EXTRACTION TECHNIQUES IN ANALYTICAL SCIENCES

Transcription

1 EXTRACTION TECHNIQUES IN ANALYTICAL SCIENCES John R. Dean The Graduate School and School of Applied Sciences Northumbria University, Newcastle, UK A John Wiley and Sons, Ltd., Publication

2

3 EXTRACTION TECHNIQUES IN ANALYTICAL SCIENCES

4 Analytical Techniques in the Sciences (AnTS) Series Editor: David J. Ando, Consultant, Dartford, Kent, UK A series of open learning/distance learning books which covers all of the major analytical techniques and their application in the most important areas of physical, life and materials sciences. Titles available in the Series Analytical Instrumentation: Performance Characteristics and Quality Graham Currell, University of the West of England, Bristol, UK Fundamentals of Electroanalytical Chemistry Paul M.S. Monk, Manchester Metropolitan University, Manchester, UK Introduction to Environmental Analysis Roger N. Reeve, University of Sunderland, UK Polymer Analysis Barbara H. Stuart, University of Technology, Sydney, Australia Chemical Sensors and Biosensors Brian R. Eggins, University of Ulster at Jordanstown, Northern Ireland, UK Methods for Environmental Trace Analysis John R. Dean, Northumbria University, Newcastle, UK Liquid Chromatography Mass Spectrometry: An Introduction Robert E. Ardrey, University of Huddersfield, UK Analysis of Controlled Substances Michael D. Cole, Anglia Polytechnic University, Cambridge, UK Infrared Spectroscopy: Fundamentals and Applications Barbara H. Stuart, University of Technology, Sydney, Australia Practical Inductively Coupled Plasma Spectroscopy John R. Dean, Northumbria University, Newcastle, UK Bioavailability, Bioaccessibility and Mobility of Environmental Contaminants John R. Dean, Northumbria University, Newcastle, UK Quality Assurance in Analytical Chemistry Elizabeth Prichard and Vicki Barwick, LGC, Teddington, UK Extraction Techniques in Analytical Sciences John R. Dean, Northumbria University, Newcastle, UK Forthcoming Titles Practical Raman Spectroscopy: An Introduction Peter Vandenabeele, Ghent University, Belgium Techniques of Modern Organic Mass Spectrometry Bob Ardrey, Alex Allan and Pete Ashton, Triple A Forensics, Ltd, Oldham, UK Forensic Analysis Techniques Barbara H. Stuart, University of Technology, Sydney, Australia

5 EXTRACTION TECHNIQUES IN ANALYTICAL SCIENCES John R. Dean The Graduate School and School of Applied Sciences Northumbria University, Newcastle, UK A John Wiley and Sons, Ltd., Publication

6 This edition first published John Wiley & Sons, Ltd Registered office John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of fitness for a particular purpose. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for every situation. In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of experimental reagents, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each chemical, piece of equipment, reagent, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. The fact that an organization or Website is referred to in this work as a citation and/or a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make. Further, readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read. No warranty may be created or extended by any promotional statements for this work. Neither the publisher nor the author shall be liable for any damages arising herefrom. Library of Congress Cataloging-in-Publication Data Record on file A catalogue record for this book is available from the British Library. Cloth Paper Set in 10/12pt Times by Laserwords Private Limited, Chennai, India. Printed and bound in Great Britain by TJ International Ltd, Padstow, Cornwall

7 To Lynne, Sam and Naomi (and the border terrier, Emmi) for allowing me the time to sit and write this book

8

9 Contents Series Preface Preface Acknowledgements Acronyms, Abbreviations and Symbols About the Author xiii xv xix xxi xxv 1 Pre- and Post-Extraction Considerations Introduction Organic Compounds of Interest Pre-Sampling Issues Sampling Strategies: Solid, Aqueous and Air Samples Practical Aspects of Sampling Soil and Sediment Practical Aspects of Sampling Water Practical Aspects of Air Sampling An Introduction to Practical Chromatographic Analysis Gas Chromatography High Performance Liquid Chromatography Sample Pre-Concentration Methods Quality Assurance Aspects Health and Safety Considerations 35 References 36

