Reference Materials for Chemical Analysis: Certification, Availability, and Proper Usage

Reference Materials for Chemical Analysis Edited by Markus Stoeppler, Wayne R. Wolf; PeterJ. Jenks

Reference Materials for Chemical Analysis Certification, Availability, and Proper Usage

Edited by Markus Stoeppler, Wayne R. Wolf; Peter]. Jenks

@WILEY-VCH Weinheim - New-York - Chichester - Brisbane - Singapore - Toronto

The Editors ofthis Volume

Or. Markus Staeppler Mariengarten Str. ra 52428 Julich Germany Wayne R. WOK Ph.D.

Human Nutrition Research Center US Department of Agridture 10300 Baltimore Blvd. Beltsville, MD 20899, USA Peterj. Jenks, B.Sc

Laboratory ofthe Gouvernment Chemist Queens Road, Teddington Middlesex TWII oLY, England Sections 3.4 (Authors Steven A. Wise and Jiirgen Jacob)and 5.4 (Authors Barbara C. Levin and Dennis J. Reeder) are contributions ofthe US National Institute of Standards and Technology (NIST) and as such are not subject to copyright. Certain commercial equipment, instrnments, materials or companies are identified in these contributions to specify the experimental procedure. Such identification does not imply recommendation or endorsement by NIST. nor does it imply that the materials or equipment identified are the best available for this purpose.

.

This book was carefully produced. Nevertheless, authors and publisher do not warrant the information contained therein to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate. Library of Congress Card No.:

applied for British LibraryCataloguingin-Publication Data

A catalogue record for this book is available from the British Library. Die Deutsche Bibliothek - CIP Cataloguingin-Publication Data

A catalogue record for this publication is available from Die Deutsche Bibliothek

0 Wiley-VCHVerlag GmbH

69469 Weinheim (Federal Republic of Germany),2001 AU rights reserved (includingthose of translation in other languages). No part of this book may be reproduced in any form - by photoprinting, microfilm, or any other means -nor transmitted or translated into machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law. Printed in the Federal Republic of Germany Printed on acid-free paper Composition Kuhn & Weyh,

Freiburg, Germany Printing Strauss Offsetdruck

Morlenbach, Germany Bookbinding J. Schaffer GmbH Griinstadt, Germany ISBN 3-527-30162-3

I"

Foreword No one would deny that the works of great philosophers of the 18th Century are very important. Using the names of Kant or Rousseau demonstrates a certain level of cultural education. Yet these works are hardly ever read. The Foreword of a text-book has this in common with the works of the philosophers. But this gives the person who writes the Foreword the opportunity to propose some more philosophical thoughts. He can even be daring, as the Foreword is not considered a part of the book and therefore it has hardly any importance. With this excuse I can use the opportunity this book gives me as an occasion for thinking, on paper! This book appears at a moment when one of the major developments of the last century in analytical chemistry, measurement science, is coming to its full maturity. The past hundred years have shown an enormous expansion in measurement activities: what is measured, the purpose of the measurements, the use of measured data, and the demands placed upon these data. From the initial, almost exclusive, use of chemical reactions to make measurement the field became wider. Introducing physical and biological reactions and sensors has enormously extended the scope of analytical chemistry. Some 15 years ago the US National Institute of Science and Technology, better known as NIST, estimated the economic impact of measurements and arrived at a figure of some G % of the GDP of a developed country. Even if this estimate is wrong by 50 %, which is unlikely, then this figure is still impressive. However, once we realize where the requests for data come from, then we may better understand the magnitude of this figure. Measurement data are being used for the diagnosis of illness in people and domestic animals, for the control of food and animal feed quality, to establish transfer of dangerous substances through the environment and ecocompartments, to find correlations that may lead to a better understanding of causeeffect relationships, to control raw materials and finished products, and for many other purposes. The rg70's demonstrated a trend: "chemistry is going out of analytical chemistry". However, what was not used anymore up-front for analysis came back in the form of sample preparation techniques. For example, IUPAC devoted as much attention as ever before, but now to the chemistry needed to prepare the sample for measurement and to avoid losses and contamination.

VI

I

Foreword

A growing tendency to take measurements away from the specialized laboratory and place them in the hands of the end-users made paramount the need for good control of produced and used results. The risk of wrong results and biased data increases rapidly in such situations. Consequently, there came about a general tendency to formalize or codify procedures to arrive at data which are sufficiently accurate for the intended purpose. The end-user of the data became increasingly aware of the risk that conclusions could be based on wrong analytical results. The increasing complexity of society (where more and more people, over greater distances, were attributing characteristics or properties to a final product) meant that often the “good reputations” of the past were no longer seen to give the certainty needed for the increasing volume of data. As everywhere in society, relationships were formalized. What started in medieval times with the standard weights and sizes in every town with market rights, was developed in the last half of the past century to a globally elaborated standards system. Standards are now used everywhere to demonstrate reliability. Standards have replaced good trust in reputations. Psychology, the relation of human understanding, has been replaced by the science of measurements. Standards are being used in the context of Analytical Quality Assurance, which is the demonstration to the end-user that the delivered product, the measurement data, are reliable and have been made according to the best practices currently possible. Standards facilitate, some would say are essential to, living and trading in the global village. Standards have become standard in everyday life. This development has taken place remarkably quickly over the past thirty years. In that period the first attempts to arrive at a proven analytical accuracy were made. Those who led the move were often considered as people with hobbies, obsessive even. Some eye-opening publications demonstrated clearly that generating analytical results could be compared with the generation of numbers in a lottery (G. Tolg), but were received skeptically by the scientific establishment. Even as recently as the late 1970’s even the most highly respected universities still had to be made aware that a result was not necessarily an accurate result. But over the past thirty years or so, with increasing awareness of analytical error, the situation changed. Global trade, environmental modelling, etc. caused a drastic change in attitude. Quality Control and Assurance have become integral parts of a scientific curriculum. It is commonly accepted now that 10-15 % of all measurement costs are Quality Assurance costs. This means that the subject of this book covers some I % of a developed country’s GDP. Such an amount is substantial, knowing that the GDP of agriculture in many developed countries does not exceed 10% of the total GDP. This book marks the conclusion of this strong period of development and is therefore a milestone in measurement science. As such, the field already has a history. But as history makes no sense without a future, the last Chapter of this book deals with expected further developments in terms of organization and needs. Between history and future the book presents, as a snap shot, the application of standards in analytical chemistry. The perspective of Quality Assurance is never forgotten.

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After so many developments (often worked out by an in-crowd of devoted, enthusiastic scientists), the time has come to transfer the results of these scientific developments to a wider audience. Not every scientist producing measurement data is interested in the theories worked out in so many vigorous discussions by leading groups. But every scientist using or producing data should be aware of the facts presented herein. The information, however, is of importance for an even wider audience than just the scientific circles. For example, if ever we want to understand whether global warming to a substantial degree is, or is not, caused by human activities, then we should first of all know and understand the performance of our models and the accuracy of data we put into these models. If ever we want to know whether all efforts to improve the quality of the sea for biota are effective, then we need to know the accuracy and uncertainty of all our data. If we do not want to take Quality Assurance into account, we will never be able to lay the solid scientific foundations for our research, political and legal actions etc. In other words: we will remain only believers. I do hope that this book will not only find a wide audience, but that it will also contribute something to progress in the world. This may sound somewhat grand and optimistic, but is it forbidden to dream that next century will indeed bring real progress to mankind? Can this progress be based on anything else except scientific developments? If this is to be so, then what other than sound measurement data can be the basis? Sound measurements mean that data are accurate for the intended purpose and that the uncertain is known and taken into full account. In that case we may have walked along with Kant, Rousseau and so many others. Bernard Griepink, Brussels, Belgium

30. December 1999

I

Contents Foreword

XV

Preface XVIl 1

Introduction

1.1 1.1.1 1.1.2 1.1.3 1.2 1.3 1.4

Historical 1 Early Developments 1 Growth and Maturity 4 Milestones and The Future G The Theoretical Basis 7 Technical Requirements 11 References 16

1

2

From Planning to Production

2.1 2.1.1 2.1.2 2.1.3 2.1.4 2.2 2.2.1 2.2.2 2.2.3 2.2.4 2.3

Material Collection and Preparation 20 Introduction 20 General Collection and Preparation Principles 22 Specific Examples 26 Concluding Remarks and Recommendations 30 Control of Material Properties 31 Particle Size and Particle Size Distribution 31 Homogeneity/Heterogeneity 33 Humidity (Water Content) 37 Degradation Studies/Shelf Life 40 References 43

3

Certification

3.1 3.1.1 3.1.2 3.1.2.1 3.1.2.2 3.1.2.3

20

49

Certification Philosophy of RM Producers 49 Introduction 49 Approaches to the Characterization/Certification of Reference Materials 50 General Principles of Certification 50 Classification of Characterization/Certification Schemes 52 Specific Examples 58

IX

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Contents

Conclusions Go Certification of Elements Go Methods Used for the Certification of RMs for Elements Go Multi-Method Elemental RM Certification 64 River Sediment 64 Lichen 65 Examples of Selected RMs Certified for Elements 66 Certification of Element Contents by Neutron Activation Analysis GG General Features GG Internal Cross-Checking(Self-verification)in NAA 68 Applications in Certification and Analysis Gg NAA for the Detection of Errors 73 Summary 74 Certification of Organometallic and Other Species 75 Introduction 75 Potential Sources of Error in Speciation Analysis 76 Restricted List of Chemical Species for Trace Elements and Their Compounds 77 3.3.3.1 Aluminum 77 3.3.3.2 Antimony 77 3.3.3.3 Arsenic 77 3.3.3.4 Bromine 78 3.3.3.5 Chromium 78 3.3.3.6 Mercury 79 3.3.3.7 Lead 80 3.3.3.8 Selenium 81 3.3.3.9 Tin 81 3.3.3.10 Metallothionein 82 3.3.4 Fractionation 82 3.3.5 Conclusions 82 3.4 Certification of Organic Substances 83 3.4.1 Introduction 83 3.4.2 CRMs Available for Organic Constituents 84 3.4.2.1 Pure Substances 84 3.4.2.2 Calibration Solution CRMs 85 3.4.2.3 Natural Matrix SRMs 85 3.4.3 Certification Approach for Organic Constituents 88 3.4.3.1 NISTApproach for Certification 89 3.4.3.2 NIST Analytical Approach for the Certification of Organic Constituents in Natural Matrix SRMs 91 3.4.3.3 BCR Approach to Certification 97 3.5 References IOI

3.1.3 3.2 3.2.1 3.2.2 3.2.2.1 3.2.2.2 3.2.2.3 3.2.3 3.2.3.1 3.2.3.2 3.2.3.3 3.2.3.4 3.2.3.5 3.3 3.3.1 3.3.2 3.3.3

4 4.1

Particular Developments

111

RMs in Quality Control and Quality Assessment

111

4.1.1 4.1.2 4.1.3 4.1.4 4.1.5 4.1.5.1 4.1.5.2 4.1.5.3 4.1.5.4 4.1.5.5 4.1.5.6 4.1.6 4.2 4.2.1 4.2.2 4.2.3 4.2.4 4.2.5 4.3 4.3.1 4.3.2 4.3.3 4.3.4 4.3.4.1 4.3.4.2 4.3.4.3 4.3.4.4 4.3.5 4.4 4.4.1 4.4.2 4.4.3 4.4.3.1 4.4.3.2 4.4.3.3 4.4.4 4.5 4.5.1 4.5.1.1 4.5.1.2 4.5.1.3 4.5.2 4.5.2.1

