Progress in Food Contaminant Analysis JOIN US ON THE INTERNET VIA WWW, GOPHER, FTP OR EMAIL: WWW: http://www.thomson.com GOPHER: gopher.thomson.com A service of ICDP® FTP: ftp.thomson.com EMAIL: [email protected] Progress in Food Contaminant Analysis Edited by 1. GILBERT Ministry of Agriculture, Fisheries and Food CSL Food Science Laboratory Norwich UK BLACKIE ACADEMIC & PROFESSIONAL An Imprint of Chapman & Hall London . Weinheim . New York· Tokyo· Melbourne· Madras Published by B1ackie Academic & Professional, an imprint of Chapman & Hall, 2-6 Boundary Row, London SEt 8HN, UK Chapman & Hall, 2-6 Boundary Row, London SEI 8HN, UK Chapman & Hall GmbH, Pappelallee 3, 69469 Weinheim, Germany Chapman & Hall USA, 115 Fifth Avenue, New York, NY 10003, USA Chapman & Hall Japan, ITP-Japan, Kyowa Building, 3F, 2-2-1 Hirakawacho, Chiyoda-ku, Tokyo 102, Japan DA Book (Aust.) Pty Ltd, 648 Whitehorse Road, Mitcham 3132, Victoria, Australia Chapman & Hall India, R. Seshadri, 32 Second Main Road, CIT East, Madras 600 035, India First edition 1996 © 1996 Chapman & Hall Softcover reprint of the hardcover I st edition 1996 Typeset in 1O/12pt Times by Academic & Technical Typesetting, Bristol ISBN-13: 978-1-4612-8425-3 e-ISBN: 978-1-4613-1117-1 DOl: 10.1007/978-1-4613-1117-1 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the UK Copyright Designs and Patents Act, 1988, this publication may not be reproduced, stored, or transmitted, in any form or by any means, without the prior permission in writing of the publishers, or in the case of repro graphic reproduction only in accordance with the terms of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to the publishers at the London address printed on this page. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. A catalogue record for this book is available from the British Library Library of Congress Catalog Card Number: 96-83055 @Printed on acid-free text paper, manufactured in accordance with ANSI/ NlSO Z39.48-1992 (Permanence of Paper). Preface 'Analysis of Food Contaminants' was published in 1984 by Elsevier Applied Science Publishers and 10 years later I was asked to consider producing an updated second edition. Surprisingly little has really changed in a decade in terms of the public interest in food safety and the continued vigilance of Government in monitoring the food supply for contaminants. This means that food contamination in itself is still a very relevant topic. However, much has changed in terms of the techniques now employed in trace analysis. The 1984 book used a combination of an analytical technique and a specific food contaminant problem area per chapter (each written by a specialist) which resulted in a multi-authored text which was mostly application based but provided a good introduction to the 'how' in terms of applying techniques to real problems. Rather than producing a second edition of this text, it seemed on reflection more sensible to produce a new and complementary book, using the same formula as before of application plus technique, but to concentrate on contaminant areas of current interest and to highlight recent advances in techniques. Thus, the present book 'Progress in Food Contaminant Analysis' has originated as a follow-up to 'Analysis of Food Contaminants'. Sampling and the application of appropriate sample plans for food analysis has always been a neglected area, and whilst this topic does not really constitute an advance in food analysis it has been included in the present book simply to emphasise its importance. Invariably the cost of adequate sampling tends to deter when planning food surveillance exercises, and in the laboratory the glamour of sophisticated instrumental techniques and ever pushing to lower limits of detection is inevitably far more attractive than development of sampling plans. The first chapter of this book draws attention to the issues that need to be considered in sampling and hopefully will be read alongside later chapters on instrumental methods. The 1984 book contained a chapter on size exclusion chromatography (gel permeation) for sample clean-up which is still relevant and remains under-utilised as a sample preparation method. In this book the same author has extended this theme and reviewed the wider area of automated clean-up techniques (including size exclusion) which is the way forward for many in terms of meeting demands for increased sample numbers and reduced cost of analysis. Of the various food contaminants mycotoxins still remain important food contaminants with particular interest today in ochratoxin A and the recently discovered fumonisins. In a chapter on chromatographic analysis of mycotoxins two authors from a world-leading mycotoxin laboratory in VI PREFACE South Africa have critically and comprehensively reviewed the relative merits of different chromatographic approaches to the analysis of