i m i t s , reanalyze the IPC solution. I f t h e second a n a l y s i s o f t h e I P C s o l u t i o n c o n f i r m s c a l i b r a t i o n t o be o u t s i d e t h e l i m i t s , sample a n a l y s i s must be d i s c o n t i n u e d , t h e cause d e t e r m i n e d and/or i n t h e case o f d r i f t t h e i n s t r u m e n t r e c a l i b r a t e d . A l l samples f o l l o w i n g t h e l a s t a c c e p t a b l e I P C s o l u t i o n must be r e a n a l y z e d . The a n a l y s i s d a t a o f t h e c a l i b r a t i o n b l a n k and I P C s o l u t i o n must be k e p t on f i l e w i t h t h e sample analyses d a t a .

ASSESSING ANALYTE RECOVERY AND DATA QUALITY 9.4.1

L a b o r a t o r y F o r t i f i e d Sample M a t r i x (LFM) -- The l a b o r a t o r y must add a known amount o f a n a l y t e t o a minimum o f 10% o f t h e r o u t i n e samples. I n each case, t h e LFM a l i q u o t must be a d u p l i c a t e o f t h e a l i q u o t used f o r sample a n a l y s i s . The a n a l y t e c o n c e n t r a t i o n must be h i g h enough t o be d e t e c t e d above t h e o r i g i n a l sample and s h o u l d n o t be l e s s t h a n f o u r t i m e s t h e MDL. The added a n a l y t e c o n c e n t r a t i o n s h o u l d be t h e same as t h a t used i n t h e l a b o r a t o r y f o r t i f i e d b l a n k .

9.4.2

C a l c u l a t e t h e p e r c e n t r e c o v e r y f o r each a n a l y t e , c o r r e c t e d f o r c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o t h e d e s i g n a t e d LFM r e c o v e r y range 90-110%. Percent r e c o v e r y may be c a l c u l a t e u s i n g t h e f o l l o w i n g equation:

where, R Cs C

= = =

percent recovery. f o r t i f i e d sample c o n c e n t r a t i o n . sample background c o n c e n t r a t i o n .

Inorganic Substances s

9.4.3

=

427

c o n c e n t r a t i o n e q u i v a l e n t o f a n a l y t e added t o sample.

I f t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e d e s i g n a t e d LFM r e c o v e r y range and t h e l a b o r a t o r y performance f o r t h a t a n a l y t e i s shown t o be i n c o n t r o l ( S e c t . 9 . 3 ) , t h e r e c o v e r y

problem encountered w i t h t h e LFM i s judged t o be e i t h e r m a t r i x o r s o l u t i o n r e l a t e d , n o t system r e l a t e d . 9.4.4

Where r e f e r e n c e m a t e r i a l s a r e a v a i l a b l e , t h e y should be analyzed t o p r o v i d e a d d i t i o n a l performance d a t a . The a n a l y s i s o f r e f e r e n c e samples i s a v a l u a b l e t o o l f o r d e m o n s t r a t i n g t h e a b i l i t y t o p e r f o r m t h e method a c c e p t a b l y .

10.0 CALIBRATION AND STANDARDIZATION

10.1 Prepare a s e r i e s o f a t l e a s t 3 s t a n d a r d s , c o v e r i n g t h e d e s i r e d range, and a b l a n k by p i p e t t i n g s u i t a b l e volumes o f w o r k i n g standard s o l u t i o n (7.12) i n t o 100 mL v o l u m e t r i c f l a s k s . To each s t a n d a r d ( e x c e p t t h o s e t o be d i s t i l l e d ) add 20 mL o f 1.25 N sodium h y d r o x i d e and d i l u t e t o 100 mL w i t h r e a g e n t w a t e r . 10.2 I t i s n o t i m p e r a t i v e t h a t a l l standards be d i s t i l l e d i n t h e same manner as t h e samples. I t i s recommended t h a t a t l e a s t two standards ( a h i g h and low) and a b l a n k be d i s t i l l e d and compared t o s i m i l a r v a l u e s on t h e s t a n d a r d c u r v e t o i n s u r e t h a t t h e d i s t i l l a t i o n t e c h n i q u e i s r e l i a b l e . I f d i s t i l l e d standards do n o t agree w i t h i n ? 10% o f t h e u n d i s t i l l e d s t a n d a r d s t h e a n a l y s t s h o u l d f i n d t h e cause o f t h e apparent e r r o r b e f o r e proceeding. B e f o r e d i s t i l l a t i o n , standards s h o u l d c o n t a i n 4 mL 0.25N NaOH (7.8) p e r 50 mL. 10.3 Set up t h e m a n i f o l d as shown i n F i g u r e 2 i n a hood o r a w e l l v e n t i l a t e d area. 10.4 A l l o w t h e nstrument t o warm up as r e q u i r e d . Pump a l l reagents, w i t h 0.25N NaOH i n t h e sample l i n e , u n t i l a s t a b l e b a s e l i n e i s ach ieved . 10.5 P l a c e a p p r o p r i a t e standards i n t h e sampler i n o r d e r o f d e c r e a s i n g c o n c e n t r a t i o n and p e r f o r m a n a l y s i s . 10.6 Prepare s t a n d a r d c u r v e by p l o t t i n g i n s t r u m e n t response a g a i n s t c o n c e n t r a t i o n v a l u e s . A c a l i b r a t i o n c u r v e may be f i t t e d t o t h e c a l i b r a t i o n s o l u t i o n s c o n c e n t r a t i o n / r e s p o n s e d a t a u s i n g computer o r c a l c u l a t o r based r e g r e s s i o n c u r v e f i t t i n g t e c h n i q u e s . Acceptance o r c o n t r o l l i m i t s s h o u l d be e s t a b l i s h e d u s i n g t h e d i f f e r e n c e between t h e measured v a l u e o f t h e c a l i b r a t i o n s o l u t i o n and t h e " t r u e v a l u e " concentration. 10.7 A f t e r t h e c a l i b r a t i o n has been e s t a b l i s h e d , i t must be v e r i f i e d by t h e a n a l y s i s o f a s u i t a b l e QCS. I f measurements exceed ? 10% o f t h e e s t a b l i s h e d QCS v a l u e , t h e a n a l y s i s should be t e r m i n a t e d and t h e

428

Methods for the Determination

instrument recalibrated. The new calibration must be verified before continuing analysis. Periodic reanalysis o f the QCS is recommended as a continuing calibration check. 11.0 PROCEDURE

11.1 Pipet 50 mL of sample or an aliquot diluted to 50 mL into the

MIDI

distillation boiling flask. Add boiling chips as required. Pipet 50 mL of sodium hydroxide 0.25 N (7.8) into the absorbing tube. Connect the boiling flask, condenser, and absorber in the train as shown in Figure 1. 11.2 Start a slow stream of air entering the boiling flask by adjusting

the vacuum source to maintain about 3 bubbles per minute. add 0 . 2 g of sulfamic acid (7.13) after the air rate is set through' the air inlet tube. Mix for 3 min prior to addition of H,SO,.

11.3 If samples contain NO, and/or NO

11.4 Slowly add 5 mL 18 N sulfuric acid (7.14) through the air inlet

tube. Rinse t h e tube with distilled water and allow the airflow to mix the flask contents for 3 min. Pour 2 mL of magnesium chloride (7.4) into the air inlet and wash down with a stream of water. 11.5 Heat the solution to boiling.

Reflux for one and one half hours. Turn off heat and continue the airflow for at least 15 min. After cooling the boiling flask, disconnect absorber and close off the vacuum source and remove absorber tube.

11.6

Fill and connect reagent containers and start system. Allow the instrument to warm up as required, Pump all reagents, with 0.25N NaOH in the sample line, until a stable baseline i s achieved.

11.7 Place standards, distilled standards and unknown samples (ALL in 0.25N NaOH) in sampler tray. Calibrate instrument and begin

analysis. 12.0 DATA ANALYSIS AND CALCULATIONS

12.1 Prepare a calibration curve by plotting instrument response against

standard concentration. Compute sample concentration by comparing sample response with the standard curve. Multiply answer by appropriate dilution factor. 1 2 . 2 Report only those values that fall between the lowest and the

highest calibration standards. Samples exceeding the highest standard should be diluted and reanalyzed. 12.3 Report results in mg/L.

Inorganic Substances

429

13.0 METHOD PERFORMANCE

13.1 The interlaboratory precision and accuracy data in Table 1 were developed using a reagent water matrix. Values are in mg CN/L.

13.2 Single laboratory precision data can be estimated at 50 to 75% of the interlaboratory precision estimates. 14.0 POLLUTION PREVENTION

14.1 Pollution prevention encompasses any technique that reduces or eliminates the quantity or toxicity of waste at the point of generation. Numerous opportunities for pollution prevention exist in laboratory operation. The USEPA has established a preferred hierarchy of environmental management techniques that places pollution prevention as the management option of first choice. Whenever feasible, laboratory personnel should use pollution prevention techniques to address their waste generation. When wastes cannot be feasibly reduced at the source, the Agency recommends recycling as the next best option. 14.2 The quantity of chemicals purchased should be based on expected usage during its shelf life and disposal cost of unused material. Actual reagent preparation volumes should reflect anticipated usage and reagent stability.

14.3 For information about pollution prevention that may be applicable to laboratories and research institutions, consult "Less is Better: Laboratory Chemical Management for Waste Reduction," available from the American Chemical Society's Department of Government Regulations and Science Policy, 1155 16th Street N.W., Washington D . C . 20036, (202)872-4477. 15.0 WASTE MANAGEMENT

15.1 The U.S. Environmental Protection Agency requires that laboratory waste management practices conducted be consistent with all applicable rules and regulations. Excess Reagents, samples, and method process wastes should be characterized and disposed o f in an acceptable manner. The Agency urges laboratories to protect the air, water and land by minimizing and controlling all releases from hoods, and bench operations, complying with the letter and spirit of any waste discharge permit and regulations, and by complying with all sol id and hazardous waste regulations, particularly the hazardous waste identification rules and land disposal restrictions. For further information on waste management consult the "Waste Management Manual for Laboratory Personnel available from the American Chemical Society at the address listed in Sect. 14.3. ,'I

430

Methods for the Determination

16.0 REFERENCES

1.

Technicon AutoAnalyzer I 1 Methodology, I n d u s t r i a l Method No. 315-74 WCUV d i g e s t i o n and d i s t i 11 a t i o n , Technicon I n d u s t r i a l Systems, T a r r y t o w n , NY 10591, ( 1 9 7 4 ) .

2.

Goulden, P . D . , Afghan, B . K . and Brooksbank, P . , A n a l . (1972).

3.

USEPA C o n t r a c t L a b o r a t o r y Program, Document Number ILMO 1.0, Method f o r T o t a l Cyanide A n a l y s i s by M I D I D i s t i l l a t i o n #335.2 CLP-M.

4.

Code o f F e d e r a l R e g u l a t i o n s 4 0 , Ch. 1, P t . 136, Appendix B.

& 1845

Inorganic Substances 17.

431

TABLES, DIAGRAMS, FLOWCHARTS, AND VALIDATION DATA TABLE 1.

NUMBER OF VALUES REPORTED

I

I

INTERLABORATORY PRECISION AND ACCURACY DATA

TRUE VALUE (T)

I

MEAN (X)

RESIDUAL FOR X

1

STANDARD DEVIATION (S)

RESIDUAL FOR S

0.0055

0.0000

126

0.020

0.0182

0.0002

94

0.055

0.0501

-0.0014

0.0092

-0.0007

158

0.090

0.0843

-0.0008

0.0171

0.0027

118

0.110

0.1045

0.0003

0.0165

-0.0004

148

0.180

0.1683

-0.0030

0.0236

-0.0023

92

0.270

0.2538

-0.0038

0.0275

-0.0099

132

0.530

0.5019

-0.0049

0.0775

0.0069

119

0.540

0.5262

0.0098

0.0679

-0.0039

148

0.610

0.5803

-0.0032

0.0851

0.0043

94

0.700

0.6803

0.0105

0.1082

0.0159

158

0.970

0.9508

0.0222

0.1464

0.0197

REGRESSIONS:

X

=

0.959T - 0.001,

S = 0.128T t 0.003

1

432

Methods for the Determination

DISTILLATION

FIGURE 1. MIDI DISTILLATION APPARATUS

mVmin

TO F/C PLMP TUBE

COLORIMHER 570 nm 15mm F K

0.32

AIR

1.oo

SAMPLE

0.42

BUTER

0.10

CKOROKNE-T

.oo 1.a

WRIOINE4ARBrTlJRIC REAGENJ

1

WASTE

l=WMF/c

~

~

PUMP r) PER HOUR

sAMpLE1msEc. WASH 17 SEC.

Figure 2 Cyanide Manifold

434

Methods for the Determination

METHOD 350.1 DETERMINATION OF AMMONIA NITROGEN BY SEMI-AUTOMATED COLORIMETRY

Edited by James W. O'Dell Inorganic Chemistry Branch Chemistry Research Division

Revision 2.0 August 1993

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

Inorganic Substances

435

METHOD 350.1 D E T E R M I N A T I O N OF AMMONIA NITROGEN BY SEMI-AUTOMATED COLORIMETRY

1.0

SCOPE AND A P P L I C A T I O N

1.1 T h i s method c o v e r s t h e d e t e r m i n a t i o n o f ammonia i n d r i n k i n g , ground, s u r f a c e , and s a l i n e w a t e r s , domestic and i n d u s t r i a l wastes.

2.0

3.0

1.2

The a p p l i c a b l e range i s 0 . 0 1 t o 2.0 mg/L NH, as N. H i g h e r c o n c e n t r a t i o n s can be determined by sample d i l u t i o n . Approximately 60 samples p e r hour can be analyzed.

1.3

T h i s method i s d e s c r i b e d f o r macro glassware; however, m i c r o d i s t i l l a t i o n equipment may a l s o be used.

SUMMARY OF METHOD

2.1

The sample i s b u f f e r e d a t a pH o f 9 . 5 w i t h a b o r a t e b u f f e r i n o r d e r t o decrease h y d r o l y s i s o f cyanates and o r g a n i c n i t r o g e n compounds, and i s d i s t i l l e d i n t o a s o l u t i o n o f b o r i c a c i d . A l k a l i n e phenol and h y p o c h l o r i t e r e a c t w i t h ammonia t o f o r m indophenol b l u e t h a t i s p r o p o r t i o n a l t o t h e ammonia c o n c e n t r a t i o n . The b l u e c o l o r formed i s i n t e n s i f i e d w i t h sodium n i t r o p r u s s i d e and measured c o l o r i m e t r i c a l l y .

2.3

Reduced volume v e r s i o n s o f t h i s method t h a t use t h e same r e a g e n t s and m o l a r r a t i o s a r e a c c e p t a b l e p r o v i d e d t h e y meet t h e q u a l i t y c o n t r o l and performance r e q u i r e m e n t s s t a t e d i n t h e method.

2.4

L i m i t e d performance-based method m o d i f i c a t i o n s may be a c c e p t a b l e p r o v i d e d t h e y a r e f u l l y documented and meet o r exceed r e q u i r e m e n t s expressed i n S e c t . 9.0, Q u a l i t y C o n t r o l .

DEFINITIONS

3.1

CALIBRATION BLANK (CB) -- A volume o f r e a g e n t w a t e r f o r t i f i e d w i t h t h e same m a t r i x as t h e c a l i b r a t i o n standards, b u t w i t h o u t t h e a n a l y t e s , i n t e r n a l standards, o r s u r r o g a t e a n a l y t e s .

3.2

CALIBRATION STANDARD (CAL) -- A s o l u t i o n p r e p a r e d f r o m t h e p r i m a r y d i l u t i o n s t a n d a r d s o l u t i o n o r s t o c k s t a n d a r d s o l u t i o n s and t h e i n t e r n a l standards and s u r r o g a t e a n a l y t e s . The CAL s o l u t i o n s a r e used t o c a l i b r a t e t h e i n s t r u m e n t response w i t h r e s p e c t t o a n a l y t e concentration.

3.3

INSTRUMENT PERFORMANCE CHECK SOLUTION (IPC) -- A s o l u t i o n o f one o r more method a n a l y t e s , s u r r o g a t e s , i n t e r n a l standards, o r o t h e r t e s t substances used t o e v a l u a t e t h e performance o f t h e i n s t r u m e n t system w i t h respect t o a defined set o f c r i t e r i a .

436

Methods for the Determination 3.4

LABORATORY F O R T I F I E D BLANK (LFB) ~- An a l i q u o t o f r e a g e n t w a t e r or o t h e r b l a n k m a t r i c e s t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e methodology i s i n c o n t r o l , and whether t h e l a b o r a t o r y i s c a p a b l e o f making a c c u r a t e and p r e c i s e measurements.

3.5

LABORATORY F O R T I F I E D SAMPLE M A T R I X (LFM) -- An a l i q u o t o f an engironmental sample t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFM i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e sample m a t r i x c o n t r i b u t e s b i a s t o t h e a n a l y t i c a l r e s u l t s . The background c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be determined i n a s e p a r a t e a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s .

3.6

LABORATORY REAGENT BLANK (LRB) -- An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a l l glassware, equipment, s o l v e n t s , reagents, i n t e r n a l standards, and s u r r o g a t e s t h a t a r e used w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e l a b o r a t o r y environment, t h e r e a g e n t s , o r t h e apparatus.

3.7

LINEAR CALIBRATION RANGE (LCR) -- The c o n c e n t r a t i o n range o v e r which t h e i n s t r u m e n t response i s l i n e a r .

3.8

MATERIAL SAFETY DATA SHEET (MSDS) -- W r i t t e n i n f o r m a t i o n p r o v i d e d by vendors c o n c e r n i n g a chemical ' s t o x i c i t y , h e a l t h hazards, p h y s i c a l p r o p e r t i e s , f i r e , and r e a c t i v i t y d a t a i n c l u d i n g s t o r a g e , s p i l l , and handling precautions.

3.9

METHOD DETECTION LIMIT (MDL) -- The minimum c o n c e n t r a t i o n o f an a n a l y t e t h a t can be i d e n t i f i e d , measured and r e p o r t e d w i t h 99% c o n f i d e n c e t h a t t h e a n a l y t e c o n c e n t r a t i o n i s g r e a t e r t h a n zero.

3.10 QUALITY CONTROL SAMPLE (QCS) -- A s o l u t i o n o f method a n a l y t e s o f known c o n c e n t r a t i o n s t h a t i s used t o f o r t i f y an a l i q u o t o f LRB o r sample m a t r i x . The QCS i s o b t a i n e d from a source e x t e r n a l t o t h e l a b o r a t o r y and d i f f e r e n t f r o m t h e source o f c a l i b r a t i o n standards. I t i s used t o check l a b o r a t o r y performance w i t h e x t e r n a l l y prepared t e s t materials. 3.11 STOCK STANDARD SOLUTION (SSS) -- A c o n c e n t r a t e d s o l u t i o n c o n t a i n i n g one o r more method a n a l y t e s p r e p a r e d i n t h e l a b o r a t o r y u s i n g assayed r e f e r e n c e m a t e r i a l s o r purchased f r o m a r e p u t a b l e commercial source.

Inorganic Substances 4.0

5.0

6.0

437

INTERFERENCES 4.1

Cyanate, which may be encountered i n c e r t a i n i n d u s t r i a l e f f l u e n t s , w i l l h y d r o l y z e t o some e x t e n t even a t t h e pH o f 9 . 5 a t which d i s t i l l a t i o n i s carried out.

4.2

Residual c h o r i n e must be removed by p r e t r e a t m e n t o f t h e sample w i t h sodium t h i o s u l f a t e o r o t h e r r e a g e n t s b e f o r e d i s t i l l a t i o n .

4.3

Method i n t e r f e r e n c e s may be caused b y contaminants i n t h e r e a g e n t w a t e r , reagents, glassware, and o t h e r sample p r o c e s s i n g apparatus t h a t b i a s a n a l y t e response.

SAFETY 5.1

The t o x i c i t y o r c a r c i n o g e n i c i t y o f each r e a g e n t used i n t h i s method have n o t been f u l l y e s t a b l i s h e d . Each chemical s h o u l d be regarded as a p o t e n t i a l h e a l t h hazard and exposure s h o u l d be as l o w as r e a s o n a b l y a c h i e v a b l e . C a u t i o n s a r e i n c l u d e d f o r known e x t r e m e l y hazardous m a t e r i a l s o r procedures.

5.2

Each 1 a b o r a t o r y i s r e s p o n s i b l e f o r m a i n t a i n i n g a c u r r e n t awareness f i l e o f OSHA r e g u l a t i o n s r e g a r d i n g t h e s a f e h a n d l i n g o f t h e c h e m i c a l s s p e c i f i e d i n t h i s method. A r e f e r e n c e f i l e o f M a t e r i a l S a f e t y Data Sheets (MSDS) s h o u l d be made a v a i l a b l e t o a l l personnel i n v o l v e d i n t h e chemical a n a l y s i s . The p r e p a r a t i o n o f a f o r m a l safety plan i s also advisable.

5.3

The f o l l o w i n g chemicals have t h e p o t e n t i a l t o be h i g h l y t o x i c o r hazardous, c o n s u l t MSDS. 5.3.1

S u l f u r i c a c i d (7.6)

5.3.2

Phenol (7.7)

5.3.3

Sodium n i t r o p r u s s i d e (7.10)

EQUIPMENT AND SUPPLIES

,

6.1

Balance - A n a l y t i c a 0.0001 g.

6.2

Glassware - Class A v o l u m e t r i c f l a s k s and p i p e t s as r e q u i r e d .

6.3

An a l l - g l a s s d i s t i l i n g apparatus w i t h an 800-1000-mL f l a s k .

6.4

Automated c o n t i n u o u s f l o w a n a l y s i s equipment designed t o d e l i v e r and r e a c t sample and r e a g e n t s i n t h e r e q u i r e d o r d e r and r a t i o s .

capable o f a c c u r a t e l y w e i g h i n g t o t h e n e a r e s t

6.4.1

Sampl ing d e v i c e (sampl e r )

6.4.2

M u l t i c h a n n e l pump

438

7.0

Methods for the Determination 6.4.3

Reaction u n i t o r manifold

6.4.4

Colorimetric detector

6.4.5

Data r e c o r d i n g d e v i c e

REAGENTS AND STANDARDS 7.1

Reagent w a t e r - Ammonia f r e e : Such w a t e r i s b e s t p r e p a r e d by passage t h r o u g h an i o n exchange column c o n t a i n i n g a s t r o n g l y a c i d i c c a t i o n exchange r e s i n mixed w i t h a s t r o n g l y b a s i c a n i o n exchange r e s i n . Regeneration o f t h e column s h o u l d be c a r r i e d o u t a c c o r d i n g t o the manufacturer's i n s t r u c t i o n s . NOTE 1:

A l l s o l u t i o n s must be made w i t h ammonia-free w a t e r .

7.2

B o r i c a c i d s o l u t i o n (20 g / L ) : D i s s o l v e 20 g HB , O, 3) i n r e a g e n t w a t e r and d i l u t e t o 1 L .

(CASRN 10043-35-

7.3

Borate t o 500 Na,B,O L) and

7.4

Sodium h y d r o x i d e , 1 N: d i l u t e t o 1 L.

7.5

D e c h l o r i n a t i n g r e a g e n t s : A number of d e c h l o r i n a t i n g r e a g e n t s may be used t o remove r e s i d u a l c h l o r i n e p r i o r t o d i s t i l l a t i o n . These include:

b u f f e r : Add 88 mL o f 0 . 1 N NaOH (CASRN 1310-73-2) s o l u t i o n mL o f 0.025 M sodium t e t r a b o r a t e s o l u t i o n (5.0 g anhydrous , Ol; HO , [CASRN 1303-96-41 p e r [CASRN 1330-43-41 o r 9.5 g Na BO d i l u t e t o 1 L w i t h reagent wafer. D i s s o l v e 40 g NaOH i n r e a g e n t w a t e r and

7.5.1

Sodium t h i o s u l f a t e : D i s s o l v e 3.5 g Na,S 05;H 0 (CASRN One mL o f 10102-17-7) i n r e a g e n t w a t e r and d i l u t e \o 1 t h i s s o l u t i o n w i l l remove 1 mg/L o f r e s i d u a l c h l o r i n e i n 500 mL o f sample.

7.5.2

Sodium s u l f i t e : D i s s o l v e 0.9 g Na2S0, (CASRN 7757-83-7) i n r e a g e n t w a t e r and d i l u t e t o 1 L. One m l removes 1 mg/L C1 p e r 500 mL o f sample.

t.

7.6

S u l f u r i c a c i d 5 N: A i r s c r u b b e r s o l u t i o n . C a r e f u l l y add 139 mL o f conc. s u l f u r i c a c i d (CASRN 7664-93-9) t o a p p r o x i m a t e l y 500 mL o f r e a g e n t w a t e r . Cool t o room t e m p e r a t u r e and d i l u t e t o 1 L w i t h reagent water.

7.7

Sodium p h e n o l a t e : U s i n g a 1-L Erlenmeyer f l a s k , d i s s o l v e 83 g phenol (CASRN 108-95-2) i n 500 mL o f d i s t i l l e d water. I n small increments, c a u t i o u s l y add w i t h a g i t a t i o n , 32 g o f NaOH. P e r i o d i c a l l y c o o l f l a s k under w a t e r f a u c e t . When c o o l , d i l u t e t o 1 L w i t h reagent water.

Inorganic Substances

439

7.8

Sodium h y p o c h l o r i t e s o l u t i o n : D i l u t e 250 mL o f a b l e a c h s o l u t i o n c o n t a i n i n g 5 . 2 5 % N a O C l (CASRN 7681-52-9) (such as " C l o r o x " ) t o 500 mL w i t h r e a g e n t w a t e r . A v a i l a b l e c h l o r i n e l e v e l s h o u l d approximate 2% t o 3%. Since " C l o r o x " i s a p r o p r i e t a r y p r o d u c t , i t s f o r m u l a t i o n i s s u b j e c t t o change. The a n a l y s t must remain a l e r t t o d e t e c t i n g any v a r i a t i o n i n t h i s p r o d u c t s i g n i f i c a n t t o i t s use i n t h i s procedure. Due t o t h e i n s t a b i l i t y o f t h i s p r o d u c t , s t o r a g e o v e r an extended p e r i o d s h o u l d be avoided.

7.9

Disodium ethylenediamine-tetraacetate (EDTA) ( 5 % ) : D i s s o l v e 50 g o f EDTA ( d i s o d i u m s a l t ) (CASRN 6381-92-6) and a p p r o x i m a t e l y s i x p e l l e t s o f NaOH i n 1 L o f r e a g e n t w a t e r .

7.10 Sodium n i t r o p r u s s i d e (0.05%): D i s s o l v e 0.5 g o f sodium n i t r o p r u s s i d e (CASRN 14402-89-2) i n 1 L o f r e a g e n t w a t e r . 7.11 Stock s o l u t i o n : D i s s o l v e 3.819 g o f anhydrous ammonium c h l o r i d e , NH C1 (CASRN 12125-02-9), d r i e d a t 105"C, i n r e a g e n t water, and d i l u t e t o 1 L. 1.0 mL = 1 . 0 mg NH,-N. 7.12 Standard S o l u t i o n A: D i l u t e 10.0 mL o f s t o c k s o l u t i o n (7.11) t o 1 L w i t h r e a g e n t w a t e r . 1.0 mL = 0.01 mg NH,-N. 7.13 Standard S o l u t i o n B: D i l u t e 10.0 mL o f s t a n d a r d s o l u t i o n A (7.12) t o 100.0 mL w i t h r e a g e n t w a t e r . 1.0 mL = 0.001 mg NH,-N. 8.0

9.0

SAMPLE COLLECTION, PRESERVATION AND STORAGE

8.1

Samples s h o u l d be c o l l e c t e d i n p l a s t i c o r g l a s s b o t t l e s . A l l b o t t l e s must be t h o r o u g h l y cleaned and r i n s e d w i t h r e a g e n t w a t e r . Volume c o l l e c t e d s h o u l d be s u f f i c i e n t t o i n s u r e a r e p r e s e n t a t i v e sample, a l l o w f o r r e p l i c a t e a n a l y s i s ( i f r e q u i r e d ) , and m i n i m i z e waste d i s p o s a l .

8.2

Samples must be p r e s e r v e d w i t h H,SO, a t the time o f collection.

8.3

Samples s h o u l d be analyzed as soon as p o s s i b l e a f t e r c o l l e c t i o n . I f s t o r a g e i s r e q u i r e d , p r e s e r v e d samples a r e m a i n t a i n e d a t 4 ° C and may be h e l d f o r up t o 28 days.

t o a pH < 2 and c o o l e d t o 4°C

g U A L I T Y CONTROL

9.1 Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a f o r m a l q u a l i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f t h i s program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y , and t h e p e r i o d i c a n a l y s i s o f l a b o r a t o r y r e a g e n t blanks, f o r t i f i e d b l a n k s and o t h e r l a b o r a t o r y s o l u t i o n s as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n p e r formance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f t h e d a t a t h a t a r e generated.

440

Methods for the Determination 9.2

INITIAL DEMONSTRATION OF PERFORMANCE 9.2.1

The initial demonstration of performance i s used to characterize inst.rument performance (determination of LCRs and analysis of QCS) and laboratory performance (determination of MDLs) prior to performing analyses by this method.

9.2.2

Linear Calibration Range (LCR) -- The LCR must be determined initially and verified every 6 months or whenever a significant change in instrument response is observed or expected. The initial demonstration of linearity must use sufficient standards to insure that the resulting curve is linear. The verification of linearity must use a minimum o f a blank and three standards. If any verification data exceeds the initial values by f lo%, linearity must be reestablished. If any portion of the range is shown to be nonlinear, sufficient standards must be used to clearly define the nonlinear portion.

9.2.3

Quality Control Sample (QCS) -- When beginning the use o f this method, on a quarterly basis or as required to meet data-quality needs, verify the calibration standards and acceptable instrument performance with the preparation and analyses of a QCS. If the determined concentrations are not within f 10% of the stated values, performance of the determinative step of the method is unacceptable. The source of the problem must be identified and corrected before either proceeding with the initial determination of MDLs or continuing with on-going analyses.

9.2.4

Method Detection Limit (MDL) -- MDLs must be established for all analytes, using reagent water (blank) fortified a t a concentration of two to three times the estimated instrument detection limit.'9' To determine MDL values, take seven replicate aliquots of the fortified reagent water and process through the entire analytical method. Perform all calculations defined in the method and report the concentration values in the appropriate units. Calculate the MDL as follows: MDL

=

(t) x (S)

where, t

=

Student's t value for a 99% confidence level and a standard deviation estimate with n-1 degrees of freedom [t = 3 . 1 4 for seven rep1 icates].

S

=

standard deviation of the replicate analyses.

Inorganic Substances

441

MDLs s h o u l d be determined e v e r y 6 months, when a new o p e r a t o r b e g i n s work o r whenever t h e r e i s a s i g n i f i c a n t change i n t h e background o r i n s t r u m e n t response. 9.3

ASSESSING LABORATORY PERFORMANCE 9.3.1

L a b o r a t o r y Reagent Blank (LRB) - - The l a b o r a t o r y must a n a l y z e a t l e a s t one LRB w i t h each b a t c h o f samples. Data produced a r e used t o assess c o n t a m i n a t i o n f r o m t h e l a b o r a t o r y environment, Values t h a t exceed t h e MDL i n d i c a t e l a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n s h o u l d be suspected and c o r r e c t i v e a c t i o n s must be t a k e n b e f o r e c o n t i n u i n g t h e analysis.

9.3.2

L a b o r a t o r y F o r t i f i e d B l a n k (LFB) -- The l a b o r a t o r y must a n a l y z e a t l e a s t one LFB w i t h each b a t c h o f samples. C a l c u l a t e accuracy as p e r c e n t r e c o v e r y (Sect. 9.4.2). If t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%, t h a t a n a l y t e i s j u d g e d o u t o f c o n t r o l , and t h e source o f t h e problem s h o u l d be i d e n t i f i e d and r e s o l v e d b e f o r e c o n t i n u i n g analyses.