Introduction 111 Proper Usage 113 Characterization of Methods 113 Internal Quality Control 115 External Quality Assurance 117 State of the Art 118 Performance of Individual Laboratories 119 Supplement Internal Quality Control 119 To Obtain Consensus Values 119 Investigate Factors Contributing to Performance 120 To Act as an Educational Stimulus To License Laboratories? 120 Conclusions 121 Fresh Materials 121 Introduction 121 Packing Materials 122 Preparation 124 Homogeneity 125 Stability 126 Certified Reference Materials for Microanalytical Methods 127 Homogeneity of Components in CRMs 129 A Priori and a Posteriori Homogeneity of Materials 130 Aspects of Homogeneity Determination 131 Examples 132 Homogeneity Determinations with Solid Sampling Atomic Absorption Spectrometry 133 Homogeneity Determinations with Instrumental Neutron Activation Analysis (INAA) 134 Uncertainty Budget of INAA 135 Homogeneity Factors in Test Materials Determined with INAA 136 Conclusion 137 CRMs as calibrants 138 Principles 138 Calibration Techniques 139 Examples 140 Biological Materials 140 Environmental and Geological Materials 141 Technical Materials ip Conclusion 143 RMs for Radioisotopes, Stable Isotopes and Radiopharmaceuticals 143 Radioisotopes 143 Requirements and uses 143 Available Reference Materials 144 Future Developments 146 Stable Isotopes I& Requirements and uses q G

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Contents

4.5.2.2 Future Developments 147 Radiopharmaceuticals 147 4.5.3 References 148 4.6 5

5.1 5.1.1 5.1.2 5.2 5.3 5.3.1 5.3.2 5.3.2.k 5.3.3 5.3.3.1 5.3.3.2 5.3.4 5.4 5.5 5.5.3 5.5.2 5.5.3 5.5.3.1 5.5.3.2 5.5.3.3 5.5.2.4 5.5.4 5.5.5 5.5.6 5.5.6.1 5.5.6.2 5.5.6.3 5.5.6.4 5.5.7 5.5.8 5.5.9 5.5.10 5.5.11 5.6 6 6.1 6.1.1 6.1.2 6.1.3

Reference Materials for “Life” Analysis 154 Standard Reference Materials for Microbiological Assays 154 Standards for Official Assays and Tests 155 Quality Management of Biological RMs 156 Certified Microbiological Culture Materials 158 Reference Materials for DNA Analysis 160 SRMzjgo 160 S R M Z ~ ~161 I Recertifiration of SRM 2391 162 SRMz392 163 DNA Source 163 Inter-Laboratory Evaluation of SRM 2392 164 Summary 164 Future Developments in Molecular Reference Materials 171 Reference Substances and Spectra for Pharmaceutical Analysis Intsductiorr 173 Definitions and Guidelines 174 Uses of Pharmacopoeia1Reference Substances 175 Reference Substances Used for Identification 175 R d a m c e Substances Used for Related Substance Tests 176 Refereme Substances Used for Assay 180 Minimizing the Use of Reference Substances 180 Procurement of Candidate Reference Substances 181 Requirements for Candidate Reference Substances 182 EFahation 182 Reheace Substances Used for Identification 182 Reference Substances Used for Related Substance Tests 183 Reference Substances Used for Assay 183 CRS as Calibrators 189 ng Programme 189 Packaging and Filling 190 Certificatesof Analysis / Expiry Date / Catalogue i g i Storage and Distribution 192 International Harmonization 192 References 193 Generd Application Fie€& igG Workplace Air Monitoring 196 Introduction 196 Solvents 197 Elements and Inorganic Compounds

198

172

6.1.4 6.2 6.2.1 6.2.2 6.2.2.1 6.2.2.2 6.2.2.3 6.2.2.4 6.2.3 6.2.3.1 6.2.3.2 6.2.3.3 6.2.3.4 6.2.4 6.2.5 6.2.6 6.3 6.3.1 6.3.2 6.3.3 6.3.4 6.3.4.1 6.3.4.2 6.3.4.3 6.3.4.4 6.3.4.5 6.4 6.4.1 6.4.2 6.4.3 6.4.4 6.4.5

Asbestos igg Clinical Application Fields igg Introduction igy Elements 201 Essential Electrolytes 202 Essential Trace Elements 202 Elements Therapeutically Used 203 Non-Essential Elements 204 Organic Compounds 206 Solvents 206 Polyaromatic Hydrocarbons (PAH) 207 Pesticides 207 Persistent Compounds 207 Proteins and Enzymes 207 Lipids 209 Other Compounds 209 Food/Biological 210 Introduction 210 Food Matrix Triangle 211 Available Reference Materials 214 Mode of Application and Application Examples 214 Procedures for Reference Material Selection and Use 217 Procedures for Reference Material Utilization 217 Performance Interpretation and Corrective Action 217 Examples of Application of RMs to Certification of other RMs 218 Examples of Applying RMs in Analyses 218 Applications of Reference Materials in the Geological Sciences 220 Introduction 220 Producers of Geochemical Reference Materials 222 General Application: Calibration of Instrumental Measurements 223 General Application: Method Development and Validation 224 General Application: Quality Control in Multilaboratory, or Long-Term Within Laboratory, Studies 224 6.4.6 Specific Application: Geochemical Exploration 22j 6.4.7 SpecificApplication: Petrogenic Modelling Based on Bulk Rock Analysis 227 6.4.8 SpecificApplication: Petrogenic Modelling Based on Microanalysis 228 6.4.9 Application: Studies of Paleoclimates 228 6.4.10 Summary 229 6.5 References 229 Proper Usage o f Reference Materials 236 7.1 Selection, Use, and Abuse of RMs 236 7.1.1 Conventional "Proper" Uses of RMs 237 7.1.1.1 Method Development and Evaluation 237

7

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XIV

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Contents

7.1.1.2 7.1.1.3 7.1.2 7.1.2.1 7.1.2.2 7.1.2.3 7.1.2.4 7.1.2.5 7.1.2.6 7.1.2.7 7.1.3 7.1.4 7.1.5 7.1.6 7.2 7.2.1 7.2.2 7.3 7.3.1 7.3.2 7.4 7.5 7.6 8

8.1 8.1.1 8.1.2 8.2 8.2.1 8.2.2 8.2.3 8.2.4 8.3 8.3.1 8.3.1.2 8.3.1.3 8.3.1.4 8.3.2 8.3.2.1 8.3.2.2 8.4 8.4.1

Assurance of Measurement Compatibility 237 Establishment of Measurement Traceability 237 Mis-Useand Other Causes of Errors 238 Documentation Errors 238 Selection Errors 239 Handling and Use Errors 241 Storage 241 Shelf Life and Expiration Dates 241 Sampling and Preparation of RMs for Analysis 242 Sample Characteristics 243 Continuity 244 Artifacts 244 Data Interpretation Errors 245 Reporting Errors 246 Statistical Consequences in the Assurance of Measurement Compatibility 247 Uncertainty 247 Indicative Approach to Quantifying Uncertainty 248 Traceability 249 Definition 249 Practical Aspects 250 Conclusions 252 References 253 Further Reading 254 Availability and Sources of Information 256 Introduction 256 Printed Publications 257 Catalogs, Lists, and Directories 257 Journals 259 Electronic Sources and the Internet 262 The “COMAR Database 262 The IAEA Database 264 WinRefPro Database of Elements in Metals 265 Website Addresses 266 Organizations and Symposia 267 organizations 267 AOAC International 267 EURACHEM 268 VAM 269 Conferences and Meetings 269 BERM 269 Other Meetings 272 The Pharmacopoeia 273 United States Pharmacopoeia 273

Contents

8.4.2 8.4.3 8.5 8.6

The European Pharmacopoeia 273 The British Pharmacopoeia 274 The Movement of Reference Materials 274 References 277

9

Future Trends for Reference Material Activity 279 Introduction 279 Overview of General Issues 280 Review of Trends 280 Projection of Challenges 280 Analysis of Driving Forces and Construction of Scenarios 281 Thinking “Outside the Box” 282 Future Projections 283 Selecting Strategies 285 Needs for Specific Reference Materials 286 Reference Material Needs for Regulatory Nutrient Analysis 287 Perspectives from Distributors of Certified Reference Materials 289 RM Needs in Developing Countries 290 References 291

9.1 9.1.1 9.1.2 9.1.3 9.1.4 9.1.5 9.1.6 9.2 9.3 9.4 9.5 9.6

About the genesis ofthis book

Subject Index 295

293

Ixv

Preface It is usual for the editors to set the scene for the writing of such a book as this. But there is a long story to tell, for the genesis of the book goes back to the early I ~ ~ o ’ s , and the story is much about us, so we invited our publisher to pull together our story: you will find his tale, should you be interested, at the end of the book. More importantly we editors want to place on record our very great gratitude to all the authors who contributed to this work, our colleagues and friends, many of whom have accompanied us for years. Without their work the history of RMs and also the RM Symposia would be less interesting and colorful. In particular we want to acknowledge Herbert Muntau working from the Joint Research Center at Ispra, Italy, who was a major influence in the evolution of RM preparation and use and did great work from the early beginnings. We deeply regret that he was not able to join the project due to his enormous workload. Many thanks go also to Robert Parr, formely IAEA, Vienna, as a contributor to many symposia and also to this book, to Milan Ihnat from Argiculture Canada for his fine texts and editorial helps, to Steve Wise and Rolf Zeisler from NIST for their valuable chapters, to Jean Pauwels, IRMM, Philippe Quevauviller, SM&T (formely BCR), and Harry Klich, BAM, Germany, for their always ready support. The names of all contributors cannot be listed here, they are acknowledged in the chapters that they wrote: even so we thank them all for t y n g to be as concise and as informative as possible in their delivery of their most instructive sections, sometimes, it must be said, under “mild pressure from the editors, on time and most importantly for the benefit of the readers. We also want to thank the team at WileyVCH for all their advice and technical help during the production of this book. Julich, Germany, Beltsville USA and Teddington, England July 2000

Markus Stoeppler, Wayne Wolf, Peter Jenlts

I

List o f Contributors Dr. Agnes Artiges

Dr. Vanessa Dekou

Director European Pharmacopoeia Commission B.P. 907 F-67029 Strasbourg Cedex, France E-mail: [email protected]

Laboratory of the Government Chemist Queens Road, Teddington Middlesex TWII oLY, England E-mail: [email protected] Dr. Vincent EgloB

Dr. Humphryj.M. Bowen

West Down, West Street Winterborne Kingston Blandford, Dorset DTII 9AT, England Dr. Anthony R. Byrne

Joief Stefan Institute Jamova 39 Slo-1001 Ljubljana, Slovenia E-mail: [email protected]

European Pharmacopoeia Commission B.P. 907 F-67029 Strasbourg Cedex, France Dr. Bernard Criepink

Commission of the European Communities 200 rue de la Loi B-1049 Brussels, Belgium E-mail: [email protected] Dr. Karl-Heinz Grobecker

European Pharmacopoeia Commission B.P. 907 F-67029 Strasbourg Cedex, France

Institute for Reference Materials and Measurements (IRMM) Retieseweg B-2240 Geel, Belgium E-mail: karl-heinz.grobeclter@i~m.jrc.be

Dr. Rita Corneh

Proj Dr. Robert F.M. Herber

Laboratory of Analytical Chemistry Rijksuniversiteit Gent Institute for Nuclear Sciences Proeftuinstraat 86 B-9000 Gent, Belgium E-mail: [email protected]

Coronel Institute for Occupational and Environmental Health Academic Medical Center P.O. Box 22700 NL-1100 DE Amsterdam, The Netherlands E-mail: [email protected]