10 viii Extraction Techniques in Analytical Sciences AQUEOUS SAMPLES 37 2 Classical Approaches for Aqueous Extraction Introduction Liquid Liquid Extraction Theory of Liquid Liquid Extraction Selection of Solvents Solvent Extraction Problems with the LLE Process Purge and Trap for Volatile Organics in Aqueous Samples 45 References 47 3 Solid Phase Extraction Introduction Types of SPE Media (Sorbent) Multimodal and Mixed-Phase Extractions Molecularly Imprinted Polymers (MIPs) SPE Formats and Apparatus Method of SPE Operation Solvent Selection Factors Affecting SPE Selected Methods of Analysis for SPE Applications of Normal Phase SPE Applications of Reversed Phase SPE Applications of Ion Exchange SPE Applications of Molecularly Imprinted Polymers (MIPs) Automation and On-Line SPE Application of Automated On-Line SPE 78 References 84 4 Solid Phase Microextraction Introduction Theoretical Considerations Experimental Methods of Analysis: SPME GC Direct Immersion SPME: Semi-Volatile Organic Compounds in Water Headspace SPME: Volatile Organic Compounds (VOCs) in Water Analysis of Compounds from Solid Matrices 94

11 Contents ix Other SPME GC Applications Methods of Analysis: SPME HPLC MS Analysis of Abietic Acid and Dehydroabietic Acid in Food Samples Analysis of Fungicides in Water Samples Automation of SPME Applications of Automated SPME 110 References New Developments in Microextraction Introduction Stir-Bar Sorptive Extraction (SBSE) Liquid-Phase Microextraction Single-Drop Microextraction (SDME) Membrane Microextraction Semipermeable Membrane Device (SPMD) Polar Organic Chemical Integrative Sampler (POCIS) Chemcatcher Ceramic Dosimeter Membrane Enclosed-Sorptive Coating (MESCO) Device Microextraction in a Packed Syringe (MEPS) 121 References 123 SOLID SAMPLES Classical Approaches for Solid Liquid Extraction Introduction Soxhlet Extraction Automated Soxhlet Extraction or Soxtec Other Approaches for Solid Liquid Extraction 132 References Pressurized Fluid Extraction Introduction Theoretical Considerations Relating to the Extraction Process Solubility and Mass Transfer Effects Disruption of Surface Equilibria 144

12 x Extraction Techniques in Analytical Sciences 7.3 Instrumentation for PFE Dionex System Applied Separations, Inc Fluid Management Systems, Inc Method Development for PFE Applications of PFE Parameter Optimization In situ Clean-Up or Selective PFE Shape-Selective, Fractionated PFE Comparative Studies Miscellaneous 160 References Microwave-Assisted Extraction Introduction Instrumentation Anton-Parr CEM Corporation Milestone Applications of MAE 174 References Matrix Solid Phase Dispersion Introduction Issues on the Comparison of MSPD and SPE A Review of Selected Applications 188 References Supercritical Fluid Extraction Introduction Instrumentation for SFE Applications of SFE Selection of SFE Operating Parameters 202 References 207 GASEOUS SAMPLES Air Sampling Introduction Techniques Used for Air Sampling 213

13 Contents xi Whole Air Collection Enrichment into Solid Sorbents Desorption Techniques 216 References 219 COMPARISON OF EXTRACTION METHODS Comparison of Extraction Methods Introduction Role of Certified Reference Materials Comparison of Extraction Techniques for (Semi)-Solid Samples A Comparison of Extraction Techniques for Solid Samples: a Case Study Comparison of Extraction Techniques for Liquid Samples Comparison of Extraction Techniques for Air Sampling 233 References 240 RESOURCES Resources for Extraction Techniques Introduction Sources of Data Role of Worldwide Web 244 Responses to Self-Assessment Questions 249 Glossary of Terms 261 SI Units and Physical Constants 269 Periodic Table 273 General Index 275 Application Index 279