9.3.3

The l a b o r a t o r y must use LFB analyses d a t a t o assess l a b o r a t o r y performance a g a i n s t t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%. When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e ( u s u a l l y a minimum o f 20-30 a n a l y s e s ) , o p t i o n a l c o n t r o l l i m i t s can be developed f r o m t h e p e r c e n t mean r e c o v e r y ( x ) and t h e s t a n d a r d d e v i a t i o n ( S ) o f t h e mean r e c o v e r y . These d a t a can be used t o e s t a b l i s h t h e upper and l o w e r c o n t r o l l i m i t s as f o l l o w s : UPPER CONTROL LIMIT = x t 3s LOWER CONTROL LIMIT = x - 3s

The o p t i o n a l c o n t r o l l i m i t s must be equal t o o r b e t t e r t h a n t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%. A f t e r each f i v e t o t e n new r e c o v e r y measurements, new c o n t r o l l i m i t s can be c a l c u l a t e d u s i n g o n l y t h e most r e c e n t 20-30 d a t a p o i n t s . A l s o , t h e s t a n d a r d d e v i a t i o n ( S ) d a t a s h o u l d be used t o e s t a b l i s h e d an on-going p r e c i s i o n statement f o r t h e l e v e l of c o n c e n t r a t i o n s i n c l u d e d i n t h e LFB. These d a t a must be k e p t on f i l e and be a v a i l a b l e f o r r e v i e w . 9.3.4

I n s t r u m e n t Performance Check S o l u t i o n ( I P C ) -- F o r a l l d e t e r m i n a t i o n s t h e l a b o r a t o r y must a n a l y z e t h e I P C ( a midrange check s t a n d a r d ) and a c a l i b r a t i o n b l a n k immediately f o l l o w i n g d a i l y c a l i b r a t i o n , a f t e r e v e r y t e n t h sample ( o r more f r e q u e n t l y , if r e q u i r e d ) and a t t h e end o f t h e sample r u n . A n a l y s i s o f t h e I P C s o l u t i o n and c a l i b r a t i o n b l a n k i m m e d i a t e l y f o l l o w i n g c a l i b r a t i o n must v e r i f y t h a t t h e i n s t r u m e n t i s w i t h i n k 10% o f c a l i b r a t i o n . Subsequent analyses o f t h e IPC s o l u t i o n must v e r i f y t h e c a l i b r a t i o n i s

442

Methods for the Determination s t i l l w i t h i n f 10%. I f t h e C a l i b r a t i o n cannot be v e r i f i e d w i t h i n the s p e c i f i e d l i m i t s , reanalyze the IPC solution. If t h e second a n a l y s i s o f t h e I P C s o l u t i o n c o n f i r m s c a l l b r a t l o n t o be o u t s i d e t h e l i m i t s , sample a n a l y s i s must be d i s c o n t i n u e d , t h e cause d e t e r m i n e d and/or i n t h e case of d r i f t , t h e i n s t r u m e n t r e c a l i b r a t e d . A l l samples f o l l o w i n g t h e l a s t a c c e p t a b l e I P C s o l u t i o n must be r e a n a l y z e d . The a n a l y s i s d a t a o f t h e c a l i b r a t i o n b l a n k and I P C s o l u t i o n must be k e p t on f i l e w i t h t h e sample analyses d a t a .

9.4

ASSESSING ANALYTE RECOVERY AND DATA QUALITY

9.4.1

L a b o r a t o r y F o r t i f i e d Sample M a t r i x (LFM) -- The l a b o r a t o r y must add a known amount o f a n a l y t e t o a minimum o f 10% o f t h e r o u t i n e samples. I n each case t h e LFM a l i q u o t must be a d u p l i c a t e o f t h e a l i q u o t used f o r sample a n a l y s i s . The a n a l y t e c o n c e n t r a t i o n must be h i g h enough t o be d e t e c t e d above t h e o r i g i n a l sample and s h o u l d n o t be l e s s t h a n f o u r t i m e s t h e MDL. The added a n a l y t e c o n c e n t r a t i o n s h o u l d be t h e same as t h a t used i n t h e l a b o r a t o r y f o r t i f i e d b l a n k .

9.4.2

C a l c u l a t e t h e p e r c e n t r e c o v e r y f o r each a n a l y t e , c o r r e c t e d f o r c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o t h e d e s i g n a t e d LFM r e c o v e r y range 90-110%. Percent r e c o v e r y may be c a l c u l a t e u s i n g t h e f o l l o w i n g equation:

R = c, - c

x 100

S

where,

R C, C s

= = = =

percent recovery. f o r t i f i e d sample c o n c e n t r a t i o n . sample background c o n c e n t r a t i o n . c o n c e n t r a t i o n e q u i v a l e n t o f a n a l y t e added t o sampl e.

9.4.3

I f t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e d e s i g n a t e d LFM r e c o v e r y range and t h e l a b o r a t o r y performance f o r t h a t a n a l y t e i s shown t o be i n c o n t r o l ( S e c t . 9 . 3 ) , t h e r e c o v e r y problem encountered w i t h t h e LFM i s judged t o be e i t h e r m a t r i x o r s o l u t i o n r e l a t e d , n o t system r e l a t e d .

9.4.4

Where r e f e r e n c e m a t e r i a1 s a r e a v a i 1a b l e , t h e y s h o u l d be analyzed t o p r o v i d e a d d i t i o n a l performance d a t a . The a n a l y s i s o f r e f e r e n c e samples i s a v a l u a b l e t o o l f o r d e m o n s t r a t i n g t h e a b i l i t y t o p e r f o r m t h e method a c c e p t a b l y .

Inorganic Substances

443

10.0 CALIBRATION AND STANDARDIZATION 10.1 Prepare a s e r i e s o f a t l e a s t 3 standards, c o v e r i n g t h e d e s i r e d range, and a b l a n k by d i l u t i n g s u i t a b l e volumes o f s t a n d a r d s o l u t i o n s (7.12, 7.13) t o 100 mL w i t h r e a g e n t w a t e r .

10.2 Process standards and b l a n k s as d e s c r i b e d i n Sect. 11, Procedure. 10.3 Set up m a n i f o l d as shown i n F i g u r e 1.

10.4 Prepare f l o w system as d e s c r i b e d i n Sect. 11, Procedure. 10.5 Place a p p r o p r i a t e standards i n t h e sampler i n o r d e r o f d e c r e a s i n g c o n c e n t r a t i o n and p e r f o r m a n a l y s i s . 10.6 Prepare s t a n d a r d c u r v e by p l o t t i n g i n s t r u m e n t response a g a i n s t c o n c e n t r a t i o n v a l u e s . A c a l i b r a t i o n c u r v e may be f i t t e d t o t h e c a l ib r a t i o n s o l u t i o n s c o n c e n t r a t i o n / r e s p o n s e d a t a u s i n g computer o r c a l c u l a t o r based r e g r e s s i o n c u r v e f i t t i n g t e c h n i q u e s . Acceptance o r c o n t r o l l i m i t s s h o u l d be e s t a b l i s h e d u s i n g t h e d i f f e r e n c e between t h e measured v a l u e o f t h e c a l i b r a t i o n s o l u t i o n and t h e " t r u e v a l u e " concentration. 10.7 A f t e r t h e c a l i b r a t i o n has been e s t a b l i s h e d , i t must be v e r i f i e d by t h e a n a l y s i s o f a s u i t a b l e Q C S . I f measurements exceed f 10% o f t h e e s t a b l i s h e d QCS value, t h e a n a l y s i s s h o u l d be t e r m i n a t e d and t h e i n s t r u m e n t r e c a l i b r a t e d . The new c a l i b r a t i o n must be v e r i f i e d b e f o r e c o n t i n u i n g a n a l y s i s . P e r i o d i c r e a n a l y s i s o f t h e QCS i s recommended as a c o n t i n u i n g c a l i b r a t i o n check.

11.0 PROCEDURE 11.1 P r e p a r a t i o n o f equipment: Add 500 mL o f r e a g e n t w a t e r t o an 800-mL K j e l d a h l f l a s k . The a d d i t i o n o f b o i l i n g c h i p s t h a t have been p r e v i o u s l y t r e a t e d w i t h d i l u t e NaOH w i l l p r e v e n t bumping. Steam o u t t h e d i s t i l l a t i o n apparatus u n t i l t h e d i s t i l l a t e shows no t r a c e o f ammon ia. 11.2 Sample p r e p a r a t i o n : Remove t h e r e s i d u a l c h o r i n e i n t h e sample by adding d e c h l o r i n a t i n g agent (7.5) e q u i v a l e n t t o t h e c h l o r i n e r e s i d u a l . To 400 mL o f sample add 1 N NaOH ( 7 . 4 ) , u n t i l t h e pH i s 9.5, check t h e pH d u r i n g a d d i t i o n w i t h a pH m e t e r o r by use o f a s h o r t r a n g e pH paper. 11.3 D i s t i l l a t i o n : T r a n s f e r t h e sample, t h e pH o f w h i c h has been a d j u s t e d t o 9.5, t o an 800-mL K j e l d a h l f l a s k and add 25 mL o f t h e b o r a t e b u f f e r (7.3). D i s t i l l 300 mL a t t h e r a t e o f 6-10 mL/min. i n t o 50 mL o f 2% b o r i c a c i d (7.2) c o n t a i n e d i n a 500-mL Erlenmeyer flask. NOTE 4: The condenser t i p o r an e x t e n s i o n o f t h e condenser t i p must extend below t h e l e v e l o f t h e b o r i c a c i d s o l u t i o n .

444

Methods for the Determination 11.4 Since t h e i n t e n s i t y o f t h e c o l o r used t o q u a n t i f y t h e c o n c e n t r a t i o n i s pH dependent, t h e a c i d c o n c e n t r a t i o n o f t h e wash w a t e r and t h e standard ammonia s o l u t i o n s should approximate t h a t o f t h e samples. 11.5 A l l o w a n a l y s i s system t o warm up as r e q u i r e d . t h r o u g h sample 1 i n e .

Feed wash w a t e r

11.6 Arrange ammonia standards i n sampler i n o r d e r o f d e c r e a s i n g c o n c e n t r a t i o n o f n i t r o g e n . Complete l o a d i n g o f sampler t r a y w i t h unknown samples. 11.7 S w i t c h sample l i n e f r o m r e a g e n t w a t e r t o sampler and b e g i n a n a l y s i s .

12.0 DATA ANALYSIS AND CALCULATIONS 12.1 Prepare a c a l i b r a t i o n c u r v e by p l o t t i n g i n s t r u m e n t response a g a i n s t s t a n d a r d c o n c e n t r a t i o n . Compute sample c o n c e n t r a t i o n by comparing sample response w i t h t h e s t a n d a r d curve. Mu1t i p l y answer by a p p r o p r i a t e d i l u t i o n f a c t o r . 12.2 Report o n l y t h o s e v a l u e s t h a t f a l l between t h e l o w e s t and t h e h i g h e s t c a l i b r a t i o n standards. Samples exceeding t h e h i g h e s t s t a n d a r d s h o u l d be d i l u t e d and r e a n a l y z e d . 12.3 Report r e s u l t s i n mg NH,-N/t. 13.0 METHOD PERFORMANCE 13.1 I n a s i n g l e l a b o r a t o r y (EMSL-Cincinnati), u s i n g s u r f a c e w a t e r samples a t c o n c e n t r a t i o n s o f 1.41, 0.77, 0.59 and 0.43 mg NH,-N/L, t h e s t a n d a r d d e v i a t i o n was f 0.005. 13.2 I n a s i n g l e l a b o r a t o r y (EMSL-Cincinnati), u s i n g s u r f a c e w a t e r recoveries samples a t c o n c e n t r a t i o n s o f 0.16 and 1.44 mg NH,-N/L, were 107% and 99%, r e s p e c t i v e l y . 13.3 The i n t e r l a b o r a t o r y p r e c i s i o n and accuracy d a t a i n T a b l e 1 were developed u s i n g a r e a g e n t w a t e r m a t r i x . Values a r e i n mg NH,-N/L.

14.0 POLLUTION PREVENTION 14.1 P o l l u t i o n p r e v e n t i o n encompasses any t e c h n i q u e t h a t reduces o r e l i m i n a t e s t h e q u a n t i t y o r t o x i c i t y o f waste a t t h e p o i n t o f g e n e r a t i o n . Numerous o p p o r t u n i t i e s f o r p o l l u t i o n p r e v e n t i o n e x i s t i n l a b o r a t o r y o p e r a t i o n . The EPA has e s t a b l i s h e d a p r e f e r r e d h i e r a r c h y o f environmental management t e c h n i q u e s t h a t p l a c e s p o l l u t i o n p r e v e n t i o n as t h e management o p t i o n o f f i r s t c h o i c e , Whenever f e a s i b l e , l a b o r a t o r y personnel s h o u l d use p o l l u t i o n p r e v e n t i o n t e c h n i q u e s t o address t h e i r waste g e n e r a t i o n . When wastes cannot be f e a s i b l y reduced a t t h e source, t h e Agency recommends r e c y c l i n g as t h e n e x t b e s t o p t i o n .

Inorganic Substances

445

14.2 The quantity of chemicals purchased should be based on expected

usage during its shelf life and disposal cost of unused material. Actual reagent preparation volumes should reflect anticipated usage and reagent stability. 14.3 For information about pollution prevention that may be applicable to

laboratories and research institutions, consult "Less is Better: Laboratory Chemical Management for Waste Reduction," available from the American Chemical Society's Department of Government Regulations and Science Policy, 1155 16th Street N.W., Washington D.C. 20036, (202)872-4477. 15.0 WASTE MANAGEMENT 15.1 The U.S.

Environmental Protection Agency requires that laboratory waste management practices be conducted consistent with all applicable rules and regulations. Excess reagents, samples and method process wastes should be characterized and disposed o f in an acceptable manner. The Agency urges laboratories to protect the air, water and land by minimizing and controlling all releases from hoods, and bench operations, complying with the letter and spirit of any waste discharge permit and regulations, and by complying with all solid and hazardous waste regulations, particularly the hazardous waste identification rules and land disposal restrictions. For further information on waste management consult the "Waste Management Manual for Laboratory Personnel available from the American Chemical Society at the address listed in Sect. ,I'

14.3. 16.0 REFERENCES

1.

Hiller, A., and Van Slyke, D., "Determination of Ammonia in Blood," J . Biol. Chem. 102, p. 499 (1933).

2.

O'Connor, B., Dobbs, R., Villiers, B . , and Dean. R., "Laboratory Distillation of Municipal Waste Effluents," JWPCF 3,R 25 (1967).

3.

Fiore, J . , and O'Brien, J.E., "Ammonia Determination by Automatic Analysis," Wastes Engineering 33, p. 352 (1962).

4.

A Wetting Agent Recommended and Supplied by the Technicon Corporation for Use in AutoAnalyzers.

5.

ASTM "Manual on Industrial Water and Industrial Waste Water," 2nd Ed., 1966 printing, p. 418.

6.

Booth, R.L., and Lobring. L.B., "Evaluation of the AutoAnalyzer 11: A Progress Report" in Advances in Automated Analysis: 1972 Technicon International Congress, Vol. 8, p. 7-10, Mediad Incorporated, Tarrytown, N . Y . , (1973).

446

Methods for the Determination 7.

Standards Methods f o r t h e Examination o f Water and Wastewater, 1 8 t h E d i t i o n , p . 4-77, Methods 4500 NH3 B and H (1992).

8.

Annual Book o f ASTM Standards, P a r t 31, "Water," Standard D142679(C).

9.

Code o f F e d e r a l R e g u l a t i o n s 40, Ch. 1, P t . 136, Appendix B.

Inorganic Substances

447

17.0 TABLES, DIAGRAMS, FLOWCHARTS. AND VALIDATION DATA

TABLE 1.

NUMBER OF VALUES REPORT ED

i

1 1 1 1

INTERLABORATORY P R E C I S I O N AND ACCURACY DATA

TRUE VALUE (T)

MEAN (X)

RESIDUAL FOR X

STANDARD DEVIATION

(S)

RESIDUAL FOR S

134

0.270

0.2670

-0.001 1

0.0342

157

0.692

0.6972

0.0059

0.0476

136

1.20

1.2008

0.0001

0.0698

-0.0112

195

1.60

1.6095

0.0076

0.1023

0.0006

142

3.00

3.0128

0.1677

-0.0067

159

3.50

3.4991

0.2168

0.0165

156

3.60

3.5955

-0.0122

0.1821

-0.0234

200

4.20

4.2271

0.0177

0.2855

0.0488

196

8.76

a. 7257

-0.0568

0.4606

-0.0127

I I

0.0069 -0.0083

I I

156

11.0

11.0747

0.0457

0.5401

-0.0495

142

13.0

12.9883

-0.0465

0.6961

0.0027

199

18.0

17.9727

-0.0765

1.1635

0.2106

REGRESSIONS:

X

=

1.003T - 0.003,

S = 0.052T t 0.019

I 1 1 1 1

WASE HEATING BATH 50°C

rnlhnin

20 TURNS

20 TURNS

TO F/C PUMP TUBE

COLORlM€TER 650-660nm 50rnm F/C

WASTE

1.60

FROM FK:

PUMP 'SCRUBBED THROUGH 5N

60 PER HOUR SAMPLE 51 SEC. WASH 9 SEC.

Figure 1 Ammonia Manifold

y SQ

Inorganic Substances METHOD 351.2 DETERMINATION OF TOTAL KJELDAHL NITROGEN BY SEMI-AUTOMATED COLORIMETRY

Edited by James W. O'Dell Inorganic Chemistry Branch Chemistry Research D i v i s i o n

Revision 2.0 August 1993

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

449

450

Methods for the Determination METHOD 3 5 1 . 2 DETERMINATION OF TOTAL KJELDAHL NITROGEN BY SEMI-AUTOMATED COLORIMETRY

1.0

2.0

3.0

SCOPE AND APPLICATION 1.1

T h i s method c o v e r s t h e d e t e r m i n a t i o n o f t o t a l K j e l d a h l n i t r o g e n i n d r i n k i n g , ground, and s u r f a c e waters, domestic and i n d u s t r i a l wastes. The procedure c o n v e r t s n i t r o g e n components o f b i o l o g i c a l o r i g i n such as amino a c i d s , p r o t e i n s and p e p t i d e s t o ammonia, b u t may n o t c o n v e r t t h e n i t r o g e n o u s compounds o f some i n d u s t r i a l wastes such as amines, n i t r o compounds, hydrazones, oximes, semicarbazones and some r e f r a c t o r y t e r t i a r y amines.

1.2

The a p p l i c a b l e r a n g e i s 0.1 t o 20 mg/L TKN. extended w i t h sample d i l u t i o n .

The range may be

SUMMARY OF METHOD

2.1

The sample i s heated i n t h e presence o f s u l f u r i c a c i d , H SO f o r two and and one h a l f hours. The r e s i d u e i s cooled, d i l u t e d t o 25 analyzed f o r ammonia. T h i s d i g e s t e d sample may a l s o be used f o r phosphorus d e t e r m i n a t i o n .

2.2

T o t a l K j e l d a h l n i t r o g e n i s t h e sum o f free-ammonia and o r g a n i c n i t r o g e n compounds which a r e c o n v e r t e d t o ammonium s u l f a t e (NH,),SO,, under t h e c o n d i t i o n s o f d i g e s t i o n d e s c r i b e d .

2.3

Organic K j e l d a h l n i t r o g e n i s t h e d i f f e r e n c e o b t a i n e d by s u b t r a c t i n g t h e free-ammonia v a l u e f r o m t h e t o t a l K j e l d a h l n i t r o g e n v a l u e .

2.4

Reduced volume v e r s i o n s o f t h i s method t h a t use t h e same r e a g e n t s and m o l a r r a t i o s a r e a c c e p t a b l e p r o v i d e d t h e y meet t h e q u a l i t y c o n t r o l and performance r e q u i r e m e n t s s t a t e d i n t h e method.

2.5

L i m i t e d performance-based method m o d i f i c a t i o n s may be a c c e p t a b l e p r o v i d e d t h e y a r e f u l l y documented and meet o r exceed r e q u i r e m e n t s expressed i n Sect. 9.0, Q u a l i t y C o n t r o l .

mi

DEFINITIONS

3.1

CALIBRATION BLANK (CB) -- A volume o f r e a g e n t w a t e r f o r t i f i e d w i t h t h e same m a t r i x as t h e c a l i b r a t i o n standards, b u t w i t h o u t t h e a n a l y t e s , i n t e r n a l standards, o r s u r r o g a t e a n a l y t e s .

3.2

CALIBRATION STANDARD (CAL) -- A s o l u t i o n p r e p a r e d f r o m t h e p r i m a r y d i l u t i o n s t a n d a r d s o l u t i o n o r s t o c k s t a n d a r d s o l u t i o n s and t h e i n t e r n a l standards and s u r r o g a t e a n a l y t e s . The CAL s o l u t i o n s a r e used t o c a l i b r a t e t h e i n s t r u m e n t response w i t h r e s p e c t t o a n a l y t e concentration.

Inorganic Substances

451

3.3

INSTRUMENT PERFORMANCE CHECK SOLUTION (IPC) - - A s o l u t i o n o f one o r more method a n a l y t e s , s u r r o g a t e s , i n t e r n a l standards, o r o t h e r t e s t substances used t o e v a l u a t e t h e performance of t h e i n s t r u m e n t system with respect t o a defined set o f c r i t e r i a .

3.4

LABORATORY FORTIFIED BLANK (LFB) -- An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e methodology i s i n c o n t r o l , and whether t h e l a b o r a t o r y i s capable o f making a c c u r a t e and p r e c i s e measurements.

3.5

LABORATORY FORTIFIED SAMPLE MATRIX (LFM) -- An a l i q u o t o f an e n v i r o n m e n t a l sample t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFM i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e sample m a t r i x c o n t r i b u t e s b i a s t o t h e a n a l y t i c a l r e s u l t s . The background c o n c e n t r a t i o n s of t h e a n a l y t e s i n t h e sample m a t r i x must be determined i n a s e p a r a t e a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s .

3.6

LABORATORY REAGENT BLANK (LRB) -- An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a l l glassware, equipment, s o l v e n t s , r e a g e n t s , i n t e r n a l standards, and s u r r o g a t e s t h a t a r e used w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e l a b o r a t o r y environment, t h e r e a g e n t s , o r t h e apparatus.

3.7

LINEAR CALIBRATION RANGE (LCR) -- The c o n c e n t r a t i o n range o v e r which t h e i n s t r u m e n t response i s l i n e a r .

-- W r i t t e n i n f o r m a t i o n p r o v i d e d by vendors c o n c e r n i n g a c h e m i c a l ' s t o x i c i t y , h e a l t h hazards, p h y s i c a l p r o p e r t i e s , f i r e , and r e a c t i v i t y d a t a i n c l u d i n g s t o r a g e , s p i l l , and hand1 i n g p r e c a u t i o n s .

3.8 MATERIAt SAFETY DATA SHEET (MSDS)

3.9

METHOD DETECTION LIMIT (MDL) -- The minimum c o n c e n t r a t i o n o f an a n a l y t e t h a t can be i d e n t i f i e d , measured and r e p o r t e d w i t h 99% c o n f i d e n c e t h a t t h e a n a l y t e c o n c e n t r a t i o n i s g r e a t e r t h a n zero.

3.10 QUALITY CONTROL SAMPLE (QCS) -- A s o l u t i o n o f method a n a l y t e s o f known c o n c e n t r a t i o n s t h a t i s used t o f o r t i f y an a l i q u o t o f LRB o r sample m a t r i x . The QCS i s o b t a i n e d f r o m a source e x t e r n a l t o t h e l a b o r a t o r y and d i f f e r e n t f r o m t h e source o f c a l i b r a t i o n standards. It i s used t o check l a b o r a t o r y performance w i t h e x t e r n a l l y prepared t e s t materials. 3.11 STOCK STANDARD SOLUTION (SSS) -- A c o n c e n t r a t e d s o l u t i o n c o n t a i n i n g one o r more method a n a l y t e s p r e p a r e d i n t h e l a b o r a t o r y u s i n g assayed r e f e r e n c e m a t e r i a l s o r purchased f r o m a r e p u t a b l e commercial source.

452

Methods for the Determination

4.0

INTERFERENCES

5.0

6.0

4.1

H i g h n i t r a t e c o n c e n t r a t i o n s (1OX o r more t h a n t h e TKN l e v e l ) r e s u l t i n l o w TKN v a l u e s . I f i n t e r f e r e n c e i s suspected, samples s h o u l d be d i l u t e d and r e a n a l y z e d .

4.2

Method i n t e r f e r e n c e s may be caused by contaminants i n t h e r e a g e n t w a t e r , r e a g e n t s , glassware, and o t h e r sample p r o c e s s i n g apparatus t h a t b i a s a n a l y t e response.

SAFETY 5.1

The t o x i c i t y o r c a r c i n o g e n i c i t y o f each r e a g e n t used i n t h i s method have n o t been f u l l y e s t a b l i s h e d . Each chemical s h o u l d be r e g a r d e d as a p o t e n t i a l h e a l t h hazard and exposure s h o u l d be as l o w as r e a s o n a b l y a c h i e v a b l e . C a u t i o n s a r e i n c l u d e d f o r known e x t r e m e l y hazardous m a t e r i a l s o r procedures.

5.2

Each l a b o r a t o r y i s r e s p o n s i b l e f o r m a i n t a i n i n g a c u r r e n t f i l e o f OSHA r e g u l a t i o n s r e g a r d i n g t h e s a f e h a n d l i n g o f chemicals s p e c i f i e d i n t h i s method. A r e f e r e n c e f i l e o f S a f e t y Data Sheets (MSDS) should be made a v a i l a b l e t o a1 i n v o l v e d i n t h e chemical a n a l y s i s . The p r e p a r a t i o n o f a safety plan i s a l s o advisable.

5.3

The f o l l o w i n g c h e m i c a l s have t h e p o t e n t i a l t o be h i g h l y t o x i c o r hazardous, c o n s u l t MSDS. 5.3.1

Mercury ( 7 . 2 , 7 . 3 )

5.3.2

Sulfuric acid (7.2, 7.3, 7.4)

5.3.3

Sodium n i t r o p r u s s i d e ( 7 . 9 )

awareness he M a t e r i a1 personnel formal

EQUIPMENT AND SUPPLIES

6.1

Balance - A n a l y t i c a l , capable o f a c c u r a t e l y w e i g h i n g t o t h e n e a r e s t 0.0001 g.

6.2

Glassware - C l a s s A v o l u m e t r i c f l a s k s and p i p e t s as r e q u i r e d

6.3

B l o c k d i g e s t o r w i t h tubes.

6.4

Automated c o n t i n u o u s f l o w a n a l y s i s equipment des gned t o d e l v e r and r e a c t sample and r e a g e n t s i n t h e r e q u i r e d o r d e r and r a t i o s . 6.4.1

Sampl ing d e v i c e (sampl e r )

6.4.2

M u l t i c h a n n e l pump

6.4.3

Reaction u n i t o r manifold

Inorganic Substances

7.0

6.4.4

Colorimetric detector

6.4.5

Data r e c o r d i n g d e v i c e

453

PEAGENTS AND STANDARDS 7.1

Reagent w a t e r : the analyte o f

7.2

M e r c u r i c s u l f a t e : D i s s o l v e 8 g r e d m e r c u r i c o x i d e (HgO) (CASRN 21908-53-2) i n 50 mL o f 1:4 s u l f u r i c a c i d (10 m L conc. H SO,,: [CASRN 7664-93-91 40 mL r e a g e n t w a t e r ) and d i l u t e t o 100 mL w i t k r e a g e n t water.

7.3

Digestion s o l u t i o n : ( S u l f u r i c acid-mercuric sulfate-potassium s u l f a t e s o l u t i o n ) : D i s s o l v e 133 g o f K,SO (CASRN 7778-80-5) i n 700 mL o f r e a g e n t w a t e r and 200 mL o f conc. H,tO,,. Add 25 mL o f m e r c u r i c s u l f a t e s o l u t i o n (7.1) and d i l u t e t o 1 L.

Ammonia f r e e d i s t i l l e d o r d e i o n i z e d water, f r e e o f i n t e r e s t . ASTM t y p e I 1 o r e q u i v a l e n t .

NOTE 1: An a l t e r n a t e m e r c u r y - f r e e d i g e s t i o n s o l u t i o n can be p r e p a r e d by d i s s o l v i n g 134 g K,SO,, and 7.3 g CuSO i n 800 mL r e a g e n t and d i l u t i n g t o 1 L. Use w a t e r and t h e n adding 134 mL conc. H,SO,, 10 mL s o l u t i o n p e r 25 mL o f sample. 7.4

S u l f u r i c A c i d s o l u t i o n (4%): Add 40 mL o f conc. s u l f u r i c a c i d t o 800 mL o f r e a g e n t w a t e r , c o o l and d i l u t e t o 1 L. NOTE 2: I f a l t e r n a t e mercury-free d i g e s t i o n s o l u t i o n i s used, a d j u s t t h e above s o l u t i o n t o equal t h e a c i d c o n c e n t r a t i o n o f t h e d i g e s t e d sample ( 1 1 . 6 ) .

7.5

S t o c k Sodium H y d r o x i d e (20%): D i s s o l v e 200 g o f sodium h y d r o x i d e (CASRN 1310-73-2) i n 900 mL o f r e a g e n t w a t e r and d i l u t e t o 1 L.

7.6

S t o c k Sodium Potassium T a r t r a t e s o l u t i o n (20%): D i s s o l v e 200 g sodium potassium t a r t r a t e (CASRN 6381-59-5) i n about 800 mL o f r e a g e n t w a t e r and d i l u t e t o 1 L.

7.7

S t o c k B u f f e r s o l u t i o n : D i s s o l v e 134.0 g o f sodium phosphate, d i b a s i c (Na,HPO,) (CASRN 7558-79-4) i n about 800 mL o f r e a g e n t w a t e r . Add 20 g o f sodium h y d r o x i d e and d i l u t e t o 1 L.

7.8

Working B u f f e r s o l u t i o n : Combine t h e r e a g e n t s i n t h e s t a t e d o r d e r , add 250 mL o f s t o c k sodium p o t a s s i u m t a r t r a t e s o l u t i o n (7.6) t o 200 mL o f s t o c k b u f f e r s o l u t i o n (7.7) and mix. Add xx mL sodium h y d r o x i d e s o l u t i o n (7.5) and d i l u t e t o 1 L . See c o n c e n t r a t i o n ranges, Table 2, f o r c o m p o s i t i o n o f w o r k i n g b u f f e r .

7.9

Sodium S a l i c y l a t e l S o d i u m N i t r o p r u s s i d e s o l u t i o n : D i s s o l v e 150 g of sodium s a l i c y l a t e (CASRN 54-21-7) and 0.3 g o f sodium n i t r o p r u s s i d e (CASRN 13755-38-9 o r 14402-89-2) i n about 600 mL of r e a g e n t w a t e r and d i l u t e t o 1 L.

454

Methods for the Determination 7.10 Sodium H y p o c h l o r i t e s o l u t i o n : D i l u t e 6 . 0 mL sodium h y p o c h l o r i t e s o l u t i o n (CASRN 7681-52-9) ( C l o r o x ) t o 100 mL w i t h r e a g e n t w a t e r . 7.11 Ammonium c h l o r i d e , s t o c k s o l u t i o n : D i s s o l v e 3.819 g NH4C1 (CASRN 12125-02-9) i n r e a g e n t w a t e r and b r i n g t o volume i n a 1 L v o l u m e t r i c f l a s k . 1 mL = 1.0 mg NH,-N. 7.12 T e f l o n b o i l i n g c h i p s .

8.0

9.0

SAMPLE COLLECTION, PRESERVATION AND STORAGE

8.1

Samples s h o u l d be c o l l e c t e d i n p l a s t i c o r g l a s s b o t t l e s . A l l b o t t l e s must be t h o r o u g h l y c l e a n e d and r i n s e d w i t h r e a g e n t w a t e r . Volume c o l l e c t e d s h o u l d be s u f f i c i e n t t o i n s u r e a r e p r e s e n t a t i v e sample, a l l o w f o r r e p l i c a t e a n a l y s i s ( i f r e q u i r e d ) , and m i n i m i z e waste d i s p o s a l .

8.2

Samples must be p r e s e r v e d w i t h H,S04 t o a pH a t the time o f collection.

8.3

Samples s h o u l d be analyzed as soon as p o s s i b l e a f t e r c o l l e c t i o n . I f s t o r a g e i s r e q u i r e d , p r e s e r v e d samples a r e m a i n t a i n e d a t 4 ° C and may be h e l d f o r up t o 28 days.

< 2 and c o o l e d t o 4 ° C

QUALITY CONTROL 9.1

Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a f o r m a l q u a l i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f t h i s program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y , and t h e p e r i o d i c a n a l y s i s o f l a b o r a t o r y r e a g e n t blanks, f o r t i f i e d b l a n k s and o t h e r l a b o r a t o r y s o l u t i o n s as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n p e r formance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f t h e d a t a t h a t a r e generated.

9.2

I N I T I A L DEMONSTRATION OF PERFORMANCE 9.2.1

The i n i t i a l d e m o n s t r a t i o n o f performance is used t o c h a r a c t e r i z e i n s t r u m e n t performance ( d e t e r m i n a t i o n o f l i n e a r c a l i b r a t i o n ranges and a n a l y s i s o f QCS) and l a b o r a t o r y performance ( d e t e r m i n a t i o n o f MDLs) p r i o r t o p e r f o r m i n g analyses by t h i s method.