Dr.jacob de Boer

Dr. Milena Horvat

DLO-Netherlands Institute for Fisheries Research (RIVO-DLO) P.O. Box 68 1970 AB Ijmuiden. The Netherlands E-mail: j [email protected]

Joief Stefan Institute Jamova 39 Slo-1001 Ljubljana, Slovenia E-mail: [email protected]

Dr. Emmanuelle Charton

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List ofcontributors

Milan /hnat, Ph.D. Pacific Agri-Food Research Centre - Summerland Agriculture and Agri-Food Canada Summerland, British Columbia, Canada VOH 120, E-mail: [email protected]

Prof: Dr. Ulrich Kufirst Fachhochschule Fulda, Fachbereich HSrE. Marquardstrage 35 36039 Fulda, Germany E-mail: [email protected]

Prof: Dr. Heinz-Dieter lsengard Universitat Hohenheim Institut fur Lebensmitteltechnologie Garbenstrage 25

Barbara C. Leuin, Ph.D. 100 Bureau Drive, Stop 8311 National Bureau of Standards and Technology (NIST) Gaithersburg, M D 20899-8311,USA E-mail: [email protected]

70593 S t U W f l E-mail: [email protected] Prof: Dr.JiirgenJacob Biochemisches Institut f i r Umweltcarcinogene Prof Dr. Gernot Grimmer Stiftung Lump 4 zag27 GroEhansdofi, Germany E-mail: [email protected] PeterJJenks, B.Sc. Laboratory of the Government Chemist Queens Road, Teddington Middlesex TWII oLY, England E-mail: pjj @lgc.co.uk Shung-ChangJong. Ph.D. American Type Culture Collection (ATCC) 10801 University Blvd. Manassas, VA 22715, USA E-mail: [email protected] Ms.Jean 5. Kane

Robert T. Kane Associates Inc. HCR 4 Box zjr Brightwood, VA 22715, USA E-mail: [email protected] Dipl. Ing, Harry Klich Bundesanstalt fiir Materialforschung und Prifung (BAM),Referat 1.01 Rudower Chaussee 5 12489 Berlin, Germany E-mail: [email protected]

Dr. Jan Kucera Nuclear Physics Institute CZ-2jo68 Re? near Prague, Czech Republic E-mai1: [email protected]

Dr. John H. McB. Miller European Pharmacopoeia Commission B.P. 907 F-67029 Strasbourg Cedex, France E-mail: [email protected] Pro$ Dr. Ing. Knut Ohls Bungerstrage 7 44267 Dortmund, Germany E-mail: [email protected] Dr. Robert M. Pan Langackergasse 28a A-1190 Vienna, Austria E-mail: [email protected]

Dr.Jean Pauwels Institute for Reference Materials and Measurements (IRMM) Retieseweg B-2240 Geel, Belgium E-mail: [email protected] Dr. Philippe Queuauuiller

European Commission DG Research (MO7j 3jg) zoo rue de la Loi B-1049 Brussels, Belgium E-mail: Philippequevauviller@ cec.eu.int DennisJ. Reeder, Ph.D. IOO Bureau Drive, Stop 8311 National Bureau of Standards and Technology (NIST) Gaithersburg, MD 20899-8311, USA E mail: [email protected] Dr. Ulrich Rose European Pharmacopoela Commission B.P- 907 F-67029 Strasbourg Cedex, France

List ofContributors Dr. Matthias Rossbach

Dr. Adriaan M.H. van der Veen

International Atomic Energy Agency (IAEA) Chemistry and Industrial Applications P.O. Box I O O A-1400 Vienna, Austria E-mail: [email protected]

Korte Slagen NL-4823 LN Breda, The Netherlands E-mail:[email protected]

Stephan Riickold, Dip/.-Lebensmittel-lng.

Institute for Reference Materials and Measurements (IRMM) Retieseweg B-2240 Geel, Belgium E-mail: [email protected]

Stephen A. Wise, Ph.D.

National Bureau of Standards and Technology (NIST) Analytical Chemistry Division, Bldg. 2 2 2 , Rm. B 208 Gaithersburg, M D 20899, USA E-mail: [email protected] Wayne R. Wolf; Ph.D.

Dr. Markus Stoeppler Mariengartenstr. Ia

52428 Jdich, Germany E-mail: Markus. [email protected] Jan Straub, M A .

Coronel Institute for Occupational and Environmental Health Academic Medical Center P.O. Box 22700 NL-1100 DE Amsterdam. The Netherlands Jane Tang, Ph.D.

American Type Culture Collection (ATCC) 10801University Blvd. Manassas, VA 22715, USA E-mail: [email protected] Dr. Andrew Taylor

Centre for Clinical Science and Measurements School of Biological Sciences University of Surrey Guildford, G U gXH, UK E-mail:[email protected] Dr. Yngvar Thomassen

National Institute of Occupational Health P.O. Box 8149 DEP N-oojj Oslo, Norway E-mail:[email protected] Dr. Barry Tylee Health & Safety Laboratory Broad Lane Sh&ieId, Sy 7HQ, UK E-maiI: barry.t/lee@hsl,gov.uk

Human Nutrition Research Center US Department of Agriculture 10300 Baltimore Blvd. Beltsville, MD 20899, USA E-mail:[email protected] Dr. RolfZeisler

National Bureau of Standards and Technology (NIST) Analytical Chemistry Division, Nuclear Methods Group, Bld. 235, Rm. B - I ~ Gaithersburg, MD 20899, USA E-mail: [email protected]

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Abbreviations General

AOAC ASTM ATTC BAM BAS BP BCR B ERM/B RM BGS BNM BRPs BRSs CBNM

CITI CRM CRS DGKC DUREM EP EURACHEM FBI GBW GMO IAEA IFCC IPCRSs IRMM

Association of Official Analytical Chemists International American Society for Testing and Materials American Type Culture Collection Federal Institute of Materials Research, Germany (Bundesanstalt fur Materialforschungund -priifung) Bureau of Analytical Samples LTD., UK British Pharmacopoeia Community Bureau of Reference International Symposia on Biological and Environmental RMs British Geological Survey Bureau National de Mktrologie, France Biological Reference Preparations Pharmaceutical Reference Substances Central Bureau for Nuclear Measurements, Geel, Belgium, now IRMM Chemicals and Inspection Testing Institute, Japan Certified Reference Material Chemical Reference Substances Deutsche Gesellschaft fur lclinische Chemie National Workshop on Development and Use of Reference Materials (India) European Pharmacopoeia Association of European Chemical Laboratories US Federal Bureau of Investigation CRMs of NRCCRM, China Genetically modified organism International Atomic Energy Agency International Federation of Clinical Chemistry International Pharmacopoeia Chemical Reference Substances Institute for Reference Materials and Measurements, Belgium, formerly CBNM

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Abbreviations

IRSID IS0 ISO-REMCO IUPAC LGC NBS NCCLS NIBSC NIES NIOH NIST

NPL NRCC NRCCRM NTRM NWRI PAHs PCBs Ph. Eur. CRSs PTB REMTAF RIVM RM SMELT SRM TPhT TBT TDRM USDOD USFDA USGS USP VAM WHO

Institut de Recherches de la Siderurgie, France International Organization for Standardization I S 0 Council Committee on Reference Materials International Union for Pure and Applied Chemistry Laboratory of the Government Chemist, UIC, formerly NPL National Bureau of Standards, USA, now: NIST National Committee for Clinical Laboratory Standards, USA National Institute for Biological Standards and Control, UK Japanese National Institute for Environmental Studies National Institute of Occup. Health, Oslo, Norway National Institute of Standards and Technology, USA, formerly NBS, National Physical Laboratory, UIC National Research Council Canada Chinese National Research Center for CRM NIST Traceable RM National Water Research Institute, Canada Polycyclic Aromatic Hydrocarbons Polychlorinated Biphenyls European Pharmacopoeia1Chemical Reference Substances Physiltalisch-TechnischeBundesanstalt, Germany National Task Force on RMs, India National Institute of Public Health and Environmental Protection, NL Reference Material Standards, Measurements and Testing Programme, EU, formerly BCR Standard Reference Material, NBS, NIST, Trade Mark Triphenyltin Tributyltin AOAC Technical Division on RMs United States Department of Defense United States Food and Drug Administration US Geological Survey United States Pharmacopoeia Valid Analytical Measurement, UK World Health Organization

Abbreviations

Analytical Methods

AAS AES AF S ASV

csv

CVAAS DCPAES DPP ENAA ET-AAS FAAS FLU GC GC-FID GC-MS G F-AAS HGAAS HGICPAES HPLC HPLC-MS ICP-AES ICP-MS IDMS INAA I PAA LAS LC-F L NAA NPLC PAA PFE PGNAA PIXE RNAA SPE ss-AAS S S-ETV-ICP-AE S SS-GFAAS SSMS ss-ZAAS XRF

Atomic Absorption Spectrometry Atomic Emission Spectrometry Atomic Fluorescence Spectrometry Anodic Stripping Voltammetry Cathodic Stripping Voltammetry Cold Vapor AAS Direct Current Plasma AES Differential Pulse Polarography Epithermal NAA Electrothermal AAS, also: GF-AAS Flame-AAS Fluorometry Gas Chromatography GC with Flame Ionization Detector GC-Mass Spectrometry Graphite Furnace-AAS, also: ET-AAS Hydride Generation AAS Hydride Generation ICP-AES IHigh Performance Liquid Chromatography High Performance Liquid Chromatography-MS Inductively Coupled Plasma-AES Inductively Coupled-Plasma MS Isotope Dilution MS Instrumental NAA Instrumental Photon Activation Analysis Molecular Light Absorption Spectrometry Liquid Chromatography with Fluorescence Detection Neutron Activation Analysis Normal Phase Liquid Chromatography Proton Activation Analysis Pressurized Fluid Extraction Prompt Gamma NAA Particle Induced X-Ray Emission Radiochemical NAA Solid Phase Extraction Solid Sampling AAS Solid Sampling-Electrothermal Vaporization-ICP-AES Solid Sampling Graphite Furnace AAS Spark Source MS Solid Sampling Zecman AAS X-Ray Fluorescence

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XXV

Reference Materials for ChemicalAnalysis Certification, Availability, and Proper Usage

Edited by Markus Stoeppler,Wayne R. WOK PeterJjenks 0 Wiley-VCH Verlag GmbH, 2001

I’ 1

Introduction Edited by Markus Stoeppler 1.1

Historical Markus Stoeppler and HumphtyJM Bowen

This Chapter reviews some selected historical examples of the development, production and use of reference materials (RMs), from the past century up to the present. It is, of necessity, a rather short and incomplete review describing international efforts in this area. From the references given at the end of this Chapter and at the end of Chapter 3, the reader may investigate further into the past. 1.1.1

Early Developments

The history of reference materials is closely linked with the development of analytical chemistry. In the 19th Century all chemicals were, in comparison with those of today, of poor purity. Thus, for volumetric analysis suitable purified materials as primary standards had to be specified. One of the first examples was the recommendation of As(II1) oxide by Gay-Lussac (1824) for this purpose. Somewhat later, Sorensen (1887) proposed criteria for the selection of primary chemical standards. These were further elaborated by Wagner (1903)at the turn of the last century. It is worthwhile mentioning that their criteria were quite similar to those used today. One of the first attempts to use a biological RM was for the analysis of the fat content of milk. This was carried out in London in the late 1880’s by a number of analpcal chemists who were trying to identify adulterated milk. At that time milk was sold unpackaged and at least 20 % of the milk sold in London was adulterated by dilution with water. This work appears to be the first empirical round-robin approach for characterization of a RM. In medicine the need for standards was just as acute. Beal (1951)mentioned that the U.S. Pharmacopoeia VI, issued in 1880,took a big step forward by adding tests for purity and quality of the materials described in it, but the use of reference materials as an integral part of the pharmaceutical monographs for drugs did not start until the 1950’s. Another example of activities at the end of the 19th Century was associated with the introduction, by Ehrlich, of the first diphtheria antitoxin and his