14

15 Series Preface There has been a rapid expansion in the provision of further education in recent years, which has brought with it the need to provide more flexible methods of teaching in order to satisfy the requirements of an increasingly more diverse type of student. In this respect, the open learning approach has proved to be a valuable and effective teaching method, in particular for those students who for a variety of reasons cannot pursue full-time traditional courses. As a result, John Wiley & Sons, Ltd first published the Analytical Chemistry by Open Learning (ACOL) series of textbooks in the late 1980s. This series, which covers all of the major analytical techniques, rapidly established itself as a valuable teaching resource, providing a convenient and flexible means of studying for those people who, on account of their individual circumstances, were not able to take advantage of more conventional methods of education in this particular subject area. Following upon the success of the ACOL series, which by its very name is predominately concerned with Analytical Chemistry, theanalytical Techniques in the Sciences (AnTS) series of open learning texts has been introduced with the aim of providing a broader coverage of the many areas of science in which analytical techniques and methods are now increasingly applied. With this in mind, the AnTS series of texts seeks to provide a range of books which will cover not only the actual techniques themselves, but also those scientific disciplines which have a necessary requirement for analytical characterization methods. Analytical instrumentation continues to increase in sophistication, and as a consequence, the range of materials that can now be almost routinely analysed has increased accordingly. Books in this series which are concerned with the techniques themselves will reflect such advances in analytical instrumentation, while at the same time providing full and detailed discussions of the fundamental concepts and theories of the particular analytical method being considered. Such books will cover a variety of techniques, including general instrumental analysis, spectroscopy, chromatography, electrophoresis, tandem techniques, electroanalytical methods, X-ray analysis and other significant topics. In addition, books in

16 xiv Extraction Techniques in Analytical Sciences the series will include the application of analytical techniques in areas such as environmental science, the life sciences, clinical analysis, food science, forensic analysis, pharmaceutical science, conservation and archaeology, polymer science and general solid-state materials science. Written by experts in their own particular fields, the books are presented in an easy-to-read, user-friendly style, with each chapter including both learning objectives and summaries of the subject matter being covered. The progress of the reader can be assessed by the use of frequent self-assessment questions (SAQs) and discussion questions (DQs), along with their corresponding reinforcing or remedial responses, which appear regularly throughout the texts. The books are thus eminently suitable both for self-study applications and for forming the basis of industrial company in-house training schemes. Each text also contains a large amount of supplementary material, including bibliographies, lists of acronyms and abbreviations, and tables of SI Units and important physical constants, plus where appropriate, glossaries and references to literature sources. It is therefore hoped that this present series of textbooks will prove to be a useful and valuable source of teaching material, both for individual students and for teachers of science courses. Dave Ando Dartford, UK

17 Preface This book introduces a range of extraction techniques as applied to the recovery of organic compounds from a variety of matrices. In line with other texts in the Analytical Techniques in the Sciences (AnTS) Series, discussion and selfassessment questions provide the reader with the opportunity to assess their own understanding of aspects of the text. This book has been designed to be userfriendly with illustrations to aid understanding. This text is arranged into thirteen chapters as follows. Chapter 1 introduces all the key aspects that need to be considered, pre- and post-extraction. In particular, it highlights the range of organic compounds that are extracted in analytical sciences. This chapter then addresses pre-sampling issues by way of a desk-top study of a contaminated land site using historic maps. Specific sampling strategies for solid, aqueous and air samples are considered. The natural progression in any analytical protocol would then be to carry out the extraction technique. However, as the rest of the book details how to perform different extractions no details are provided at this point. Post-extraction details focus on the main chromatographic approaches for analysing organic compounds, i.e. gas chromatography and high performance liquid chromatography. Both techniques are covered from a practical perspective. Issues around sample pre-concentration post-extraction are also discussed in terms of the most popular approaches used. Finally, quality assurance aspects and health and safety issues are considered. Chapter 2 considers the classical approaches for extracting organic compounds from aqueous samples, namely liquid liquid extraction (LLE). Details of the basic theory applicable to LLE are explained together with important practical aspects, including choice of solvents, the apparatus and procedure to undertake LLE and practical problems and remedies for undertaking LLE. Finally, the specific extraction technique of purge and trap and its application for recovering volatile organic compounds from aqueous samples is explained.