9.2.2

L i n e a r C a l i b r a t i o n Range (LCR) -- The LCR must be determined i n i t i a l l y and v e r i f i e d e v e r y 6 months o r whenever a s i g n i f i c a n t change i n i n s t r u m e n t response i s observed o r expected. The i n i t i a l d e m o n s t r a t i o n o f l i n e a r i t y must use s u f f i c i e n t standards t o i n s u r e t h a t t h e r e s u l t i n g c u r v e i s l i n e a r . The v e r i f i c a t i o n o f l i n e a r i t y must use a minimum o f a b l a n k and t h r e e s t a n d a r d s . I f any v e r i f i c a t i o n d a t a exceeds t h e i n i t i a l v a l u e s b y & lo%, l i n e a r i t y must be r e e s t a b l i s h e d . I f any p o r t i o n o f t h e range i s shown t o be

Inorganic Substances

455

non i n e a r , s u f f i c i e n t standards must be used t o c l e a r l y d e f ne t h e n o n l i n e a r p o r t i o n . 9.2.3

Qua i t y C o n t r o l Sample (QCS) -- When b e g i n n i n g t h e use o f t h i s method, on a q u a r t e r l y b a s i s , o r as r e q u i r e d t o meet d a t a - q u a l i t y needs, v e r i f y t h e c a l i b r a t i o n standards and a c c e p t a b l e i n s t r u m e n t performance w i t h t h e p r e p a r a t i o n and analyses o f a QCS. I f t h e determined c o n c e n t r a t i o n s a r e n o t w i t h i n f 10% o f t h e s t a t e d values, performance o f t h e d e t e r m i n a t i v e s t e p o f t h e method i s unacceptable. The source o f t h e problem must be i d e n t i f i e d and c o r r e c t e d before e i t h e r proceeding w i t h the i n i t i a l determination o f MDLs o r c o n t i n u i n g w i t h on-going analyses.

9.2.4

Method D e t e c t i o n L i m i t (MDL) -- MDLs must be e s t a b l i s h e d f o r a l l analytes, using reagent water (blank) f o r t i f i e d a t a c o n c e n t r a t i o n o f two t o t h r e e t i m e s t h e e s t i m a t e d i n s t r u m e n t detection limit.'6' To d e t e r m i n e MDL values, t a k e seven r e p l i c a t e a l i q u o t s o f t h e f o r t i f i e d r e a g e n t w a t e r and process t h r o u g h t h e e n t i r e a n a l y t i c a l method. P e r f o r m a l l c a l c u l a t i o n s d e f i n e d i n t h e method and r e p o r t t h e concentration values i n t h e appropriate u n i t s . Calculate t h e MDL as f o l l o w s : MDL = ( t ) x ( S ) where, t = S t u d e n t ' s t v a l u e f o r a 99% c o n f i d e n c e l e v e l and a s t a n d a r d d e v i a t i o n e s t i m a t e w i t h n - 1 degrees o f freedom [ t = 3.14 f o r seven r e p l i c a t e s ] . S = s t a n d a r d d e v i a t i o n o f t h e r e p l i c a t e analyses.

MDLs s h o u l d be determined e v e r y s i x months, when a new o p e r a t o r b e g i n s work, o r whenever t h e r e i s a s i g n i f i c a n t change i n t h e background o r i n s t r u m e n t response. 9.3

ASSESSING LABORATORY PERFORMANCE

9.3.1

L a b o r a t o r y Reagent B l a n k (LRB) -- The l a b o r a t o r y must a n a l y z e a t l e a s t one LRB w i t h each b a t c h o f samples. Data produced a r e used t o assess c o n t a m i n a t i o n f r o m t h e l a b o r a t o r y environment. Values t h a t exceed t h e MDL i n d i c a t e l a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n s h o u l d be suspected and c o r r e c t i v e a c t i o n s must be t a k e n b e f o r e c o n t i n u i n g t h e analysis.

9.3.2

L a b o r a t o r y F o r t i f i e d B1 ank (LFB) -- The 1a b o r a t o r y must a n a l y z e a t l e a s t one LFB w i t h each b a t c h o f samples. C a l c u l a t e accuracy as p e r c e n t r e c o v e r y ( S e c t . 9.4.2). If t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%, t h a t a n a l y t e i s judged o u t o f

456

Methods for the Determination c o n t r o l , and t h e source of t h e problem should be i d e n t i f i e d and resolved before continuing a n a l y s e s . 9.3.3

The l a b o r a t o r y must use LFB a n a l y s e s d a t a t o a s s e s s l a b o r a t o r y performance a g a i n s t the r e q u i r e d c o n t r o l l i m i t s of 90-110%. When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e ( u s u a l l y a minimum of 20-30 a n a l y s e s ) , o p t i o n a l c o n t r o l l i m i t s can be developed from the p e r c e n t mean recovery ( x ) and t h e standard d e v i a t i o n ( S ) of t h e mean recovery. These d a t a can be used t o e s t a b l i s h the upper and lower c o n t r o l l i m i t s a s follows: UPPER CONTROL LIMIT LOWER CONTROL LIMIT

= =

x x

t -

3s 3s

The oDtional c o n t r o l l i m i t s must be equal t o o r b e t t e r than t h e r e q u i r e d c o n t r o l l i m i t s of 90-110%. A f t e r each f i v e t o t e n new recovery measurements, new c o n t r o l l i m i t s can be c a l c u l a t e d using only the most r e c e n t 20-30 d a t a p o i n t s . Also, the s t a n d a r d d e v i a t i o n ( S ) d a t a should be used t o e s t a b l i s h an on-going p r e c i s i o n statement f o r t h e l e v e l o f c o n c e n t r a t i o n s included i n t h e LFB. These d a t a must be kept on f i l e and be a v a i l a b l e f o r review. 9.3.4

9.4

Instrument Performance Check S o l u t i o n (IPC) -- For a l l d e t e r m i n a t i o n s t h e l a b o r a t o r y must analyze the IPC ( a midrange check s t a n d a r d ) and a c a l i b r a t i o n blank immediately following d a i l y c a l i b r a t i o n , a f t e r every tenth sample ( o r more f r e q u e n t l y , i f r e q u i r e d ) , and a t t h e end o f the sample run. Analysis of t h e IPC s o l u t i o n and c a l i b r a t i o n blank immediately following c a l i b r a t i o n must v e r i f y t h a t the instrument i s w i t h i n k 10% of c a l i b r a t i o n . Subsequent a n a l y s e s of the IPC s o l u t i o n must v e r i f y the c a l i b r a t i o n i s s t i l l w i t h i n f 10%. I f the c a l i b r a t i o n cannot be v e r i f i e d w i t h i n the s p e c i f i e d limits, r e a n a l y z e the IPC s o l u t i o n . If the second a n a l y s i s of t h e IPC s o l u t i o n confirms c a l i b r a t i o n t o be o u t s i d e t h e l i m i t s , sample a n a l y s i s must be d i s c o n t i n u e d , the cause determined and/or i n t h e c a s e of d r i f t t h e instrument r e c a l i b r a t e d . All samples following t h e l a s t a c c e p t a b l e IPC s o l u t i o n must be reanalyzed. The a n a l y s i s d a t a of t h e c a l i b r a t i o n blank and IPC s o l u t i o n must be kept on f i l e with the sample a n a l y s e s d a t a .

ASSESSING ANALYTE RECOVERY AND DATA QUALITY 9.4.1

Laboratory F o r t i f i e d Sample Matrix (LFM) -- The l a b o r a t o r y must add a known amount of a n a l y t e t o a minimum of 10% o f t h e r o u t i n e samples. In each c a s e t h e LFM a l i q u o t must be a d u p l i c a t e of th e a l i q u o t used f o r sample a n a l y s i s . The a n a l y t e c o n c e n t r a t i o n must be high enough t o be d e t e c t e d above t h e o r i g i n a l sample and should not be l e s s than f o u r

Inorganic Substances

457

t i m e s t h e MDL. The added a n a l y t e c o n c e n t r a t i o n s h o u l d be t h e same a s t h a t used i n t h e l a b o r a t o r y f o r t i f i e d b l a n k .

9.4.2

C a l c u l a t e t h e p e r c e n t r e c o v e r y f o r each a n a l y t e , c o r r e c t e d f o r c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o t h e d e s i g n a t e d LFM r e c o v e r y range 90-11096. Percent r e c o v e r y may be c a l c u l a t e d u s i n g t h e f o l 1owing e q u a t i o n :

c,

R =

-

c

x 100

S

where, R

C, C s

percent recovery. f o r t i f i e d sample c o n c e n t r a t i o n . = sample background c o n c e n t r a t i o n . = c o n c e n t r a t i o n e q u i v a l e n t o f a n a l y t e added t o sample. =

=

9.4.3

I f t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e d e s i g n a t e d LFM r e c o v e r y range and t h e l a b o r a t o r y performance f o r t h a t a n a l y t e i s shown t o be i n c o n t r o l (Sect. 9.3), t h e r e c o v e r y problem encountered w i t h t h e LFM i s j u d g e d t o be e i t h e r m a t r i x o r s o l u t i o n r e l a t e d , n o t system r e l a t e d .

9.4.4

Where r e f e r e n c e m a t e r i a l s a r e a v a i l a b l e , t h e y s h o u l d be analyzed t o p r o v i d e a d d i t i o n a l performance d a t a . The a n a l y s i s o f r e f e r e n c e samples i s a v a l u a b l e t o o l f o r d e m o n s t r a t i n g t h e a b i l i t y t o p e r f o r m t h e method a c c e p t a b l y .

10.0 CALIBRATION AND STANDARDIZATION 10.1 Prepare a s e r i e s o f a t l e a s t 3 standards, c o v e r i n g t h e d e s i r e d range, and a b l a n k by d i l u t i n g s u i t a b l e volumes o f s t a n d a r d s o l u t i o n (7.11) w i t h r e a g e n t w a t e r . 10.2 Process s t a n d a r d s and b l a n k s as d e s c r i b e d i n Sect. 11, Procedure. 10.3 Set up m a n i f o l d as shown i n F i g u r e 1 and T a b l e 2. 10.4 Prepare f l o w system as d e s c r i b e d i n Sect. 11, Procedure.

10.5 P l a c e a p p r o p r i a t e standards i n t h e sampler i n o r d e r o f d e c r e a s i n g c o n c e n t r a t i o n and p e r f o r m a n a l y s i s . 10.6 Prepare s t a n d a r d c u r v e by p l o t t i n g i n s t r u m e n t response a g a i n s t c o n c e n t r a t i o n values. A c a l i b r a t i o n c u r v e may be f i t t e d t o t h e c a l i b r a t i o n s o l u t i o n s c o n c e n t r a t i o n / r e s p o n s e d a t a u s i n g computer o r c a l c u l a t o r based r e g r e s s i o n c u r v e f i t t i n g t e c h n i q u e s . Acceptance o r c o n t r o l l i m i t s s h o u l d be e s t a b l i s h e d u s i n g t h e d i f f e r e n c e between

458

Methods for the Determination t h e measured v a l u e o f t h e c a l i b r a t i o n s o l u t i o n and t h e " t r u e v a l u e " concentration. 10.7 A f t e r t h e c a l i b r a t i o n has been e s t a b l i s h e d , i t must be v e r i f i e d by If t h e a n a l y s i s o f a s u i t a b l e q u a l i t y c o n t r o l sample (QCS) measurements exceed f 10% o f t h e e s t a b l i s h e d QCS v a l u e , t h e a n a l y s i s should be t e r m i n a t e d and t h e i n s t r u m e n t r e c a l i b r a t e d . he new c a l i b r a t i o n must be v e r i f i e d b e f o r e c o n t i n u i n g a n a l y s i s Periodic r e a n a l y s i s o f t h e QCS i s recommended as a c o n t i n u i n g ca i b r a t i o n check.

11.0 PROCEDURE

11.1 P i p e t 25.0 mL o f sample, s t a n d a r d o r b l a n k i n t h e d i g e s t o r tube. 11.2 Add 5 mL of d i g e s t i o n s o l u t i o n (7.3) and m i x w i t h a v o r t e x m i x e r (See Note 1). 11.3 Add 4-8 T e f l o n b o i l i n g c h i p s ( 7 . 1 2 ) . CAUTION: c h i p s may cause t h e sample t o b o i l over.

An excess o f T e f l o n

11.4 Place t u b e s i n b l o c k d i g e s t o r p r e h e a t e d t o 160°C and m a i n t a i n t e m p e r a t u r e f o r 1 h. 11.5 Reset t e m p e r a t u r e t o 380°C and c o n t i n u e t o h e a t f o r one and one h a l f hour. (380°C MUST BE MAINTAINED FOR 30 MIN.) 11.6 Remove d i g e s t i o n tubes, c o o l and d i l u t e t o 25 mL w i t h r e a g e n t w a t e r . 11.7 E x c l u d i n g t h e s a l i c y l a t e l i n e , p l a c e a l l r e a g e n t l i n e s i n t h e i r r e s p e c t i v e c o n t a i n e r s , connect t h e sample probe t o t h e sampler and s t a r t t h e pump. 11.8 F l u s h t h e sampler wash r e c e p t a c l e w i t h about 25 a c i d (7.4) (See Note 2 ) .

ml o f 4% s u l f u r i c

11.9 When r e a g e n t s have been pumping f o r a t l e a s t 5 min, p l a c e t h e s a l i c y l a t e l i n e i n i t s r e s p e c t i v e c o n t a i n e r and a l l o w t h e system t o e q u i l i b r a t e . I f a p r e c i p i t a t e forms a f t e r t h e a d d i t i o n o f s a l i c y l a t e , t h e pH i s t o o low. I m m e d i a t e l y s t o p t h e p r o p o r t i o n i n g pump and f l u s h t h e c o i l s w i t h w a t e r u s i n g a s y r i n g e . B e f o r e r e s t a r t i n g t h e system, check t h e c o n c e n t r a t i o n o f t h e s u l f u r i c a c i d s o l u t i o n s and/or t h e w o r k i n g b u f f e r s o l u t i o n . 11.10 To p r e v e n t p r e c i p i t a t i o n o f sodium s a l i c y l a t e i n t h e waste t r a y , which can c l o g t h e t r a y o u t l e t , keep t h e n i t r o g e n f l o w c e l l pump t u b e and t h e n i t r o g e n C o l o r i m e t e r "TO Waste" t u b e s e p a r a t e f r o m a l l o t h e r l i n e s o r keep t a p w a t e r f l o w i n g i n t h e waste t r a y . 11.11 A f t e r a s t a b l e b a s e l i n e has been o b t a i n e d , s t a r t t h e sampler and perform analysis.

Inorganic Substances

459

12.0 DATA ANALYSIS AND CALCULATIONS

1 2 . 1 Prepare a c a l i b r a t i o n c u r v e by p l o t t i n g i n s t r u m e n t response Compute sample c o n c e n t r a t i o n by a y a i n s t standard c o n c e n t r a t i o n . M u l t i p l y answer comparing sample response w i t h t h e s t a n d a r d c u r v e . by a p p r o p r i a t e d i l u t i o n f a c t o r . 12.2 Report o n l y t h o s e v a l u e s t h a t f a l l between t h e l o w e s t and t h e Samples exceeding t h e h i g h e s t h i y h e s t c a l i b r a t i o n standards. s t a n d a r d should be d i l u t e d and r e a n a l y z e d . 12.3 Report r e s u l t s i n mg N/L. 13.0 METHOD PERFORMANCE

13.1 I n a s i n g l e l a b o r a t o r y (EMSL-Cinc n n a t ) u s i n g sewage samples a t c o n c e n t r a t i o n s o f 1.2. 2.6. and 1 7 ma N/L, t h e p r e c i s i o n was f 0.07, f 0.03, and f 0.15, r e s p e c t i v e l y . 13.2 I n a s i n g l e l a b o r a t o r y (EMSL-Cincinnati) u s i n g sewage samples a t c o n c e n t r a t i o n s 4.7 and 8.74 mg N/L, t h e r e c o v e r i e s were 99% and 99%, respectively. 13.3 The i n t e r l a b o r a t o r y p r e c i s i o n and accuracy d a t a i n Table 1 were developed u s i n g a r e a g e n t w a t e r m a t r i x . Values a r e i n mg N/L. 14.0 POLLUTION PREVENTION 14.1 P o l l u t i o n p r e v e n t i o n encompasses any t e c h n i q u e t h a t reduces o r e l i m i n a t e s t h e q u a n t i t y o r t o x i c i t y o f waste a t t h e p o i n t o f g e n e r a t i o n . Numerous o p p o r t u n i t i e s f o r p o l l u t i o n p r e v e n t i o n e x i s t i n l a b o r a t o r y o p e r a t i o n . The EPA has e s t a b l i s h e d a p r e f e r r e d h i e r a r c h y o f e n v i r o n m e n t a l management t e c h n i q u e s t h a t p l a c e s p o l l u t i o n p r e v e n t i o n as t h e management o p t i o n o f f i r s t c h o i c e . Whenever f e a s i b l e , 1 a b o r a t o r y personnel s h o u l d use p o l l u t i o n p r e v e n t i o n t e c h n i q u e s t o address t h e i r waste g e n e r a t i o n . When wastes cannot be f e a s i b l y reduced a t t h e source, t h e Agency recommends r e c y c l i n g as t h e n e x t b e s t o p t i o n . 14.2 The q u a n t i t y o f c h e m i c a l s purchased s h o u l d be based on expected usage d u r i n g i t s s h e l f l i f e and d i s p o s a l c o s t o f unused m a t e r i a l . A c t u a l r e a g e n t p r e p a r a t i o n volumes s h o u l d r e f l e c t a n t i c i p a t e d usage and r e a g e n t s t a b i l i t y . 14.3 F o r i n f o r m a t i o n about p o l l u t i o n p r e v e n t i o n t h a t may be a p p l i c a b l e t o l a b o r a t o r i e s and r e s e a r c h i n s t i t u t i o n s , c o n s u l t "Less i s B e t t e r : L a b o r a t o r y Chemical Management f o r Waste Reduction," a v a i l a b l e from t h e American Chemical S o c i e t y ' s Department o f Government R e g u l a t i o n s and Science P o l i c y , 1155 1 6 t h S t r e e t N.W., Washington D . C . 20036, (202) 872-4477.

460

Methods for the Determination

15.0 WASTE MANAGEMENT

15.1 The Environmental Protection Agency requires that laboratory waste

management practices be conducted consistent with all applicable rules and regulations. Excess Reagents and samples and method process wastes should be characterized and disposed o f in an acceptable manner. The Agency urges laboratories to protect the air, water, and land by minimizing and controlling all releases from hoods and bench operations, complying with the letter and spirit of any waste discharge permit and regulations, and by complying with all solid and hazardous waste regulations, particularly the hazardous waste identification rules and land disposal restrictions. For further information on waste management consult "The Waste Management Manual for Laboratory Personnel available from the American Chemical Society at the address listed in Sect. 14.3. ,'I

16.0 REFERENCES

1.

McDaniel, W.H., Hemphill, R.N. and Donaldson, W.T., "Automatic Determination o f total Kjeldahl Nitrogen in Estuarine Water," Technicon Symposia, pp. 362-367, Vol. 1, 1967.

2.

Gales, M.E. and Booth, R.L., "Evaluation of Organic Nitrogen Methods," EPA Office of Research and Monitoring, June, 1972.

3.

Gales, M.E. and Booth, R.L., "Simultaneous and Automated Determination of Total Phosphorus and Total Kjeldahl Nitrogen, 'I Methods Development and Quality Assurance Research Laboratory, May 1974.

4.

Technicon "Total Kjeldahl Nitrogen and Total Phosphorus ED-40 Digestion Procedure for Water," August 1974.

5.

Gales, M.E., and Booth, R.L., "Evaluation of the Technicon Block Digestor System for the Measurement o f Total Kjeldahl Nitrogen and Total Phosphorus, EPA-600/4-78-015, Environmental Monitoring and Support Laboratory, Cincinnati , Ohio, 1978. It

6.

Code of Federal Regulations 40, Ch. 1, Pt. 136, Appendix B.

Inorganic Substances

461

17.0 TABLES, DIAGRAMS, FLOWCHARTS, AND VALIDATION DATA TABLE 1. NUMBER OF VALUES REPORTED

INTERLABORATORY P R E C IS ION AND ACCURACY DATA

TRUE VALUE

0

MEAN (X)

RESIDUAL FOR X

STANDARD D E V IA T ION (S)

RESIDUAL FOR S

115

0.380

0.3891

-0.0091

0.0750

-0.0135

134 ~. .

0.451

0.4807

0.0125

0.1181

0.0238

127

1.oo

1.0095

-0.0000

0.1170

-0.0227

164

3.10

3.0992

0.0191

0.2821

-0.0310

138 ~..

3.50

3.4765

0.0020

0.3973

0.0512

115

5.71

5.6083

-0.0452

0.4869

-0.0417

175

7.00

6.9246

-0.0008

0.6623

0.0272

121

8.00

7.9991

0.0877

0.6283

- 0.0894

120

15.0

15.0213

0.2080

1.2495

-0.0462

127

21 .o

20.4355

-0.2937

1.7267

-0.0644

164

25.0

24.7157

0.0426

2.0147

-0.1067

175

26.9

26.1464

-0.4000

2.9743

0.6960

REGRESSIONS: X

=

0.986T t 0.024, S

=

0.083T

+

0.057

462

Methods for the Determination TABLE 2.

Range mq/LN

CONCENTRATION RANGES

Pump m L / m i n S a m 1e ResamDl e

mL NaOH B u f f e r (7.71

0-1.5

0.80

0.32

2 50

0-5.0

0.16

0.32

120

0-10.0

0.16

0.16

80

m

m 1-00

TO RESAMPLE

0.32

AIR

0.80

OIL WATER

10 TURNS

5 TURNS

37"c

10TURNS

4%t-&sQ

SAMPLE"

20 TURNS

TO FK: PLMP TUBE

WCYlAlEf4~PR~SE

COLORIMETEFI BQO nrn

SO mm FlC

PWP 90 PER HOUR

SAMPLE B6 SEC. WASH 24 SEC.

figure 1 Ammonia Manifold

464

Methods for the Determination METHOD 353.2 DETERMINATION OF NITRATE-NITRITE NITROGEN BY AUTOMATED COLORIMETRY

Edited by James W. O'Dell Inorganic Chemistry Branch Chemistry Research D i v i s i o n

Revision 2.0 August 1993

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

Inorganic Substances

465

METHOD 3 5 3 . 2 DETERMINATION OF NITRATE-NITRITE NITROGEN BY AUTOMATED COLORIMETRY 1.0

2.0

3.0

SCOPE AND APPLICATION 1.1

T h i s method c o v e r s t h e d e t e r m i n a t i o n o f n t r i t e s i n g l y , o r n i t r t e and n i t r a t e combined i n d r i n k i n g , ground, s u r f a c e , domestic and i n d u s t r i a l wastes.

1.2

The a p p l i c a b l e range i s 0.05 t o 10.0 mg/L n i t r a t e - n i t r i t e n i t r o g e n . The range may be extended w i t h sample d i l u t i o n .

SUMMARY OF METHOD 2.1

A f i l t e r e d sample i s passed t h r o u g h a column c o n t a i n i n g g r a n u l a t e d copper-cadmium t o reduce n i t r a t e t o n i t r i t e . The n i t r i t e ( t h a t was o r i g i n a l l y p r e s e n t p l u s reduced n i t r a t e ) i s determined by d i a z o t i z i n g w i t h s u l f a n i l a m i d e and c o u p l i n g w i t h N-(1-naphthy1)e t h y l e n e d i a m i n e d i h y d r o c h l o r i d e t o f o r m a h i g h l y c o l o r e d azo dye which i s measured c o l o r i m e t r i c a l l y . Separate, r a t h e r t h a n combined n i t r a t e - n i t r i t e , v a l u e s a r e r e a d i l y o b t a i n e d by c a r r y i n g o u t t h e p r o c e d u r e f i r s t w i t h , and t h e n w i t h o u t , t h e Cu-Cd r e d u c t i o n s t e p .

2.2

Reduced volume v e r s i o n s o f t h i s method t h a t use t h e same r e a g e n t s and m o l a r r a t i o s a r e a c c e p t a b l e p r o v i d e d t h e y meet t h e q u a l i t y c o n t r o l and performance r e q u i r e m e n t s s t a t e d i n t h e method.

2.3

L i m i t e d performance-based method m o d i f i c a t i o n s may be a c c e p t a b l e p r o v i d e d t h e y a r e f u l l y documented and meet o r exceed r e q u i r e m e n t s expressed i n S e c t . 9.0, Q u a l i t y C o n t r o l .

DEFINITIONS 3.1

CALIBRATION BLANK (CB) -- A volume o f r e a g e n t w a t e r f o r t i f i e d w i t h t h e same m a t r i x as t h e c a l i b r a t i o n standards, b u t w i t h o u t t h e a n a l y t e s i n t e r n a l standards, o r s u r r o g a t e a n a l y t e s .

3.2

CALIBRAT ON STANDARD (GAL) -- A s o l u t i o n p r e p a r e d f r o m t h e p r i m a r y d i l u t i o n s t a n d a r d s o l u t i o n o r s t o c k s t a n d a r d s o l u t i o n s and t h e i n t e r n a l standards and s u r r o g a t e a n a l y t e s . The CAL s o l u t i o n s a r e used t o a1 ib r a t e t h e i n s t r u m e n t response w i t h r e s p e c t t o a n a l y t e concentration.

3.3

INSTRUMENT PERFORMANCE CHECK SOLUTION (IPC) -- A s o l u t i o n o f one o r more method a n a l y t e s , s u r r o g a t e s , i n t e r n a l standards, o r o t h e r t e s t substances used t o e v a l u a t e t h e performance o f t h e i n s t r u m e n t system with respect t o a defined set o f c r i t e r i a .

466

Methods for the Determination 3.4

LABORATORY F O R T I F I E D BLANK (LFB) - - An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e methodology i s i n c o n t r o l , and whether t h e l a b o r a t o r y i s capable o f making a c c u r a t e and p r e c i s e measurements.

3.5

LABORATORY F O R T I F I E D SAMPLE M A T R I X (LFM) -- An a l i q u o t o f an environmental sample t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFM i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e sample m a t r i x c o n t r i b u t e s b i a s t o t h e a n a l y t i c a l r e s u l t s . The background c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be determined i n a s e p a r a t e a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s .

3.6

LABORATORY REAGENT BLANK (LRB) -- An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a l l glassware, equipment, s o l v e n t s , r e a g e n t s , i n t e r n a l standards, and s u r r o g a t e s t h a t a r e used w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e l a b o r a t o r y environment, t h e reagents, o r t h e apparatus.

3.7

LINEAR CALIBRATION RANGE (LCR) -- The c o n c e n t r a t i o n range o v e r which t h e i n s t r u m e n t response i s l i n e a r .

3.8

MATERIAL SAFETY DATA SHEET (MSDS) -- W r i t t e n i n f o r m a t i o n p r o v i d e d by vendors c o n c e r n i n g a chemical ' s t o x i c i t y , h e a l t h hazards, p h y s i c a l p r o p e r t i e s , f i r e , and r e a c t i v i t y d a t a i n c l u d i n g storage, s p i l l , and handling precautions.

3.9

METHOD DETECTION LIMIT (MDL) -- The minimum c o n c e n t r a t i o n o f an a n a l y t e t h a t can be i d e n t i f i e d , measured and r e p o r t e d w i t h 99% confidence t h a t t h e analyte concentration i s g r e a t e r than zero.

3.10 QUALITY CONTROL SAMPLE (QCS) -- A s o l u t i o n o f method a n a l y t e s o f known c o n c e n t r a t i o n s t h a t i s used t o f o r t i f y an a l i q u o t o f LRB o r sample m a t r i x . The QCS i s o b t a i n e d f r o m a source e x t e r n a l t o t h e l a b o r a t o r y and d i f f e r e n t f r o m t h e source o f c a l i b r a t i o n standards. I t i s used t o check 1 a b o r a t o r y performance w i t h e x t e r n a l l y prepared t e s t materials. 3.11 STOCK STANDARD SOLUTION ( S S S ) -- A c o n c e n t r a t e d s o l u t i o n c o n t a i n i n g one o r more method a n a l y t e s p r e p a r e d i n t h e l a b o r a t o r y u s i n g assayed r e f e r e n c e m a t e r i a l s o r purchased f r o m a r e p u t a b l e commercial source. 4.0

INTERFERENCES 4.1

B u i l d up o f suspended m a t t e r i n t h e r e d u c t i o n column w i l l r e s t r i c t sample f l o w . S i n c e n i t r a t e and n i t r i t e a r e found i n a s o l u b l e s t a t e , samples may be p r e - f i l t e r e d .

Inorganic Substances

5.0

6.0

467

4.2

Low r e s u l t s m i g h t be o b t a i n e d f o r samples t h a t c o n t a i n h i g h c o n c e n t r a t i o n s o f i r o n , copper o r o t h e r m e t a l s . EDTA i s added t o t h e samples t o e l i m i n a t e t h i s i n t e r f e r e n c e .

4.3

Residual c h l o r i n e can produce a n e g a t i v e i n t e r f e r e n c e by l i m i t i n g r e d u c t i o n e f f i c i e n c y . B e f o r e a n a l y s i s , samples s h o u l d be checked and i f r e q u i r e d , d e c h l o r i n a t e d w i t h sodium t h i o s u l f a t e .

4.4

Samples t h a t c o n t a i n l a r g e c o n c e n t r a t i o n s o f o i l and grease w i l l c o a t t h e s u r f a c e o f t h e cadmium. T h i s i n t e r f e r e n c e i s e l i m i n a t e d by p r e - e x t r a c t i n g t h e sample w i t h an o r g a n i c s o l v e n t .

4.5

Method i n t e r f e r e n c e s may be caused by contaminants i n t h e r e a g e n t w a t e r , r e a g e n t s , glassware, and o t h e r sample p r o c e s s i n g apparatus t h a t b i a s a n a l y t e response.

SAFETY 5.1

The t o x i c i t y o r c a r c i n o g e n i c i t y o f each r e a g e n t used i n t h i s method have n o t been f u l l y e s t a b l i s h e d . Each chemical s h o u l d be regarded as a p o t e n t i a l h e a l t h hazard and exposure s h o u l d be as l o w as r e a s o n a b l y a c h i e v a b l e . C a u t i o n s a r e i n c l u d e d f o r known e x t r e m e l y hazardous m a t e r i a l s o r procedures.

5.2

Each l a b o r a t o r y i s r e s p o n s i b l e f o r m a i n t a i n i n g a c u r r e n t awareness f i l e o f OSHA r e g u l a t i o n s r e g a r d i n g t h e s a f e h a n d l i n g o f t h e chemicals s p e c i f i e d i n t h i s method. A r e f e r e n c e f i l e o f M a t e r i a l S a f e t y Data Sheets (MSDS) s h o u l d be made a v a i l a b l e t o a l l personnel i n v o l v e d i n t h e chemical a n a l y s i s . The p r e p a r a t i o n o f a f o r m a l safety plan i s also advisable.

5.3

The f o l l o w i n g c h e m i c a l s have t h e p o t e n t i a l t o be h i g h l y t o x i c or hazardous, c o n s u l t MSDS. 5.3.1

Cadmium (7.1)

5.3.2

Phosphoric a c i d (7.5)

5.3.3

H y d r o c h l o r i c a c i d (7.6)

5.3.4

Sulfuric acid

5.3.5

C h l o r o f o r m (7.10, 7.11)

(7.8)

EQUIPMENT AND SUPPLIES

6.1

Balance -- A n a l y t i c a l , c a p a b l e o f a c c u r a t e l y w e i g h i n g t o t h e n e a r e s t 0.0001 g.

6.2

Glassware -- C l a s s A v o l u m e t r i c f l a s k s and p i p e t s as r e q u i r e d .

468

Methods for the Determination 6.3

7.0

Automated c o n t i n u o u s f l o w a n a l y s i s equipment designed t o d e l i v e r and r e a c t sample and r e a g e n t s i n t h e r e q u i r e d o r d e r and r a t i o s . 6.3.1

Sampling d e v i c e (sampler)

6.3.2

Mu1t i channel pump

6.3.3

Reaction u n i t o r manifold

6.3.4

Colorimetric detector

6.3.5

Data r e c o r d i n g d e v i c e

REAGENTS AND STANDARDS 40-60 mesh (CASRN 7440-43-9).

O t h e r mesh s t z e s

7.1

G r a n u l a t e d cadmium: may be used.

7.2

Copper-cadmium: The cadmium g r a n u l e s (new o r used) a r e cleaned w i t h d i l u t e HC1 ( 7 . 6 ) and c o p p e r i z e d w i t h 2% s o l u t i o n o f copper s u l f a t e (7.7) i n t h e f o l l o w i n g manner:

7.3

7.2.1

Wash t h e cadmium w i t h HC1 (7.6) and r i n s e w i t h d i s t i l l e d w a t e r . The c o l o r o f t h e cadmium so t r e a t e d s h o u l d be silver.

7.2.2

S w i r l 10 g cadmium i n 100 mL p o r t i o n s o f 2% s o l u t i o n o f copper s u l f a t e (7.7) f o r 5 min o r u n t i l b l u e c o l o r p a r t i a l l y fades, decant and r e p e a t w i t h f r e s h copper s u l f a t e u n t i l a brown c o l l o i d a l p r e c i p i t a t e forms.

7.2.3

Wash t h e copper-cadmium w i t h r e a g e n t w a t e r ( a t l e a s t 10 t i m e s ) t o remove a l l t h e p r e c i p i t a t e d copper. The c o l o r o f t h e cadmium so t r e a t e d s h o u l d be b l a c k .