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7 Introduction

discovery of Salvarsan (arsphenamine), the first effective cure for syphilis. Whilst these were by no means the first such medicines, Ehrlich was the first to calibrate the purity of the preparations of these substances by bio-assay against an arbitrary standard kept at low temperature (Ehrlich et al. 1894; Ehrlich 1910).Others followed his lead, from 1921the State Serum Institution of Copenhagen, Denmark, collected a set of international standards for therapeutic agents including diphteria antitoxin as well as arsphenamines. These standards were increased in number after the discovery of vitamins and sex hormones in the 1930’s (e.g. Dale 1939).A main source of these clinical standards was the National Institute of Medical Research in London. In 1948 a total of 35 International Standards were held at this institute (Miles 1948). In the 1960’s the need for reliable quality control of clinical chemistry determinations had been highlighted in the USA and England following the introduction of the first reliable automated analytical systems, the Technicon Auto-Analyzer Whiteheads work at the University of Birmingham led to the introduction of routine inter-laboratoryperformance testing schemes and the regular use of thoroughly validated reference materials (Radin 1967; Meinke 1971; Booth et al. 1974; Whitehead 1976).Today the UK-EQAS scheme and the CAP scheme in the USA share a common philosophy of continuous quality improvement through repeated use of inter-laboratory studies - a concept far from the “pass-fail” mentality common in other disciplines, see also Sections 4.1 and 6.2. Other scientific disciplines required standards. When the American Type Culture Collection (ATCC) was founded in 1925,one of its chief roles was to be a source of standards for the rapidly developing public health laboratory activity in the USA. In this context we mean standard organisms, rather than standard materials or chemicals, but their use was analogous, they helped produce better analpcal data. In 1901, the U.S. National Bureau of Standards (NBS) - now the National Institute of Standards and Technology (NIST) - was founded because of the increasing demand for various kinds of standards in the rapidly developing engineering industries. The early history of the NBS reference material program started in 1905 with a cooperative effort within the iron and steel industry whereby industrial analysts helped characterize the individual reference materials. Cooperation with NB S was recognized as a mark of achievement for the laboratory, so this effort served a dual purpose. It both helped the laboratory develop its measurement skills and also helped NI ST understand the measurement problems associated with a given matrix. The analysis of irons and steels is mostly about the measurement of inorganic elements in an inorganic matrix. Hence a variety of separation and measurement techniques could be used, compared and evaluated to arrive at the best answer. Problems were usually solved by looking for complete dissolution and understanding the interferences affecting the various methods that were employed. Since most methods used were related to gravirnetric quantities (i.e. weighed quantities of pure inorganic substances), traceability to the mole was not an issue and comparability and compatibility of measurements is what was sought. NIST’s first four certified reference materials were steel samples, and these were followed by many others. The program supplied analytically well characterized homogeneous materials. This program included, from the beginning, homogeneity

7 . 7 Historical

evaluation, cooperative multi-laboratory characterization and an evaluation of the measurement process to assure accurate values (Cochrane 1966; Uriano and Gravatt 1977).The success of this work initiated many requests from other industries for the development of appropriate materials and led to a rapid growth of this part of the NBS program and the adoption of the name “Standard Reference Material” or “SRM”; later these terms were registered as Trade Marks of NIST. By 1951NBS was advertizing 541 SRMs, of which 2 0 0 were alloys, ores or ceramics and 204 were hydrocarbons or oils (Bright 1951). Similar work for RMs in the fields of metallurgy and ceramics was performed by many U.S. commercial sources and in other countries as well. Examples of early suppliers of appropriate RMs include in the United Kingdom the Bureau of Analyzed Samples Ltd. (BAS), who issued RMs from 1916; in Germany the Federal Institute of Materials Research and Testing (BAM), founded 1904 as the “Royal Bureau of Materials Testing” and who issued RMs from 1912, and the Physikalisch-Technische Bundesanstalt (PTB), the Japanese Iron and Steel Institute, the French BNM (Bureau National de Mktrologie) and IRSID (Institut de Recherches de la Siderurgie FranGaise) and the Polish Committee on Standardization and Measures. All of these organizations still carry out their work; and their RMs have developed and evolved as the demands of the metallurgy industry have increased. In geochemistry, the introduction of RMs did not take place until 1951but, once RM usage became a regular part of geochemical analysis, the consequences were not far short of amazing. For many years geochemical analysts had been concerned about the accuracy of their determinations of major elements in rocks, but it was the potential of emission spectrometry for the determination of trace elements which set off the production of the first rock Certified Reference Materials (CRMs), G-I and W-I by the U.S. geological Survey (USGS) (Ahrens 1951). Geochemical CRMs characterized by a number of different institutes, including NBS, were distributed in increasing numbers by the USGS. This led in the following years to remarkable improvements in resolving major disagreements between analysts using similar or distinct techniques in geochemical analysis. From about 1965 many other international organizations were supplying geochemical RMs, (e.g. Richardson 1995; Imai et al. 1996;Potts 1997). For details see Section 6.4. Until the 1950’s the only “biological” reference materials available were a few commercial sera produced by Seronorm A/S, the Welcome Foundation and others, as a result of the U.K. and U.S. clinical chemists’ initiatives. As many elements are found in biological matrices at much lower levels than in industrial and geological samples, improvement of the quality of elemental analysis in agricultural applications was the aim of a committee convened at Michigan State University in November 1950. About g kg of leaves from four orchard trees, apple, cherry, peach, and orange were homogenized and distributed to 16 U.S. laboratories in a round-robin exercise. The results showed good agreement for the major elements Ca, K, Mg, N, and P, but were much less precise for essential trace elements (Kenworthyet al. 1956).A similar collaborative study using nine vegetable RMs sent out to 13 Canadian laboratories was reported somewhat later (Ward and Heeney

1960).

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Humphry Bowen did pioneering work for the development and use of appropriate biological matrix reference materials. He was at that time developing techniques for radiochemical neutron activation analysis (RNAA) and realized that there were no standards or RMs to check the accuracy of results in this work. He had some geochemical CRMs but these were unsuitable because biological materials have a different matrix and contain orders of magnitude lower concentrations of most trace elements. Thus he prepared in 1960 IOO kg of kale (Brassica oleracea) powder, a large amount for the time (Bowen 1965);for details of the preparation see Section 2.1. Indeed, Bowen’s kale served for more than two decades as a reference and valuable aid for many analysts (Wainerdi 1979; Bowen 1984). Thus his work and the wide demand for his kale RM was pivotal to the future direction of biological reference material and stimulated the planning, preparation, distribution and analysis of further materials of similar kind. 1.1.2 Growth and Maturity

The production of biological matrix RMs for elemental analysis began in national and international institutions in the late 1g60’s.The National Bureau of Standards, now NIST, announced its intention to produce biological RMs in 1967. Orchard leaves, its first botanical reference material, was certified and distributed in 1971 (Meinke 1971).Workers at NIST were also the first to see the need to introduce sterilization of CRMs using y-radiation for longer shelf life. In 1911 NBS offered just 23 certified reference materials, by 1975 more than 1000 SRMs were available with approximately 700 of these intended for use in chemical analysis (Cali and Stanley 1975). At the end of the last century ( ~ g g g )about , the same number of NIST SRMs were available, with many now including a considerable percentage certified for organic constituents and other analytes never dreamed of by Bowen (Trahey 1998).As we enter the zIst Century, attention turns to the measurement of DNA in plant material as the arbiter of genetic identity, and RMs will be required, see Section 5.4. Another important part of the history of reference materials has been the contribution of the International Atomic Energy Agency (IAEA) in Vienna. The IAEA began an analytical quality control service (AQCS) aiming at assisting its Member states to maintain and improve the quality of analytical data obtained in their laboratories. Indeed in the 1960’sAQCS was concerned primarily with radioactive measurements. Later it became involved with the reliability of nuclear methods in elemental analysis and practically all IAEA AQCS RMs started out as intercomparison materials. The first five IAEA biological reference materials were issued in 1970. They included a marine RM (mussel shells) from the IAEA laboratory at Monaco, and by 1983 the IAEA had issued 28 CRMs, but most of them were quickly exhausted because of their popularity (Parr 1984). The 1998199 IAEA AQCS catalogue contains more than 90 CRMs of environmental and biological origin for a wide range of determinedness, encompassing radionuclides, trace elements, petroleum hydrocarbons, pesticides, and PCBs (International Atomic Energy Agency 1998).

1. I Historical

In the 1970’s and 1980’s,a number of other organizations started programs designed to provide biological, environmental, and food RMs and CRMs. Projects for the development and certification of food matrices were initiated by the U.S. Department of Agriculture, Agriculture Canada and the U.S. Food and Drug Administration (Wolf and Ihnat 1984; Ihnat and Wolf 1984; Tanner 1984) in co-operationwith NIST. Examples are a total diet SRM (Wolf et al. 1990) and a series of agricultural/ food RMs (Ihnat and Wolynetz 1993). Early in the 1970’s the then European Economic Community (EEC) established a community-wide CRM program in order to pull together many of the diverse and widespread RM activities under the direction of the Community Bureau of Reference (BCR) (van der Eijk 1979). BCR made first a compilation that covered the major producers, both governmental and private, not only in Europe but on a worldwide basis (Commission of the European Communities 1973; Cali and Stanley 1975).The BCR of the EEC, Brussels, now the 5th framework program of the European Comissions DG Research, initiated in 1970 a program to make available a broad range of CRMs (Griepink et al. 1991);the first biological CRMs were issued in 1983. A large number of candidate materials were initially prepared within that program at the Joint Research Centre Ispra (Rossi and Colombo 1979). It should be mentioned that the continuous efforts of Herbert Muntau at the Ispra Laboratories were the basis for many new environmental and biological CRMs (Muntau 1979, 1980, 1984). BCR started also the production and certification of food CRMs in cooperation with several qualified European laboratories (Wagstaffe 1984). In 1984 the Institute for Reference Materials and Measurements (IRMM), previously called Central Bureau for Nuclear Measurements (CBNM), initially purely nuclear, was given a major role in the storage and distribution of BCR RMs. At the same time a series of major investments were started at the IRMM to set up facilities for the preparation of highest quality candidate RMs in economically attractive conditions (Kramer et al. 1998);see also Section 2.2. From 1995 IRMM had complete responsibility for stock management, sales policy, and renewal of sold-out materials. The increase in production and certification is significant: in 1984 BCR issued about IOO individual CRMs, in 1999 this number had increased to 570, including nuclear and isotopic materials (IRMM 1999). Valuable contributions were made by two Canadian agencies, particularly by the National Research Council Canada (NRCC) who, from about 1976, provided marine and marine biological CRMs certified for metals, metal species and organic constituents (Berman 1984; Willie 1997). More recently their Halifax laboratories have issued a highly respected range of CRMs for the determination of shellfish toxins. Another Canadian producer, the National Water Research Institute (NWRI) specialized in marine (water and sedimentary) CRMs, and from the late 1980’s their matrix materials certified also for organic compounds (Chau et al. 1979; Lee and Chau 1987). In the United Kingdom chemical RMs were first produced some time in the late 1960’s at the National Physical Laboratory (NPL) Division of Chemical Standards at Teddington. This Division was transferred to the Laboratory of the Government Chemist LGC in November 1978. Early work was based on the development of highly

