Environmental trace analysis techniques and applications

Dean Environmental Trace Analysis T E C H N I Q U E S A N D A P P L I C AT I O N S Department of Applied Sciences, Northumbria University, UK Increasing environmental regulations have resulted in the need for new methods of analysis for environmental samples A number of techniques have been developed that reduce or eliminate the need for toxic organic solvents to be used, and the field of environmental trace analysis continues to develop and expand both in terms of its application and in the range of analytical techniques that are applied Building upon the knowledge presented in the author’s previous title, Methods for Environmental Trace Analysis, this book provides new areas of investigation and over 10 years of developments Environmental Trace Analysis: Techniques and Applications covers the essentials of • • • • • • • good laboratory housekeeping making and recording practical results principles of quantitative analysis sampling protocols and sample storage sample preparation for inorganic analysis sample preparation for organic analysis the wide range of analytical techniques that are applied to environmental trace elemental and organic analyses Including case studies that highlight the application of the techniques, this book is intended to provide practical information and a comparison of methods applied to environmental samples This text is suitable for students studying environmental science as well as related chemistry and biology study programmes Also available as an e-book Tai Lieu Chat Luong ISBN 978-1-119-96271-7 Environmental Trace Analysis : T E C H N I Q U E S A N D A P P L I C AT I O N S John R Dean Environmental Trace Analysis T E C H N I Q U E S A N D A P P L I C AT I O N S John R Dean Environmental Trace Analysis Environmental Trace Analysis Techniques and Applications John R Dean Department of Applied Sciences, Northumbria University, UK This edition first published 2014 # 2014 John Wiley & Sons, Ltd Registered office JJohn 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 www wiley.com 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 1988 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 Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose It is sold on the understanding that the publisher is not engaged in rendering professional services and neither the publisher nor the author shall be liable for damages arising herefrom If professional advice or other expert assistance is required, the services of a competent professional should be sought 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 Dean, John R., author Environmental trace analysis : techniques and applications / John R Dean pages cm Includes bibliographical references and index ISBN 978-1-119-96270-0 (hardback) — ISBN 978-1-119-96271-7 (pbk.) Trace analysis—Methodology Environmental chemistry—Methodology Sampling I Title TD193.D428 2014 2013024965 577.270280 7–dc23 A catalogue record for this book is available from the British Library HB ISBN: 978-1-119-96270-0 PB ISBN: 978-1-119-96271-7 Set in 10.5/13pt, Sabon by Thomson Digital, Noida, India 2014 To my wife Lynne And our children Sam and Naomi Contents About the Author xv Preface xvii Acknowledgements xix Acronyms and Abbreviations xxi Basic Laboratory Procedures 1.1 Introduction 1.2 Health and Safety Issues 1.3 Sample Handling: Solid Samples 1.4 Sample Handling: Liquid Samples 1.5 Sample Handling: Gases/Vapour Samples 1.6 Summary Further Reading 1 4 5 Investigative Approach for Environmental Analysis 2.1 Introduction 2.2 Recording of Practical Results 2.2.1 Useful Tips on Presenting Data in Tables 2.2.2 Useful Tips on Presenting Data in Graphical Form 2.2.3 Useful Tips for Templates for Presenting Data in Your Notebook 2.3 Significant Figures 2.4 Units 2.5 Summary 7 9 12 13 viii CONTENTS Appendix Example Template A: Sample Collection Example Template B: Sample Treatment Example Template C: Sample Preparation for Inorganic Analysis Example Template D: Instrumental Analysis Example Template E: Sample Preparation for Organic Analysis Example Template F: Instrumental Analysis Further Reading 14 14 14 15 17 18 20 20 Principles of Quantitative Environmental Analysis 3.1 Introduction 3.2 Preparing Solutions for Quantitative Work 3.3 Calibration Graphs 3.4 Limits of Detection/Quantitation 3.5 Calculations: Dilution or Concentration Factors 3.6 Quality Assurance 3.6.1 Certified Reference Materials 3.7 Summary References Further Reading 21 21 23 24 27 27 29 30 36 36 36 Environmental Sampling 4.1 Introduction 4.2 Sampling Soil (and Sediments) 4.3 Sampling Water 4.4 Sampling Air 4.5 Summary Further Reading 37 37 39 40 42 44 44 Storage of Samples for Analysis 5.1 Introduction 5.2 Choice of Storage Container for Liquid Samples 5.3 Preservation Techniques for Liquid Samples 5.4 Storage and Preservation of Solid Samples 5.5 Storage and Preservation of Gaseous Samples 5.6 Summary Further Reading 45 45 45 47 48 48 50 50 Preparation of Environmental Solid Samples for Inorganic Analysis 6.1 Introduction 6.2 Decomposition Techniques 51 51 53 240