P r e p a r a t i o n o f r e d u c t i o n column. The r e d u c t i o n column i s a Ushaped, 35 cm l e n g t h , 2 mm I . D . g l a s s t u b e (Note 1 ) . F i l l t h e r e d u c t i o n column w i t h d i s t i l l e d w a t e r t o p r e v e n t entrapment o f a i r bubbles d u r i n g t h e f i l l i n g o p e r a t i o n s . T r a n s f e r t h e copper-cadmium g r a n u l e s (7.2) t o t h e r e d u c t i o n column and p l a c e a g l a s s wool p l u g i n each end. To p r e v e n t entrapment o f a i r b u b b l e s i n t h e r e d u c t i o n column, be s u r e t h a t a l l pump t u b e s a r e f i l l e d w i t h r e a g e n t s b e f o r e p u t t i n g t h e column i n t o t h e a n a l y t i c a l system. NOTE 1: O t h e r r e d u c t i o n t u b e c o n f i g u r a t i o n s , i n c l u d i n g a 0.081 I.D. pump tube, can be used i n p l a c e o f t h e 2-mm g l a s s tube, i f checked as i n 10.1.

7.4

Reagent w a t e r : Because o f p o s s i b l e c o n t a m i n a t i o n , t h i s s h o u l d be p r e p a r e d by passage t h r o u g h an i o n exchange column comprised o f a m i x t u r e o f b o t h s t r o n g l y a c i d i c - c a t i o n and s t r o n g l y b a s i c - a n i o n

Inorganic Substances

469

exchange resins. The regeneration o f the ion exchange column should be carried out according to the manufacturer’s instructions. 7.5

Color reagent: To approximately 800 mL of reagent water, add, while stirring, 100 mL conc. phosphoric acid (CASRN 7664-38-2), 40 g sulfanilamide (CASRN 63-74-1) and 2 g N-1-naphthylethylenediamine dihydrochloride (CASRN 1465-25-4). Stir until dissolved and dilute t o 1 L. Store in brown bottle and keep in the dark when not in use. This solution is stable for several months.

7.6

Dilute hydrochloric acid, 6N: Add 50 mL of conc. HC1 (CASRN 764701-0) to reagent water, cool and dilute to 100 ml.

7.7

Copper sulfate solution, 2%: Dissolve 20 g of CuS0,’5H20 (CASRN 7758-99-8) in 500 mL of reagent water and dilute to 1 L.

7.8

Wash solution: Use reagent water for unpreserved samples. For samples preserved with H,SO,, use 2 mL H,SO, (CASRN 7764-93-9), per liter of wash water.

7.9

Ammonium chloride-EDTA solution: Dissolve 85 g of reagent grade ammonium chloride (CASRN 12125-02-9) and 0.1 g of disodium ethylenediamine tetracetate (CASRN 6381-92-6) in 900 mL of reagent water. Adjust the pH to 9 . 1 for preserved or 8.5 for non-preserved samples with conc. ammonium hydroxide (CASRN 1336-21-6) and dilute to 1 L. Add 0.5 mL Brij-35 (CASRN 9002-92-0).

7.10 Stock nitrate solution: Dissolve 7.218 g KNO, (CASRN 7757-79-1) and dilute to 1 L in a volumetric flask with reagent water. Preserve with 2 mL of chloroform (CASRN 67-66-3) per liter. Solution is stable for 6 months. 1 mL = 1.0 mg NO,-N. 7.11 Stock nitrite solution: Dissolve 6.072 g KNO, in 500 mL of reagent water and dilute t o 1 L in a volumetric flask. Preserve with 2 mL of chloroform and keep under refrigeration. 1.0 mL = 1.0 mg NO,-N. 7.12 Standard nitrate solution: Dilute 1.0 mL of stock nitrate solution (7.10) t o 100 mL. 1.0 mL = 0.01 mg NO,-N. Preserve with .2 mL of chloroform. Solution is stable for 6 months. 7.13 Standard nitrite solution: Dilute 10.0 mL of stock nitrite (7.11) solution to 1000 mL. 1.0 mL = 0.01 mg NO,-N. Solution is unstable;

prepare as required. 8.0

SAMPLE COLLECTION, PRESERVATION AND STORAGE

8.1

Samples should be collected in plastic or glass bottles. All bottles must be thoroughly cleaned and rinsed with reagent water. Volume collected should be sufficient to insure a representative sample, allow for replicate analysis (if required), and minimize waste disposal .

470

9.0

Methods for the Determination t o a pH < 2 and c o o l e d t o 4 ° C

8.2

Samples must be p r e s e r v e d w i t h H,SO, a t the time o f c o l l e c t i o n .

8.3

Samples should be analyzed a s soon as p o s s i b l e a f t e r c o l l e c t i o n . I f s t o r a g e i s r e q u i r e d , p r e s e r v e d samples a r e m a i n t a i n e d a t 4°C and may be h e l d f o r up t o 28 days.

8.4

Samples t o be analyzed f o r n i t r a t e o r n i t r i t e o n l y s h o u l d be c o o l e d t o 4°C and analyzed w i t h i n 48 h o u r s .

QUALITY CONTROL 9.1

Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a f o r m a l qua1 it y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f t h i s program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y and t h e p e r i o d i c a n a l y s i s o f l a b o r a t o r y r e a g e n t b l a n k s , f o r t i f i e d b l a n k s , and o t h e r l a b o r a t o r y s o l u t i o n s as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n performance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f t h e d a t a t h a t a r e generated.

9.2

I N I T I A L DEMONSTRATION OF PERFORMANCE 9.2.1

The i n i t i a l d e m o n s t r a t i o n o f performance i s used t o c h a r a c t e r i z e i n s t r u m e n t performance ( d e t e r m i n a t i o n o f LCR and a n a l y s i s o f QCS) and l a b o r a t o r y performance ( d e t e r m i n a t i o n o f MDLs) p r i o r t o p e r f o r m i n g analyses by t h i s method.

9.2.2

L i n e a r C a l i b r a t i o n Range (LCR) -- The LCR must be d e t e r m i n e d i n i t i a l l y and v e r i f i e d e v e r y 6 months o r whenever a s i g n i f i c a n t change i n i n s t r u m e n t response i s observed o r expected. The i n i t i a l d e m o n s t r a t i o n o f l i n e a r i t y must use s u f f i c i e n t standards t o i n s u r e t h a t t h e r e s u l t i n g c u r v e i s l i n e a r . The v e r i f i c a t i o n o f l i n e a r i t y must use a minimum o f a b l a n k and t h r e e standards. If any v e r i f i c a t i o n d a t a exceeds t h e i n i t i a l v a l u e s b y f lo%, l i n e a r i t y must be r e e s t a b l i s h e d . I f any p o r t i o n o f t h e range i s shown t o be n o n l i n e a r , s u f f i c i e n t s t a n d a r d s must be used t o c l e a r l y define the nonlinear portion.

9.2.3

Q u a l i t y C o n t r o l Sample (QCS) -- When b e g i n n i n g t h e use o f t h i s method, on a q u a r t e r l y b a s i s o r as r e q u i r e d t o meet data-qua1 i t y needs, v e r i f y t h e c a l i b r a t i o n s t a n d a r d s and a c c e p t a b l e i n s t r u m e n t performance w i t h t h e p r e p a r a t i o n and analyses o f a QCS. I f t h e d e t e r m i n e d c o n c e n t r a t i o n s a r e n o t w i t h i n f 10% o f t h e s t a t e d values, performance o f t h e d e t e r m i n a t i v e s t e p o f t h e method i s unacceptable. The source o f t h e problem must be i d e n t i f i e d and c o r r e c t e d before e i t h e r proceeding w i t h t h e i n i t i a l determination o f MDLs o r c o n t i n u i n g w i t h on-going analyses,

Inorganic Substances 9.2.4

471

Method D e t e c t i o n L i m i t (MDL) -- MDLs must be e s t a b l i s h e d f o r a l l analytes, using reagent water (blank) f o r t i f i e d a t a c o n c e n t r a t i o n o f two t o t h r e e t i m e s t h e e s t i m a t e d i n s t r u m e n t detection l i m i t . ' 6 ' To d e t e r m i n e MDL v a l u e s , t a k e seven rep1 i c a t e a1 i q u o t s o f t h e f o r t i f i e d r e a g e n t w a t e r and process t h r o u g h t h e e n t i r e a n a l y t i c a l method. Perform a l l c a l c u l a t i o n s d e f i n e d i n t h e method and r e p o r t t h e concentration values i n t h e appropriate u n i t s . Calculate t h e MDL as f o l l o w s : MDL

=

( t ) x (S)

where, t = S t u d e n t ' s t v a l u e f o r a 99% c o n f i d e n c e l e v e l and a s t a n d a r d d e v i a t i o n e s t i m a t e w i t h n-1 degrees o f freedom [ t = 3.14 f o r seven r e p l i c a t e s ] . S = s t a n d a r d d e v i a t i o n o f t h e r e p l i c a t e analyses.

MDLs s h o u l d be determined e v e r y 6 months, when a new o p e r a t o r b e g i n s work, o r whenever t h e r e i s a s i g n i f i c a n t change i n t h e background o r i n s t r u m e n t response. 9.3

ASSESSING LABORATORY PERFORMANCE 9.3.1

L a b o r a t o r y Reagent B l a n k (LRB) -- The l a b o r a t o r y must ana?yze a t l e a s t one LRB w i t h each b a t c h o f samples. Data produced a r e used t o assess c o n t a m i n a t i o n f r o m t h e l a b o r a t o r y environment. Values t h a t exceed t h e MDL i n d i c a t e l a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n s h o u l d be suspected and c o r r e c t i v e a c t i o n s must be t a k e n b e f o r e c o n t i n u i n g t h e analysis.

9.3.2

L a b o r a t o r y F o r t i f i e d B1 ank (LFB) -- The 1 a b o r a t o r y must a n a l y z e a t l e a s t one LFB w i t h each b a t c h o f samples. C a l c u l a t e accuracy as p e r c e n t r e c o v e r y (Sect. 9.4.2). If t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%, t h a t a n a l y t e i s j u d g e d o u t o f c o n t r o l , and t h e source o f t h e problem s h o u l d be i d e n t i f i e d and r e s o l ved b e f o r e c o n t i n u i n g analyses.

9.3.3

The l a b o r a t o r y must use LFB analyses d a t a t o assess 1 a b o r a t o r y performance a g a i n s t t h e r e q u i r e d c o n t r o l 1i m i t s o f 90-110%. When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i 1a b l e ( u s u a l l y a minimum o f 20-30 analyses), o p t i o n a l c o n t r o l l i m i t s can be developed f r o m t h e p e r c e n t mean r e c o v e r y (x) and t h e s t a n d a r d d e v i a t i o n ( S ) o f t h e mean r e c o v e r y . These d a t a can be used t o e s t a b l i s h t h e upper and l o w e r c o n t r o l l i m i t s as f o l l o w s : UPPER CONTROL LIMIT LOWER CONTROL LIMIT

= =

x t 3s x - 3s

472

Methods for the Determination The o p t i o n a l c o n t r o l l i m i t s must be equal t o o r b e t t e r t h a n t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%. A f t e r each f i v e t o t e n new r e c o v e r y measurements, new c o n t r o l l i m i t s can be c a l c u l a t e d u s i n g o n l y t h e most r e c e n t 20-30 d a t a p o i n t s . A l s o , t h e s t a n d a r d d e v i a t i o n ( S ) d a t a should be used t o e s t a b l i s h e d an on-going p r e c i s i o n statement f o r t h e l e v e l o f c o n c e n t r a t i o n s i n c l u d e d i n t h e LFB. These d a t a must be k e p t on f i l e and be a v a i l a b l e f o r r e v i e w . 9.3.4

9.4

I n s t r u m e n t Performance Check S o l u t i o n (IPC) - - F o r a l l d e t e r m i n a t i o n s t h e l a b o r a t o r y must analyze t h e I P C ( a midrange check s t a n d a r d ) and a c a l i b r a t i o n b l a n k i m m e d i a t e l y f o l l o w i n g d a i l y c a l i b r a t i o n , a f t e r e v e r y t e n t h sample ( o r more f r e q u e n t l y , i f r e q u i r e d ) , and a t t h e end o f t h e sample r u n . A n a l y s i s o f t h e I P C s o l u t i o n and c a l i b r a t i o n b l a n k i m m e d i a t e l y f o l l o w i n g c a l i b r a t i o n must v e r i f y t h a t t h e i n s t r u m e n t i s w i t h i n f 10% o f c a l i b r a t i o n . Subsequent analyses o f t h e I P C s o l u t i o n must v e r i f y t h e c a l i b r a t i o n i s s t i l l w i t h i n k 10%. I f t h e c a l i b r a t i o n cannot be v e r i f i e d w i t h i n t h e s p e c i f i e d l i m i t s , r e a n a l y z e t h e I P C s o l u t i o n . If t h e second a n a l y s i s o f t h e I P C s o l u t i o n c o n f i r m s c a l i b r a t i o n t o be o u t s i d e t h e l i m i t s , sample a n a l y s i s must be d i s c o n t i n u e d , t h e cause determined and/or i n t h e case o f d r i f t , t h e i n s t r u m e n t r e c a l i b r a t e d . A l l samples f o l l o w i n g t h e l a s t a c c e p t a b l e I P C s o l u t i o n must be r e a n a l y z e d . The a n a l y s i s d a t a o f t h e c a l i b r a t i o n b l a n k and I P C s o l u t i o n must be k e p t on f i l e w i t h t h e sample analyses d a t a .

ASSESSING ANALYTE RECOVERY AND DATA QUALITY

9.4.1

L a b o r a t o r y F o r t i f i e d Sample M a t r i x (LFM) -- The l a b o r a t o r y must add a known amount o f a n a l y t e t o a minimum o f 10% o f t h e r o u t i n e samples. I n each case, t h e LFM a l i q u o t must be a d u p l i c a t e o f t h e a l i q u o t used f o r sample a n a l y s i s . The a n a l y t e c o n c e n t r a t i o n must be h i g h enough t o be d e t e c t e d above t h e o r i g i n a l sample and s h o u l d n o t be l e s s t h a n f o u r t i m e s t h e MDL. The added a n a l y t e c o n c e n t r a t i o n s h o u l d be t h e same as t h a t used i n t h e l a b o r a t o r y f o r t i f i e d b l a n k .

9.4.2

C a l c u l a t e t h e p e r c e n t r e c o v e r y f o r each a n a l y t e , c o r r e c t e d f o r c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o t h e d e s i g n a t e d LFM r e c o v e r y range 90-110%. Percent r e c o v e r y may be c a l c u l a t e u s i n g t h e f o l l owing e q u a t i o n :

c,

R =

-

c

x 100

S

where, R

C, C s

= = = =

percent recovery. f o r t i f i e d sample c o n c e n t r a t i o n . sample background c o n c e n t r a t i o n . c o n c e n t r a t i o n e q u i v a l e n t o f a n a l y t e added t o sample.

Inorganic Substances 9.4.3

473

I f t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e d e s i g n a t e d LFM r e c o v e r y range and t h e l a b o r a t o r y performance f o r t h a t

a n a l y t e i s shown t o be i n c o n t r o l ( S e c t . 9 . 3 ) , t h e r e c o v e r y problem encountered w i t h t h e LFM i s j u d g e d t o be e i t h e r m a t r i x o r s o l u t i o n r e l a t e d , n o t system r e l a t e d . 9.4.4

Where r e f e r e n c e m a t e r i a l s a r e a v a i l a b l e , t h e y s h o u l d be analyzed t o p r o v i d e a d d i t i o n a l performance d a t a . The a n a l y s i s o f r e f e r e n c e samples i s a v a l u a b l e t o o l f o r d e m o n s t r a t i n g t h e a b i l i t y t o p e r f o r m t h e method a c c e p t a b l y .

10.0 CALIBRATION AND STANDARDIZATION 10.1 Prepare a s e r i e s o f a t l e a s t 3 standards, c o v e r i n g t h e d e s i r e d range, and a b l a n k by d i l u t i n g s u i t a b l e volumes o f s t a n d a r d n i t r a t e s o l u t i o n ( 7 . 1 2 ) . A t l e a s t one n i t r i t e s t a n d a r d s h o u l d be compared t o a n i t r a t e s t a n d a r d a t t h e same c o n c e n t r a t i o n t o v e r i f y t h e e f f i c i e n c y o f t h e r e d u c t i o n column. 10.2 Set up m a n i f o l d as shown i n F i g u r e 1. Care s h o u l d be t a k e n n o t t o i n t r o d u c e a i r i n t o t h e r e d u c t i o n column. 10.3 P l a c e a p p r o p r i a t e standards i n t h e sampler i n o r d e r o f d e c r e a s i n g c o n c e n t r a t i o n and p e r f o r m a n a l y s i s . 10.4 Prepare s t a n d a r d c u r v e by p l o t t i n g i n s t r u m e n t response a g a i n s t c o n c e n t r a t i o n values. A c a l i b r a t i o n c u r v e may be f i t t e d t o t h e c a l i b r a t i o n s o l u t i o n s c o n c e n t r a t i o n / r e s p o n s e d a t a u s i n g computer o r c a l c u l a t o r based r e g r e s s i o n c u r v e f i t t i n g t e c h n i q u e s . Acceptance o r c o n t r o l l i m i t s s h o u l d be e s t a b l i s h e d u s i n g t h e d i f f e r e n c e between t h e measured v a l u e o f t h e c a l i b r a t i o n s o l u t i o n and t h e " t r u e v a l u e " concentration.

10.5 A f t e r t h e c a l i b r a t i o n has been e s t a b l i s h e d , i t must be v e r i f i e d by If t h e a n a l y s i s o f a s u i t a b l e q u a l i t y c o n t r o l sample (QCS). measurements exceed f 10% o f t h e e s t a b l i s h e d QCS value, t h e a n a l y s i s s h o u l d be t e r m i n a t e d and t h e i n s t r u m e n t r e c a l i b r a t e d . The new c a l i b r a t i o n must be v e r i f i e d b e f o r e c o n t i n u i n g a n a l y s i s . P e r i o d i c r e a n a l y s i s o f t h e QCS is recommended as a c o n t i n u i n g c a l i b r a t i o n check.

NOTE 3: C o n d i t i o n column by r u n n i n g 1 mg/L s t a n d a r d f o r 10 mln I f a new r e d u c t i o n column i s b e i n g used. w i t h r e a g e n t s f o r 20 min.

Subsequently wash t h e column

11.0 PROCEDURE 11.1 I f t h e pH o f t h e sample i s below 5 o r above 9, a d j u s t t o between 5 and 9 w i t h e i t h e r conc. HC1 o r conc. NH,OH. 11.2 Set up t h e m a n i f o l d as shown i n F i g u r e 1. t o i n t r o d u c e a i r i n t o r e d u c t i o n column.

Care s h o u l d be t a k e n n o t

474

Methods for the Determination

11.3 Allow system to equilibrate as required. Obtain a stable baseline

with all reagents, feeding reagent water through the sample line. 11.4 Place appropriate nitrate and/or nitrite standards in sampler in

order o f decreasing concentration and complete loading o f sampler tray. 11.5 Switch sample line to sampler and start analysis. 12.0 DATA ANALYSIS AND CALCULATIONS 12.1 Prepare a calibration curve by plotting instrument response

against standard concentration. Compute sample concentration by comparing sample response with the standard curve. Multiply answer by appropriate dilution factor. 12.2 Report only those values that fall between the lowest and the

highest calibration standards. Samples exceeding the highest standard should be diluted and reanalyzed. 12.3 Report results in mg/L as nitrogen.

13.0 METHOD PERFORMANCE 13.1 Three laboratories participating in an EPA Method Study analyzed

four natural water samples containing exact increments o f inorganic nitrate, with the following results: Accuracy as Increment as Nitrate Nitrogen mq N/liter 0.29 0.35 2.31 2.48

Precision as Standard Deviation mq N/liter 0.012 0.092 0.318 0.176

Bias,

% t 5.75 t 18.10 t 4.47

- 2.69

Bi as, mq N/liter 0.017 0.063 0.103 - 0.067

t t t

13.2 The interlaboratory precision and accuracy data in Table 1 were

developed using a reagent water matrix. Values are in mg NO,-N/L. 13.3 Single laboratory precision data can be estimated at 50% to 75% o f

the interlaboratory precision estimates. 14.0

POLLUTION PREVENTION 14.1 Pollution prevention encompasses any technique that reduces or

eliminates the quantity or toxicity o f waste at the point of generation. Numerous opportunities for pollution prevention exist in laboratory operation. The EPA has established a preferred hierarchy o f environmental management techniques that places pollution prevention as the management option of first choice.

Inorganic Substances

475

Whenever f e a s i b l e , l a b o r a t o r y personnel s h o u l d use p o l l u t i o n p r e v e n t i o n t e c h n i q u e s t o address t h e i r waste g e n e r a t i o n . When wastes cannot be f e a s i b l y reduced a t t h e source, t h e Agency recommends r e c y c l i n g as t h e n e x t b e s t o p t i o n . 14.2 The q u a n t i t y o f chemicals purchased s h o u l d be based on expected usage d u r i n g i t s s h e l f l i f e and d i s p o s a l c o s t o f unused m a t e r i a l . A c t u a l r e a g e n t p r e p a r a t i o n volumes s h o u l d r e f l e c t a n t i c i p a t e d usage and r e a g e n t s t a b i l i t y . 14.3 For i n f o r m a t i o n about p o l l u t i o n p r e v e n t i o n t h a t may be a p p l i c a b l e t o l a b o r a t o r i e s and r e s e a r c h i n s t i t u t i o n s , c o n s u l t "Less i s B e t t e r : L a b o r a t o r y Chemical Management f o r Waste Reduction," a v a i l a b l e from t h e American Chemical S o c i e t y ' s Department o f Government R e g u l a t i o n s and Science P o l i c y , 1155 16th S t r e e t N.W., Washington D.C. 20036, (202) 872-4477.

15.0 WASTE MANAGEMENT 15.1 The Environmental P r o t e c t i o n Agency r e q u i r e s t h a t l a b o r a t o r y waste management p r a c t i c e s be conducted c o n s i s t e n t w i t h a l l a p p l i c a b l e r u l e s and r e g u l a t i o n s . Excess r e a g e n t s , samples, and method process wastes s h o u l d be c h a r a c t e r i z e d and d i s p o s e d o f i n an a c c e p t a b l e manner. The Agency u r g e s l a b o r a t o r i e s t o p r o t e c t t h e a i r , w a t e r , and l a n d by m i n i m i z i n g and c o n t r o l l i n g a l l r e l e a s e s f r o m hoods and bench o p e r a t i o n s , complying w i t h t h e l e t t e r and s p i r i t o f any waste d i s c h a r g e p e r m i t and r e g u l a t i o n s , and by complying w i t h a l l s o l i d and hazardous waste r e g u l a t i o n s , p a r t i c u l a r l y t h e hazardous waste i d e n t i f i c a t i o n r u l e s and l a n d d i s p o s a l r e s t r i c t i o n s . For f u r t h e r i n f o r m a t i o n on waste management c o n s u l t t h e "Waste Management Manual f o r L a b o r a t o r y Personnel, I' a v a i l a b l e f r o m t h e American Chemical S o c i e t y a t t h e address l i s t e d i n Sect. 14.3. 16.0 REFERENCES

1.

F i o r e , J., and O ' B r i e n , J.E., "Automation i n S a n i t a r y Chemistry P a r t s 1 & 2: D e t e r m i n a t i o n o f N i t r a t e s and N i t r i t e s , " Wastes E n g i n e e r i n g 33, 128 &238 (1962).

2.

Armstrong, F.A., Stearns, C.R., and S t r i c k l a n d , J.D., "The Measurement o f Upwell i n g and Subsequent B i o l o g i c a l Processes by Means o f t h e Technicon AutoAnalyzer and A s s o c i a t e d Equipment," Deep Sea Research 14, pp. 381-389 (1967).

3.

Annual Book o f ASTM Standards, P a r t 31, "Water," 366 (1976).

4.

Standard Methods f o r t h e Examination o f Water and Wastewater, 1 7 t h E d i t i o n , pp. 4-91, Method 4500-NO3 F (1992).

Standard D1254, p.

476

Methods for the Determination 5.

Chemical Analyses f o r Water Q u a l i t y Manual, Department o f t h e I n t e r i o r , FWPCA, R.A. T a f t E n g i n e e r i n g Center T r a i n i n g Program, C i n c i n n a t i , Ohio 45226 (January, 1966).

6.

Code o f Federal R e g u l a t i o n s 40, Ch. 1, P t . 136, Appendix

B.

Inorganic Substances

477

17.0 TABLES. DIAGRAMS, FLOWCHARTS AND V A L I D A T I O N DATA

TABLE 1. NUMBER OF VALUES REPORTED

INTERLABORATORY P R E C I S I O N AND ACCURACY DATA

TRUE VALUE

0

MEAN (X)

RESIDUAL FOR X

STANDARD DEVIATION (S)

RESIDUAL FOR S

163

0.250

0.2479

0,0007

0.0200

-0.0001

183

0.451

0.4441

-0.0039

0.0289

-0.0002

213

0.650

0.6479

0.0012

0.0398

0.0017

170

0.950

0.9537

0.0074

0.0484

-0.0031

163

1.90

1.8987

0.0037

0.0918

-0.0024

172

2.20

2.1971

0.0025

0.1164

0.0087

183

2.41

2.3732

-0.0312

0.1273

0.0102

214

3.20

3.2042

0.0109

0.1456

-0.0070

172

6.50

6.4978

0.0089

0.3156

0.0148

213

8.00

7.9814

-0.0055

0.3673

-0.0008

170

8.50

8.5135

0.0273

0.3635

-0.0271

9.9736

-0.0106

0.4353

-0.0227

214

REGRESSIONS: X

10.0 =

0.999T t 0.002,

S = 0.045T t 0.009

r

l

1

REDUCTKlN COLUMN WASTE

1.20

AMMONIUM CHLORDE

0.32

SAMPLE

?

s rn

I

I

0.32

AIR

COLOR FPEAGENT

COLORIMETER 520 nrn 15nm F/C

SAMPLEWASTE

40 PER HOUR SAMPLE 7L SEC. WASH 18 SEC

Figure 1 Nitrate-Nitrite Manifold

Inorganic Substances METHOD 365.1 DETERMINATION OF PHOSPHORUS BY SEMI-AUTOMATED COLORIMETRY

E d i t e d by James W. O ' D e l l I n o r g a n i c Chemistry Branch Chemistry Research D i v i s i o n

R e v i s i o n 2.0 August 1993

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, O H I O 45268

479

480

Methods for the Determination METHOD 3 6 5 . 1 DETERMINATION OF PHOSPHORUS BY AUTOMATED COLORIMETRY

1.0

SCOPE AND APPLICATION

1.1

This method covers the determination of specified forms of phosphorus in drinki.ng, ground, and surface waters, and domestic and industrial wastes.

1.2

The methods are based on reactions that are specific for the orthophosphate ion. Thus, depending on the prescribed pretreatment of the sample, the various forms of phosphorus that may be determined are defined in Section 3 and given in Figure 1. 1.2.1

1.3 2.0

Except for in-depth and detailed studies, the most commonly measured forms are total and dissolved phosphorus, total and dissolved orthophosphate. Hydrolyzable phosphorus is normal ly found only in sewage-type samples. Insoluble forms of phosphorus are determined by calculation.

The applicable range is 0.01 to 1.0 mg P/L. samples per hour can be analyzed.

Approximately 20-30

SUMMARY OF METHOD

2.1

Ammonium molybdate and antimony potassium tartrate react in an acid medium with dilute solutions of phosphorus to form an antimonyphospho-molybdate complex. This complex is reduced to an intensely blue-colored complex by ascorbic acid. The color is proportional to the phosphorus concentration.

2.2

Only orthophosphate forms a blue color in this test. Polyphosphates (and some organic phosphorus compounds) may be converted to the orthophosphate form by manual sulfuric acid hydrolysis. Organic phosphorus compounds may be converted to the orthophosphate form by manual persulfate digestion.'2' The developed color i s measured automatically.

2.3

Reduced volume versions of this method that use the same reagents and molar ratios are acceptable provided they meet the quality control and performance requirements stated in the method.

2.4

Limited performance-based method modifications may be acceptable provided they are fully documented and meet or exceed requirements expressed in Sect. 9.0, Quality Control.

Inorganic Substances 3.0

481

DEFINITIONS

3.1

CALIBRATION BLANK (CB) - - A volume o f r e a g e n t w a t e r f o r t i f i e d w i t h t h e same m a t r i x as t h e c a l i b r a t i o n s t a n d a r d s , b u t w i t h o u t t h e analytes, i n t e r n a l standards, o r surrogate analytes.

3.2

CALIBRATION STANDARD (CAL) -- A s o l u t i o n p r e p a r e d f r o m t h e p r i m a r y d i l u t i o n s t a n d a r d s o l u t i o n o r s t o c k s t a n d a r d s o l u t i o n s and t h e i n t e r n a l s t a n d a r d s and s u r r o g a t e a n a l y t e s . The CAL s o l u t i o n s a r e used t o c a l i b r a t e t h e i n s t r u m e n t response w i t h r e s p e c t t o a n a l y t e concentration.

3.3

INSTRUMENT PERFORMANCE CHECK SOLUTION ( I P C ) -- A s o l u t i o n o f one o r more method a n a l y t e s , s u r r o g a t e s , i n t e r n a l s t a n d a r d s , o r o t h e r t e s t s u b s t a n c e s used t o e v a l u a t e t h e p e r f o r m a n c e o f t h e i n s t r u m e n t system w i t h respect t o a defined set o f c r i t e r i a .

3.4

LABORATORY FORTIFIED BLANK (LFB) -- An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t o w h i c h known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB i s a n a l y z e d e x a c t l y l i k e a sample, and i t s p u r p o s e i s t o d e t e r m i n e w h e t h e r t h e m e t h o d o l o g y i s i n c o n t r o l , and w h e t h e r t h e l a b o r a t o r y i s c a p a b l e o f m a k i n g a c c u r a t e and p r e c i s e measurements.

3.5

LABORATORY FORTIFIED SAMPLE MATRIX (LFM) -- An a l i q u o t o f an e n v i r o n m e n t a l sample t o w h i c h known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFM i s a n a l y z e d e x a c t l y l i k e a sample, and i t s p u r p o s e i s t o d e t e r m i n e w h e t h e r t h e sample m a t r i x c o n t r i b u t e s b i a s t o t h e a n a l y t i c a l r e s u l t s . The background c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be d e t e r m i n e d i n a s e p a r a t e a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s .

3.6

LABORATORY REAGENT BLANK (LRB) -- An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y a s a sample i n c l u d i n g e x p o s u r e t o a l l g l a s s w a r e , equipment, s o l v e n t s , r e a g e n t s , i n t e r n a l s t a n d a r d s , and s u r r o g a t e s t h a t a r e u s e d w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e present i n t h e l a b o r a t o r y environment, t h e reagents, o r t h e apparatus.

3.7

LINEAR CALIBRATION RANGE (LCR) -- The c o n c e n t r a t i o n r a n g e o v e r w h i c h t h e instrument response i s l i n e a r .

3 . 8 MATERIAL SAFETY DATA SHEET (MSDS) -- W r i t t e n i n f o r m a t i o n p r o v i d e d by vendors concerning a c h e m i c a l ' s t o x i c i t y , h e a l t h hazards, p h y s i c a l p r o p e r t i e s , f i r e , and r e a c t i v i t y d a t a i n c l u d i n g s t o r a g e , s p i l l , and handling precautions. -- The minimum c o n c e n t r a t i o n o f an a n a l y t e t h a t can be i d e n t i f i e d , measured and r e p o r t e d w i t h 99% confidence t h a t t h e a n a l y t e c o n c e n t r a t i o n i s g r e a t e r than zero.

3.9 METHOD DETECTION L I M I T (MDL)

482

Methods for the Determination

3.10 QUALITY CONTROL SAMPLE ( Q C S ) - - A s o l u t i o n of method a n a l y t e s of known c o n c e n t r a t i o n s t h a t i s used t o f o r t i f y an a l i q u o t of LRB o r sample m a t r i x . The QCS i s obtained from a source e x t e r n a l t o the l a b o r a t o r y and d i f f e r e n t from t h e source of c a l i b r a t i o n s t a n d a r d s . I t i s used t o check 1 aboratory performance with e x t e r n a l l y prepared t e s t materi a1 s . 3.11 STOCK STANDARD SOLUTION (SSS) -- A concentrated s o l u t i o n c o n t a i n l n g one o r more method a n a l y t e s prepared in t h e l a b o r a t o r y using assayed r e f e r e n c e m a t e r i a l s o r purchased from a r e p u t a b l e commercial source

3.12 TOTAL PHOSPHORUS (P) -- All of the phosphorus p r e s e n t i n the sample r e g a r d l e s s of forms, a s measured by t h e p e r s u l f a t e d i g e s t i o n procedure. 3.12.1

TOTAL ORTHOPHOSPHATE (P-ortho) -- Inorganic phosphorus [(PO,),-3] in the sample as measured by t h e d i r e c t c o l o r i m e t r i c a n a l y s i s procedure.

3.12.2

TOTAL HYDROLYZABLE PHOSPHORUS (P-hydro) -- Phosphorus in t h e sample a s measured by t h e s u l f u r i c acid h y d r o l y s i s procedure, and minus predetermined orthophosphates. Thjs hydro1y:able phosphorus includes polyphosphates [ (P207)' , (P30,0)- , e t c . ] p l u s some organic phosphorus.