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1 Introduction

purified and certified pesticides, issued as CRMs. Further developments continued under LGC and the range expanded steadily. In the 1980’sthe Validity of Analytical Measurement (VAM) programme started to consider the role CRMs play in the production of valid results. Following a number of consultation exercises a list of needed matrix CRMs was developed and during the 1990’s a wide range of matrix CRMs were produced and certified. At present it offers about 300 CRMs. Further afield, in 1978 the Japanese National Institute for Environmental Studies (NIES) started the production of a series of biological and environmental matrix CRMs, certified for a number of trace elements (Okamoto and Fuwa 1985).Recently also the certification of metal species in some materials was reported (Okamoto and Yoshinaga 1999). A remarkable level of activity can be seen in China. The National Research Center for CRM (NRCCRM) was founded in 1980 and the certification and accreditation program for “ G B W RMs started in 1983 by co-operation with many Chinese Institutions. In 1993 around Go RMs and CRMs were available (Chai Chifang 1993) and in 1999 the availability of about 1000 CRMs was reported, around 30 of them clinical, IOO environmental, zoo geological, and 300 metallic matrix materials (Rong and Min 1999). Increasing activities for the production and certification of biological, environmental and geological CRMs from the late 1980’s have been also reported from Poland (Dybczyhslti 1995) and the Czech Republic (ICutera et al. 1995,1998). From 1983 to 1997, seven international symposia on biological and environmental reference materials have been alternately held in the USA and Europe. The proceedings mirror the global developments and problems that were discussed during these meetings including also the needs of developing countries. These symposia are described together with other RM meetings in some detail in Chapter 8. 1.1.3

Milestones and The Future

Finally some additional milestones in organization, research and development of RMs need to be mentioned. The large increase in the number of reference materials being produced led in 1975 to the formation of an I S 0 Council Committee on Reference Materials (ISO-REMCO) charged with the establishment of international guidelines on principles of certification, methods of use, needs, availability and nomenclature (Klich 1999). see also Sections 1.2 and 1.3. Significant improvements in analytical methodology and better controlled sampling procedures for environmental and biological materials led in the 1980’sto the recognition that older data describing the analysis of trace metals in, for example, natural waters and biological fluids were erroneously high, sometimes by orders of magnitude. The causes have been found to be due to inadequate methods and contamination from sampling and analytical tools. This reality must be reflected in the preparation of a new class of, as far as possible, contamination-free reference materials prepared with utmost care and reflecting the state of the art at the end of the 20th Century. Examples for this are the procedures applied at NRCC for the prep-

7.2 The Theoretical Basis 17

aration of natural water CRMs (Berman et al. 1983)and the efforts to produce similarly contamination-free bovine (Veillon et al. 1984) and human serum CRMs. The latter were prepared under rigid quality control by a group of expert laboratories and called “second generation biological RMs” (Versieck et al. 1988);for more details of preparation of this material see Section 2.1. Another step forward was the introduction of milling of solid, mainly biological, materials at liquid nitrogen (cryogenic) temperatures. These techniques allowed homogenization under “contamination minimized” conditions, previously thought impossible to achieve. Cryogenic techniques were used to prepare materials like hair. Another advantage of the cryogenic procedures is that smaller particle sizes can be obtained than with most conventional procedures (Zeisler et al. 1983; Schladot and Backhaus 1988;Kramer et al. 1993).The technique was successfully applied and tested in the preparation of Specimen Bank materials for long-term stored under cryogenic temperatures without any change of chemical composition. From the experience gained during these programs, cryogenic milling and long-term cryogenic storage offers unique possibilities to prepare RMs with practically indefinitely long shelf-lives (Stoeppler and Zeisler 1993; Emons 1997). Two challenging, but very difficult tasks have been tackled mainly or increasingly during the last two decades: the certification of organometallic species and valency states of elements (see Section 3.3), and organic compounds (see Section 3.4). But doubtless this was just the beginning and a wealth of work waits in the future to serve all needs of the analytical community (Quevauvillerand Maier 1999). From the mid 1980’s the rise of Quality Standards, Total Quality Management and Accreditation schemes created a booming demand for RMs and CRMs. Thus, the use and production of matrix RMs rapidly increased the new IAEA database lists 56 producers from 22 countries and about 1640 RMs. The 1998 Comar database, which covers a much wider scope, lists more than 200 producers and around 10ooo RMs; see Chapter 8 for more details. The demand for RMs and CRMs continues to grow. As traditional chemical analysis moves into biochemistry and molecular biology the demand for RMs does not abate: the only question is “what is next?” Chapter g considers these, and other future issues critically.

1.2

The Theoretical Basis Adriaan van der Veen

The basis for the preparation and use of reference materials (RMs) is given in I S 0 Guides 30-35. These documents deal with the following aspects of the preparation and use of RMs 30. Terms and definitions 31. Certificates, reports, and labels 32. Calibration using RMs 33. Other uses of RMs

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34. Quality systems of RM producers 35. General and statistical principles of the preparation of RMs Each of these documents will be reviewed briefly in this Section. The definition of a certified reference material (CRM) is given in I S 0 Guide 30 (1992)and it forms the root of all other I S 0 Guides: Reference material, accompanied by a certificate, one or more of whose property values are certified by a procedure which establishes its traceability to a n accurate realization Ofthe unit in which the property values are expressed, andfou which each certij?ed value is accompanied by a n uncertainty at a stated level of conjidence. Additionally,there is also a definition for a RM:

Material or substance, one or more of whose property values are suflciently homogeneous and well established to be used for the calibration of a n apparatus, the assessment Ofa measurement method, or f o r assigning values to materials. The key difference between a CRM and an RM is the traceability. In order to play any role at all in metrology, traceability is a key property. “Traceability” refers to a property value of the CRM, and thus to the underlying measurements. Insufficient traceability of these measurement results will eventually lead to a RM that cannot be certified, as the property value cannot be related to other standards. In the ideal case, traceability is realized up to the International System of Units, SI, but this is only feasible for a very small number of CRMs. Most CRMs are so-called “matrix-CRMs”,identifying that they have been made from material sampled in nature. For these materials, it is impossible to come up with property values traceable to SI, as preparation steps cannot directly be related to that. At best, a comparison can be made among methods, from which usually one is the technically best established method, and the results of such a comparison may flow into the establishment of the property values and their respective uncertainties. The most important document, accompanying a CRM is its certificate. I S 0 Guide 31 (1981)provides guidance for the establishment of certificates, labeling of CRMs, and certification reports. The certificate contains among other information the certified values and their respective uncertainties. As important as this information is the traceability statement, which defines to what references the CRM is traceable. Ideally, a CRM is traceable to a suitable (combination) of SI units. This is not always possible, so other “stated references” may appear here. Especially when certifying matrix reference materials, malting the measurements traceable to SI does not imply that the CRM is traceable to SI as well. The steps necessary to transform the sample into a state that can be measured may have a serious impact on the traceability of the values, and thus on the traceability statement. Although labels and certificates are mandatory, certification reports are not. It also depend on the kind of RM, whether such a report is of any relevance. For instance, for the certification of gas mixtures, a certification report would not usually

7.2 The Theoretical Basis

contain more information than is already presented on the certificate. In other cases, a certification report might be of interest, but for other reasons (economical, political) is not feasible. For many matrix RMs, brief or extensive certification reports are made available, containing for instance the results of the homogeneity and stability studies, as well as the results from the characterization measurements. This allows the user to gain some extra insight in the properties of the RM, and possibly about problems in measuring the CRM with certain methods. There are t w o main uses of a RM: calibration and method performance checking. I S 0 Guide 32 (1997)deals with the use of RMs for calibration purposes. RMs used for calibration purposes are usually RMs prepared by synthetic means. Commonly, the property values of these RMs are known from preparation, and verified by some kind of suitable measurement technique. This can be a technique directly providing a value for a property of interest, or a technique that allows the comparison of the new material against older measurement standards. I S 0 Guide 32 provides guidance in two ways. Apart from the guidance on using RMs for calibration purposes, it also provides information on the preparation and use of calibrants in a laboratory, and checking them against other RMs or measurement standards. I S 0 Guide 33 (1998)deals with other uses of RMs. It elaborates on various uses of RMs, excluding calibration, which is the subject of I S 0 Guide 32. In most cases, RMs are used as a quality control measure, i.e. to assess the performance of a measurement method. Most matrix RMs are produced with this purpose in mind. Other purposes of RMs are the maintenance of conventional scales, such as the octane number and the pH scale. I S 0 Guide 33 provides guidance on the proper use of RMs, and therefore it is together with I S 0 Guide 32 the most important document for users of CRMs. The assessment of the performance of a method is commonly checked by means of a (C)RM. In those cases where there is no RM available, considerable effort is requested from the laboratory to assess the performance of their own methods. The aspect of traceability of the certified value(s) is also of great importance: whenever necessary, the laboratory will make modifications in its procedures if the result of a measurement using the RM appears to be unsatisfactory. If the traceability of the values to other references is not fully established, then this judgement may be clouded by doubts about the certified value(s). Another question to be addressed by the laboratory is the portability of the measurement results on the RM to their common test samples. The behaviour of matrices that are named the same may still widely differ. There are also examples known where, for selected parameters, it is very well possible to transfer the results on the RM directly to the daily practice. As a rule, this is not possible. The conchsions drawn from a measurement on a RM should be translated with care to the measurement practice. The result from a measurement on a RM is commonly a difference between the observed value and the certified value. This difference is called measurement bias, and can, appreciating both the uncertainty on the RM as well as the uncertainty added during the measurement, be tested for (statistical)significance. I S 0 Guide 33

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provides the uncertainty calculations necessary to carry out such an assessment. Commonly, if a measurement bias appears to be significant, the laboratory attempts to improve the measurement procedure, effectively reducing the measurement bias. It should be noted that a measurement bias smaller than the expanded combined uncertainty from the RM and measurement is not meaningful, unless a history record exists that shows trends. This kind of trend analysis may be important for the laboratory, but falls outside the scope of I S 0 Guide 33. Another important use of RMs is the maintenance of conventional scales. The octane number of gasoline is an example of such a scale. The scale is defined through chemicals. This definition can be realized through RMs. Another example is the pH scale, which is defined by buffers with pH = 4, pH = 7, and pH = 10. These buffers are defined as mixtures of salts, dissolved in water. These define the pH scale can be used by laboratories for the purpose of calibrating their pH meters. By now, it should be clear what role RMs play in measurement science. This puts great responsibility on the producers of RMs, as they must see how to satisfy the requirements set implicitly or explicitly by the users regarding matrix, parameters, uncertainty, and traceability. Laboratories use RMs often as a quality control measure, but it this obviously only valid if the RM is produced under proper conditions. In order to ensure the quality of RMs, it is highly recommended that producers work under a quality system. I S 0 Guide 34 (1996) provides guidance on how to set up a quality system for the production of RMs. It builds on I S 0 Guide 25 ( ~ g g o ) , setting apart from the same requirements a series of extra requirements related to material and sample management, homogeneity and stability testing, and the traceability of the property values. In the first edition, I S 0 Guide 34 was a document to be used on top of I S 0 Guide 25. In the voting draft of I S 0 Guide 34:1ggg, the document has become stand-alone, thus fully discussing the requirements for a quality system. Demonstrating competence in this field is of particular interest. Field laboratories are required to demonstrate their traceability through using RMs where possible and appropriate. Obviously, the producers of these RMs must also be able to demonstrate quality and traceability, as otherwise the international measurement infrastructure becomes a set of isolated smaller networks, rather than one big network. So, providing traceability is one of the key issues in the production of RMs. Whereas I S 0 Guide 34 sets requirements for the quality system of a CRM producer, I S 0 Guide 35 (1989) provides guidance on how to implement many of these requirements. Among these, the document also provides a general and statistical outline of the process that leads to CRMs. The current edition of I S 0 Guide 35 is a little outdated, but still most of the contents are valid. The preparation of RMs is possibly the most complex subject dealt with in the I S 0 Guides 30-35. In I S 0 Guide 35, the general requirements as well as the statistical frame for setting up certifications of RMs are discussed. As RMs cover a very wide area, ranging from high-quality gas mixtures with very tight uncertainties, via soils certified for organic contaminants up to microbiological RMs, the exact implementation of these requirements is as manifold as there are RMs.