mycotoxins. The 1984 book contained a chapter which reviewed analytical approaches to trace element determinations in foods. This is still up-to-date in terms of sample preparation which has essentially remained unchanged and in respect of techniques such as AAS. However, ICP-MS has subsequently revolutionised trace element analysis and in this new book a chapter is devoted exclusively to this topic. In 1984 a chapter covered immunoassay techniques applied to veterinary drug residue analysis-in this book the remarkable advances in immunochemical analysis in the last few years are reviewed but applied to pesticides analysis as opposed to drug residues. The remaining chapters of this book deviate somewhat from the earlier text but nevertheless are still complementary. Instead of reviewing quantita tive GC-MS this present book concentrates on LC-MS which, in less than 10 years, has moved from being a relatively esoteric technique to being routinely applied in many laboratories world-wide. Despite tremendous advances in instrumental techniques, the use of biological-based methods is still, in many areas, irreplaceable at the present time. This is illustrated by a chapter looking at approaches used to monitor the presence of phycotoxins in shellfish. The ultimate state-of-the-art in terms of requirements for sensitivity and specificity for contaminant analysis is in the area of dioxins and PCBs, where high resolution GC-MS remains the only method capable of meeting stringent demands, and a chapter is dedicated to this topic. Perhaps the most specialised chapter concerns testing of food packaging materials for migration into foods and this concentrates on high temperature testing which has become important with changes in lifestyle towards greater use of microwave convenience foods. Finally this book concludes with an insight into some of the developments that are being made internationally in terms of harmonisation of analytical methods, analytical quality assurance and proficiency testing. Developments in this area do represent an advance, and this chapter provides an insight into the workings of frequently impene trable international committees involved in food analysis. It is not only a pleasure but also an honour to draw together contributions from friends and colleagues who are renowned specialists in their own fields into the form of an edited book. It is hoped that the end-product will provide for those unfamiliar with the field of food contaminant analysis much stimulating reading, and an overview of trends and developments in this fascinating area. J.G. Contributors T.H. Begley Indirect Additives Section, Division of Product Manu facture and Use, Center for Food and Applied Nutrition, Food and Drug Administration, 200 C Street SW, Washington DC 20204, USA S.J. Buckland ESR Environmental, PO Box 30 547, Lower Hutt, New Zealand P .A. Burdaspal Centro Nacional de Alimentaci6n Instituto de Salud Carlos III, Ministerio de Sanidad y Consumo 28220 Majadahonda, Madrid, Spain H.M. Crews Ministry of Agriculture, Fisheries and Food, CSL Food Science Laboratory, Norwich Research Park, Colney, Norwich NR4 7UQ, UK N.T. Crosby Laboratory of the Government Chemist, Queen's Road, Teddington, Middlesex TWII OL Y, UK J. Gilbert Ministry of Agriculture, Fisheries and Food, CSL Food Science Laboratory, Norwich Research Park, Colney, Norwich NR4 7UQ, UK D.J. Hannah ESR Environmental, PO Box 30 547, Lower Hutt, New Zealand H.C. Hollifield Indirect Additives Section, Division of Product Manu facture and Use, Center for Food and Applied Nutrition, Food and Drug Administration, 200 C Street SW, Washington DC 20204, USA B.M. Kaufman Novavax Inc, 12111 Park lawn Drive, Rockville, MD 20852, USA L.J. Porter ESR Environmental, PO Box 30 547, Lower Hutt, New Zealand G.S. Shephard Programme on Mycotoxins and Experimental Carcino genesis, Medical Research Council, PO Box 19070, Tygerberg 7505, South Africa Vlll CONTRIBUTORS M.J. Shepherd Ministry of Agriculture, Fisheries and Food, CSL Food Science Laboratory, Norwich Research Park, Colney, Norwich NR4 7UQ, UK E.W. Sydenham Programme on Mycotoxins and Experimental Carcino genesis, Medical Research Council, PO Box 19070, Tygerberg 7505, South Africa R. Wood Ministry of Agriculture, Fisheries and Food, Food Labelling and Standards Division, Norwich Research Park, Colney, Norwich NR4 7UQ, UK Contents 1 Sampling and sample plans for food surveillance exercises 1 NEIL T. CROSBY Summary I l.l Introduction 1 1.1.1 Sampling procedures 3 1.2 Design of a sampling plan 6 1.2.1 Objectives and scope 7 1.2.2 Analytes 8 1.2.3 Methods of analysis 9 1.2.4 Types of analytical methods used for surveillance 9 1.2.5 Selection of foods 14 1.2.6 Pretreatment, transport and storage of the samples 15 I. 3 Food surveillance exercises 16 1.3.1 Total diet studies 16 1.4 Sampling of commodities for aflatoxins 17 1.5 Some other