3.12.3

TOTAL ORGANIC PHOSPHORUS (P-org) -- Phosphorus ( i n o r g a n i c plus o x i d i z a b l e organic) in t h e sample as measured by t h e p e r s u l f a t e d i g e s t i o n procedure, and minus hydrolyzable phosphorus and orthophosphate.

3.13 DISSOLVED PHOSPHORUS (P-D) -- All of the phosphorus p r e s e n t i n the f i l t r a t e of a sample f i l t e r e d through a phosphorus-free f i l t e r of 0.45 micron pore s i z e and measured by t h e p e r s u l f a t e d i g e s t i o n procedure.

3.13.1

DISSOLVED ORTHOPHOSPHATE (P-D o r t h o ) -- As measured by he d i r e c t c o l o r i m e t r i c a n a l y s i s procedure.

3.13.2

DISSOLVED HYDROLYZABLE PHOSPHORUS (P-D, hydro) -- As measured by the s u l f u r i c a c i d h y d r o l y s i s procedure and minus predetermined d i s s o l v e d orthophosphates.

3.13.3

DISSOLVED ORGANIC PHOSPHORUS (P-D, o r g ) -- As measured by t h e p e r s u l f a t e d i g e s t i o n procedure, and minus d i s s o l v e d hydrolyzable phosphorus and orthophosphate.

3.14 The following forms, when s u f f i c i e n t amounts of phosphorus a r e p r e s e n t in t h e sample t o warrant such c o n s i d e r a t i o n , may be calculated: 3.14.1

INSOLUBLE PHOSPHORUS (P-I)

=

(P)-(P-D).

Inorganic Substances

3.14.1.1

INSOLUBLE ORTHOPHOSPHATE ( P - I , - (P-D,

3-14.1.2 3.14.1.3

483

ortho) =(P, ortho)

ortho).

INSOLUBLE HYDROLYZABLE PHOSPHORUS ( P - I , (P, hydro) - (P-D, hydro). INSOLUBLE ORGANIC PHOSPHORUS ( P - I ,

o r g ) -(P-D,

org)

hydro) =

=

(P,

org).

3.15 All phosphorus forms s h a l l be r e p o r t e d a s P, mg/L, t o t h e t h i r d place. 4.0

INTERFERENCES

4.1

No i n t e r f e r e n c e i s caused by copper, i r o n , o r s i l i c a t e a t

c o n c e n t r a t i o n s many times g r e a t e r than t h e i r r e p o r t e d c o n c e n t r a t i o n i n seawater. However, high i r o n c o n c e n t r a t i o n s can cause p r e c i p i t a t i o n o f , and subsequent l o s s , of phosphorus.

5.0

4.2

The s a l t e r r o r f o r samples ranging from 5% t o 20% s a l t c o n t e n t was found t o be l e s s than 1%.

4.3

Arsenate i s determined s i m i l a r l y t o phosphorus and should be considered when p r e s e n t i n c o n c e n t r a t i o n s h i g h e r than phosphorus. However, a t c o n c e n t r a t i o n s found i n s e a w a t e r , i t does not interfere.

4.4

Sample t u r b i d i t y must be removed by f i l t r a t i o n p r i o r t o a n a l y s i s f o r orthophosphate. Samples f o r t o t a l o r t o t a l hydrolyzable phosphorus should be f i l t e r e d only a f t e r d i g e s t i o n . Sample c o l o r t h a t absorbs i n t h e photometric range used f o r a n a l y s i s w i l l a l s o i n t e r f e r e .

4.5

Method i n t e r f e r e n c e s may be caused by contaminants i n t h e reagent w a t e r , r e a g e n t s , glassware, and o t h e r sample processing apparatus t h a t b i a s a n a l y t e response.

SAFETY

5.1

The t o x i c i t y o r c a r c i n o g e n i c i t y o f each r e a g e n t used i n this method have not been f u l l y e s t a b l i s h e d . Each chemical should be regarded a s a p o t e n t i a l h e a l t h hazard and exposure should be a s low a s reasonably achievable. Cautions a r e included f o r known extremely hazardous materi a1 s o r procedures.

5.2

Each l a b o r a t o r y i s r e s p o n s i b l e f o r maintaining a c u r r e n t awareness f i l e of OSHA r e g u l a t i o n s r e g a r d i n g t h e s a f e handling of the chemicals s p e c i f i e d i n t h i s method. A r e f e r e n c e f i l e of Material S a f e t y Data Sheets (MSDS) should be made a v a i l a b l e t o a l l personnel involved i n the chemical a n a l y s i s . The p r e p a r a t i o n of a formal s a f e t y plan i s a l s o a d v i s a b l e .

484

Methods for the Determination 5.3

The following chemicals have the p o t e n t i a l t o be highly t o x i c o r hazardous, consul t MSDS . 5.3.1

6.0

EOUIPMENT AND SUPPLIES

6.1

Balance -- A n a l y t i c a l , capable of a c c u r a t e l y weighing t o the n e a r e s t 0.0001 g.

6.2

Glassware -- Class A volumetric f l a s k s and p i p e t s a s r e q u i r e d .

6.3

Hot p l a t e o r autoclave.

6.4

Automated continuous flow analys s equipment designed t o d e l i v e r and r e a c t sample and r e a g e n t s in the required o r d e r and r a t i o s .

6.5

7.0

S u l f u r i c acid ( 7 . 2 , 7.7)

6.4.1

Sampl i ng device (sampler

6.4.2

Mu1 t i channel pump

6.4.3

Reaction u n i t o r manifold

6.4.4

Colorimetric detector

6.4.5

Data recording device

Acid-washed glassware: All glassware used i n t h e determination should be washed with hot 1:l HC1 and r i n s e d w i t h d i s t i l l e d water. The acid-washed glassware should be f i l l e d with d i s t i l l e d water and t r e a t e d with a l l the r e a g e n t s t o remove the l a s t t r a c e s of phosphorus t h a t might be adsorbed on the glassware. P r e f e r a b l y , t h i s glassware should be used only f o r the determination o f phosphorus and a f t e r use i t should be r i n s e d w i t h d i s t i l l e d water and kept covered u n t i l needed again. I f t h i s i s done, the t r e a t m e n t with 1:l HC1 and r e a g e n t s i s only required o c c a s i o n a l l y . Commercial d e t e r g e n t should never be used.

REAGENTS AND STANDARDS

7.1

Reagent water: D i s t i l l e d o r deionized w a t e r , free o f the a n a l y t e o f i n t e r e s t . ASTM type I 1 o r e q u i v a l e n t .

7.2

S u l f u r i c acid s o l u t i o n , 5N: Slowly add 70 mL of conc. H SO (CASRN 7664-93-9) t o approximately 400 mL o f d i s t i l l e d water. Eooj t o room temperature and d i l u t e t o 500 mL w i t h d i s t i l l e d water.

7.3

Antimony potassium t a r t r a t e s o l u t i o n : Weight 0 . 3 g K(SbO)C4H,0,.1/2H,0 (CASRN 28300-74-5), d i s s o l v e d i n 50 mL d i s t i l l e d water i n 100-mL volumetric f l a s k , d i l u t e t o volume. S t o r e a t 4°C in a d a r k , glass-stoppered b o t t l e .

Inorganic Substances

485

7.4 Ammonium molybdate s o l u t i o n : Dissolve 4 g (NH,),Mo70,,.4ti 0 (CASRN 12027-67-7) i n 100 mL reagent w a t e r . S t o r e i n a p l a s t i c i o t t l e a t 4°C.

7.5 Ascorbic a c i d , 0.1M: Dissolve 1 . 8 g of a s c o r b i c acid (CASRN 50-817) i n 100 m L of r e a g e n t w a t e r . The s o l u t i o n i s s t a b l e f o r about a week i f prepared with water c o n t a i n i n g no more t h a n t r a c e amounts o f heavy metals and s t o r e d a t 4°C. 7.6 Combined r e a g e n t : Mix t h e above r e a g e n t s i n t h e following proportions f o r 100 m L of t h e mixed r e a g e n t : 50 m L o f 5N H SO, (7.2), 5 m L of antimony potassium t a r t r a t e s o l u t i o n (7.3), $5 m L of ammonium molybdate s o l u t i o n ( 7 . 4 ) , and 30 m L of a s c o r b i c a c i d s o l u t i o n (7.5). Mix a f t e r a d d i t i o n o f each r e a q e n t . All r e a g e n t s must reach room temperature before they a r e mixed and must be mixed i n t h e o r d e r given. I f t u r b i d i t y forms i n t h e combined r e a g e n t , shake and l e t s t a n d f o r a few minutes u n t i l t h e t u r b i d i t y d i s a p p e a r s before processing. This volume i s s u f f i c i e n t f o r 4 h o p e r a t i o n . Since the s t a b i l i t y of t h i s s o l u t i o n i s l i m i t e d , i t must be f r e s h l y prepared f o r each run. NOTE 1: A s t a b l e s o l u t i o n can be prepared by not including t h e

a s c o r b i c a c i d i n t h e combined r e a g e n t . I f t h i s i s done, t h e mixed reagent (molybdate, t a r t r a t e , and a c i d ) i s pumped through t h e d i s t i l l e d water l i n e and t h e a s c o r b i c a c i d s o l u t i o n (30 mL of 7.5 d i l u t e d t o 100 m L with reagent w a t e r ) through t h e o r i g i n a l mixed reagent l i n e .

7.7

S u l f u r i c acid s o l u t i o n , 1 1 N: Slowly add 155 m L conc. H,SO, When c o o l , d i l u t e t o 500 ml .

t o 600

m L reagent water. 7.8

Ammonium p e r s u l f a t e (CASRN 7727-54-0).

7.9

Acid wash water: Add 40 mL of s u l f u r i c a c i d s o l u t i o n (7.7) t o 1 L of reagent water and d i l u t e t o 2 L. (Not t o be used when only orthophosphate i s being determined).

7:lO

Phenolphthalein i n d i c a t o r s o l u t i o n (5 g / L ) : Dissolve 0 . 5 g of phenolphthalein (CASRN 77-09-8) i n a s o l u t i o n of 50 m L o f isopropyl alcohol (CASRN 67-63-0) and 50 mL o f reagent water.

7.11 Stock phosphorus s o l u t i o n : Dissolve 0.4393 g of p r e d r i e d (105°C f o r 1 h ) Potassium phosphate monobasic KH,PO, (CASRN 7778-77-0) i n reagent water and d i l u t e t o 1000 mL. 1.0 m L = 0.1 mg P. 7.12 Standard phosphorus s o l u t i o n : D i l u t e 10.0 m L of s t o c k so ution (7.11) t o 100 m L with reagent water. 1.0 mL = 0.01 mg P. 7.13 Standard phosphorus s o l u t i o n : D i l u t e 10.0 m L of standard sol u t i on (7.12) t o 100 m L with r e a g e n t water. 1.0 m L = 0.001 mg P

486

8.0

9.0

Methods for the Determination

SAMPLE COLLECTION, PRESERVATION AND STORAGE 8.1

Samples should be c o l l e c t e d i n p l a s t i c o r g l a s s b o t t l e s . All b o t t l e s must be thoroughly cleaned and r i n s e d with reagent water. Volume c o l l e c t e d should be s u f f i c i e n t t o i n s u r e a r e p r e s e n t a t i v e sample, allow f o r r e p l i c a t e a n a l y s i s ( i f r e q u i r e d ) , a n d minimize waste d i s p o s a l .

8.2

Samples must be preserved with H,SO, t o a pH < 2 and cooled t o 4°C a t t h e time of c o l l e c t i o n .

8.3

Samples should be analyzed a s soon a s p o s s i b l e a f t e r c o l l e c t i o n . I f s t o r a g e i s r e q u i r e d , preserved samples a r e maintained a t 4°C and may be held f o r u p t o 28 days.

OUALITY CONTROL

9.1

Each l a b o r a t o r y using t h i s method i s r e q u i r e d t o o p e r a t e a formal q u a l i t y c o n t r o l (QC) program. The minimum requirements o f t h i s program c o n s i s t of an i n i t i a l demonstration of l a b o r a t o r y c a p a b i l i t y , and t h e p e r i o d i c a n a l y s i s of l a b o r a t o r y reagent blanks, f o r t i f i e d blanks and o t h e r l a b o r a t o r y s o l u t i o n s as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o maintain performance r e c o r d s t h a t d e f i n e the q u a l i t y of t h e d a t a t h a t a r e generated.

9.2

INITIAL DEMONSTRATION OF PERFORMANCE 9.2.1

The i n i t i a l demonstration of performance i s used t o c h a r a c t e r i z e instrument performance (determination o f LCRs and a n a l y s i s of QCS) and l a b o r a t o r y performance ( d e t e r m i n a t i o n of MDLs) p r i o r t o performing a n a l y s e s by t h i s method.

9.2.2

Linear C a l i b r a t i o n Range (LCR) -- The LCR must be determined i n i t i a l l y and v e r i f i e d every 6 months o r whenever a s i g n i f i c a n t change i n instrument response i s observed or expected. The i n i t i a l demonstration of l i n e a r i t y must use s u f f i c i e n t s t a n d a r d s t o i n s u r e t h a t the r e s u l t i n g curve i s l i n e a r . The v e r i f i c a t i o n of l i n e a r i t y must use a minimum of a blank and t h r e e s t a n d a r d s . I f any v e r i f i c a t i o n d a t a exceeds t h e i n i t i a l v a l u e s by t 10%,l i n e a r i t y must be r e e s t a b l i s h e d . I f any p o r t i o n of t h e range i s shown t o be n o n l i n e a r , s u f f i c i e n t s t a n d a r d s must be used t o c l e a r l y d e f i n e the n o n l i n e a r p o r t i o n .

9.2.3

Q u a l i t y Control Sample (QCS) -- When beginning t h e use of t h i s method, on a q u a r t e r l y b a s i s o r a s r e q u i r e d t o meet d a t a - q u a l i t y needs, v e r i f y t h e c a l i b r a t i o n s t a n d a r d s and a c c e p t a b l e instrument performance with the p r e p a r a t i o n and a n a l y s e s o f a QCS. I f t h e determined c o n c e n t r a t i o n s a r e not w i t h i n f 10% o f t h e s t a t e d v a l u e s , performance of t h e

Inorganic Substances

487

d e t e r m i n a t i v e s t e p of t h e method i s unacceptable. The source of t h e problem must be i d e n t i f i e d and c o r r e c t e d before e i t h e r proceeding with t h e i n i t i a l determination of MDLs o r c o n t i n u i n g with on-going a n a l y s e s . 9.2.4

Method Detection Limit (MDL) - - MDLs must be e s t a b l i s h e d f o r a l l a n a l y t e s , using reagent water ( b l a n k ) f o r t i f i e d a t a c o n c e n t r a t i o n of two t o t h r e e times t h e estimated instrument d e t e c t i o n 1 imit."' To determine MDL v a l u e s , t a k e seven r e p l i c a t e a l i q u o t s of t h e f o r t i f i e d reagent water and process through the entire a n a l y t i c a l method. Perform a l l c a l c u l a t i o n s d e f i n e d i n the method and r e p o r t the c o n c e n t r a t i o n v a l u e s i n the a p p r o p r i a t e u n i t s . C a l c u l a t e t h e MDL a s follows:

MDL

=

( t ) x (S)

where, t

=

S t u d e n t ' s t value f o r a 99% confidence l e v e l and a s t a n d a r d d e v i a t i o n e s t i m a t e with n-1 degrees o f freedom [t = 3.14 f o r seven r e p l i c a t e s ] .

S

=

s t a n d a r d d e v i a t i o n of t h e r e p l i c a t e a n a l y s e s .

MDLs should be determined every 6 months, when a new o p e r a t o r begins work, o r whenever t h e r e i s a s i g n i f i c a n t change i n the background o r instrument response. 9.3

ASSESSING LABORATORY PERFORMANCE 9.3.1

Laboratory Reagent Blank (LRB) -- The l a b o r a t o r y must analyze a t l e a s t one LRB with each batch of samples. Data produced a r e used t o a s s e s s contamination from the l a b o r a t o r y environment. Values t h a t exceed t h e MDL i n d i c a t e l a b o r a t o r y o r r e a g e n t contamination should be suspected and c o r r e c t i v e a c t i o n s must be taken before continuing t h e anal y s i s .

9.3.2

Laboratory F o r t i f i e d Blank (LFB) -- The l a b o r a t o r y must analyze a t l e a s t one LFB with each batch o f samples. Cal cul a t e accuracy a s percent recovery ( S e c t . 9 . 4 . 2 ) . I f the recovery o f any a n a l y t e f a l l s o u t s i d e t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%, t h a t a n a l y t e i s judged o u t of c o n t r o l , and t h e source of t h e problem should be i d e n t i f i e d and r e s o l v e d b e f o r e c o n t i n u i n g a n a l y s e s .

9.3.3

The l a b o r a t o r y must use LFB a n a l y s e s d a t a t o a s s e s s l a b o r a t o r y performance a g a i n s t t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%. When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e ( u s u a l l y a minimum of 20-30 a n a l y s e s ) , o p t i o n a l c o n t r o l l i m i t s can be developed from the percent mean recovery ( x ) and t h e s t a n d a r d d e v i a t i o n ( S ) of t h e mean

488

Methods for the Determination r e c o v e r y . These d a t a can be used t o e s t a b l i s h t h e upper and l o w e r control l i m i t s as follows: UPPER CONTROL LIMIT LOWER CONTROL L I M I T

= =

x t 3s x - 3s

The o p t i o n a l c o n t r o l l i m i t s must be equal t o o r b e t t e r t h a n t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%. A f t e r each f i v e t o t e n new r e c o v e r y measurements, new c o n t r o l l i m i t s can be c a l c u l a t e d u s i n g o n l y t h e most r e c e n t 20-30 d a t a p o i n t s . A l s o , t h e s t a n d a r d d e v i a t i o n ( S ) d a t a should be used t o e s t a b l i s h an on-going p r e c i s i o n statement f o r t h e l e v e l of c o n c e n t r a t i o n s i n c l u d e d i n t h e LFB. These d a t a must be k e p t on f i l e and be a v a i l a b l e f o r r e v i e w . 9.3.4

9.4

I n s t r u m e n t Performance Check S o l u t i o n (IPC) -- For a l l d e t e r m i n a t i o n s t h e l a b o r a t o r y must analyze t h e IPC ( a midrange check standard) and a c a l i b r a t i o n b l a n k i m m e d i a t e l y f o l l o w i n g d a i l y c a l i b r a t i o n , a f t e r e v e r y t e n t h sample ( o r more f r e q u e n t l y , i f r e q u i r e d ) and a t t h e end o f t h e sample r u n . A n a l y s i s o f t h e I P C s o l u t i o n and c a l i b r a t i o n b l a n k i m m e d i a t e l y f o l l o w i n g c a l i b r a t i o n must v e r i f y t h a t t h e i n s t r u m e n t i s w i t h i n t 10% o f c a l i b r a t i o n . Subsequent analyses o f t h e I P C s o l u t i o n must v e r i f y t h e c a l i b r a t i o n i s s t i l l w i t h i n t 10%. I f t h e c a l i b r a t i o n cannot be v e r i f i e d w i t h i n t h e s p e c i f i e d l i m i t s , r e a n a l y z e t h e I P C s o l u t i o n . If t h e second a n a l y s i s o f t h e IPC s o l u t i o n c o n f i r m s c a l i b r a t i o n t o be o u t s i d e t h e l i m i t s , sample a n a l y s i s must be d i s c o n t i n u e d , t h e cause d e t e r m i n e d and/or i n t h e case o f d r i f t t h e i n s t r u m e n t r e c a l i b r a t e d . A l l samples f o l l o w i n g t h e l a s t a c c e p t a b l e I P C s o l u t i o n must be reanalyzed. The a n a l y s i s d a t a o f t h e c a l i b r a t i o n b l a n k and I P C s o l u t i o n must be k e p t on f i l e w i t h t h e sample analyses d a t a .

ASSESSING ANALYTE RECOVERY AND DATA QUALITY

9.4.1

L a b o r a t o r y F o r t i f i e d Sample M a t r i x (LFM) -- The l a b o r a t o r y must add a known amount o f a n a l y t e t o a minimum o f 10% o f t h e r o u t i n e samples. I n each case t h e LFM a l i q u o t must be a d u p l i c a t e o f t h e a l i q u o t used f o r sample a n a l y s i s . The a n a l y t e c o n c e n t r a t i o n must be h i g h enough t o be d e t e c t e d above t h e o r i g i n a l sample and s h o u l d n o t be l e s s t h a n f o u r t i m e s t h e MDL. The added a n a l y t e c o n c e n t r a t i o n s h o u l d be t h e same as t h a t used i n t h e l a b o r a t o r y f o r t i f i e d b l a n k .

9.4.2

C a l c u l a t e t h e p e r c e n t r e c o v e r y f o r each a n a l y t e , c o r r e c t e d f o r c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o t h e d e s i g n a t e d LFM r e c o v e r y range 90-110%. Percent r e c o v e r y may be c a l c u l a t e u s i n g t h e f o l l owing e q u a t i o n :

Inorganic Substances

c,

R =

-

c

489

x 100

S

where, R

=

C, =

C

s

= =

percent recovery. f o r t i f i e d sample c o n c e n t r a t i o n . sample background c o n c e n t r a t i o n . c o n c e n t r a t i o n e q u i v a l e n t o f a n a l y t e added t o sample.

9.4.3

I f t h e recovery of any a n a l y t e f a l l s o u t s i d e the designated LFM recovery range and the l a b o r a t o r y performance f o r t h a t a n a l y t e i s shown t o be i n c o n t r o l ( S e c t . 9 . 3 ) , the recovery problem encountered with the LFM i s judged t o be e i t h e r matrix o r s o l u t i o n r e l a t e d , not system r e l a t e d .

9.4.4

Where r e f e r e n c e m a t e r i a l s a r e a v a i l a b l e , they should be analyzed t o provide a d d i t i o n a l performance d a t a . The a n a l y s i s of r e f e r e n c e samples i s a v a l u a b l e t o o l f o r demonstrating t h e a b i l i t y t o perform t h e method acceptably.

10.0 CALIBRATION AND STANDARDIZATION 10.1 Prepare a s e r i e s o f a t l e a s t 3 s t a n d a r d s , covering t h e d e s i r e d range, and a blank by p i p e t t i n g and d i l u t i n g s u i t a b l e volumes o f working s t a n d a r d s o l u t i o n s (7.12 o r 7.13) i n t o 100 mL volumetric f l a s k s . Suggested ranges i n c l u d e 0 . 0 0 t o 0.10 and 0.20 t o 1.00 mg/L. 10.2 Process s t a n d a r d s and blanks a s d e s c r i b e d i n S e c t . 11, Procedure 10.3 S e t up manifold a s shown i n f i g u r e 2 . 10.4 Prepare flow system a s d e s c r i b e d i n S e c t . 11, Procedure. 10.5 Place a p p r o p r i a t e s t a n d a r d s i n t h e sampler i n o r d e r o f decreasing c o n c e n t r a t i o n and perform a n a l y s i s . 10.6 Prepare s t a n d a r d curve by p l o t t i n g instrument response a g a i n s t c o n c e n t r a t i o n v a l u e s . A c a l i b r a t i o n curve may be f i t t e d t o t h e c a l i b r a t i o n s o l u t i o n s c o n c e n t r a t i o n / r e s p o n s e d a t a using computer o r c a l c u l a t o r based r e g r e s s i o n curve f i t t i n g techniques. Acceptance o r c o n t r o l 1 i m i t s should be e s t a b l i s h e d using t h e d i f f e r e n c e between t h e measured value of t h e c a l i b r a t i o n s o l u t i o n and t h e " t r u e value" concentration.

10.7 A f t e r t h e c a l i b r a t i o n has been e s t a b l i s h e d , i t must be v e r i f i e d by t h e a n a l y s i s of a s u i t a b l e q u a l i t y c o n t r o l sample (QCS). I f measurements exceed f 10% of t h e e s t a b l i s h e d QCS v a l u e , the a n a l y s i s should be terminated and t h e instrument r e c a l i b r a t e d . The new c a l i b r a t i o n must be v e r i f i e d before c o n t i n u i n g a n a l y s i s . P e r i o d i c

490

Methods for the Determination r e a n a l y s i s of t h e QCS i s recommended as a c o n t i n u i n g c a l i b r a t i o n check.

11.0 PROCEDURE

11.1 Phosphorus 11.1.1

Add 1 mL o f s u l f u r i c a c i d s o l u t i o n (7.7) t o a 50 mL sample and/or s t a n d a r d i n a 125-mL Erlenmeyer f l a s k .

11.1.2' Add 0.4 g of ammonium p e r s u l f a t e (7.8). 11.1.3

B o i l g e n t l y on a pre-heated h o t p l a t e f o r a p p r o x i m a t e l y 3040 m i n o r u n t i l a f i n a l volume o f about 10 mL i s reached. Do n o t a l l o w sample t o go t o dryness.

A l t e r n a t e l y , heat f o r

30 min i n an a u t o c l a v e a t 121°C (15-20 p s i ) . Ifsample i s n o t c l e a r

11.1.4

Cool and d i l u t e t h e sample t o 50 mL. a t t h i s point, f i l t e r .

11.1.5

Determine phosphorus as o u t l i n e d (11.3.2) w i t h a c i d wash w a t e r (7.9) i n wash tubes.

11.2 H y d r o l y z a b l e Phosphorus 11.2.1. Add 1 mL o f s u l f u r i c a c i d s o l u t i o n (7.7) t o a 50 mL sample and/or s t a n d a r d i n a 125 mL Erlenmeyer f l a s k . 11.2.2

B o i l g e n t l y on a pre-heated h o t p l a t e f o r 30-40 min u n t i l a f i n a l volume o f about 10 mL i s reached. Do n o t a l l o w sample t o go t o dryness. A l t e r n a t i v e l y , h e a t f o r 30 m i n i n an a u t o c l a v e a t 121°C (15-20 p s i ) .

11.2.3

Determine phosphorus as o u t l i n e d (11.3.2) w i t h a c i d wash w a t e r (7.9) i n wash tubes.

11.3 Orthophosphate 11.3.1

Add 1 d r o p o f p h e n o l p h t h a l e i n i n d i c a t o r s o l u t i o n (7.10) t o a p p r o x i m a t e l y 50 mL o f sample. I f a r e d c o l o r develops, add s u l f u r i c a c i d s o l u t i o n (7.7) drop-wise t o j u s t d i s c h a r g e t h e c o l o r . A c i d samples must be n e u t r a l i z e d w i t h 1 N sodium h y d r o x i d e (40 g NaOH/L).

11.3.2

Set up m a n i f o l d as shown i n F i g u r e 1.

11.3.3

A l l o w system t o e q u i l i b r a t e as r e q u i r e d . O b t a i n a s t a b l e base1 i n e w i t h a l l r e a g e n t s , f e e d i n g r e a g e n t w a t e r t h r o u g h t h e sample l i n e .

11.3.4

P l a c e standards i n sampler i n o r d e r o f d e c r e a s i n g c o n c e n t r a t i o n . and complete f i l l i n g o f sampler t r a y .

Inorganic Substances 11.3.5

491

S w i t c h sample l i n e f r o m r e a g e n t w a t e r t o Sampler and b e g i n analysis.

12.0 DATA ANALYSIS AND CALCULATIONS 12.1 Prepare a c a l i b r a t i o n c u r v e by p l o t t i n g i n s t r u m e n t response Compute sample c o n c e n t r a t i o n by against standard concentration. M u l t i p l y answer comparing sample response w i t h t h e s t a n d a r d c u r v e . by a p p r o p r i a t e d i l u t i o n f a c t o r . 12.2 Report o n l y t h o s e v a l u e s t h a t f a l l between t h e l o w e s t and t h e h i g h e s t c a l i b r a t i o n standards, Samples exceeding t h e h i g h e s t s t a n d a r d s h o u l d be d i l u t e d and r e a n a l y z e d . Any sample whose computed v a l u e i s l e s s t h a n 5% of i t s immediate predecessor must be rerun. 12.3 Report r e s u l t s i n mg P/L. 13.0 METHOD PERFORMANCE 13.1 S i x l a b o r a t o r i e s ( u s i n g Technicon AAI equipment) p a r t i c i p a t i n g i n an EPA Method Study, analyzed f o u r n a t u r a l w a t e r samples c o n t a i n i n g e x a c t i n c r e m e n t s o f orthophosphate, w i t h t h e f o l l o w i n g r e s u l t s : Increment as Orthophosphate m q P/1 i t e r 0.04 0.04 0.29 0.30

P r e c i s i o n as Standard D e v i a t i o n ms P / l i t e r 0.019 0.014 0.087 0.066

Accuracy as Bias % t16.7 -8.3 -15.5 -12.8

Bias mq P / l i t e r

to. 007

-0.003 -0.05 -0.04

13.2 I n a s i n g l e l a b o r a t o r y (EMSL), u s i n g s u r f a c e w a t e r samples a t c o n c e n t r a t i o n s o f 0.04, 0.19, 0.35, and 0.84 mg P/L, s t a n d a r d d e v i a t i o n s were +0.005, kO.000, k0.003, and fO.OOO, r e s p e c t i v e l y . 13.3 I n a s i n g l e l a b o r a t o r y (EMSL), u s i n g s u r f a c e w a t e r samples a t c o n c e n t r a t i o n s o f 0.07 and 0.76 mg P/L, r e c o v e r i e s were 99% and loo%, r e s p e c t i v e l y . 13.4 The i n t e r l a b o r a t o r y p r e c i s i o n and accuracy d a t a i n T a b l e 1 were developed u s i n g a r e a g e n t w a t e r m a t r i x . Values a r e i n mg PO,-P/L.

14.0 POLLUTION PREVENTION 14.1 P o l l u t i o n p r e v e n t i o n encompasses any t e c h n i q u e t h a t reduces o r e l i m i n a t e s t h e q u a n t i t y o r t o x i c i t y o f waste a t t h e p o i n t o f g e n e r a t i o n . Numerous o p p o r t u n i t i e s f o r p o l l u t i o n p r e v e n t i o n e x i s t i n l a b o r a t o r y o p e r a t i o n . The EPA has e s t a b l i s h e d a p r e f e r r e d h i e r a r c h y o f e n v i r o n m e n t a l management t e c h n i q u e s t h a t p l a c e s p o l l u t i o n p r e v e n t i o n as t h e management o p t i o n o f f i r s t c h o i c e .

492

Methods for the Determination Whenever f e a s i b l e , l a b o r a t o r y p e r s o n n e l s h o u l d use p o l l u t i o n p r e v e n t i o n t e c h n i q u e s t o a d d r e s s t h e i r w a s t e g e n e r a t i o n . When wastes c a n n o t be f e a s i b l y r e d u c e d a t t h e s o u r c e , t h e Agency recommends r e c y c l i n g as t h e n e x t b e s t o p t i o n . 14.2 The q u a n t i t y o f c h e m i c a l s p u r c h a s e d s h o u l d be based on e x p e c t e d usage d u r i n g i t s s h e l f l i f e and d i s p o s a l c o s t o f unused m a t e r i a l . A c t u a l r e a g e n t p r e p a r a t i o n volumes s h o u l d r e f l e c t a n t i c i p a t e d usage and r e a g e n t s t a b i l i t y . 14.3 F o r i n f o r m a t i o n a b o u t p o l l u t i o n p r e v e n t i o n t h a t may be a p p l i c a b l e t o l a b o r a t o r i e s and r e s e a r c h i n s t i t u t i o n s , c o n s u l t " L e s s i s B e t t e r : L a b o r a t o r y Chemical Management f o r Waste R e d u c t i o n , " a v a i l a b l e f r o m t h e American Chemical S o c i e t y ' s D e p a r t m e n t o f Government R e g u l a t i o n s and S c i e n c e P o l i c y , 1155 1 6 t h S t r e e t N.W., Washington D.C. 20036, (202) 872-4477.

15.0 WASTE MANAGEMENT 1 5 . 1 The E n v i r o n m e n t a l P r o t e c t i o n Agency r e q u i r e s t h a t l a b o r a t o r y w a s t e management p r a c t i c e s b e c o n d u c t e d c o n s i s t e n t w i t h a l l a p p l i c a b l e r u l e s and r e g u l a t i o n s . Excess r e a g e n t s , samples and method p r o c e s s w a s t e s s h o u l d b e c h a r a c t e r i z e d and d i s p o s e d o f i n an a c c e p t a b l e manner. The Agency u r g e s l a b o r a t o r i e s t o p r o t e c t t h e a i r , w a t e r , and l a n d by m i n i m i z i n g and c o n t r o l l i n g a l l r e l e a s e s from hoods, and bench o p e r a t i o n s , c o m p l y i n g w i t h t h e l e t t e r and s p i r t o f any w a s t e r d i s c h a r g e p e r m i t and r e g u l a t i o n s , and b y c o m p l y i n g w t h a l l s o l i d and h a z a r d o u s w a s t e r e g u l a t i o n s , p a r t i c u l a r l y t h e hazardous w a s t e i d e n t i f i c a t i o n r u l e s and l a n d d i s p o s a l r e s t r i c t ons. F o r f u r t h e r i n f o r m a t i o n on w a s t e management c o n s u l t t h e "Waste Management Manual f o r L a b o r a t o r y P e r s o n n e l ," a v a i l a b l e f r o m t h e American Chemical S o c i e t y a t t h e a d d r e s s l i s t e d i n S e c t . 14.3. 16.0 REFERENCES

1.