7.3 Technical Requirements

I S 0 Guide 35 provides details on how to implement homogeneity testing, stability testing, and different ways of characterizing RMs. The document also provides a statistical framework on how to evaluate the results of these measurements and how to establish the certified value and its uncertainty. For the producer of a RM, this guide is probably the most important one, as it details a possible implementation of the production of traceable RMs. The next Section gives an overview of the technical requirements when producing RMs, along the lines of I S 0 Guide 35.

1.3 Technical Requirements Adriaan van der k e n

The preparation of a reference material requires a great deal of planning prior to undertaking any actual activity in the project. A substantial part of the planning deals with the amounts of material needed, as well as with the design of the homogeneity, stability, and characterization studies. The design also includes the choice of appropriate measurement methods for these studies. The number of samples to be produced is also a very important variable in the planning process. With a basic outline of the items mentioned, the amount of raw material to be sampled can be estimated. The planning of a project starts with the definition of what reference material is to be produced. Usually, this definition just say is something like: 8

“preparation of a soil reference material containing a series of trace elements at relevant concentration levels for environmental analytical chemistry”

Although this definition might need some further specification, it is satisfactory to start the design of the project. The first task in such a project is to obtain a sufficient amount of raw material with the desired properties. The amount of material needed is dictated by the following parts of the projects:

8

the number of samples of reference material needed the need for a feasibility study the number of samples needed for the homogeneity study the number of samples needed for the stability study the number of samples needed for a characterization of the reference rnaterial

Each of these aspects will be addressed briefly in this Section. The number of samples of reference material needed is a commercial issue in the first place. An important variable is the number of samples likely to be sold during the lifetime (“shelf life”) of the reference material. As the lifetime is a function of the intrinsic stability of the material, this variable also affects the amount of raw material is needed. For instance, microbiological materials have limited intrinsic stability, and therefore their lifetime is expected to be shorter than for a dry sediment certified for trace elements. So, under the assumption of an equal number of sam-

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7 Introduction

ples to be dispatched per year, the number of samples needed for the rnicrobiological material is greater than for the dry sediment. In those cases where there are any doubts about the feasibility of producing a sufficiently homogeneous and stable reference material, a feasibility study might be needed. For this study, an extra amount of material is needed. Questions regarding the best way of preparing the sample, the stability of the material, or the fitness for purpose might justify the inclusion of a feasibility study in the project. In the BCR projects, it is common practice to have a feasibility study, which usually has as the sole purpose of assessing the performance of the laboratories in the collaborative study in relation to the certification of the reference material. The feasibility study allows the participants to fine-tune their equipment, their methods, and their procedures in view of the characterization measurements. In each of these cases, a considerable extra number of samples is needed. The design of a project aiming to produce a new reference material may also include aspects of blending of materials. In several areas, like for instance in environmental chemistry, reference materials are needed with a very wide range of parameters at appropriate (concentration) levels. Often, it is impossible to find all parameters in one material. In those cases, blending two or a few similar matrices may lead to a batch of raw material suitable for the project. The problems associated with this practice are potentially greater regarding homogeneity and stability of the reference material. The extra problems with obtaining sufficient homogeneity are obvious. Extra problems regarding stability usually come from differences in the matrix, allowing for physical and/or chemical processes that would not take place otherwise. Adaptation of the preparation procedures may very well solve these (potential)problems. Another issue in the preparation of reference material is the required shelf life. The shelf life of reference material is the time that it remains stable under proper storage conditions. Depending on the nature of the mechanisms affecting the stability of the material, various actions can be taken to improve the shelf life. Reduction of the moisture content is one of the first options to be considered. In many cases, moisture plays a key role in mechanisms leading to instability of the matrix and/or parameters. In other cases, sterilization or pasteurization of the material might be considered in order to stop bacterial activity. When preparing solutions, additives may increase the shelf life. Obviously, the shelf life of material is also a function of the storage conditions. In the preparation of many solid state reference materials, reduction of the grain size plays an important role. Usually this reduction is required because of the measurement methods to be used both in the projects and later by the users of the reference material, as well as to come to an acceptable minimum sample intake. The minimum sample intake can be defined as the minimum amount of material needed, so that the heterogeneity of the material does not affect the repeatability of the measurement method. The reduction of the grain size is usually implemented by crushing and/or grinding techniques. The techniques employed and the equipment used must be suitable for the purpose of processing the material. Potential problems of contamination, loss of volatile components, and/or other physical and

1.3 Technical Requirements

chemical changes during grinding must be addressed in advance and evaluated during the project whenever necessary. After reduction of the grain size, the material can be divided into portions appropriate for use as a reference material in a laboratory. The size of these portions depends on the expectations of the users, and what is technically possible. In some cases, these test portions are intended for use as such, but in most cases some subsampling is needed. Both approaches have their advantages and disadvantages.The need for sub-sampling can be both: on one hand if no sub-sampling by the user is needed, the producer will have less concern about possible complaints from customers with respect to the homogeneity of the material. On the other hand however, many written standards and other procedures involve some kind of sub-sampling, and having a reference material that does not require sub-sampling implies that the user does not have the option of verifying this step with the reference material. In some cases, providing samples for single-use is a necessity: after opening, the material has so little stability that it is unlikely that it could be used again. In those cases, the desired size of the sample is a portion suitable for single-use only. There is a wide choice of method and equipment for dividing the material into portions. Again, the choice of the method as well as the equipment depends on the nature of the material. A basic requirement however is that the method used guarantees within certain limits that it may be expected that the first sample produced will have the same properties as the last one. The use of dynamic riffling techniques is only one option. Automated subdivision techniques and equipment is becoming increasingly popular, as these systems allow producing batches of a few thousands of samples; and they can also be linked to a labelling system. Especially in those projects, where portions for single use are produced the number of samples is usually large. The whole process so far dealt with obtaining the raw material and the production of sub-samples from it. The issue of homogeneity and stability, as well as the characterization of the material under proper conditions now needs full attention. In the past, homogeneity and stability testing were primarily intended to see whether the sample preparation was completed successfully. This is perfectly reflected in I SO Guide 35 (1989).In recent years, complete new categories of reference materials have come to existence which cannot be dealt with that way. Despite all the effort put in the preparation and conservation of the material, there still may be some heterogeneity and instability left. Just testing for significance with respect to the repeatability of the test method is incorrect in two ways. It does not answer the question of how this remaining heterogeneity and instability affects the uncertainty of the reference material. Furthermore, it leaves open the option of selecting measurement method with a poor repeatability, so that the homogeneity study will not demonstrate any heterogeneity. In cases where test pieces (or items) are prepared, the issue of obtaining a homogeneous batch of items is even more complex. Here the preparation procedure sets limits, in combination with the properties to be certified. The uncertainty of the property values should appreciate this fact, as otherwise the uncertainty of the reference material is only valid for the batch, not for a single item from the batch. This

14

I is an essential requirement, which obviously may also have an impact 7 Introduction

on the design of the project. In doubtful cases, a feasibility study might be needed to investigate whether a reference material can be obtained with an appropriate level of uncertainty. For the issue of stability, the same reasoning holds. In heavy metals analysis, limitations of stability are only an issue for solutions and for some highly unstable matrices. In most matrices, heavy metals are fairly stable and a lifetime of these materials typically exceeds ten years. In organic analysis, as well as in microbiological analysis, materials usually have limited stability. These judgements can obviously only be made when comparing data from the stability study with the uncertainty from the characterization of the reference material. For most proper reference materials in these categories, some uncertainty from limited stability should be taken into consideration. Obviously, if a material shows a slow but steady degradation, the data should be analyzed critically in order to find out whether material could be certified. An additional problem is that usually the stability study is also accompanied by a considerable uncertainty, which should be taken into account somehow. After the verification of homogeneity and stability,the characterization of material can take place. Frequently, this step is named certification rather than characterization, which is wrong in view of the discussion about homogeneity and stability and their impact on the reference material. The certification of our reference material is more than the characterization of the material. However, for most people working on the development of measurement methods, the characterization is the most interesting part of the project. This probably explains the huge amount of literature available. The characterization of a reference material can take place in different ways. Depending on the source cited, there are three or four mainstream approaches; I S 0 Guide 35 (1989)distinguishes between three:

characterization by a single method characterization by multiple methods characterization by means of an inter-laboratory study The third approach is also known as a collaborative study or a collaborative trial. Both names underpin the joint effort of the coordinator and participants to characterize the reference material. In any case, the measurement methods used in the characterization should be traceable to what is called “stated references”,and preferably to SI. The aspect of traceability of measurement results goes well beyond the actual measurements; it also includes the transformation of the sample from the state of the reference material to the state in which it can be measured. An example of such a transformation is the destruction of the sample. Traceability of measurement results is essential in the establishment of a certified reference material. As stipulated in I S 0 Guides 3 0 and 35, a certified reference material can only be certified if there is an uncertainty statement with a traceability statement. Basically, traceability means anchoring. In classical analytical chemistry, that SI system is often the best choice as a reference (= “anchoring point”). However, there is a wide range of parameters either defined by a method or defined by the

7.3 Technical Requirements

conditions under which the measurements take place; and for these measurements another reference might be more appropriate. The choice of the references is primarily the responsibility of the producer. However, he has to look at the measurement practice in the particular area. Another aspect of traceability of the results is the linkage of data from the homogeneity study, the stability study, and the characterization study of the reference material. In order to establish this link, the coordinator must be in the position to demonstrate that the results of these three studies have a common reference. Such a reference can be a calibrant, reference material, or possibly some realization by means of a suitable method. If such a common reference is not available, it is impossible to link the data sets, and therefore it is impossible to translate the results from the homogeneity and stability studies to the characterization of the material. This is also an aspect that should be addressed in the design of the project. In addition to the requirements regarding traceability of measurement results, the measurement methods employed should represent “state-ofithe-arY‘ in the particular field. Failing to do so would lead to a reference material with an uncertainty that has become too large to serve as a quality control. The better the methods perform in terms of uncertainty and traceability, the better the reference material will serve the interests of the (potential)users. The measurement method used for the homogeneity study should have a very good repeatability. For a stability study, where often samples are measured at different days, the reproducibility of the measurement method is of primary importance. So, the methods for homogeneity and stability studies are not necessarily the same. This is not a problem, as long as this common reference already mentioned is available. For the characterization of the reference material, especially in the case of matrix reference materials, it is often desirable to use multiple methods, and often also multiple laboratories. Under these conditions, it is easier to arrive at an uncertainty that represents the “state-of-the-art”of the laboratories. In summary, the preparation of reference material involves the following steps: Definition of the reference material, i.e. the matrix, the properties to be certified, and their desired levels Design of a sampling procedure Design of a sample preparation procedure Selection of method appropriate for homogeneity and stability testing Design of the characterization of the reference material Sampling Sample preparation Homogeneity testing Stability testing Characterization of the reference material Combination of the results from homogeneity testing, stability testing, and characterization and assembling an uncertainty statement Set-up of a certificate and, if appropriate, a certification report

115

16

I

1 Introduction

It should always be kept in mind that certified reference materials are used by laboratories, authorities, and regulating bodies for quality control purposes. The primary objective of a reference material is therefore the anchoring of measurements. This anchoring of the measurements of a laboratory using the reference material under ideal conditions i s as good as the anchoring of the measurements used for establishing the reference material. So, there i s a great responsibility for all persons involved in certification projects to work under proper “traceable” conditions, because otherwise the resulting reference material is useless. A reference material with a lack of traceability to stated and acceptable references cannot be used as such. Moreover, the users of reference materials expect to buy traceability, and their interests are only served if the producers paid sufficient attention to these aspects.