18 xvi Extraction Techniques in Analytical Sciences Chapter 3 considers the use of solid phase extraction (or SPE) for the recovery of organic compounds from aqueous samples. The different types of SPE media are considered as well as the different formats in which SPE can be performed, solvent selection and factors influencing SPE. The five main aspects of SPE operation are reviewed both generically and then via a series of applications using normal phase, reversed phase, ion exchange and molecularly imprinted polymers. Finally, the use of automated and in-line SPE is considered using a selected example. Chapter 4 considers the use of solid phase microextraction (or SPME) for the recovery of organic compounds from aqueous samples (although mention is also made of its applicability for headspace sampling), followed by either GC or HPLC. The practical aspects of using the fibres are described in detail as well as their applicability for a range of sample types in different modes of operation. Chapter 5 describes new developments in microextraction. Particular developments highlighted include stir-bar sorptive extraction (SBSE), liquid phase microextraction (specifically, single drop microextraction (SDME)), membrane microextraction (specifically, the semipermeable membrane device (SPMD), the polar organic chemical integrative sampler (POCIS), Chemcatcher, the ceramic dosimeter and membrane enclosed-sorptive coating (MESCO)), as well as microextraction in a packed syringe (MEPS). Chapter 6 considers the classical approaches for extracting organic compounds from solid samples, namely Soxhlet extraction (LLE). Practical guidance on the use of Soxhlet extraction is provided along with choice of solvent, and the apparatus and procedure to undertake extraction. In addition, automated Soxhlet (or Soxtec ) extraction is discussed alongside other approaches that utilize sonication or shake-flask extraction for the recovery of organic compounds from solid matrices. Chapter 7 describes the use of pressurized fluid extraction (PFE) (also known as accelerated solvent extraction or pressurized liquid extraction) for the recovery of organic compounds from solid matrices. The theoretical aspects of the approach are described, as well as the range of commercial apparatus that is currently available. Approaches for method development for PFE are described, as well as a range of applications including approaches for parameter optimization, in situ clean-up (also known as selective PFE) and shape selective, fractionation PFE. Chapter 8 describes the use of microwave-assisted extraction (MAE) for the recovery of organic compounds from solid matrices. Instrumentation for both atmospheric and pressurized MAE are highlighted, with the latter dominating in its applicability. A range of applications is considered, as well as some recommendations on the use of MAE in analytical sciences. Chapter 9 considers developments in matrix solid phase dispersion (MSPD) for solid samples. The procedure for performing MSPD is highlighted, as well as its applicability to a range of sample types. A range of factors that can influence

19 Preface xvii MSPD is then discussed. Finally, a comparison between MSPD and solid phase extraction is made. Chapter 10 describes the technique of supercritical fluid extraction (SFE). After an initial description of what is a supercritical fluid, the option of carbon dioxide as the fluid of choice is discussed. A detailed description of the instrumentation for SFE is outlined, together with the options for adding modifiers to the system. Finally, a range of applications for SFE in analytical sciences is described. Chapter 11 considers the analysis of volatile organic compounds (VOCs) in gaseous samples. A discussion on the techniques for air sampling, including whole air collection in containers, enrichment into solid sorbents (active and passive sampling), desorption techniques and on-line sampling, is also included. Chapter 12 includes a detailed discussion on the important extraction method criteria, namely, sample mass/volume, extraction time, solvent type and consumption, extraction method, sequential or simultaneous extraction, method development time, operator skill, equipment cost, level of automation and extraction method approval. This chapter then considers the above criteria in the context of comparing extraction techniques for (semi-) solid samples and liquid samples. A comparison is also made of the approaches for air samples. In addition, this chapter also considers the role and use of certified reference materials. The final chapter (Chapter 13) considers the resources available when considering the use of extraction techniques in analytical sciences. The role of the Worldwide Web in accessing key sources of information (publishers, companies supplying instrumentation and consumables, institutions and databases) is highlighted. John R. Dean Northumbria University, Newcastle, UK

20

21 Acknowledgements This present text includes material which has previously appeared in three of the author s earlier books, i.e. Extraction Methods for Environmental Analysis (1998), Methods for Environmental Trace Analysis (AnTS Series, 2003) and Bioavailability, Bioaccessibility and Mobility of Environmental Contaminants (AnTS Series, 2007), all published by John Wiley & Sons, Ltd. The author is grateful to the copyright holders for granting permission to reproduce figures and tables from his three earlier publications. Dr Marisa Intawongse is acknowledged for her assistance with the compilation of Chapters 3 and 4. Dr Pinpong Kongchan is thanked for the drawing of Figures 6.3, 8.2, 8.3, 8.5 and 8.6, Dr Michael Deary for providing Figure 1.1 and Naomi Dean for the drawing of Figures 1.5 and 1.6. The front cover shows a photograph of Sycamore Gap located on Hadrian s Wall in Northumberland, UK, where the tree, sky and ground symbolize the areas of soil, air and water aspects of this book. This location was used in the 1991 film Robin Hood Prince of Thieves starring Kevin Costner and so to my family it is known as Robin s tree Robin Hood is also immortalized in my family with the phrase after them you hools!. Picture provided by John R. Dean, Northumbria University, Newcastle, UK.