Murphy, J. and R i l e y , J., "A M o d i f i e d S i n g l e S o l u t i o n f o r t h e D e t e r m i n a t i o n o f Phosphate i n N a t u r a l Waters." A n a l . Chim. Acta., 2 7 , 31 (1962).

2.

G a l e s , M., J r . , J u l i a n , E., and K r o n e r , R., "Method f o r Q u a n t i t a t i v e D e t e r m i n a t i o n o f T o t a l Phosphorus i n Water." J o u r . AWWA, 3,No. 10, 1363 (1966).

3.

L o b r i n g , L.B. and Booth, R.L., " E v a l u a t i o n o f t h e A u t o A n a l y z e r 11; A P r o g r e s s R e p o r t , " T e c h n i c o n I n t e r n a t i o n a l Symposium, June, 1972, New Y o r k , N.Y.

4.

S t a n d a r d Methods f o r t h e E x a m i n a t i o n o f Water and Wastewater, 1 8 t h E d i t i o n , p . 4-116, Method 4500-P F ( 1 9 9 2 ) .

5.

Code o f F e d e r a l R e g u l a t i o n s 40, Ch. 1, P t . 136, A p p e n d i x B.

Inorganic Substances

493

17.0 TABLES, DIAGRAMS, FLOWCHARTS, AND VALIDATION DATA

TABLE 1 .

INTERLABORATORY PRECISION AND ACCURACY DATA

TRUE VALUE (T)

UUMBER OF VALUES REPORTED

MEAN (X)

RESIDUAL FOR X

STANDARD DEVIATION

(S)

RESIDUAL FOR S

54

0.150

0.1530

-0.0017

0.0128

-0.0010

69

0.351

0.3670

0.0140

0.0368

0.0084

88

0.625

0.6090

-0.01 41

0.0413

-0.0069

87

1.80

1.7374

-0.0444

0.1259

-0.0072

57

2.50

2 4867

0.0146

0.1637

-0.0200

69

2.75

2.8344

0.1158

0.2019

0.0002

53

3.50

3.5619

0.1038

0.2854

0.0295

87

3.60

3.4957

-0.0610

0.2137

-0.0495

64

4.00

3.8523

-0.0989

0.3158

0.0237

57

7.01

6.9576

0.0383

0.5728

0.0632

88

8.20

8.0995

0.0068

0.5428

-0.0528

63

9.00

8.6717

-0.2099

0.6770

0.0236

REGRESSIONS:

X

= 0.986T t 0.007,

S = 0.0721

+

0.003

m ct 0

Di r e c t

"2"4

Colorimetry Orthophosphate

r"l Residue

Hydrolyzable f, Orthophosphate

,t , ;i , , Filtrate

J,

~irect

~ 2 ~ 0 4

Colorimetry

Hydrolysis & Colorimetry

Dissolved Orthophosphate

D i s s . Hydrolyzable 6 Orthophosphate

j,

Persulfate Digestion & Colorimetry

Dissolved Phosphorus

FIGURE 1. ANALYTICAL SCHEME FOR DIFFERENTIATION OF PHOSPHORUS FORMS

Persul f a t e Digest ion

?

ml/min

WASTE

--

HEATING BATH

3%

5 TURNS 5 TURNS

-

0.42

SAMPLE

0.32

AIR

0.32

DISTILLED WATER

0.23

MIXED REAGENT

0.60

FROM F/C

TO F/C PUMP TUBE

COLORIMRER 650-660nmw880nm 50mm F/C

WASTE

-

PUMP

30 PER HOUR SAMPLE 80 SEC. WASH40 SEC.

Figure 2 Phosphorus Manifold

496

Methods for the Determination METHOD 3 7 5 . 2 DETERMINATION OF SULFATE BY AUTOMATED COLORIMETRY

Edited by James W . O'Dell Inorganic Chemistry Branch Chemistry Research Division

Revision 2.0 August 1993

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

Inorganic Substances

497

METHOD 375.2 DETERMINATION OF SULFATE I N WATER BY AUTOMATED COLORIMETRY 1.0

2.0

3.0

SCOPE AND APPLICATION

1.1

This automated method i s a p p l i c a b l e t o d r i n k i n g , ground and s u r f a c e w a t e r , domestic and i n d u s t r i a l wastes.

1.2

The a p p l i c a b l e range i s 3 t o 300 mg S04/L. The s e n s i t i v i t y o f t h e method can be i n c r e a s e d by a minor m o d i f i c a t i o n t o analyze samples Approximately 30 samples per i n t h e range of 0.5 t o 30 mg SOJL. hour can be analyzed.

SUMMARY OF METHOD

2.1

The sample i s f i r s t passed through a sodium form cation-exchange column t o remove m u l t i v a l e n t metal i o n s . The sample c o n t a i n i n g s u l f a t e i s then r e a c t e d with an alcohol s o l u t i o n of barium c h l o r i d e and methylthymol b l u e (MTB) a t a pH of 2.5-3.0 t o form barium s u l f a t e . The combined s o l u t i o n i s r a i s e d t o a pH of 12.5-13.0 so t h a t excess barium r e a c t s with MTB. The uncomplexed MTB c o l o r i s g r a y ; i f i t i s a l l c h e l a t e d with barium, the c o l o r i s b l u e . I n i t i a l l y , t h e barium and MTB a r e equimolar and e q u i v a l e n t t o 300 mg SOJL; thus t h e amount of uncomplexed MTB i s equal t o t h e s u l f a t e present.

2.2

Reduced volume v e r s i o n s o f t h i s method t h a t use t h e same r e a g e n t s and molar r a t i o s a r e a c c e p t a b l e provided they meet t h e q u a l i t y c o n t r o l and performance requirements s t a t e d i n t h e method.

2.3

Limited performance-based method m o d i f i c a t i o n s may be a c c e p t a b l e provided t h e y a r e f u l l y documented and meet o r exceed requirements expressed i n S e c t . 9.0, Q u a l i t y Control.

DEFINITIONS

3.1

CALIBRATION BLANK (CB) -- A volume of reagent water f o r t i f i e d with t h e same m a t r i x a s the c a l i b r a t i o n s t a n d a r d s , but without the analytes, internal standards, o r surrogate analytes.

3.2

CALIBRATION STANDARD (CAL) -- A s o l u t i o n prepared from t h e primary d i l u t i o n s t a n d a r d s o l u t i o n o r s t o c k s t a n d a r d s o l u t i o n s and the i n t e r n a l s t a n d a r d s and s u r r o g a t e a n a l y t e s . The CAL s o l u t i o n s a r e used t o c a l i b r a t e the instrument response with r e s p e c t t o a n a l y t e concentration.

3.3

INSTRUMENT PERFORMANCE CHECK SOLUTION (IPC) -- A s o l u t i o n of one o r more method a n a l y t e s , s u r r o g a t e s , i n t e r n a l s t a n d a r d s , o r o t h e r t e s t

498

Methods for the Determination s u b s t a n c e s used t o e v a l u a t e t h e p e r f o r m a n c e o f t h e i n s t r u m e n t s y s t e m w i t h respect t o a defined set o f c r i t e r i a .

3.4

LABORATORY FORTIFIED BLANK (LFB) - - An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t o w h i c h known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB i s a n a l y z e d e x a c t l y l i k e a sample, and i t s p u r p o s e i s t o d e t e r m i n e w h e t h e r t h e m e t h o d o l o g y i s i n c o n t r o l , and w h e t h e r t h e l a b o r a t o r y i s c a p a b l e o f m a k i n g a c c u r a t e and p r e c i s e measurements.

3.5

LABORATORY FORTIFIED SAMPLE MATRIX (LFM) -- An a l i q u o t o f an e n v i r o n m e n t a l sample t o w h i c h known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFM i s a n a l y z e d e x a c t l y l i k e a sample, and i t s p u r p o s e i s t o d e t e r m i n e w h e t h e r t h e sample m a t r i x c o n t r i b u t e s b i a s t o t h e a n a l y t i c a l r e s u l t s . The b a c k g r o u n d c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must b e d e t e r m i n e d i n a s e p a r a t e a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s .

3.6

LABORATORY REAGENT BLANK (LRB) -- An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y as a sample i n c l u d i n g e x p o s u r e t o a l l g l a s s w a r e , equipment, s o l v e n t s , r e a g e n t s , i n t e r n a l s t a n d a r d s , and s u r r o g a t e s t h a t a r e u s e d w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e present i n t h e l a b o r a t o r y environment, t h e reagents, o r t h e apparatus.

3.7

LINEAR CALIBRATION RANGE (LCR) -- The c o n c e n t r a t i o n r a n g e o v e r w h i c h t h e i n s t r u m e n t response i s l i n e a r .

3.8

MATERIAL SAFETY DATA SHEET (MSDS) -- W r i t t e n i n f o r m a t i o n p r o v i d e d by vendors concerning a c h e m i c a l ' s t o x i c i t y , h e a l t h hazards, p h y s i c a l p r o p e r t i e s , f i r e , and r e a c t i v i t y d a t a i n c l u d i n g s t o r a g e , s p i l l , and handling precautions.

3.9

METHOD DETECTION L I M I T (MDL) -- The minimum c o n c e n t r a t i o n o f an a n a l y t e t h a t can be i d e n t i f i e d , measured and r e p o r t e d w i t h 99% confidence t h a t t h e a n a l y t e c o n c e n t r a t i o n i s g r e a t e r than zero.

3.10 QUALITY CONTROL SAMPLE (QCS) -- A s o l u t i o n o f method a n a l y t e s o f known c o n c e n t r a t i o n s t h a t i s u s e d t o f o r t i f y an a l i q u o t o f LRB o r sample m a t r i x . The QCS i s o b t a i n e d f r o m a s o u r c e e x t e r n a l t o t h e l a b o r a t o r y and d i f f e r e n t f r o m t h e s o u r c e of c a l i b r a t i o n s t a n d a r d s . I t i s used t o c h e c k 1a b o r a t o r y p e r f o r m a n c e w i t h e x t e r n a l l y p r e p a r e d t e s t materials.

3.11 STOCK STANDARD SOLUTION (SSS) -- A c o n c e n t r a t e d s o l u t i o n c o n t a i n i n g one o r more method a n a l y t e s p r e p a r e d i n t h e l a b o r a t o r y u s i n g assayed r e f e r e n c e m a t e r i a l s o r purchased f r o m a r e p u t a b l e commercial source.

Inorganic Substances 4.0

5.0

6.0

499

INTERFERENCES

4.1

The ion exchange column e l i m i n a t e s i n t e r f e r e n c e s from m u l t i v a l e n t c a t i o n s . A mid-scale s u l f a t e s t a n d a r d c o n t a i n i n g Ca++ should be analyzed p e r i o d i c a l l y t o i n s u r e t h a t the column i s f u n c t i o n i n g properly.

4.2

Samples with pH below 2 should be n e u t r a l i z e d because high a c i d c o n c e n t r a t i o n s e l u t e c a t i o n s from t h e ion exchange r e s i n .

4.3

Turbid samples should be f i l t e r e d o r c e n t r i f u g e d .

4.4

Method i n t e r f e r e n c e s may be caused by contaminants i n the r e a g e n t w a t e r , r e a g e n t s , glassware, and o t h e r sample processing apparatus t h a t b i a s a n a l y t e response.

SAFETY

5.1

The t o x i c i t y o r c a r c i n o g e n i c i t y of each r e a g e n t used i n t h i s method have not been f u l l y e s t a b l i s h e d . Each chemical should be regarded a s a p o t e n t i a l h e a l t h hazard and exposure should be a s low a s reasonably a c h i e v a b l e . Cautions a r e included f o r known extremely hazardous m a t e r i a l s o r procedures.

5.2

Each l a b o r a t o r y i s r e s p o n s i b l e f o r maintaining a c u r r e n t awareness f i l e of OSHA r e g u l a t i o n s r e g a r d i n g t h e s a f e handling of the chemicals s p e c i f i e d i n t h i s method. A r e f e r e n c e f i l e of Material S a f e t y Data S h e e t s (MSDS) should be made a v a i l a b l e t o a l l personnel involved i n the chemical a n a l y s i s . The p r e p a r a t i o n of a formal s a f e t y plan i s a l s o a d v i s a b l e .

5.3

The following chemicals have t h e p o t e n t i a l t o be highly t o x i c o r hazardous, c o n s u l t MSDS. 5.3.1

Barium c h l o r i d e (7.2)

5.3.2

Hydrochloric a c i d (7.3)

EQUIPMENT AND SUPPLIES

6.1

Balance -- A n a l y t i c a l , c a p a b l e of a c c u r a t e l y weighing t o t h e n e a r e s t 0.0001 g .

6.2

Glassware -- C l a s s A volumetric f l a s k s and p i p e t s a s r e q u i r e d .

6.3

Automated continuous flow a n a l y s i s equipment designed t o d e l i v e r and r e a c t sample and r e a g e n t s i n t h e r e q u i r e d o r d e r and r a t i o s . 6.3.1

Sampl i ng d e v i c e (sampl e r )

6.3.2

Mu1 t i channel pump

500

7.0

Methods for the Determination 6.3.3

Reaction u n i t o r manifold

6.3.4

Colorimetric detector

6.3.5

Data r e c o r d i n g d e v i c e

REAGENTS AND STANDARDS

7.1

Reagent w a t e r : D i s t i l l e d o r d e i o n i z e d w a t e r , f r e e o f t h e a n a l y t e o f i n t e r e s t . ASTM t y p e I 1 o r e q u i v a l e n t .

7.2

Barium c h l o r i d e : D i s s o l v e 0.7630 g o f b a r i u m c h l o r i d e d i h y d r a t e (BaC1;2H2O) (CASRN 10326-27-9) i n 250 mL o f r e a g e n t w a t e r and d i l u t e t o 500 mL.

7.3

Methylthymol b l u e : D i s s o l v e 0.1182 g o f methylthymol b l u e ( 3 ' 3 - b i s N ,N- b i scarboxyme t h y l ) -ami no methyl t hymol s u l f one-ph t h a l e in pentasodium s a l t ) (CASRN 1945-77-3) i n 25 mL o f b a r i u m c h l o r i d e s o l u t i o n (7.2). Add 4 mL o f 1.0 N h y d r o c h l o r i c a c i d (CASRN 7647-010) which changes t h e c o l o r t o b r i g h t orange. Add 71 mL o f r e a g e n t w a t e r and d i l u t e t o 500 mL w i t h e t h a n o l . The pH o f t h i s s o l u t i o n i s 2.6. T h i s r e a g e n t s h o u l d be p r e p a r e d t h e day b e f o r e and s t o r e d i n a brown p l a s t i c b o t t l e i n t h e r e f r i g e r a t o r .

7.4

B u f f e r , pH 10.5 k 0.5: D i s s o l v e 6.75 g o f ammonium c h l o r i d e (CASRN 12125-02-9) i n 500 mL o f r e a g e n t w a t e r . Add 57 mL o f c o n c e n t r a t e d ammonium h y d r o x i d e fCASRN 1336-21-61 and d i l u t e t o 1 L w i t h d i s t i 11ed w a t e r .

7.5

B u f f e r e d EDTA: D i s s o l v e 20 g o f t e t r a s o d i u m EDTA (CASRN 64-02-8) pH 10.5 b u f f e r (7.4), and d i l u t e t o 500 mL w i t h b u f f e r .

7.6

Sodium h y d r o x i d e s o l u t i o n (50%): D i s s o l v e 250 g NaOH (CASRN 1310 73-2) i n 300 mL o f r e a g e n t water, c o o l , and d i l u t e t o 500 mL.

7.7

Sodium h y d r o x i d e , 0.18N: (7.6) t o 500 mL.

7.8

I o n exchange r e s i n : Bio-Rex 70, 20-50 mesh, sodium form, Bio-Rad L a b o r a t o r i e s , Richmond, C a l i f o r n i a . Free f r o m f i n e s by s t i r r i n g w i t h s e v e r a l p o r t i o n s o f r e a g e n t w a t e r and decant t h e s u p e r n a t e b e f o r e s e t t l i n g i s complete.

7.9

D i l u t i o n Water: Add 0.75 mL o f s u l f a t e s t o c k s o l u t i o n (7.10) and 3 d r o p s o f B r i j - 3 5 (CASRN 9002-92-0) t o 2 L o f r e a g e n t w a t e r .

in

D i l u t e 7 . 2 mL o f sodium h y d r o x i d e s o l u t on

7.10 S u l f a t e s t o c k s o l u t i o n , 1 mL = 1 mg SO,: D i s s o l v e 1.479 g o f d r i e d (105°C) Na,SO, (CASRN 7757-82-6) i n r e a g e n t w a t e r and d i l u t e t o 1 L. 7.11 D i l u t e s u l f a t e s o l u t i o n , 1 mL = 0 . 1 mg SO,: D i l u t e 50 mL o f s u l f a t e s t o c k s o l u t i o n (7.10) t o 500 m l w i t h r e a g e n t w a t e r .

Inorganic Substances

501

8.0 SAMPLE COLLECTION, PRESERVATION AND STORAGE 8.1

Samples should be collected in plastic or glass bottles. All bottles must be thoroughly cleansed and rinsed with reagent water. Volume collected should be sufficient to insure a representative sample, allow for replicate analysis (if required), and minimize waste disposal .

8.2

No chemical preservation required. Cool sample to 4°C.

8.3 Samples should be analyzed as soon as possible after col ection. If storage is required, samples maintained at 4°C may be he d for up to 28 days, 9.0 QUALITY CONTROL

9.1

Each laboratory using this method is required to operate a formal quality control (QC) program. The minimum requirements f this program consist of an initial demonstration of laboratory capability, and the periodic analysis of laboratory reagent blanks, fortified blanks and other laboratory solutions as a continuing check on performance. The laboratory is required to maintain performance records that define the quality of the data that are generated.

9.2 INITIAL DEMONSTRATION

OF

PERFORMANCE

9.2.1

The initial demonstration of performance is used to characterize instrument performance (determination of LCRs and analysis o f QCS) and laboratory performance (determination of MDLs) prior to performing analyses by this method.

9.2.2

Linear Calibration Range (LCR) -- The LCR must be determined initially and verified every 6 months or whenever a significant change in instrument response is observed or expected. The initial demonstration of linearity must use sufficient standards to insure that the resulting curve is linear. The verification of linearity must use a minimum of a blank and three standards. If any verification data exceeds the initial values by k lo%, linearity must be reestablished. If any portion of the range is shown to be nonlinear, sufficient standards must be used to clearly define the nonlinear portion.

9.2.3

Quality Control Sample (QCS) -- When beginning the use of this method, on a quarterly basis or as required to meet data-quality needs, verify the calibration standards and acceptable instrument performance with the preparation and analyses of a QCS. If the determined concentrations are not within f 10% of the stated values, performance of the

502

Methods for the Determination

d e t e r m i n a t i v e s t e p of t h e method i s unacceptable. The source of t h e problem must be i d e n t i f i e d and c o r r e c t e d before e i t h e r proceeding with the i n i t i a l d e t e r m i n a t l o n of MDLs o r continuing with on-going a n a l y s e s . 9.2.4

Method Detection Limit (MDL) -- MDLs must be e s t a b l i s h e d f o r a l l a n a l y t e s , using reagent water (blank) f o r t i f i e d a t a c o n c e n t r a t i o n of two t o t h r e e times t h e e s t i m a t e d instrument d e t e c t i o n limit.'3' To determine MDL v a l u e s , t a k e seven r e p l i c a t e a l i q u o t s of t h e f o r t i f i e d reagent w a t e r and process through t h e e n t i r e a n a l y t i c a l method. Perform a l l c a l c u l a t i o n s d e f i n e d i n t h e method and r e p o r t the c o n c e n t r a t i o n v a l u e s i n the a p p r o p r i a t e u n i t s . C a l c u l a t e t h e MDL a s follows: MDL

=

( t ) x (S)

where, t

=

S t u d e n t ' s t value f o r a 99% confidence l e v e l and a standard d e v i a t i o n e s t i m a t e with n-1 degrees of freedom [t = 3.14 f o r seven r e p l i c a t e s ] .

S

=

s t a n d a r d d e v i a t i o n of t h e r e p l i c a t e a n a l y s e s .

MDLs should be determined every 6 months, when a new o p e r a t o r begins work, o r whenever t h e r e i s a s i g n i f i c a n t change i n t h e background o r instrument response. 9.3

ASSESSING LABORATORY PERFORMANCE 9.3.1

Laboratory Reagent Blank ( L R B ) -- The l a b o r a t o r y must analyze a t l e a s t one LRB with each batch of samples. Data produced a r e used t o a s s e s s contamination from the l a b o r a t o r y environment. Values t h a t exceed the MDL i n d i c a t e 1 a b o r a t o r y o r reagent contamination should be suspected and c o r r e c t i v e a c t i o n s must be taken b e f o r e c o n t i n u i n g t h e analysis.

9.3.2

Laboratory F o r t i f i e d Blank (LFB) -- The l a b o r a t o r y must analyze a t l e a s t one LFB with each batch of samples. C a l c u l a t e accuracy a s percent recovery ( S e c t . 9 . 4 . 2 ) . If t h e recovery of any a n a l y t e f a l l s o u t s i d e the r e q u i r e d c o n t r o l l i m i t s of 90-110%, t h a t a n a l y t e i s judged o u t of c o n t r o l , and t h e source o f t h e problem should be i d e n t i f i e d and resolved before continuing a n a l y s e s .

9.3.3

The l a b o r a t o r y must use LFB a n a l y s e s d a t a t o a s s e s s l a b o r a t o r y performance a g a i n s t t h e r e q u i r e d c o n t r o l l i m i t s of 90-110%. When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e ( u s u a l l y a minimum of 20-30 a n a l y s e s ) , o p t i o n a l c o n t r o l l i m i t s can be developed from t h e percent mean recovery ( x ) and t h e standard d e v i a t i o n (S) of the mean

Inorganic Substances

503

recovery. These d a t a can be used t o e s t a b l i s h t h e upper and lower c o n t r o l l i m i t s a s f o l l o w s : UPPER CONTROL L I M I T LOWER CONTROL LIMIT

=

x

=

x - 3s

t

3s

The o p t i o n a l c o n t r o l l i m i t s must be equal t o o r b e t t e r t h a n t h e r e q u i r e d c o n t r o l l i m i t s of 90-110%. A f t e r each f i v e t o t e n new recovery measurements, new c o n t r o l l i m i t s can be c a l c u l a t e d using only the most recent 20-30 d a t a p o i n t s . Also, the s t a n d a r d d e v i a t i o n ( S ) d a t a should be used t o e s t a b l i s h e d an on-going p r e c i s i o n s t a t e m e n t f o r the l e v e l of c o n c e n t r a t i o n s included i n t h e LFB. These d a t a must be kept on f i l e and be a v a i l a b l e f o r review. 9.3.4

9.4

Instrument Performance Check S o l u t i o n (IPC) - - For a l l d e t e r m i n a t i o n s the l a b o r a t o r y must analyze t h e IPC ( a midrange check s t a n d a r d ) and a c a l i b r a t i o n blank immediately following d a i l y c a l i b r a t i o n , a f t e r every t e n t h sample ( o r more f r e q u e n t l y , i f r e q u i r e d ) and a t t h e end of t h e sample run. Analysis of the IPC s o l u t i o n and c a l i b r a t i o n blank immediately following c a l i b r a t i o n must v e r i f y t h a t t h e instrument i s w i t h i n f 10% of c a l i b r a t i o n . Subsequent a n a l y s e s of the IPC s o l u t i o n must v e r i f y t h e c a l i b r a t i o n i s s t i l l w i t h i n k 10%. I f t h e c a l i b r a t i o n cannot be v e r i f i e d w i t h i n t h e s p e c i f i e d l i m i t s , r e a n a l y z e t h e IPC s o l u t i o n . I f t h e second a n a l y s i s of t h e IPC s o l u t i o n confirms c a l i b r a t i o n t o be o u t s i d e t h e l i m i t s , sample a n a l y s i s must be d i s c o n t i n u e d , t h e cause determined and/or i n t h e c a s e of d r i f t the instrument r e c a l i b r a t e d . All samples following t h e l a s t a c c e p t a b l e IPC s o l u t i o n must be reanalyzed. The a n a l y s i s d a t a o f the c a l i b r a t i o n blank and IPC s o l u t i o n must be kept on f i l e with t h e sample a n a l y s e s d a t a .

ASSESSING ANALYTE RECOVERY AND DATA QUALITY 9.4.1

Laboratory F o r t i f i e d Sample Matrix (LFM) -- The l a b o r a t o r y must add a known amount o f a n a l y t e t o a minimum o f 10% o f t h e r o u t i n e samples. In each c a s e , t h e LFM a l i q u o t must be a d u p l i c a t e o f t h e a l i q u o t used f o r sample a n a l y s i s . The a n a l y t e c o n c e n t r a t i o n must be high enough t o be d e t e c t e d above the o r i g i n a l sample and should not be l e s s than f o u r times t h e MDL. The added a n a l y t e c o n c e n t r a t i o n should be

the same a s t h a t used i n t h e l a b o r a t o r y f o r t i f i e d blank. 9.4.2

C a l c u l a t e the p e r c e n t recovery f o r each a n a l y t e , c o r r e c t e d f o r c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o the d e s i g n a t e d LFM recovery range 90-110%. Percent recovery may be c a l c u l a t e using t h e following e q u a t i o n :

504

Methods for the Determination

where, R

=

C,

C

= =

s

=

percent r e c o v e r y . f o r t i f i e d sample c o n c e n t r a t i o n . sample background c o n c e n t r a t i o n . c o n c e n t r a t i o n e q u i v a l e n t of a n a l y t e added t o sampl e .

9.4.3

I f t h e recovery of any a n a l y t e f a l l s o u t s i d e t h e d e s i g n a t e d LFM recovery range and t h e l a b o r a t o r y performance f o r t h a t a n a l y t e i s shown t o be i n c o n t r o l ( S e c t . 9 . 3 ) , t h e recovery problem encountered with the LFM i s judged t o be e i t h e r matrix o r s o l u t i o n r e l a t e d , not system r e l a t e d .

9.4.4

Where r e f e r e n c e m a t e r i a l s a r e a v a i l a b l e , they should be analyzed t o provide a d d i t i o n a l performance d a t a . The a n a l y s i s of r e f e r e n c e samples i s a v a l u a b l e t o o l f o r demonstrating t h e a b i l i t y t o perform t h e method acceptably.

10.0 CALIBRATION A N D STANDARDIZATION 10.1 S e t up t h e manifold f o r high (0-300 mg SO,/L) o r low (0-30 mg SO,/L) l e v e l samples a s d e s c r i b e d i n Figure 1. 10.1.1

High l e v e l working s t a n d a r d s , 10-300 mg/L: A s a minimum, prepare high l e v e l working s t a n d a r d s by d i l u t i n g t h e following volumes of s t o c k s t a n d a r d (7.10) t o 100 m L .

mL Stock 1 5 10 15 25 30

10.1.2

mq/L SO,

10 50 100 150 250 300

Low l e v e l working s t a n d a r d s , 1-30 mg/L: Prepare a t l e a s t t h i s number o f low l e v e l working s t a n d a r d s by d i l u t i n g the following volumes of d i l u t e s u l f a t e s o l u t i o n (7.11) t o 100 mL.

Inorganic Substances mL Stock

ms/L SO,

1 5 10 15 25 30

1 .o 5.0 10.0 15.0 25.0 30.0

505

10.2 The ion exchange column is prepared by pulling a slurry of the resin into a piece of glass tubing 7 . 5 inches long, 2.0 mm ID and 3.6 mm OD. This is conveniently done by using a pipet and a loose fitting

glass wool plug in the tubing. Care should be taken to avoid allowing air bubbles to enter the column. If air bubbles become trapped, the column should be prepared over again. The column can exchange the equivalent of 35 mg of calcium. For the high level manifold this corresponds to about 900 samples with 200 mg/L Ca. The column should be prepared as often as necessary to assure that no more than 50% of its capacity is used up. 10.3 Allow the instrument to warm up as required.

Pump all reagents

until a stable baseline is achieved. 10.4 Analyze all working standards in duplicate at the beginning of a run

to develop a standard curve. Control standards are analyzed every hour to assure that the system remains properly calibrated. Since the chemistry is non-linear, data recording devices should be adjusted accordingly. 10.5 Prepare standard curve by plotting instrument response against

concentration values. A calibration curve may be fitted to the calibration solutions concentration/response data using computer or calculator based on regression curve fitting techniques. Acceptance or control limits should be established using the difference the measured value of the calibration solution and the "true value" concentration. 10.6 After the calibration has been established, it must be verified by

the analysis o f a suitable quality control sample (QCS). If measurements exceed k 10% of the established QCS value, the analysis should be terminated and the instrument recalibrated. The new calibration must be verified before continuing analysis. Periodic reanalysis of the QCS is recommended as a continuing calibration check. 11.0 PROCEDURE

11.1 Set up instrument as specified under calibration and standardization (10.0).

506

Methods for the Determination 11.2 F i l l and connect r e a g e n t c o n t a i n e r s and s t a r t system. A l l o w t h e system t o e q u i l i b r a t e as r e q u i r e d . Pump a l l r e a g e n t s u n t i l a s t a b l e b a s e l i n e i s achieved. 11.3 Place standards and samples i n sampler t r a y . and b e g i n a n a l y s i s .

C a l i b r a t e instrument,

11.4 A t t h e end o f each day, t h e s y s t e m s h o u l d be washed w i t h t h e b u f f e r e d EDTA s o l u t i o n ( 7 . 5 ) . T h i s i s done by p l a c i n g t h e methylthymol b l u e l i n e and t h e sodium h y d r o x i d e l i n e i n r e a g e n t w a t e r f o r a few m i n u t e s and t h e n i n t h e b u f f e r e d EDTA s o l u t i o n f o r 10 min. Wash t h e system w i t h r e a g e n t w a t e r f o r 15 min b e f o r e s h u t t i n g down.

12.0 DATA ANALYSIS AND CALCULATIONS 12.1 Prepare a c a l i b r a t i o n c u r v e by p l o t t i n g i n s t r u m e n t response against standard concentration. Compute sample c o n c e n t r a t i o n by comparing sample response with t h e s t a n d a r d curve. M u l t i p l y answer by a p p r o p r i a t e d i l u t i o n f a c t o r .

12.2 Report o n l y t h o s e v a l u e s t h a t f a l l between t h e l o w e s t and t h e h i g h e s t c a l i b r a t i o n standards. Samples exceeding t h e h i g h e s t s t a n d a r d s h o u l d be d i l u t e d and r e a n a l y z e d . 12.3 Report r e s u l t s i n mg/L. 13.0 METHOD PERFORMANCE

13.1 In a s i n g l e l a b o r a t o r y t h e e s t i m a t e d s t a n d a r d d e v i a t i o n , c a l c u l a t e d from d u p l i c a t e analyses o f 26 s u r f a c e and wastewaters a t a mean c o n c e n t r a t i o n o f 100 mg/L was i: 1 . 6 mg/L. 13.2 The mean r e c o v e r y f r o m 24 s u r f a c e and wastewaters was 102%. 14.0 POLLUTION PREVENTION

14.1 P o l l u t i o n p r e v e n t i o n encompasses any t e c h n i q u e t h a t reduces o r e l i m i n a t e s t h e q u a n t i t y o r t o x i c i t y o f waste a t t h e p o i n t o f g e n e r a t i o n . Numerous o p p o r t u n i t i e s f o r p o l l u t i o n p r e v e n t i o n e x i s t i n l a b o r a t o r y o p e r a t i o n . The EPA has e s t a b l i s h e d a p r e f e r r e d h i e r a r c h y o f e n v i r o n m e n t a l management t e c h n i q u e s t h a t p l a c e s p o l l u t i o n p r e v e n t i o n as t h e management o p t i o n o f f i r s t c h o i c e . Whenever f e a s i b l e , l a b o r a t o r y personnel s h o u l d use p o l l u t i o n p r e v e n t i o n t e c h n i q u e s t o address t h e i r waste g e n e r a t i o n . When wastes cannot be f e a s i b l y reduced a t t h e source, t h e Agency recommends r e c y c l i n g as t h e n e x t b e s t o p t i o n . 14.2 The q u a n t i t y o f chemicals purchased should be based on expected usage d u r i n g i t s s h e l f 1 i f e and d i s p o s a l c o s t o f unused m a t e r i a l . A c t u a l r e a g e n t p r e p a r a t i o n volumes should r e f l e c t a n t i c i p a t e d usage and r e a g e n t s t a b i l i t y .