1.4 References

AHRENSLH (1951)A story of two rocks. Geostds Newslett 1x57-161. BEAL(1951) The basic philosophy of standards. Anal Chem 23:1528-1531. BERMANSS, STURGEON RE, DESAULNIERS JAH and MYKYTIUKAP (1983) Preparation of the sea water reference material for trace metals, NASS-I. Mar Pollution Bull 14:69-73. BERMANSS (1984) Marine biological reference materials for trace metals. In: Wolf WR, ed. Biological Reference Materials, pp79-88. John Wiley & Sons. BOOTH E, CROFTON P and ROBERTSLB (1974)The influence of standards on interlaboratory quality control programmes. Clin Chim Acta 55:367-375. BOWENHJM (1965) A standard biological material for elementary analysis. In: SHALLISPW, ed. Proc of the SAC Conference, Nottingham, pp 25-31, W Heffer and Sons, Cambridge. BOWENHJM (1984) Kale as a reference material. In: WOLFWR, ed. Biological reference materials. Availability, uses and need for validation of nutrient measurement, pp3-17. John Wiley Sr Sons. BRIGHT HA (1951) Standard sample program of the National Bureau of Standards. Anal Chem 23344-1547. CALIJP and Stanley CL (1975) Measurement compatibility and standard reference materials. Annu Rev Mat Sci 5:3zg-343. CALIJP, MEARSTW,MICHAELISRE, REEDWP, SEWARDRW, STANLEYCL, YOLKENHT, and Ku HH (1975) The role of standard reference materials in measurement systems. NBS Monograph 148, Washington DC. CHAICHIFANG (1993) Present status and future trends in biological and environmental reference materials in China. Fresenius J Anal Chem 345:93-98. J and LEE H-B (1979) Analytical reference materials. TI. Preparation and samCHAUASY, CARRON ple integrity of homogeneous fortified wet sediment for polychlorinated biphenyl quality control studies. J Assoc Off Anal Chem Gz:1312-1314. COCHRANE RC (1966) Measures for progress - a history of the National Bureau of Standards. US Library of congress catalog card 65-62472, p 93. Commission of the European Communities (1973) Reference Materials (Provisional) RM-19730001 or ISP-1973-01,Community Reference Bureau. DALEH (1939) Biological standarchsation. Analyst 64:554-567. R (1995) The contribution of various analytical techniques to the certification of refDYBCZYNSKI erence materials. Fresenius J Anal Chem 352:120-124. EHRLICH P (1910) (Lecturewithout title) Deutsche Med Wochenschr 36:1893-1896.

1.4 References I 1 7

EHRLICH P, Kossel H and von Wassermann A (1894) Ueber Gewinnung und Verwendung des Diphterieheilserums.Deutsche Med Wochenschr zo:y,3-255. EMONS H, ed. (1997) Biological Environmental Specimen Banking (besb 2 ) 2nd International Symposium and Workshop held at Stockholm, Sweden 20-23 May 1996. Chemosphere Vol34 Nos. 9 and 10. FAJCELJA and PARKANY M, eds.(Iggg)The Use of Matrix Reference Materials in Environmental Analytical Processes. The Royal Society of Chemistry. GAY-LUSSAC JL (1824)Instruction sur 1’Essaidu Chlorure de chaux. Ann Chim Phys 26:162-175. GRIEPINK B, MAIEREA, QUEVAUVILLER P and MUNTAUH (1991)Certified reference materials for the quality control of analysis in the environment. Fresenius J Anal Chem 339:599-603. IHNAT, WOLFWR (1984) Maize and beef muscle agricultural and biological reference materials. In: WOLF WR, ed. Biological Reference Materials, pp 141-165. John Wiley & Sons. IHNAT M, WOLYNETZ MS (1993) Summary of an interlaboratory characterization (certification) campaign to establish the elemental composition of a new series of agriculture/food reference materials. Fresenius J Anal Chem 345:185-187. IMAIN, TERASHIMA S, ITOH S, ANDOA (1996) 1996 compilation of analytical data on nine GSJ geochemical reference samples “SedimentaryRock Series”.Geostds Newslett ~0:165-216. International Atomic Energy Agency (1998) IAEA AQCS catalogue for reference materials and intercomparison exercises 1998/1999. IRMM (1999) BCR Reference Materials. Institute for Reference Materials and Measurements, (IRMM) Reference Materials Unit, European Commission Joint Research Centre, Retieseweeg, 244.0 Geel, Belgium. I S 0 Guide 25 (1990) Guidelines for assessing the competence of calibration and testing laboratories. International Organizationfor Standardization,Geneva. I S 0 Guide 30 (1992)Terms and definitions used in connectionwith reference Materials. International Organization for Standardization,Geneva. I S 0 Guide 31 (1981) Contents of certificates of reference materials. (Revised April 1996 as ISO/ REMCO document N 382. Actual update 20 July 2000.) International Organization for Standardization, Geneva. I S 0 Guide 32 (1997) Calibration in analytical chemistry and use of certified reference materials. International Organization for Standardization,Geneva. I S 0 Guide 33 (1998) Uses of certified reference materials. Actual update 20 July 2000. International Organization for Standardization,Geneva. I S 0 Guide 34 (1996) Quality system guidelines for the production of reference materials. (Revised March 1998 as ISO/REMCO document No 464 “Generalrequirements for the competence of reference material producers”.The revised Guide 34 will appear early zooo.) International Organization for Standardization,Geneva. I S 0 Guide 35 (1989) Certification of reference Materials-General and statistical principles. International Organization for Standardization,Geneva. KENWORTHYAL, MILLEREj and MATHIS WT (1956) Nutrient-element analysis of h i t tree and leaf samples by several laboratories.Proc Amer SOCHortic Sci 67x6-21. KLICH H (1999) Overview on the activities of ISO/REMCO. In: FAJGELJ A and PARKANY M, eds. The use of matrix reference materials in environmental analytical processes, pp 188-195. The Royal Society of Chemistry, Cambridge. KRAMERGN, MUNTAUH, MAIERE, PAUWELSJ (1998) The production of powdered candidate biological and environmental reference materials in the laboratories of the Joint Research Centre. Fresenius J Anal Chem 360: 299-301. KRAMERGN, PAUWELSJ and BELLIARDOJJ (1993) Preparation of biological and environmental reference materials at CBNM. Fresenius J Anal Chem 345:133-136. K U ~ E R J,A MADERP, M I H O L O VD, ~ CIBULKA J, FALTETSEK J and KORDIKD (1995)Preparation of the bovine kidney and bovine muscle reference materials and the certificationof element contents from interlaboratorycomparisons. Fresenius J Anal Chem 35~:66-72.

18

I

7 introduction

KUEERAJ, SYCHRAV and KOUBEKJ (1998) A set of four soil reference materials with certified values of total element contents and their extractable fractions. Fresenius J Anal Chem 360: 402-405. LEEH-B and CHAUASY (1987)Analytical reference materials Part VII. development and certification of a sediment reference material for total polychlorinated biphenyls. Analyst 112:37-40. MEINKEWW (1971) Standard reference materials for clinical measurements. Anal Chem 43(6):28A-47A. MILESAA (1948) Some observations on biological standards. Analyst 73:530-538. MUNTAUH (1979) Five years of environmental candidate reference material production at the Joint Research Centre Ispra. In: Proc of the First International Symposium on Production and Use of Reference Materials, Berlin, pp 185-218. MUNTAUH (1980) Measurement quality improvements by application of reference materials. In: BRLTTERP and SCHRAMEL P, eds. Trace Element Analytical Chemistry in Medicine and Biology, pp707-726. Walter de Gruyter & Co Berlin New York. MUNTAUH (1984) Ispra activities in the production of candidate biological reference materials. In: WOLFWR, ed. Biological Reference Materials, pp. 109-140. John Wiley & Sons New York. K and FUWA K (1985)Certified reference material program at the National Institute for OKAMOTO Environmental Studies. Anal Sci 1:206-207. OKAMOTO K and YOSHINAGAJ (1999) Proper use of reference materials for elemental speciation M, eds. The use of matrix reference materials in environstudies. In: FAIGELIA and PARKANY mental analytical processes, pp 46-56. Royal Society of Chemistry, Cambridge. PARRRM (1984) IAEA biological reference materials. In: WOLFWR, ed. Biological Reference Materials, pp 45-62, John Wiley & Sons. P o n s PJ (1997) Geoanalysis: Past, present and future. Analyst 122:1179-1186. QUEVAUVILLER Ph (1995) Certified reference materials for specific chemical forms of elements. Analyst 120:597-602. QUEVAUVILLER Ph (1999) The BCR framework: 25 years of quality measurements within the European Union. Trends Anal Chem 18(5):302-311. QUEVAUVILLER Ph and MAIEREA (1999). Interlaboratory Studies and Certified Reference Materials for EnvironmentalAnalysis. Elsevier Publishers B.V., Amsterdam. RADIN N (1967)What is a standard? Clin Chem 13:55-76. RICHARDSON J M (1995) Certified reference materials programme at the Geoscience Laboratories, Sudbury, Ontario, Canada. Analyst 120:1513-1518. RONG PX and MIN 2 (1999) China GBW reference materials. In: FAJGELJA and PARKANY, eds. The use of matrix reference materials in environmental analytical processes, pp 1-30. Royal Society of Chemistry, Cambridge. ROSSI G and COLOMBO A (1979) Reference materials for chemical analysis. Highlights on the activity of JRC-Ispralaboratories. Fresenius 2 Anal Chem .zg7:13-17. JD and BACKHAUSFW (1988) Preparation of sample material for Environmental SpeciSCHLADOT men Banking purposes-Milling and homogenization at cryogenic temperatures. In: WISESA, ZEISLER R and GOLDSTEINGM, eds. Progress in Environmental Specimen Banking, pp 184193. NBS Special Publication 740. U.S. Government Printing Office, Washington. SL (1897) Ueber die Anwendung des Natriumoxdats in der Titrieranalyse. 2 Anal SORENSEN Chem 36:639-648 STOEPPLERM and ZEISLERR, eds. (1993) Biological environmental specimen banking. A collection of papers presented at the 1st International Symposium on Biological Environmental Specimen Banking, Vienna, Austria, 22-25 September 1991. Sci Total Environ, Vols. 139 and 140. JT (1984) The FDA-IFC infant formula methods study and standards for organic nutriTANNER ents. In: Wolf WR, ed. Biological Reference Materials, pp 197-205. John Wiley & Sons. TRAHEY NM (1998) NIST Standard Reference Materials Catalog 1998-99. NIST Special Publication 260. National Institute of Standards and Technology, Gaithersburg. URIANOGA and GRAVATICC (1977) The role of reference materials and reference methods in chemical analysis. CRC Crit Rev Anal Chem 6:361-411.