22

23 Acronyms, Abbreviations and Symbols ACN ACS AOAC APCI ASE ASTM BAM BCR BNAs BTEX CAR CI COSHH CRM DCM DIN DVB ECD EI ES EU EVACS FDA FID GC acetonitrile American Chemical Society Association of Official Analytical Chemists atmospheric pressure chemical ionization accelerated solvent extraction American Society for Testing and Materials The Federal Institute for Materials Research and Testing Community Bureau of Reference bases, neutral species, acids benzene, toluene, ethylbenzene and xylenes carboxen chemical ionization Control of Substances Hazardous to Health certified reference material dichloromethane Deutsches Institut für Normung divinylbenzene electron capture detector electron impact electrospray European Union evaporative concentration system Food and Drug Administration flame ionization detector gas chromatography

24 xxii Extraction Techniques in Analytical Sciences HPLC high performance liquid chromatography HS headspace HTML hypertext markup language ICP inductively coupled plasma ID GC MS isotope dilution gas chromatography mass spectrometry IR infrared IRMM Institute for Reference Materials and Measurements IT MS ion trap mass spectrometry LC liquid chromatography LDPE low-density polyethylene LGC Laboratory of the Government Chemist LLE liquid liquid extraction LOD limit of detection LOQ limit of quantitation MAE microwave accelerated extraction MCL maximum concentration level MEPS microextraction in a packed syringe MESCO membrane enclosed-sorptive coating MIP molecularly imprinted polymer MS mass spectrometry MSD mass selective detector MSPD matrix solid phase dispersion NIST National Institute of Science and Technology NMIJ National Metrology Institute of Japan NP (HPLC) normal phase (high performance liquid chromatography) NRC National Research Council (of Canada) NRCCRM National Research Centre for Certified Reference Materials NWRI National Water Research Institute ODS octadecylsilane PAHs polycyclic aromatic hydrocarbons PCBs polychlorinated biphenyls pdf portable document format PDMS polydimethylsiloxane PEEK poly(ether ether ketone) PFAs perfluoroalkoxy fluorocarbons PFE pressurized fluid extraction PHWE pressurized hot water extraction PLE pressurized liquid extraction POCIS polar organic chemical integrative sampler POPs persistent organic pollutants ppb parts per billion (10 9 )

25 Acronyms, Abbreviations and Symbols xxiii ppm parts per million (10 6 ) ppt parts per thousand (10 3 ) PSE pressurized solvent extraction PTV programmed temperature vaporizer PVC poly(vinyl chloride) QA quality assurance RAM restricted access media RP (HPLC) reversed phase (high performance liquid chromatography) RSC The Royal Society of Chemistry RSD relative standard deviation SCX strong cation exchange SBSE stir-bar sorptive extraction SDME single drop microextraction SFC supercritical fluid chromatography SFE supercritical fluid extraction SIM single (or selected) ion monitoring SPE solid phase extraction SPLE selective pressurized liquid extraction SPMD semipermeable membrane device SPME solid phase microextraction SSSI site of special scientific interest SI (units) Système International (d Unitès) (International System of Units) TFM tetrafluoromethoxy (polymer) TIC total ion current TOF MS time-of-flight mass spectrometry TSD thermionic specific detector URL uniform resource locator USEPA United States Environmental Protection Agency UV ultraviolet VOCs volatile organic compounds WWW Worldwide Web c D E f I K d K ow log P m speed of light; concentration distribution ratio energy; electric field strength (linear) frequency electric current distribution coefficient octanol water partition coefficient log of octanol water partition coefficient mass

26 xxiv Extraction Techniques in Analytical Sciences P R t V z λ ν σ σ 2 pressure molar gas constant time; Student factor electric potential ionic charge wavelength frequency (of radiation) measure of standard deviation variance