Inorganic Substances

507

14.3 For information about pollution prevention that may be applicable to

laboratories and research institutions, consult "Less is Better: Laboratory Chemical Management for Waste Reduction," available from the American Chemical Society's Department of Government Regulations and Science Policy, 1155 16th Street N.W., Washington D . C . 20036, (202) 872-4477. 15.0 WASTE MANAGEMENT

15.1 The Environmental Protection Agency requires that laboratory waste management practices be conducted consistent with all applicable rules and regulations, Excess Reagents and samples and method process wastes should be characterized and disposed of in an acceptable manner. The Agency urges laboratories to protect the air, water, and land by minimizing and controlling all releases from hoods and bench operations, complying with the letter and spirit o f any waster discharge permit and regulations, and by complying with all sol id and hazardous waste regulations, particularly the hazardous waste identification rules and land disposal restrictions. For further information on waste management consult the "Waste Management Manual for Laboratory Personnel, avai 1 able from the American Chemical Society at the address listed in Sect. 14.3. I'

16.0 REFERENCES

1.

Lazrus, A.L., Hill, K.C. and Lodge, J . P . , "Automation in Analytical Chemistry," Technicon Symposia, 1965.

2.

Coloros, E., Panesar, M.R. and Parry, F.P., "Linearizing the Calibration Curve in Determination o f Sulfate by the Methylthymol Blue Method," Anal. Chem. 48, 1693 (1976).

3.

Code of Federal Regulations 40, Ch. 1, Pt. 136, Appendix B.

r

W r n T U B E 1.00 [

I

5mNs SLEEWffi

WASTE

II

COLORIMETER 460nm 15mm F/C

rnWn 0.92

II

n ION EXCHANGE COLUMN

11

I

I* I

I

II

2.00

D I L W N WATER

0.10

SAMPLE

1.00

WASE

0.52

AIR

0.70

METMZTHYMOC BLUE

O.q*

1 I SODlclM HYDROXIDE II

II

WASTE

I (AIR

2.00

FFmM FIC

PClMP %.094 WCYETHYLEM:

*SILICONE RUBBER 9opERHOuR

SAMPLE 1 0 3 SEC. To analyze sanples in me range 0-30ry$l, change wabx m d sanple a e s b 1.O.

Figure 1 Sulfate Manifold

WASH 17 SEC.

Inorganic Substances METHOD 410.4 THE DETERMINATION OF CHEMICAL OXYGEN DEMAND BY SEMI-AUTOMATED COLORIMETRY

Edited by James W. O'Dell Inorganic Chemistry Branch Chemistry Research Division

Revision 2.0 August 1993

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U . S . ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, O H I O 45268

509

510

Methods for the Determination METHOD 410.4 THE DETERMINATION OF CHEMICAL OXYGEN DEMAND BY SEMI-AUTOMATED COLORIMETRY

1.0

SCOPE AND APPLICATION 1.1 T h i s method c o v e r s t h e d e t e r m i n a t i o n o f chemical oxygen demand (COD) i n ground and s u r f a c e w a t e r s , domestic and i n d u s t r i a l wastes. 1.2

2.0

3.0

The a p p l i c a b l e range i s 3-900 mg/L.

SUMMARY OF METHOD 2.1

Sample, b l a n k s , and standards i n s e a l e d t u b e s a r e h e a t e d i n an oven o r b l o c k d i g e s t o r i n t h e presence of d i c h r o m a t e a t 150°C. A f t e r two hours, t h e tubes a r e removed f r o m t h e oven o r d i g e s t e r , cooled, and measured s p e c t r o p h o t o m e t r i c a l l y a t 600 nm. The c o l o r i m e t r i c d e t e r m i n a t i o n may a l s o be performed m a n u a l l y .

2.2

Reduced volume v e r s i o n s o f t h i s method t h a t use t h e same r e a g e n t s and m o l a r r a t i o s a r e a c c e o t a b l e D r o v i d e d t h e y meet t h e q u a l i t y c o n t r o l and performance r e q u i r e m e n t s s a t e d i n t h e method.

2.3

L i m i t e d performance-based method m o d i f c a t i o n s may be a c c e p t a b l e p r o v i d e d t h e y a r e f u l l y documented and meet o r exceed r e q u i r e m e n t s expressed i n Sect. 9 . 0 , Q u a l i t y C o n t r o

DEFINITIONS 3.1

CALIBRAT ON BLANK (CB) -- A volume of r e a g e n t w a t e r f o r t i f i e d w i t h t h e same m a t r i x as t h e c a l i b r a t i o n standards, b u t w i t h o u t t h e a n a l y t e s i n t e r n a l standards, o r s u r r o g a t e a n a l y t e s .

3.2

CALI BRAT ON STANDARD (CAL) -- A s o l u t i o n p r e p a r e d f r o m t h e p r i m a r y d i 1u t i on s t a n d a r d s o l u t i o n o r s t o c k s t a n d a r d s o l u t i o n s and t h e i n t e r n a l standards and s u r r o g a t e a n a l y t e s . The CAL s o l u t i o n s a r e used t o c a l ib r a t e t h e i n s t r u m e n t response w i t h r e s p e c t t o a n a l y t e concentration.

3.3

INSTRUMENT PERFORMANCE CHECK SOLUTION ( I P C ) -- A s o l u t i o n o f one o r more method a n a l y t e s , s u r r o g a t e s , i n t e r n a l standards, o r o t h e r t e s t substances used t o e v a l u a t e t h e performance of t h e i n s t r u m e n t system w i t h respect t o a defined set o f c r i t e r i a .

3.4

LABORATORY FORTIFIED BLANK (LFB) -- An a l i q u o t o t h e r b l a n k m a t r i c e s t o which known q u a n t i t i e s a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFB l i k e a sample, and i t s purpose i s t o d e t e r m i n e

o f reagent water o r o f t h e method i s analyzed e x a c t l y whether t h e

Inorganic Substances

511

methodology i s n c o n t r o l , and whether t h e l a b o r a t o r y i s capable o f making a c c u r a t e and p r e c i s e measurements.

3.5

LABORATORY FORT F I E D SAMPLE M A T R I X (LFM) -- An a l i q u o t o f an e n v i r o n m e n t a l sample t o which known q u a n t i t i e s o f t h e method a n a l y t e s a r e added i n t h e l a b o r a t o r y . The LFM i s analyzed e x a c t l y l i k e a sample, and i t s purpose i s t o d e t e r m i n e whether t h e sample m a t r i x c o n t r i b u t e s b i a s t o t h e a n a l y t i c a l r e s u l t s . The background c o n c e n t r a t i o n s o f t h e a n a l y t e s i n t h e sample m a t r i x must be d e t e r m i n e d i n a s e p a r a t e a l i q u o t and t h e measured v a l u e s i n t h e LFM c o r r e c t e d f o r background c o n c e n t r a t i o n s .

3.6

LABORATORY REAGENT BLANK (LRB) -- An a l i q u o t o f r e a g e n t w a t e r o r o t h e r b l a n k m a t r i c e s t h a t a r e t r e a t e d e x a c t l y as a sample i n c l u d i n g exposure t o a l l glassware, equipment, s o l v e n t s , reagents, i n t e r n a l standards, and s u r r o g a t e s t h a t a r e used w i t h o t h e r samples. The LRB i s used t o d e t e r m i n e i f method a n a l y t e s o r o t h e r i n t e r f e r e n c e s a r e p r e s e n t i n t h e l a b o r a t o r y environment, t h e r e a g e n t s , o r t h e apparatus.

3.7

LINEAR CALIBRATION RANGE (LCR) -- The c o n c e n t r a t i o n range o v e r which t h e i n s t r u m e n t response i s l i n e a r .

3.8

MATERIAL SAFETY DATA SHEET (MSDS) -- W r i t t e n i n f o r m a t i o n p r o v i d e d by vendors c o n c e r n i n g a c h e m i c a l ' s t o x i c i t y , h e a l t h hazards, p h y s i c a l p r o p e r t i e s , f i r e , and r e a c t i v i t y d a t a i n c l u d i n g s t o r a g e , s p i l l , and handling precautions.

3.9 METHOD DETECTION LIMIT (MDL) -- The minimum c o n c e n t r a t i o n o f an a n a l y t e t h a t can be i d e n t i f i e d , measured and r e p o r t e d w i t h 99% c o n f i d e n c e t h a t t h e a n a l y t e c o n c e n t r a t i o n i s g r e a t e r t h a n zero.

3.10 QUALITY CONTROL SAMPLE (QCS) -- A s o l u t i o n o f method a n a l y t e s o f known c o n c e n t r a t i o n s t h a t i s used t o f o r t i f y an a l i q u o t o f LRB or sample m a t r i x . The QCS i s o b t a i n e d from a source e x t e r n a l t o t h e l a b o r a t o r y and d i f f e r e n t f r o m t h e source o f c a l i b r a t i o n standards. I t i s used t o check l a b o r a t o r y performance w i t h e x t e r n a l l y prepared t e s t materials. 3.11 STOCK STANDARD SOLUTION (SSS) -- A c o n c e n t r a t e d s o l u t i o n c o n t a i n i n g one o r more method a n a l y t e s p r e p a r e d i n t h e l a b o r a t o r y u s i n g assayed r e f e r e n c e m a t e r i a l s o r purchased f r o m a r e p u t a b l e commercial source. 4.0

INTERFERENCES

4.1

C h l o r i d e s a r e q u a n t i t a t i v e l y o x i d i z e d by dichromate and r e p r e s e n t a p o s i t i v e i n t e r f e r e n c e . M e r c u r i c s u l f a t e i s added t o t h e d i g e s t i o n tubes t o complex t h e c h l o r i d e s .

4.2

Method i n t e r f e r e n c e s may be caused by contaminants i n t h e r e a g e n t w a t e r , r e a g e n t s , glassware, and o t h e r sample p r o c e s s i n g apparatus t h a t b i a s a n a l y t e response.

512 5.0

6.0

Methods for the Determination SAFETY

5.1

The t o x i c i t y o r c a r c i n o g e n i c i t y o f each r e a g e n t used i n t h i s method has n o t been f u l l y e s t a b l i s h e d . Each chemical s h o u l d be r e g a r d e d as a p o t e n t i a l h e a l t h hazard and exposure s h o u l d be as l o w as r e a s o n a b l y a c h i e v a b l e . C a u t i o n s a r e i n c l u d e d f o r known e x t r e m e l y hazardous m a t e r i a l s o r procedures.

5.2

Each l a b o r a t o r y i s r e s p o n s i b l e f o r m a i n t a i n i n g a c u r r e n t awareness f i l e o f OSHA r e g u l a t i o n s r e g a r d i n g t h e s a f e h a n d l i n g o f t h e chemicals s p e c i f i e d i n t h i s method. A r e f e r e n c e f i l e o f M a t e r i a l S a f e t y Data Sheets (MSDS) s h o u l d be made a v a i l a b l e t o a l l personnel i n v o l v e d i n t h e chemical a n a l y s i s . The p r e p a r a t i o n o f a f o r m a l s a f e t y p l a n i s a l s o advisable.

5.3

The f o l l o w i n g c h e m i c a l s have t h e p o t e n t i a l t o be h i g h l y t o x i c o r hazardous, c o n s u l t MSDS. 5.3.1

M e r c u r i c s u l f a t e (7.2)

5.3.2

Potassium d i c h r o m a t e (7.2)

5.3.3

S u l f u r i c a c i d (7.2,

7.3, 7.4)

EQUIPMENT AND SUPPLIES 6.1

Balance -- A n a l y t i c a l , capable o f a c c u r a t e l y w e i g h i n g t o t h e n e a r e s t 0.0001 g.

6.2

Glassware -- Class A v o l u m e t r i c f asks and p i p e t s as r e q u i r e d .

6.3

B l o c k d i g e s t o r o r d r y i n g oven capable o f m a i n t a i n i n g 150°C.

6.4

M u f f l e f u r n a c e c a p a b l e o f 500°C.

6.5

C u l t u r e t u b e w i t h T e f l o n - l i n e d screw cap, 16 x 100 mm o r 25 x 150 mm .

6.6

Automated c o n t i n u o u s f l o w a n a l y s i s equipment designed t o d e l i v e r and r e a c t sample and r e a g e n t s i n t h e r e q u i r e d o r d e r and r a t i o s . 6.6.1

Sampl ing d e v i c e (sampler)

6.6.2

M u l t i c h a n n e l pump

6.6.3

Reaction u n i t o r manifold

6.6.4

Colorimetric detector

6.6.5

Data r e c o r d i n g d e v i c e

Inorganic Substances 7.0

513

REAGENTS AND STANDARDS

7.1

Reagent w a t e r : D i s t i l l e d o r d e i o n i z e d w a t e r , f r e e o f t h e a n a l y t e o f i n t e r e s t . ASTM t y p e I 1 o r e q u i v a l e n t .

7.2 D i g e s t i o n s o l u t i o n : Add 5.1 g p o t a s s i u m d i c h r o m a t e K,Cr 0, (CASRN 7778-50-9), 84 mL conc. s u l f u r i c a c i d H SO (CASRN 8014-65-7) and 16.7 g m e r c u r i c s u l f a t e HgSO (CASRN 7763-35-9) t o 250 mL o f r e a g e n t w a t e r , c o o l and d i l u t e t o 50b mL. CAUTION: CAN BE VERY HOT!

8.0

9.0

7.3

C a t a l y s t s o l u t i o n : Add 22 g s i l v e r s u l f a t e Ag2S0, (CASRN 10294-265) t o a 4.09 kg b o t t l e o f conc. H2S0,. Stir u n t i l d i s s o l v e d .

7.4

Sampler wash s o l u t i o n : Add 250 mL o f conc. H SO, t o 250 mL o f r e a g e n t w a t e r . CAUTION: PREPARE CAREFULLY , H ~ G HHEAT GENERATION!

7.5

S t o c k potassium hydrogen p h t h a l a t e standard: D i s s o l v e 0.425 g KHP (CASRN 877-24-7) i n 400 mL o f r e a g e n t w a t e r and d i l u t e t o 500 mL. 1 mL = 1 mg COD.

SAMPLE COLLECTION, PRESERVATION AND STORAGE

8.1

Samples s h o u l d be c o l l e c t e d i n p l a s t i c o r g l a s s b o t t l e s . A l l b o t t l e s must be t h o r o u g h l y c l e a n s e d and r i n s e d w i t h r e a g e n t w a t e r . Volume c o l l e c t e d s h o u l d be s u f f i c i e n t t o i n s u r e a r e p r e s e n t a t i v e sample, a l l o w f o r r e p l i c a t e a n a l y s i s ( i f r e q u i r e d ) , and m i n i m i z e waste d i s p o s a l ,

8.2

Samples must be p r e s e r v e d w i t h H,SO, a t the time o f collection.

8.3

Samples s h o u l d be analyzed as soon as p o s s i b l e a f t e r c o l l e c t i o n . I f s t o r a g e i s r e q u i r e d , p r e s e r v e d samples m a i n t a i n e d a t 4°C may be h e l d f o r up t o 28 days.

t o a pH < 2 and c o o l e d t o 4°C

QUALITY CONTROL

9.1

Each l a b o r a t o r y u s i n g t h i s method i s r e q u i r e d t o o p e r a t e a formal q u a l i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f t h i s program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y , and t h e p e r i o d i c a n a l y s i s o f l a b o r a t o r y r e a g e n t blanks, f o r t i f i e d b l a n k s , and o t h e r l a b o r a t o r y s o l u t i o n s as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n p e r formance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f t h e d a t a t h a t a r e generated.

9.2

I N I T I A L DEMONSTRATION OF PERFORMANCE

9.2.1

The i n i t i a l d e m o n s t r a t i o n o f performance i s used t o c h a r a c t e r i z e i n s t r u m e n t performance ( d e t e r m i n a t i o n o f l i n e a r c a l i b r a t i o n ranges and a n a l y s i s o f QCS) and l a b o r a t o r y

514

Methods for the Determination performance ( d e t e r m i n a t i o n o f MDLs) p r i o r t o p e r f o r m i n g analyses by t h i s method. 9.2.2

L i n e a r C a l i b r a t i o n Range (LCR) -- The LCR must be determined i n i t i a l l y and v e r i f i e d e v e r y 6 months o r whenever a s i g n i f i c a n t change i n i n s t r u m e n t response i s observed o r expected. The i n i t i a l d e m o n s t r a t i o n o f l i n e a r i t y must use s u f f i c i e n t standards t o i n s u r e t h a t t h e r e s u l t i n g c u r v e i s l i n e a r . The v e r i f i c a t i o n o f l i n e a r i t y must use a minimum o f a b l a n k and t h r e e s t a n d a r d s . I f any v e r i f i c a t i o n d a t a exceeds t h e i n i t i a l v a l u e s by k lo%, l i n e a r i t y must be r e e s t a b l i s h e d . I f any p o r t i o n o f t h e range i s shown t o be n o n l i n e a r , s u f f i c i e n t standards must be used t o c l e a r l y define the nonlinear portion.

9.2.3

Q u a l i t y C o n t r o l Sample (QCS) -- When b e g i n n i n g t h e use o f t h i s method, on a q u a r t e r l y b a s i s o r as r e q u i r e d t o meet data-qua1 i t y needs, v e r i f y t h e c a l i b r a t i o n standards and a c c e p t a b l e i n s t r u m e n t performance w i t h t h e p r e p a r a t i o n and analyses o f a QCS. I f t h e d e t e r m i n e d c o n c e n t r a t i o n s a r e n o t w i t h i n f 10% o f t h e s t a t e d v a l u e s , performance o f t h e d e t e r m i n a t i v e s t e p o f t h e method i s unacceptable. The source o f t h e problem must be i d e n t i f i e d and c o r r e c t e d before e i t h e r proceeding w i t h t h e i n i t i a l determination o f MDLs o r c o n t i n u i n g w i t h on-going analyses.

9.2.4

Method D e t e c t i o n L i m i t (MDL) -- MDLs must be e s t a b l i s h e d f o r a l l analytes, using reagent water (blank) f o r t i f i e d a t a c o n c e n t r a t i o n o f two t o t h r e e t i m e s t h e e s t i m a t e d i n s t r u m e n t d e t e c t i o n 1i m i t . ' 2 ' To d e t e r m i n e MDL v a l u e s , t a k e seven r e p l i c a t e a l i q u o t s of t h e f o r t i f i e d r e a g e n t w a t e r and process t h r o u g h t h e e n t i r e a n a l y t i c a l method. P e r f o r m a l l c a l c u l a t i o n s d e f i n e d i n t h e method and r e p o r t t h e concentration values i n t h e appropriate u n i t s . Calculate t h e MDL as f o l l o w s : MDL

=

(t) x (S)

where, t

=

S t u d e n t ' s t v a l u e f o r a 99% c o n f i d e n c e l e v e l and a s t a n d a r d d e v i a t i o n e s t i m a t e w i t h n-1 degrees o f freedom [ t = 3.14 f o r seven r e p l i c a t e s ] .

S

=

s t a n d a r d d e v i a t i o n o f t h e r e p l i c a t e analyses.

MDLs s h o u l d be determined e v e r y 6 months, when a new o p e r a t o r b e g i n s work, o r whenever t h e r e i s a s i g n i f i c a n t change i n t h e background o r i n s t r u m e n t response. 9.3

ASSESSING LABORATORY PERFORMANCE

9.3.1

L a b o r a t o r y Reagent B l a n k (LRB) -- The l a b o r a t o r y must analyze a t l e a s t one LRB w i t h each b a t c h of samples. Data

Inorganic Substances

515

produced a r e used t o assess c o n t a m i n a t i o n from t h e l a b o r a t o r y environment. Values t h a t exceed t h e MDL i n d i c a t e l a b o r a t o r y o r r e a g e n t c o n t a m i n a t i o n should be suspected and c o r r e c t i v e a c t i o n s must be t a k e n b e f o r e c o n t i n u i n g t h e analysis. 9.3.2

L a b o r a t o r y F o r t i f i e d B l a n k (LFB) -- The l a b o r a t o r y must a n a l y z e a t l e a s t one LFB w i t h each b a t c h o f samples. Cal c u l a t e accuracy as p e r c e n t r e c o v e r y ( S e c t . 9.4.2). If t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%, t h a t a n a l y t e i s judged o u t o f c o n t r o l , and t h e source o f t h e problem should be i d e n t i f i e d and r e s o l v e d b e f o r e c o n t i n u i n g analyses.

9.3.3

The l a b o r a t o r y must use LFB analyses d a t a t o assess l a b o r a t o r y performance a g a i n s t t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%. When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e ( u s u a l l y a minimum o f 20-30 analyses), o p t i o n a l c o n t r o l l i m i t s can be developed from t h e p e r c e n t mean r e c o v e r y ( x ) and t h e s t a n d a r d d e v i a t i o n ( S ) o f t h e mean r e c o v e r y . These d a t a can be used t o e s t a b l i s h t h e upper and l o w e r c o n t r o l l i m i t s as f o l l o w s : UPPER CONTROL LIMIT = x t 3s LOWER CONTROL LIMIT = x - 3s The o p t i o n a l c o n t r o l l i m i t s must be equal t o o r b e t t e r t h a n t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%. A f t e r each f i v e t o t e n new r e c o v e r y measurements, new c o n t r o l l i m i t s can be c a l c u l a t e d u s i n g o n l y t h e most r e c e n t 20-30 d a t a p o i n t s . Also, t h e s t a n d a r d d e v i a t i o n ( S ) d a t a should be used t o e s t a b l i s h e d an on-going p r e c i s i o n statement f o r t h e l e v e l o f c o n c e n t r a t i o n s i n c l u d e d i n t h e LFB. These d a t a must be k e p t on f i l e and be a v a i l a b l e f o r r e v i e w .

9.3.4

I n s t r u m e n t Performance Check S o l u t i o n (IPC) -- For a l l d e t e r m i n a t i o n s , t h e l a b o r a t o r y must analyze t h e I P C ( a midrange check s t a n d a r d ) and a c a l i b r a t i o n b l a n k immediately f o l l o w i n g d a i l y c a l i b r a t i o n , a f t e r e v e r y t e n t h sample ( o r more f r e q u e n t l y , i f r e q u i r e d ) , and a t t h e end o f t h e sample r u n . A n a l y s i s o f t h e I P C s o l u t i o n and c a l i b r a t i o n b l a n k i m m e d i a t e l y f o l l o w i n g c a l i b r a t i o n must v e r i f y t h a t t h e i n s t r u m e n t i s w i t h i n ? 10% o f c a l i b r a t i o n . Subsequent analyses o f t h e I P C s o l u t i o n must v e r i f y t h e c a l i b r a t i o n i s s t i l l w i t h i n ? 10%. I f t h e c a l i b r a t i o n cannot be v e r i f i e d w i t h i n t h e s p e c i f i e d l i m i t s , reanalyze the IPC solution. I f t h e second a n a l y s i s o f t h e I P C s o l u t i o n c o n f i r m s c a l i b r a t i o n t o be o u t s i d e t h e l i m i t s , sample a n a l y s i s must be d i s c o n t i n u e d , t h e cause determined and/or i n t h e case o f d r i f t , t h e i n s t r u m e n t r e c a l i b r a t e d . A l l samples f o l l o w i n g t h e l a s t a c c e p t a b l e I P C s o l u t i o n must be reanalyzed. The

516

Methods for the Determination a n a l y s i s d a t a o f t h e c a l i b r a t i o n b l a n k and I P C s o l u t i o n must be k e p t on f i l e w i t h t h e sample analyses d a t a . 9.4

ASSESSING ANALYTE RECOVERY AND DATA QUALITY

9.4.1

L a b o r a t o r y F o r t i f i e d Sample M a t r i x (LFM) -- The l a b o r a t o r y must add a known amount o f a n a l y t e t o a minimum o f 10% o f t h e r o u t i n e samples. I n each case, t h e LFM a l i q u o t must be a d u p l i c a t e o f t h e a l i q u o t used f o r sample a n a l y s i s . The a n a l y t e c o n c e n t r a t i o n must be h i g h enough t o be d e t e c t e d above t h e o r i g i n a l sample and s h o u l d n o t be l e s s t h a n f o u r t i m e s t h e MDL. The added a n a l y t e c o n c e n t r a t i o n s h o u l d be t h e same as t h a t used i n t h e l a b o r a t o r y f o r t i f i e d b l a n k .

9.4.2

C a l c u l a t e t h e p e r c e n t r e c o v e r y f o r each a n a l y t e , c o r r e c t e d f o r c o n c e n t r a t i o n s measured i n t h e u n f o r t i f i e d sample, and compare t h e s e v a l u e s t o t h e d e s i g n a t e d LFM r e c o v e r y range 90-110%. Percent r e c o v e r y may be c a l c u l a t e d u s i n g t h e f o l l o w i n g equation:

R = c, - c

x 100

S

where, R C, C s

percent recovery. f o r t i f i e d sample c o n c e n t r a t i o n . sample background c o n c e n t r a t i o n . = c o n c e n t r a t i o n e q u i v a l e n t o f a n a l y t e added t o sampl e.

= = =

9.4.3

I f t h e r e c o v e r y o f any a n a l y t e f a l l s o u t s i d e t h e d e s i g n a t e d LFM r e c o v e r y range and t h e l a b o r a t o r y performance f o r t h a t a n a l y t e i s shown t o be i n c o n t r o l (Sect. 9.3), t h e r e c o v e r y problem encountered w i t h t h e LFM i s j u d g e d t o be e i t h e r m a t r i x o r s o l u t i o n r e l a t e d , n o t system r e l a t e d .

9.4.4

Where r e f e r e n c e m a t e r i a l s a r e a v a i l a b l e , t h e y s h o u l d be analyzed t o p r o v i d e a d d i t i o n a l performance d a t a . The a n a l y s i s o f r e f e r e n c e samples i s a v a l u a b l e t o o l f o r d e m o n s t r a t i n g t h e a b i l i t y t o p e r f o r m t h e method a c c e p t a b l y .

10.0 CALIBRATION AND STANDARDIZATION 10.1 Prepare a s e r i e s o f a t l e a s t 3 standards, c o v e r i n g t h e d e s i r e d range, by d i l u t i n g a p p r o p r i a t e volumes o f t h e s t o c k s t a n d a r d (7.5)and a b l a n k . 10.2 Process standards and b l a n k s as d e s c r i b e d under Procedure (11.0). 10.3 Set up m a n i f o l d as shown i n F i g u r e 1.

Inorganic Substances 10.4 A l l o w t h e i n s t r u m e n t t o w a r m up as r e q u i r e d . u n t i l a s t a b l e b a s e l i n e i s achieved.

517

Pump a l l r e a g e n t s

10.5 P l a c e a p p r o p r i a t e standards i n t h e sampler i n o r d e r o f d e c r e a s i n g c o n c e n t r a t i o n and p e r f o r m a n a l y s i s , 10.6 Prepare a s t a n d a r d c u r v e by p l o t t i n g i n s t r u m e n t response a g a i n s t c o n c e n t r a t i o n v a l u e s . A c a l i b r a t i o n c u r v e may be f i t t e d t o t h e c a l i b r a t i o n s o l u t i o n s c o n c e n t r a t i o n / r e s p o n s e d a t a u s i n g computer o r c a l c u l a t o r based r e g r e s s i o n c u r v e f i t t i n g t e c h n i q u e s . Acceptance o r c o n t r o l l i m i t s s h o u l d be e s t a b l i s h e d u s i n g t h e d i f f e r e n c e between t h e measured v a l u e o f t h e c a l i b r a t i o n s o l u t i o n and t h e " t r u e v a l u e " concentration. 10.7 A f t e r t h e c a l i b r a t i o n has been e s t a b l i s h e d , i t must be v e r i f i e d by t h e a n a l y s i s o f a s u i t a b l e QCS. If measurements exceed f 10% o f t h e e s t a b l i s h e d QCS v a l u e , t h e a n a l y s i s s h o u l d be t e r m i n a t e d and t h e i n s t r u m e n t r e c a l i b r a t e d . The new c a l i b r a t i o n must be v e r i f i e d b e f o r e c o n t i n u i n g a n a l y s i s . P e r i o d i c r e a n a l y s i s o f t h e QCS i s recommended as a c o n t i n u i n g c a l i b r a t i o n check. 11.0 PROCEDURE 11.1 Wash a l l c u l t u r e t u b e s and screw caps w i t h 20% H,SO, b e f o r e t h e i r f i r s t use t o p r e v e n t c o n t a m i n a t i o n . Trace c o n t a m i n a t i o n may be removed f r o m t h e t u b e s by i g n i t i n g them i n a m u f f l e f u r n a c e a t 500°C f o r 1 h. 11.2 P i p e t 2.5 mL o f sample, s t a n d a r d or b l a n k , i n t o 16 x 100 mm tubes o r 10 mL i n t o 25 x 100 mm t u b e s . 11.3 Add 1.5 mL o f d i g e s t i o n s o l u t i o n (7.2) t o t h e 16 x 100 mm tubes o r 6.0 mL t o t h e 25 x 150 mm t u b e s and mix. 11.4 Add 3.5 mL o f c a t a l y s t s o l u t i o n (7.3) c a r e f u l l y down t h e s i d e o f t h e 16 x 100 mm t u b e s o r 14.0 mL t o t h e 25 x 150 mm tubes. 11.5 Cap t u b e s t i g h t l y and shake t o m i x l a y e r .

CAUTION:

Tubes a r e h o t .

11.6 P l a c e t u b e s i n t o a b l o c k d i g e s t e r o r oven a t 150°C and h e a t f o r 2 h. 11.7 Remove, mix, and c o o l tubes.

A l l o w any p r e c i p i t a t e t o s e t t l e .

11.8 F i l l and connect r e a g e n t c o n t a i n e r s and s t a r t system. A l l o w t h e i n s t r u m e n t t o warm up as r e q u i r e d . Pump a l l r e a g e n t s u n t i l a s t a b l e b a s e l i n e i s achieved. 11.9 P l a c e standards, b l a n k s , and samples i n sampler t r a y . i n s t r u m e n t , and b e g i n a n a l y s i s .

Calibrate

518

Methods for the Determination

12.0 DATA ANALYSIS AND CALCULATIONS

1 2 . 1 Prepare a c a l i b r a t i o n c u r v e by p l o t t i n g i n s t r u m e n t response a g a i n s t s t a n d a r d c o n c e n t r a t i o n . Compute sample c o n c e n t r a t i o n by comparing sample response w i t h t h e s t a n d a r d c u r v e . M u l t i p l y answer by a p p r o p r i a t e d i l u t i o n f a c t o r . 12.2 Report o n l y t h o s e v a l u e s t h a t f a l l between t h e l o w e s t and t h e h i g h e s t c a l i b r a t i o n standards. Samples exceeding t h e h i g h e s t s t a n d a r d s h o u l d be d i l u t e d and r e a n a l y z e d . 12.3 Report r e s u l t s i n mg/L. 13.0 METHOD PERFORMANCE

13.1 The i n t e r l a b o r a t o r y p r e c i s i o n and accuracy d a t a i n T a b l e 1 were developed u s i n g a r e a g e n t w a t e r m a t r i x . Values a r e i n mg COD/L. 13.2 S i n g l e l a b o r a t o r y p r e c i s i o n d a t a can be e s t i m a t e d a t 50 t o 75% o f the i n t e r l a b o r a t o r y p r e c i s i o n estimates. 14.0 POLLUTION PREVENTION 14.1 P o l l u t i o n p r e v e n t i o n encompasses any t e c h n i q u e t h a t reduces o r e l i m i n a t e s t h e q u a n t i t y o r t o x i c i t y o f waste a t t h e p o i n t o f g e n e r a t i o n . Numerous o p p o r t u n i t i e s f o r p o l l u t i o n p r e v e n t i o n e x i s t i n l a b o r a t o r y o p e r a t i o n . The EPA has e s t a b l i s h e d a p r e f e r r e d h i e r a r c h y o f e n v i r o n m e n t a l management t e c h n i q u e s t h a t p l a c e s p o l l u t i o n p r e v e n t i o n as t h e management o p t i o n o f f i r s t c h o i c e . Whenever f e a s i b l e , l a b o r a t o r y p e r s o n n e l s h o u l d use p o l l u t i o n p r e v e n t i o n t e c h n i q u e s t o address t h e i r waste g e n e r a t i o n . When wastes cannot be f e a s i b l y reduced a t t h e source, t h e Agency recommends r e c y c l i n g as t h e n e x t b e s t o p t i o n . 14.2 The q u a n t i t y o f c h e m i c a l s purchased s h o u l d be based on expected usage d u r i n g i t s s h e l f l i f e and d i s p o s a l c o s t o f unused m a t e r i a l . A c t u a l r e a g e n t p r e p a r a t i o n volumes s h o u l d r e f l e c t a n t i c i p a t e d usage and r e a g e n t s t a b i l i ty. 14.3 F o r i n f o r m a t i o n about p o l l u t i o n p r e v e n t i o n t h a t may be a p p l i c a b l e t o 1 a b o r a t o r i e s and r e s e a r c h i n s t i t u t i o n s , c o n s u l t "Less i s B e t t e r : L a b o r a t o r y Chemical Management f o r Waste Reduction," a v a i l a b l e f r o m t h e American Chemical S o c i e t y ' s Department o f Government R e g u l a t i o n s and Science P o l i c y , 1155 1 6 t h S t r e e t N.W., Washington D.C. 20036, (202) 872-4477. 15.0 WASTE MANAGEMENT

15.1 The Environmental P r o t e c t i o n Agency r e q u i r e s t h a t l a b o r a t o r y waste management p r a c t i c e s be conducted c o n s i s t e n t w i t h a l l a p p l i c a b l e r u l e s and r e g u l a t i o n s . Excess r e a g e n t s , samples, and method process wastes s h o u l d be c h a r a c t e r i z e d and d i s p o s e d o f i n an

Inorganic Substances

519

acceptable manner. The Agency urges laboratories to protect the air, water, and land by minimizing and controlling all releases from hoods and bench operations, complying with the letter and spirit o f any waste discharge permit and regulations, and by complying with all solid and hazardous waste regulations, particularly the hazardous waste identification rules and land disposal restrictions. For further information on waste management consult the "Waste Management Manual for Laboratory Personnel available from the American Chemical Society at the address listed in Sect. 1 4 . 3 . ,I'

16.0 REFERENCES

1.