VAN der EIJK W (1979) The activities of the European Community Bureau of Reference - BCR. Fresenius 2 Anal Chem 297:10-12. VEILLONC, PATTERSON KY and REAMERDC (1984) Preparation of a bovine serum pool for trace element analysis. In: WOLFWR, ed. Biological Reference Materials, pp167-177. John Wiley &

Sons. VERSIECKJ , VANBALLENBERGHE L, de KESELA, BAECICN, STEYART H, BYRNEAR and SUNDERMAN FW Jr. (1988) Certification of a second-generation biological reference material (freeze dried human serum) for trace element determinations. Anal Chim Acta 204:63-75. J (1903)Proc 5th Internat Congr Appl Chem 5314. WAGNER P J (1984) Development of food-oriented reference materials by the Community WAGSTAFFE Bureau of Reference (BCR) In: Wolf WR, ed. Biological Reference Materials, pp 63-78. Wiley & Sons. WAINERDI (1979) Reference material for trace analysis by radioanalytical methods: Bowen’s Kale. Pure Appl Chem 51:1183-1193. WARDGM and HEENEY HB (1960) A collaborative study of methods for the determination of potassium, calcium and magnesium in plant materials. Canad J Plant Sci 40:589-595. TP (1976) Quality Control in Clinical Chemistry. Wiley, Chichester. WHITEHEAD WILLIESN (1997) The preparation of National Research Council Certified Reference Materials. In: CLEMENT RE, KEITH LH and SIUKWM, eds. Reference Materials for Environmental Analysis, pp 43-59. CRC Press Inc. WOLFWR and IHNATM (1984) Evaluation of available certified biological reference materials for inorganic nutrient analysis. In: WOLFWR, ed. Biological Reference Materials, pp 89-105. John Wiley & Sons. WOLFWR, IYENGAR GC and TANNER JT (1990) Mixed diet reference materials for nutrient analysis of foods: preparation of SRM-1545Total diet. Fresenius J Anal Chem 338:473-475. R, LANGJAND J K and HARRISON SH (1983) Cryogenic homogenization procedure for bioZEISLER logical tissues. Anal Chem 55:2431-2434.

Reference Materials for ChemicalAnalysis Certification, Availability, and Proper Usage

Edited by Markus Stoeppler,Wayne R. WOK PeterJjenks 0 Wiley-VCH Verlag GmbH, 2001

*O

I 2

From Planning to Production Edited by Markus Stoeppler 2.1

Material Collection and Preparation Milan Ihnat')

2.1.1

Introduction

A large number of considerations and factors must be entertained for the conception, development, preparation, assessment, characterization, and certification of RMs, including (a) end use requirements, (b) selection of materials, (c) preparation, (d) physical characterization, (e) chemical characterization, (f) certification, (g) documentation, and (h) distribution. Most of these have an overwhelming impact on the finally developed RM and on its credibility. This section deals with the steps, collectively denoted as collection and preparation, occurring early in the scheme of RM development. It treats general collection and preparation principles, and provides specific examples of preparative procedures. No. 2069 from Pacific Agri-Food Research Centre - Summerland

1) Contribution

2. 7 Material Collection and Preparation

Table 2.1

Classes o f biological and environmental RMs for chemical analysis with examples

Main class

Subclass

Examples

Biological

Animal tissues (see also foods) Plant tissues (see also foods) Foods and agricultural products

Animal bone, ground whole carp, cod muscle, tuna, dogfish liver Chlorella, aquatic plant, grass, hay, spruce twigs and needles, olive leaves, peach leaves, tobacco leaves Bovine muscle, bovine liver, pig kidney, milk powder, cereals, single cell protein, butterfat, fish oil, animal feedstuffs, textiles Whole blood, blood serum. Urine, human hair, blood plasma and serum proteins, enzymes Spray-driedmilk matrix with stabilized micro-organisms

Clinical tissues and fluids Microbiological materials Environmental Ashes and dusts

Wastes and sludges Waters

Coal ash, coal fly ash, power station fly ash, incinerator ash, vehicle exhaust particulates, urban dust, atmospheric dust, metal smelter dust, welding dust, diesel particulates, particulates on filter media Sewage sludge, wastewater Seawater, rainwater, river water, estuarine water, open ocean water, fresh water, ground water, drinking water

Rocks and ores

Geological

Basalt, granite, manganese nodules, shale, flint clay, iron formation materials, phosphate rock, fertilizers Soils Calcareous loam soil, loess, polluted farmland soil, sand soil Sediments Marine sediments, estuarine sediments, freshwater pond sediments, harbour sediments, stream sediments, lake sediments Blast furnace slag, concentrates, ore mill tailings, plating Mineral processing products sludge Ceramics and glasses Silicon carbide, high boron borosilicate glass, trace elements in glass Fossil fuels Coal, coke, petroleum crude oil, residual fuel oil

Other

Synthetic and spiked materials Pure elements and compounds

Instrument performance Stable isotope RMs RMs for determination of radionuclides

Gelatin, trace elements in glass, glass fdters, graphite, synthetic materials High purity elements and compounds, organic compounds, organo-metalliccompounds, high purity compounds for microchemical and microanalyticaltechniques, pharmaceuticals Pure element and compound solutions for calibration and instrument performance, trace elements in glass, glasses, glass filters Water, pure compounds, biological materials, minerals Animal tissues, plant tissues, sediments, soils, radiopharmaceuticals

I

21

22

I

2 From Planning to Production

At the outset, it may be useful to list the major classes of RMs, and measurands therein, of interest to this book (generally biological, environmental, and geological; and generally for chemical analysis). Table 2.1 presents the major RM classes with subclasses; Table 2.2 lists some of the most prevalent examples of measurands (analytes) for which RMs have been produced. Table2.z

Examples of measurands (analytes)for which RMs have been produced

Measurand class

Examples

Elements

Major, minor and trace elements of nutritional, environmental, clinical, toxicological significance: Al, As, Ba, Be, Br, Ca, Cd, Cs, Cu, F, Hg, I, Li, Mn, Mo, N,P, S, Sb, Se, Sn, Th, Tl, U, V, W, rare earth elements. Stable isotopes: 'H,I3C,I5N, l80.Radionuclides: 401

i i ; .. ,. . .:. . . . . ’’...... :i.

z 20 20

0

40

60

Normalized Percent

80

100

Fig. 6.2 Plot of6675 foods from the USDA Databasefor Food Consumption Survey (USDA 1989-91)

1

F

20

40

60

Fig. 6.3

Number offoods and mean point per sector from Figure 6-2

The resulting tables (i.e. Table 6.5) list commonly consumed foods that are near the mean x and y for each sector. Commonly consumed foods are a real advantage when preparing RMs, because they tend to be readily available and inexpensive. In Table 6.5 (sector 4), eggs, cheese, and chicken are commonly consumed foods and are possible candidates for RMs for foods falling into the proximate ranges for this sector (fat content 34-66 %, protein content 34-66 %, and carbohydrate content 0-33 %). Multi-ingredient items like soups, sandwiches and low-fat frozen dinners are the commonly consumed foods whose proximate contents are close to the mean for sector 7. These mixed dishes are possible candidates for RMs for foods with fat

I

213

214

I

G General Application Fields Tab. 6.5

List of commonly consumed foods closest to the sector 4 mean (Wolf and Andrews 1995)

(57)

Description

Fat

Egg, whole boiled Cheese, swiss Egg, whole poached Egg, omelet/scrambled egg, no fat added Chicken wing with skin, baked

43.5 46.3 42.2 40.2 43.7

Protein

51.8 47.9 52.6 48.8 51.5

(55)

Carbohydrate (57)

4.6 5.7 5.1 10.9 4.8

content 0-33 %, protein content 34-66 %, and carbohydrate content 34-66 %. A list of key foods that supply 75 % of a given nutrient to the population has been developed (Haytowitz et al. 1996). It would be of interest to examine this list using this food matrix triangle approach to develop further recommendations for candidate RMs. The Standard Reference Materials Program of NIST has utilized this approach in setting priorities for development of several new food-based RMs. One outcome was the additional characterization of proximate contents for a number of RMs presently available from NIST. 6.3.3 Available Reference Materials

Table 6.6 lists most of the available RMs, a listing of major producers and suppliers of all kinds of RMs is given in Chapter 8. Many materials have been characterized for elemental, isotopic and radionuclide content, but increasingly, materials are becoming available for a wide variety of organic measurands; see Section 2.1. An example of concentrations of nitrogen in biologicallfood RMs is given in Table 6.7. Tabulations as in Tables 6.6 and 6.7 (e.g. Ihnat 1988,1998b; International Atomic Energy Agency 1995; National Oceanic and Atmospheric Administration 1995) enable the analyst to locate materials of appropriate natural matrix composition and measurand concentration.Individual catalogues and reports (e.g. Bowman 1994; International Atomic Energy Agency 1998; Trahey 1998; Institute for Reference Materials and Measurements 1999) and appropriatewebsites should also be consulted. 6.3.4 Mode o f Application and Application Examples

A good presentation of general principles relating to RM and data quality concepts and use is given by Taylor (1993).Specific guidelines for the selection and utilization of RMs for monitoring and maintaining analpcal data quality in the measurement of inorganic measurands in plants and soils have been published (Ihnat 1993, 1998a, b). In order to properly use RMs, it is imperative that compliance with several preliminary requirements be established (I) An appropriate analytical method must be applied to the task on hand by appropriately qualified and trained personnel.

6 3 Food/Bio/ogica/ Tab. 6.6

Examples of biological, food, agricultural and related RMs for chemical composition available from, principally, government agency suppliers (Ihnat 1988, 1992,1998a; International Atomic Energy Agency 1998; Institute for Reference Materials and Measurements 1999; National Oceanic and Atmospheric Administration 1995; Trahey 1998)4 RM group

SupplieF:

Material

Animal tissues

BCR

Bovine liver, pig kidney, mussel tissue (also for butyltin compounds),tuna fish (methylmernuy),tuna fish tissue (As speciation) Non-defatted lobster hepatopancreas, lobster hepatopancreas, dogfish liver, dogfish muscle Fish flesh Fish tissue Bovine liver, oyster tissue Animal muscle (pork),carrot powder, total diet, wheat flour Skim milk powder (elements),whole meal flour, bovine muscle, wholemeal flour, brown bread, cod liver oil (PCBs),rye flour, haricots verts (beans),pork muscle, mixed vegetables, carrot, bran breakfast cereal, unspiked milk powder (PCDDs, PCDFs), spiked milk powder (PCDDs, PCDFs), milk powder Rye flour, milk powder, whey powder Pork meat Tea leaves, rice flour, oyster tissue, wheat flour, rice flour Nonfat milk powder, spinach leaves, corn kernel, bovine muscle powder, whole egg powder, microcrystalline cellulose, wheat gluten, whole milk powder, durum wheat flour Aquatic phnts (Lugurosiphonmajor, Platihypnidium riparioides), olive leaves, beech leaves, hay powder, lichen, single cell protein, sea lettuce, rye grass, white glover, plankton Spruce twigs and needles Cotton cellulose, hay powder, grass Oriental tobacco leaves, Virginia tobacco leaves Pepperbush, chlorella, sargasso, Apple leaves, citrus leaves, pine needles, corn stalk Sewage sludge (PAHs),sewage sludge (domestic origin), sewage sludge (industrial origin), waste mineral oil (low level PCBs)

NRCC

Foodstuffs

IAEA EPA NIST ARC BCR

IAEA LIVSVER NIES NIST

Plants

Biological waste materials 4

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