27 About the Author John R. Dean, B.Sc., M.Sc., Ph.D., D.I.C., D.Sc., FRSC, C.Chem., C.Sci., Cert. Ed., Registered Analytical Chemist John R. Dean took his first degree in Chemistry at the University of Manchester Institute of Science and Technology (UMIST), followed by an M.Sc. in Analytical Chemistry and Instrumentation at Loughborough University of Technology, and finally a Ph.D. and D.I.C. in Physical Chemistry at the Imperial College of Science and Technology (University of London). He then spent two years as a postdoctoral research fellow at the Food Science Laboratory of the Ministry of Agriculture, Fisheries and Food in Norwich, in conjunction with the Polytechnic of the South West in Plymouth (now the University of Plymouth). His work there was focused on the development of directly coupled high performance liquid chromatography and inductively coupled plasma mass spectrometry methods for trace element speciation in foodstuffs. This was followed by a temporary lectureship in Inorganic Chemistry at Huddersfield Polytechnic (now the University of Huddersfield). In 1988, he was appointed to a lectureship in Inorganic/Analytical Chemistry at Newcastle Polytechnic (now Northumbria University). This was followed by promotion to Senior Lecturer (1990), Reader (1994), Principal Lecturer (1998) and Associate Dean (Research) (2004). He was also awarded a personal chair in In 2008 he became the Director of The Graduate School at Northumbria University as well as Professor of Analytical and Environmental Sciences in the School of Applied Sciences. In 1998, he was awarded a D.Sc. (University of London) in Analytical and Environmental Science and was the recipient of the 23rd Society for Analytical Chemistry (SAC) Silver Medal in He has published extensively in analytical and environmental science. He is an active member of The Royal Society of Chemistry (RSC) Analytical Division, having served as a member of the Atomic

28 xxvi Extraction Techniques in Analytical Sciences Spectroscopy Group for 15 years (10 as Honorary Secretary) as well as a Past Chairman ( ). He has served on the RSC Analytical Division Council for three terms and is a former Vice-President ( ), as well as a past-chairman of the North-East Region of the RSC ( ).

29 Chapter 1 Pre- and Post-Extraction Considerations Learning Objectives To appreciate the wide ranging types of organic compounds that are investigated in environmental and food matrices. Using an example, to be aware of pre-sampling issues associated with a contaminated land site. To be aware of the information required for a desk-top study (in a contaminated land situation). To understand the different sampling strategies associated with solid, aqueous and air samples. To be aware of the different types of contaminant distribution on a site. To understand the practical aspects of soil and sediment sampling. To understand the practical aspects of water sampling. To understand the practical aspects of air sampling. To be aware of the different analytical techniques available to analyse organic compounds. To understand and explain the principle of operation of a gas chromatography system. To understand and explain the principle of operation of a high performance liquid chromatography system. To be able to understand the principles of quantitative chromatographic analysis. Extraction Techniques in Analytical Sciences 2009 John Wiley & Sons, Ltd John R. Dean

30 2 Extraction Techniques in Analytical Sciences To be aware of the approaches and limitations for sample pre-concentration in the analysis of organic compounds. To appreciate the importance of quality assurance in quantitative analysis. To understand the health and safety aspects of performing laboratory work and the consequences for non-compliance. 1.1 Introduction This book is concerned with the removal of organic compounds, principally persistent organic compounds (POPs), from a range of sample matrices including environmental matrices (soil, water and air samples), but also some other matrices including foodstuffs. The book is designed to be an informative guide to a range of extraction techniques that are used to remove organic compounds from various matrices. The use of discussion questions (DQs) and self-assessment questions (SAQs) throughout the text should allow you (the reader) to think about the main issues and to allow you to consider alternative approaches. 1.2 Organic Compounds of Interest The range of organic compounds of interest in the environment and in other matrices varies enormously. They range from simple aromatic cyclic structures, for example, benzene, toluene, ethylbenzene and xylene(s) (collectively known as BTEX), to larger molecular weight compounds, such as polycyclic aromatic hydrocarbons (PAHs), and more complicated structures, e.g. pesticides and polychlorinated biphenyls (PCBs). A list of organic compounds that are measured in environmental (and other) matrices is shown in Table 1.1. SAQ 1.1 What are the important physical and chemical properties of these organic compounds that are useful to know when extracting them from sample matrices? 1.3 Pre-Sampling Issues Prior to sampling it is necessary to consider a whole range of issues that are directly/indirectly going to influence the quality of the final data that is produced after what is often a long and costly process. Therefore it is imperative to think