practical problems in food sampling 19 1.5.1 Trace metals in packeted teas 19 1.5.2 Trace metals in canned foods 20 1.5.3 Vitamin D in cereals 22 1.5.4 Monomers in plastics 23 1.6 Sample pretreatment 23 I. 7 Sampling equipment for foodstuffs 25 1.7.1 Sub-division of solids 27 1.8 Conclusions 30 References 30 Appendix I Glossary of terms used in sampling 31 2 Automated clean-up techniques for trace component analysis in complex biological matrices including foods 32 MARTIN J. SHEPHERD Summary 32 Abbreviations 32 2.1 Introduction 33 2.2 Rationale for automating trace analysis 36 2.3 Criteria for selecting methods for automation 37 2.4 Advantages of automation 37 2.5 Disadvantages of automation 38 2.6 Methods for automation 39 2.6.1 Headspace GC and purge and trap 39 2.6.2 Auto-samplers 39 2.6.3 Liquid handling systems 40 2.6.4 Dialysis 42 2.6.5 Column switching 45 2.6.6 LC-LC column switching 47 2.6.7 GC-GC column switching 54 2.6.8 LC-GC column switching 56 2.6.9 Supercritical fluid switching 58 x CONTENTS 2.7 Electrophoresis 59 2.8 Data reduction 60 2.9 Conclusions 60 References 61 3 Chromatographic and allied methods of analysis for selected mycotoxins 65 ERIC W. SYDENHAM and GORDON S. SHEPHARD Summary 65 3.1 Introduction 65 3.2 Aflatoxins in food commodities 67 3.2.1 Introduction 67 3.2.2 Application of TLC techniques 68 3.2.3 Application of HPLC techniques 69 3.2.4 Application of immunochemical techniques 72 3.2.5 Application of alternative/confirmation techniques 74 3.3 Aflatoxin M, in milk 75 3.3.1 Introduction 75 3.3.2 Application of TLC and HPLC techniques 75 3.3.3 Application of immunochemical techniques 76 3.3.4 Application of alternative/confirmation techniques 79 3.4 Fumonisins 79 3.4.1 Introduction 79 3.4.2 Application of TLC techniques 80 3.4.3 Application of HPLC techniques 81 3.4.4 Application of GC techniques 85 3.4.5 Application of immunochemical techniques 86 3.4.6 Application of alternative/confirmation techniques 87 3.5 Ochratoxin A 89 3.5.1 Introduction 89 3.5.2 Application of TLC techniques 90 3.5.3 Application of HPLC techniques 91 3.5.4 Application of immunochemical techniques 92 3.5.5 Application of alternative/confirmation techniques 94 3.6 Patulin 95 3.6.1 Introduction 95 3.6.2 Application of TLC techniques 96 3.6.3 Application of HPLC techniques 96 3.6.4 Application of GC techniques 99 3.6.5 Application of alternative/confirmation techniques 99 3.7 Trichothecenes (deoxynivalenol, nivalenol, diacetoxyscirpenol and T-2 toxin) 101 3.7.1 Introduction 101 3.7.2 Application of TLC techniques 103 3.7.3 Application of HPLC techniques 104 3.7.4 Application of GC techniques 105 3.7.5 Application ofimmunochemical techniques 108 3.7.6 Application of alternative/confirmation techniques 111 3.8 Zearalenone 112 3.8.1 Introduction 112 3.8.2 Application of TLC techniques 114 3.8.3 Application of HPLC techniques 115 3.8.4 Application of GC techniques 119 3.8.5 Application of immunochemical techniques 119 3.8.6 Application of alternative/confirmation techniques 122 3.9 Multi-mycotoxin methods 123 3.9.1 Introduction 123 CONTENTS Xl 3.9.2 Application of TLC techniques 124 3.9.3 Application of HPLC techniques 125 3.9.4 Application of GC techniques 126 3.9.5 Application of immunochemical techniques 128 3.9.6 Application of dual and/or alternative techniques 129 3.10 Conclusions 130 References 131 4 Inductively coupled plasma-mass spectrometry (ICP-MS) for the analysis of trace element contaminants in foods 147 HELEN M. CREWS Summary 147 Abbreviations 147 4.1 Introduction 148 4.2 Principles of ICP-MS 149 4.2.1 The ICP ion source 149 4.2.2 The ICP-MS interface lSI 4.2.3 The quadrupole 153 4.2.4 The detector 154 4.3 The advantages and disadvantages of ICP-MS 155 4.3.1 Isobaric overlap 155 4.3.2 Polyatomic interferences 156 4.3.3 Doubly charged species 158 4.3.4 Transport effects 158 4.3.5 Ionisation interferences 159 4.3.6 Ion sampling effect 159 4.3.7 Sensitivity and dynamic range 159 4.3.8 Multi-element and multi-isotope capability 161 4.4 Sample preparation 169 4.5 Total analyte determinations 169 4.5.1 Minimum sample preparation and isotope dilution analysis 169 4.5.2 Measurement by ICP-MS after digestion of foods and related samples with acid(s) 171 4.6 Speciation studies of foods 174 4.7 Future developments 179 References 180 5 Applications of immunoassay to pesticide analysis 187 BENNETT M. KAUFMAN Summary 187 5.1 Introduction 187 5.1.1 Immunoassay technology 188 5.1.2 Advantages and disadvantages of immunoassay 192 5.2 Pesticide determination by immunoassay 193 5.2.1 Paraquat 193 5.2.2 Organophosphorus compounds 194 5.2.3 Carbamates 196 5.2.4 Organohalogens 199 5.2.5 Triazines 202 5.2.6 Substituted urea compounds 204 5.2.7 Pyrethroids 206 5.2.8 Miscellaneous pesticide compounds 207 5.3 Commercial pesticide immunoassay kits 207 5.4 Official evaluation/acceptance of pesticide immunoassay kits 207 5.4.1 US EPA 209