Jirka, A.M., and M.J. Carter, "Micro-Semi-Automated Analysis o f Surface and Wastewaters f o r Chemical Oxygen Demand." Anal. Chem. 47: 1397, ( 1 9 7 5 ) .

2.

Code of Federal Regulations 40, Ch. 1 , Pt. 136, Appendix B.

520

Methods for the Determination

17.0 TABLES. DIAGRAMS, FLOWCHARTS, AND VALIDATION DATA TABLE 1. NUMBER OF VALUES REPORTED

TRUE VALUE (1)

INTERLABORATORY PRECISION AND ACCURACY DATA MEAN (X)

RESIDUAL FOR X

STANDARD DEVIATION (S)

RESIDUAL FOR S

241

18.2

18.9398

-0.4220

5.2026

-0.0964

144

26.3

26.1454

- 1.0445

5.6142

-0.0888

140

28.5

32.7275

3.4115

6.2230

0.4103

112

43.5

42.8360

-0.9763

6.4351

-0.1257

261

46.6

45.3034

-1.5049

6.7677

0.0523

181

50.0

49.4740

-0.6201

7.0494

0.1644

262

65.4

63.2876

-1.6894

7.6041

-0.0489

182

76.2

75.7960

0.3816

8.4490

0.2573

141

91.7

94.0772

3.6833

7.9289

-1.0358

250

-121

117.7424

-0.9678

9.6197

-0.8063

144

201

196.9391

0.9151

14.6995

0.2837

113

229

221.8109

-1.2730

17.3403

1.5280

REGRESSIONS:

X

=

0.966T - 1.773, S

=

0.050T t 4.391

m m n

1oTuRNs

0.32

AIR

1.60

SAMPLE

1.60

DlsTllLEDWATER

0.32

AIR

1.60

R=MPLE

0.70

FROMFK

WASTE

I 1

'+

TO F/C PUMPTUBE

WASTE

-

COLORlMmR 660 nm 50mm F/C

PUMP *GLASS TRM&MISSION TIBE

40 PER HOUR SAMPLE 67SEC. WASH 23 SEC.

Inorganic Substances

Figure 1 C 0 D Manifold

521

522

Methods for the Determination

METHOD 420.4 DETERMINATION OF TOTAL RECOVERABLE PHENOLICS BY SEMI-AUTOMATED COLORIMETRY

Edited by James W. O'Dell Inorganic Chemistry Branch Chemistry Research Division

Revision 1.0 August 1993

ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268

Inorganic Substances

523

METHOD 420.4 DETERMINATION OF TOTAL RECOVERABLE PHENOLICS BY SEMI-AUTOMATED COLORIMETRY

1.0

2.0

3.0

SCOPE AND APPLICATION

1.1

T h i s method c o v e r s t h e d e t e r m i n a t i o n o f p h e n o l i c m a t e r i a l s i n d r i n k i n g , ground, surface, and s a l i n e waters, and domestic and i n d u s t r i a l wastes.

1.2

The a p p l i c a b l e range i s f r o m 2 t o 500 pg/L. 2 t o 200 p g / L and 10 t o 500 pg/L.

The w o r k i n g ranges a r e

SUMMARY OF METHOD

2.1

T h i s semi-automated method i s based on t h e d i s t i l l a t i o n o f phenol and subsequent r e a c t i o n o f t h e d i s t i l l a t e w i t h a l k a l i n e f e r r i c y a n i d e and 4 - a m i n o a n t i p y r i n e t o f o r m a r e d complex which i s measured a t 505 o r 520 nm.

2.2

C o l o r response of p h e n o l i c m a t e r i a l s w i t h 4 - a m i n o a n t i p y r i n e i s n o t t h e same f o r a l l compounds. Because p h e n o l i c t y p e wastes u s u a l l y c o n t a i n a v a r i e t y o f phenols, i t i s n o t p o s s i b l e t o d u p l i c a t e a m i x t u r e o f phenols t o be used as a s t a n d a r d . F o r t h i s reason, phenol has been s e l e c t e d as a s t a n d a r d and any c o l o r produced by t h e r e a c t i o n o f o t h e r p h e n o l i c compounds i s r e p o r t e d as phenol. T h i s v a l u e w i l l r e p r e s e n t t h e minimum c o n c e n t r a t i o n o f p h e n o l i c compounds p r e s e n t i n t h e sampl e.

2.3

Reduced volume v e r s i o n s o f t h i s method t h a t use t h e same r e a g e n t s and m o l a r r a t i o s a r e a c c e p t a b l e p r o v i d e d t h e y meet t h e q u a l i t y c o n t r o l and per,formance r e q u i r e m e n t s s t a t e d i n t h e method.

2.4

L i m i t e d performance based method m o d i f i c a t i o n s may be a c c e p t a b l e p r o v i d e d t h e y a r e f u l l y documented and meet o r exceed r e q u i r e m e n t s expressed i n Sect. 9.0, Q u a l i t y C o n t r o l .

DEFINITIONS

3.1

CALIBRATION BLANK (CB) -- A volume o f r e a g e n t w a t e r f o r t i f i e d w i t h t h e same m a t r i x as t h e c a l i b r a t i o n standards, b u t w i t h o u t t h e a n a l y t e s , i n t e r n a l standards, o r s u r r o g a t e a n a l y t e s .

3.2

CALIBRATION STANDARD (CAL) -- A s o l u t i o n prepared f r o m t h e p r i m a r y d i l u t i o n s t a n d a r d s o l u t i o n o r s t o c k s t a n d a r d s o l u t i o n s and t h e i n t e r n a l standards and s u r r o g a t e a n a l y t e s . The CAL s o l u t i o n s a r e used t o c a l i b r a t e t h e i n s t r u m e n t response w i t h r e s p e c t t o a n a l y t e concentration.

524

Methods for the Determination 3.3

INSTRUMENT PERFORMANCE CHECK SOLUTION (IPC) - - A solution of one or more method analytes, surrogates, internal standards, or other test substances used to evaluate the performance of the instrument system with respect to a defined set of criteria.

3.4

LABORATORY FORTIFIED BLANK (LFB) -- An aliquot of reagent water or other bTank matrices to which known quantities of the method analytes are added in the laboratory, The LFB is analyzed exactly like a sample, and its purpose is to determine whether the methodology is in control, and whether the laboratory is capable of making accurate and precise measurements.

3.5

LABORATORY FORTIFIED SAMPLE MATRIX (LFM) -- An aliquot of an environmental sample to which known quantities of the method analytes are added in the laboratory. The LFM is analyzed exactly like a sample, and its purpose is to determine whether the sample matrix contributes bias to the analytical results. The background concentrations of the analytes in the sample matrix must be determined in a separate aliquot and the measured values in the LFM corrected for background concentrations.

3.6 LABORATORY REAGENT BLANK (LRB) -- An aliquot o f reagent water or other blank matrices that are treated exactly as a sample including exposure to all glassware, equipment, solvents, reagents, internal standards, and surrogates that are used with other samples. The LRB is used t o determine if method analytes or other interferences are present in the laboratory environment, the reagents, or the apparatus. 3.7

LINEAR CALIBRATION RANGE (LCR) -- The concentration range over which the instrument response is linear.

-- Written information provided by vendors concerning a chemical’s toxicity, health hazards, physical properties, fire, and reactivity data including storage, spill, and handling precautions.

3 . 8 MATERIAL SAFETY DATA SHEET (MSDS)

3.9

METHOD DETECTION LIMIT (MDL) -- The minimum concentration o f an analyte that can be identified, measured and reported with 99% confidence that the analyte concentration is greater than zero.

3.10 QUALITY CONTROL SAMPLE (QCS) -- A solution of method analytes o f known concentrations that is used to fortify an aliquot of LRB or sample matrix. The QCS is obtained from a source external to the laboratory and different from the source of calibration standards. It is used to check laboratory performance with externally prepared test materi a1 s. 3.11 STOCK STANDARD SOLUTION (SSS) -- A concentrated solution containing

one or more method analytes prepared in the laboratory using assayed reference materials or purchased from a reputable commercial source.

Inorganic Substances 4.0

525

INTERFERENCES

4.1

Interferences from su fur compounds are eliminated by ac.idifying the sample to a pH of 4.0 and aerating briefly by stirring.

4.2 Oxidizing agents such as chlorine, detected by the liberation of

iodine upon acidification in the presence of potassium iodide, are removed immediately after sampling by the addition of an excess of ferrous ammonium sulfate (7.11). If chlorine is not removed, the phenolic compounds may be partially oxidized and the results may be low.

5.0

4.3

Background contamination from plastic tubing and sample containers is eliminated by filling the wash receptacle by siphon (using Kel-F tubing) and using glass tubes for the samples and standards.

4.4

Method interferences may be caused by contaminants in the reagent water, reagents, glassware, and other sample processing apparatus that bias analyte response.

SAFETY

5.1

The toxicity or carcinogenicity of each reagent used in this method have not been fully established. Each chemical should be regarded as a potential health hazard and exposure should be as low as reasonably achievable. Cautions are included for known extremely hazardous materials or procedures.

5.2

Each laboratory is responsible for maintaining a current awareness file of OSHA regulations regarding the safe handling of the chemicals specified in this method. A reference file of Material Safety Data Sheets (MSDS) should be made available to all personnel involved in the chemical analysis. The preparation o f a formal safety plan is also advisable.

5.3 The following chemicals have the potential to be highly toxic or

hazardous, consult MSDS.

6.0

5.3.1

Potassium ferricyanide (7.2)

5.3.2

Phenol (7.5)

5.3.3

Sulfuric acid (7.10)

EQUIPMENT AND SUPPLIES

6.1

Balance

--

Analytical, capable of accurately weighing to the nearest

0.0001 g. 6.2 Glassware

--

Class A volumetric flasks and pipets as required.

526

7.0

Methods for the Determination 6.3

D i s t i l l a t i o n apparatus, a l l g l a s s c o n s i s t i n g o f a l - L p y r e x d i s t i l l i n g apparatus w i t h Graham condenser. Reduced volume apparatus a l s o may be used.

6.4

pH meter w i t h e l e c t r o d e s .

6.5

Automated c o n t i n u o u s f l o w a n a l y s i s equipment designed t o d e l i v e r and r e a c t sample and r e a g e n t s i n t h e r e q u i r e d o r d e r and r a t i o s . 6.5.1

Sampling d e v i c e (sampler)

6.5.2

M u l t i c h a n n e l pump

6.5.3

Reaction u n i t o r manifold

6.5.4

Colorimetric detector

6.5.5

Data r e c o r d i n g d e v i c e

REAGENTS AND STANDARDS

7.1

Reagent w a t e r : D i s t i l l e d o r d e i o n i z e d water, f r e e o f t h e a n a l y t e o f i n t e r e s t . ASTM t y p e I 1 o r e q u i v a l e n t .

7.2

B u f f e r e d p o t a s s i u m f e r r i c y a n i d e : D i s s o l v e 1.0 g p o t a s s i u m f e r r i c y a n i d e (CSRN 13746-66-2) , 1.55 g b o r i c a c i d (CASRN 10043-353 ) , and 1.875 g p o t a s s i u m c h l o r i d e (CASRN 7447-40-7) i n 400 mL o f r e a g e n t w a t e r . A d j u s t t o pH o f 10.3 w i t h 1 N sodium h y d r o x i d e (CASRN 1310-73-2) (7.3) and d i l u t e t o 500 mL. Add 0.25 mL o f B r i j 35 (CASRN 9002-92-0). Prepare f r e s h weekly.

7.3

Sodium h y d r o x i d e (1N): D i s s o l v e 20 g NaOH i n 250 mL o f r e a g e n t water, c o o l and d i l u t e t o 500 mL.

7.4

4 - A m i n o a n t i p y r i n e : D i s s o l v e 0.13 g o f 4 - a m i n o a n t i p y r i n e (CASRN 8307-8) i n 150 mL o f r e a g e n t w a t e r and d i l u t e t o 200 mL. Prepare f r e s h each day.

7.5

S t o c k phenol: D i s s o l v e 0.50 g phenol (CASRN 108-95-2) i n 500 mL o f r e a g e n t w a t e r and d i l u t e t o 500 mL. Add 0.25 mL conc. H,SO, (CASRN 7664-93-9) as p r e s e r v a t i v e . 1 .O mL = 1.O mg phenol.

7.6

Standard phenol s o l u t i o n A: D i l u t e 1.0 mL o f s t o c k phenol s o l u t i o n (7.5) t o 100 mL w i t h r e a g e n t water. 1.0 mL = 0.01 mg phenol.

7.7

Standard phenol s o l u t i o n B: D i l u t e 10.0 mL o f s t a n d a r d phenol s o l u t i o n A (7.6) t o 100 mL w i t h r e a g e n t w a t e r . 1.0 mL = 0.001 mg phenol.

7.8

Standard s o l u t i o n C: D i l u t e 10.0 mL o f s t a n d a r d phenol s o l u t i o n B ( 7 . 7 ) t o 100 mL w i t h r e a g e n t w a t e r . 1.0 mL = 0.0001 mg phenol.

Inorganic Substances 7.9

Sodium h y d r o x i d e , 1 t 9 : reagent water.

527

D i l u t e 10 mL o f 1N NaOH ( 7 . 3 ) t o 100 mL w i t h

(CASRN 7764-93-9) 7.10 S u l f u r i c a c i d , 1 t 9 : S l o w l y add 10 mL conc. H,SO, t o 70 mL o f r e a g e n t w a t e r . Cool and d i l u t e t o 100 mL w i t h r e a g e n t water. 7.11 Ferrous ammonium s u l f a t e : D i s s o l v e 0.55 g f e r r o u s ammonium s u l f a t e , O, and d i l u t e t o 500 mL i n 250 mL r e a g e n t w a t e r c o n t a i n i n g 0.5 mL HS w i t h f r e s h l y b o i l e d and c o o l e d r e a g e n t w a t e r . 8.0

9.0

SAMPLE COLLECTION, PRESERVATION AND STORAGE

8.1

Samples s h o u l d be c o l l e c t e d i n g l a s s b o t t l e s o n l y . A l l b o t t l e s must be t h o r o u g h l y cleansed and r i n s e d w i t h r e a g e n t w a t e r . Volume c o l l e c t e d s h o u l d be s u f f i c i e n t t o i n s u r e a r e p r e s e n t a t i v e sample, a l l o w f o r r e p l i c a t e a n a l y s i s ( i f r e q u i r e d ) , and m i n i m i z e waste disposal .

8.2

Samples must be p r e s e r v e d a t t i m e o f c o l l e c t i o n w i t h HS , O, o f < 2 and c o o l e d t o 4°C.

8.3

Samples s h o u l d be analyzed as soon as p o s s i b l e a f t e r c o l l e c t i o n . I f s t o r a g e i s r e q u i r e d , p r e s e r v e d samples a r e m a i n t a i n e d a t 4°C and may be h e l d up t o 28 days.

t o a pH

QUALITY CONTROL 9.1

Each l a b o r a t o r y u s i n g t h i s me hod i s r e q u i r e d t o o p e r a t e a formal q u a l i t y c o n t r o l (QC) program. The minimum r e q u i r e m e n t s o f t h i s program c o n s i s t o f an i n i t i a l d e m o n s t r a t i o n o f l a b o r a t o r y c a p a b i l i t y , and t h e p e r i o d i c n a l y s i s o f l a b o r a t o r y r e a g e n t blanks, f o r t i f i e d b l a n k s and o t h e r l a b o r a t o r y s o l u t i o n s as a c o n t i n u i n g check on performance. The l a b o r a t o r y i s r e q u i r e d t o m a i n t a i n performance r e c o r d s t h a t d e f i n e t h e q u a l i t y o f t h e d a t a t h a t a r e generated.

9.2

I N I T I A L DEMONSTRATION OF PERFORMANCE 9.2.1

The i n i t i a l d e m o n s t r a t i o n o f performance i s used t o c h a r a c t e r i z e i n s t r u m e n t performance ( d e t e r m i n a t i o n o f LCRs and a n a l y s i s o f QCS) and l a b o r a t o r y performance ( d e t e r m i n a t i o n o f MDLs) p r i o r t o p e r f o r m i n g analyses by t h i s method.

9.2.2

L i n e a r C a l i b r a t i o n Range (LCR) -- The LCR must be determined i n i t i a l l y and v e r i f i e d e v e r y 6 months o r whenever a s i g n i f i c a n t change i n i n s t r u m e n t response i s observed o r expected. The i n i t i a l d e m o n s t r a t i o n o f l i n e a r i t y must use s u f f i c i e n t standards t o i n s u r e t h a t t h e r e s u l t i n g c u r v e i s l i n e a r . The v e r i f i c a t i o n o f l i n e a r i t y must use a minimum o f a b l a n k and t h r e e s t a n d a r d s . I f any v e r i f i c a t i o n d a t a

528

Methods for the Determination

exceeds the initial values by f: lo%, linearity must be reestablished. If any portion of the range is shown to be nonlinear, sufficient standards must be used to clearly define the nonlinear portion. 9.2.3

Quality Control Sample (QCS) -- Wheri beginning the use of this method, on a quarterly basis or as required to meet data-qua1 ity needs, verify the calibration standards and acceptable instrument performance with the preparation and analyses of a QCS. If the determined concentrations are not within f 10% of the stated values, performance of the determinative step o f the method i s unacceptable. The source of the problem must be identified and corrected before either proceeding with the initial determination of MDLs or continuing with on-going analyses.

9.2.4

Method Detection Limit (MDL) -- MDLs must be established for all analytes, using reagent water (blank) fortified at a concentration of two to three times the estimated instrument detection limit.'4' To determine MDL values, take seven replicate aliquots of the fortified reagent water and process through the entire analytical method. Perform all calculations defined in the method and report the concentration values in the appropriate units. Calculate the MDL as follows: MDL

=

(t) x (S)

where, t

=

Student's t value for a 99% confidence level and a standard deviation estimate with n-1 degrees of freedom [t = 3.14 for seven replicates].

S

=

standard deviation of the replicate analyses.

MDLs should be determined every 6 months, when a new operator begins work or whenever there is a significant change in the background or instrument response. 9.3 ASSESSING LABORATORY PERFORMANCE 9.3.1

Laboratory Reagent Blank (LRB) -- The laboratory must analyze at least one LRB with each batch of samples. Data produced are used to assess contamination from the laboratory environment. Values that exceed the MDL indicate laboratory or reagent contamination should be suspected and corrective actions must be taken before continuing the anal ysi s .

9.3.2

Laboratory Fortified Blank (LFB) -- The laboratory must analyze at least one LFB with each batch of samples. Calculate accuracy as percent recovery (Sect. 9.4.2). If the recovery of any analyte falls outside the required

Inorganic Substances

529

c o n t r o l l i m i t s o f 90-110%, t h a t a n a l y t e i s judged o u t o f c o n t r o l , and t h e source o f t h e problem s h o u l d be i d e n t i f i e d and r e s o l v e d b e f o r e c o n t i n u i n g a n a l y s e s . 9.3.3

The l a b o r a t o r y must use LFB analyses d a t a t o assess l a b o r a t o r y performance a g a i n s t t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%. When s u f f i c i e n t i n t e r n a l performance d a t a become a v a i l a b l e ( u s u a l l y a minimum o f 20-30 a n a l y s e s ) , o p t i o n a l c o n t r o l l i m i t s can be developed from t h e p e r c e n t mean r e c o v e r y ( x ) and t h e s t a n d a r d d e v i a t i o n ( S ) o f t h e mean r e c o v e r y . These d a t a can be used t o e s t a b l i s h t h e upper and l o w e r c o n t r o l l i m i t s as f o l l o w s : UPPER CONTROL LIMIT LOWER CONTROL LIMIT

= =

x t 3s x - 3s

The o p t i o n a l c o n t r o l l i m i t s must be equal t o o r b e t t e r t h a n t h e r e q u i r e d c o n t r o l l i m i t s o f 90-110%. A f t e r each f i v e t o t e n new r e c o v e r y measurements, new c o n t r o l l i m i t s can be c a l c u l a t e d u s i n g o n l y t h e most r e c e n t 20-30 d a t a p o i n t s . Also, t h e s t a n d a r d d e v i a t i o n ( S ) d a t a s h o u l d be used t o e s t a b l i s h e d an on-going p r e c i s i o n statement f o r t h e l e v e l o f c o n c e n t r a t i o n s i n c l u d e d i n t h e LFB. These d a t a must be k e p t on f i l e and be a v a i l a b l e f o r r e v i e w . 9.3.4

9.4

I n s t r u m e n t Performance Check S o l u t i o n (IPC) -- F o r a l l d e t e r m i n a t i o n s t h e l a b o r a t o r y must a n a l y z e t h e I P C ( a midrange check s t a n d a r d ) and a c a l i b r a t i o n b l a n k immediately f o l l o w i n g d a i l y c a l i b r a t i o n , a f t e r e v e r y t e n t h sample ( o r more f r e q u e n t l y , i f r e q u i r e d ) , and a t t h e end o f t h e sample r u n . A n a l y s i s o f t h e I P C s o l u t i o n and c a l i b r a t i o n b l a n k i m m e d i a t e l y f o l l o w i n g c a l i b r a t i o n must v e r i f y t h a t t h e i n s t r u m e n t i s w i t h i n k 10% o f c a l i b r a t i o n . Subsequent analyses o f t h e I P C s o l u t i o n must v e r i f y t h e c a l i b r a t i o n i s s t i l l w i t h i n ? 10%. I f t h e c a l i b r a t i o n cannot be v e r i f i e d w i t h i n t h e s p e c i f i e d l i m i t s , r e a n a l y z e t h e I P C s o l u t i o n . If t h e second a n a l y s i s o f t h e I P C s o l u t i o n c o n f i r m s c a l i b r a t i o n t o be o u t s i d e t h e l i m i t s , sample a n a l y s i s must be d i s c o n t i n u e d , t h e cause determined and/or i n t h e case o f d r i f t t h e i n s t r u m e n t r e c a l i b r a t e d . A l l samples f o l l o w i n g t h e l a s t a c c e p t a b l e I P C s o l u t i o n must be r e a n a l y z e d . The a n a l y s i s d a t a o f t h e c a l i b r a t i o n b l a n k and I P C s o l u t i o n must be k e p t on f i l e w i t h t h e sample analyses data.

ASSESSING ANALYTE RECOVERY AND DATA QUALITY 9.4.1

L a b o r a t o r y F o r t i f i e d Sample M a t r i x (LFM) -- The l a b o r a t o r y must add a known amount o f a n a l y t e t o a minimum o f 10% o f t h e r o u t i n e samples. I n each case t h e LFM a l i q u o t must be a d u p l i c a t e o f t h e a l i q u o t used f o r sample a n a l y s i s . The a n a l y t e c o n c e n t r a t i o n must be h i g h enough t o be d e t e c t e d above t h e o r i g i n a l sample and should n o t be l e s s t h a n f o u r

530

Methods for the Determination

times t h e MDL. The added a n a l y t e c o n c e n t r a t i o n should be the same as t h a t used in t h e l a b o r a t o r y f o r t i f i e d blank. 9.4.2

C a l c u l a t e t h e percent recovery f o r each a n a l y t e , c o r r e c t e d f o r c o n c e n t r a t i o n s measured i n the u n f o r t i f i e d sample, and compare t h e s e values t o t h e designated LFM recovery range 90-110%. Percent recovery may be c a l c u l a t e d using t h e f o l l owing equation: R =

c,

___

-

c

x 100

S

where, R C, C s 9.4.3

=

= = =

percent recovery. f o r t i f i e d sample c o n c e n t r a t i o n . sample background c o n c e n t r a t i o n . c o n c e n t r a t i o n e q u i v a l e n t of a n a l y t e added t o sample.

I f t h e recovery of any a n a l y t e f a l l s o u t s i d e t h e designated LFM recovery range and the l a b o r a t o r y performance f o r t h a t

a n a l y t e i s shown t o be i n c o n t r o l ( S e c t . 9 . 3 ) , t h e recovery problem encountered with t h e LFM i s judged t o be e i t h e r matrix o r s o l u t i o n r e l a t e d , not system r e l a t e d . 9.4.4

Where r e f e r e n c e m a t e r i a l s a r e a v a i l a b l e , they should be analyzed t o provide a d d i t i o n a l performance d a t a . The a n a l y s i s o f r e f e r e n c e samples i s a v a l u a b l e t o o l f o r demonstrating t h e a b i l i t y t o perform the method acceptably.

10.0 CALIBRATION AND STANDARDIZATION

10.1 Prepare a series o f a t l e a s t 3 s t a n d a r d s , covering the d e s i r e d range, and a blank by p i p e t t i n g s u i t a b l e volumes o f working standard s o l u t i o n s (7.6, 7.7, 7.8) i n t o 100-mL volumetric f l a s k s . Suggested ranges include 1 t o 5 , 10 t o 100, and 200 t o 500 pg/L.

10.2 I t i s not imperative t h a t a l l s t a n d a r d s be d i s t i l l e d i n the same manner a s t h e samples. I t i s recommended t h a t a t l e a s t one standard and a blank be d i s t i l l e d and compared t o s i m i l a r values on the s t a n d a r d curve t o insure t h a t the d i s t i l l a t i o n technique i s r e l i a b l e . I f d i s t i l l e d s t a n d a r d s do not agree w i t h i n f 10% o f the u n d i s t i l l e d s t a n d a r d s , t h e a n a l y s t should f i n d t h e cause of the apparent e r r o r before proceeding. Before d i s t i l l a t i o n , s t a n d a r d s should be a d j u s t e d t o a pH of 4 with H,SO,. 10.3 S e t u p t h e manifold a s shown i n Figure 1 i n a hood o r a wellventilated area. 10.4 Allow t h e instrument t o warm u p a s r e q u i r e d . u n t i l a s t a b l e b a s e l i n e i s achieved.

Pump a l l r e a g e n t s

Inorganic Substances

531

in the sampler in order of decreasing concentration and perform analysis.

10.5 Place appropriate standards

10.6 Prepare standard curve by plotting instrument response concentration

values. A calibration curve may be fitted to the calibration solutions concentration/response data using computer or calculator based regression curve fitting techniques. Acceptance or control limits should be established using the difference between the measured value of the calibration solution and the "true value" concentration.

10.7 After the calibration has been established, it must be verified by the analysis o f a suitable quality control sample (QCS). If measurements exceed f 10% of the established QCS value, the analysis should be terminated and the instrument recalibrated. The new calibration must be verified before continuing analysis. Periodic reanalysis o f the QCS is recommended as a continuing calibration check. 11.0 PROCEDURE 11.1 Distil 1 ation 11.1.1

Measure 500 mL sample into a beaker. Adjust the pH to approximately 4 with 1 t 9 NAOH (7.9) or 1 t 9 H,SO, (7.10), and transfer to the distillation apparatus.

11.1.2

Distill 450 mL of sample, stop the distillation, and when boiling ceases add 50 mL of warm reagent water to the flask and resume distillation until 500 mL have been collected.

11.1.3

If the distillate i s turbid, filter through a prewashed membrane fi 1 ter.

11.2 Set up the manifold as shown in Figure 1. 11.3 Fill the wash receptacle by siphon with reagent water. tubing with a fast flow (1 L/h).

Use Kel-F

11.4 Allow the instrument to warm up as required.

Run a baseline with all reagents, feeding reagent water through the sample line. Use polyethylene tubing for sample line. When new tubing i s used, about 2 hours may be required to obtain a stable baseline. This two hour time period may be necessary to remove the residual phenol from the tubing.

11.5 Place appropriate phenol standards in sampler in order of decreasing

concentration. Complete loading of sampler tray with unknown samples, using glass tubes. 11.6 Switch sample line from reagent water to sampler and begin analysis.

532 12.0

Methods for the Determination

DATA ANALYSIS AND CALCULATIONS 12.1 Prepare a calibration curve by plotting instrument response against standard concentration. Compute sample concentration by comparing sample response with the standard curve. Mu1 tiply answer by appropriate dilution factor. 12.2 Report only those values that fall between the lowest and the highest calibration standards. Samples exceeding the highest standard should be diluted and reanalyzed. 12.3 Report results in pg/L.

13.0 YETHOD PERFORMANCE

13.1 The interlaboratory precision and accuracy data in Table 1 were developed using a reagent water matrix. Values are in mg Phenol/L. 13.2 Single laboratory precision data can be estimated at 50 to 75% o f the interlaboratory precision estimates. 14.0 POLLUTION PREVENTION

14.1 Pollution prevention encompasses any technique that reduces or eliminates the quantity or toxicity of waste at the point of generation. Numerous opportunities for pollution prevention exist in laboratory operation. The EPA has established a preferred hierarchy o f environmental management techniques that places pollution prevention as the management option of first choice. Whenever feasible, laboratory personnel should use pollution prevention techniques to address their waste generation. When wastes cannot be feasibly reduced at the source, the Agency recommends recycling as the next best option.

14.2 The quantity of chemicals purchased should be based on expected usage during its shelf life and disposal cost of unused material. Actual reagent preparation volumes should reflect anticipated usage and reagent stability. 14.3 F o r information about pollution prevention that may be applicable t o laboratories and research institutions, consult "Less is Better: Laboratory Chemical Management for Waste Reduction," available from the American Chemical Society's Department of Government Regulations and Science Policy, 1155 16th Street N.W., Washington D.C. 20036, (202) 872-4477. 15.0 WASTE MANAGEMENT

15.1 The Environmental Protection Agency requires that laboratory waste management practices be conducted consistent with all applicable rules and regulations. Excess Reagents and samples and method process wastes should be characterized and disposed o f in an

Inorganic Substances

533

a c c e p t a b l e manner. The Agency u r g e s l a b o r a t o r i e s t o p r o t e c t t h e a i r , w a t e r , and l a n d by m i n i m i z i n g and c o n t r o l l i n g a l l r e l e a s e s from hoods, and bench o p e r a t i o n s , complying w i t h t h e l e t t e r and s p i r i t o f any waste d i s c h a r g e p e r m i t and r e g u l a t i o n s , and by complying w i t h a l l s o l i d and hazardous waste r e g u l a t i o n s , p a r t i c u l a r l y t h e hazardous waste i d e n t i f i c a t i o n r u l e s and l a n d d i s p o s a l r e s t r i c t i o n s . For f u r t h e r i n f o r m a t i o n on waste management c o n s u l t t h e "Waste Management Manual f o r L a b o r a t o r y Personnel , ' I a v a i l a b l e f r o m t h e American Chemical S o c i e t y a t t h e address l i s t e d i n Sect. 14.3. 16.0 REFERENCES

I 1 Methodology, I n d u s t r i a l Method No. 127-

1.

Technicon AutoAnalyzer 71W, A A I I .

2.

Standard Methods f o r t h e Examination o f Water and Wastewater, 1 4 t h E d i t i o n , p . 574, Method 510 (1975).

3.

Gales, M.E.

and Booth, R.L.,

"Automated 4 AAP P h e n o l i c Method," AWWA

68, 540 (1976). 4.

Code o f Federal R e g u l a t i o n s 40, Ch. 1, P t . 136, Appendix B.

534

Methods for the Determination

17.0 TABLES, DIAGRAMS, FLOWCHARTS, AND V A L I D A T I O N DATA TABLE 1. UMBER OF VALUES IEPORTED

INTERLABORATORY P R E C I S I O N AND ACCURACY DATA

TRUE VALUE (T)

MEAN (X)

RESIDUAL FOR X

STANDARD DEVIATION

(S)

RESIDUAL FOR S

0.0000

99

0.020

0.0149

0.0000

0.0074

87

0.250

0.1443

-0.0052

0.0268

-0.0038

76

0.400

0.2352

-0.002 1

0.0422

-0.0036

110

0.545

0.3364

0.0142

0.0681

0.0076

89

0.604

0.3610

0.0043

0.0625

-0.0039

107

0.660

0.3959

0.0064

0.0894

0.0173

86

0.800

0.4627

-0.0087

0.0806

-0.0057

62

0.817

0.4692

-0.0122

0.0776

-0.0104

76

0.970

0.5680

-0.0029

0.1017

-0.0017

89

2.96

1.7734

0.0377

0.3065

0.0018

61

4.18

2.3916

-0.0582

0.4044

-0.0237

110

4.54

2.7150

0.0545

0.5382

0.0737

REGRESSIONS:

X

=

0.585T t 0.003, S

=

0.101T t 0.005

WASTE

mmn 0.32

I

TO F/C PUMPTUBE C0U)RIMETDI 505 nm 50 mm F/C

WASTE

AIR

1.20

SAMPLE

0.23

4

w

20 PEFi HOUR SAMPLE 120 SEC. WASH 80 S I X .

Inorganic Substances

Figure 1 Phenol Manifold

535

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