ENVIRONMENTAL TRACE ANALYSIS concentration (in appropriate units) and c is the intercept of the line of best fit on the x-axis] Calculate, using the equation y ẳ mx ỵ c, the concentration (in appropriate units) of the sample based on its generated signal response [Practical point: this can be done by re-arranging the equation y ẳ mx ỵ c such that the concentration of the sample, x, can be determined as follows: x ¼ (y  c)/m] Then, establish the dilution/concentration factor associated with the sample preparation (see Section 3.5) Calculate the concentration (in appropriate units) based on the dilution/concentration factor (in appropriate units) multiplied by the sample concentration (in appropriate units) as determined from the calibration graph Finally, check that the reported concentration in the original sample is in appropriate units Example 14.1 An aqueous sample was analysed by GC-FID for pentachlorophenol The sample was extracted by placing mL of the aqueous sample in to a separating funnel with  mL of dichloromethane The extract was quantitatively transferred to a volumetric flask (25 mL) and made up to volume with dichloromethane (including the addition of internal standard) A calibration plot was generated by diluting a 500 ppm stock solution of pentachlorophenol Then, mL of the stock solution was placed in a 10 mL volumetric flask and made up to the mark with acetone (working solution) This solution was diluted to make the following standard solutions: Flask PCP working solution (mL) Final volume (mL) GC–FID (signal) Diluted sample 0.00 0.50 1.50 3.00 6.00 10 10 10 10 10 1523 3567 6235 13563 8563 Plot a fully annotated calibration graph of signal response (y-axis) versus concentration (mg/mL) (x-axis) Then, determine the concentration SOME NUMERICAL WORKED EXAMPLES 241 of pentachlorophenol, in units of mg/mL, as determined from the graph Calculate the dilution/concentration factor and units of the sample extract Finally, determine the concentration of pentachlorophenol, in units of mg/L, in the original aqueous sample Answer 14.1
Determine the concentration of the working solutions 0; 2:5; 7:5; 15:0 and 30:0 ppm
Plot the calibration graph (concentration versus signal response) [Practical point: graph plotting can be done using either a suitable spreadsheet, for example Microsoft Excel, or on graph paper]
Determine the best fit for the calibration data If we assume that a straight line graph is obtained then the following applies [Practical point: if using a suitable spreadsheet, for example Microsoft Excel, then this can be done by selecting ‘add trendline’ followed by ‘display equation on chart’ and ‘display r squared value on chart’ If using graph paper manually plot the data points; then by using a ruler or flexi curve establish the best fit of the data points to each other Determine the intercept of the fitted line on the x-axis and calculate the slope of the line In either case you should now have the formula for a straight line equation that is y ẳ mx ỵ c, where y is the signal response, m is the slope of the graph, x is the concentration (in appropriate units) and c is the intercept of the line of best fit on the xaxis] 242 ENVIRONMENTAL TRACE ANALYSIS
Calculate, using the equation y ẳ mx ỵ c, the concentration (in appropriate units) of the sample based on its generated signal response [Practical point: this can be done by re-arranging the equation y ẳ mx ỵ c such that the concentration of the sample, x, can be determined as follows: x ¼ (y  c)/m] x ẳ y  cị=m x ẳ 8563  120:5ị=441:6 x ẳ 19:1 ppm
Then, establish the dilution/concentration factor associated with the sample preparation (see Section 3.5) Dilution=concentration factor is 25 mLị=5 mLị ẳ
Calculate the concentration (in appropriate units) based on the dilution/concentration factor (in appropriate units) multiplied by the sample concentration (in appropriate units) as determined from the calibration graph Concentration is 19:1 ppm  ¼ 95:5 ppm
Finally, check that the reported concentration in the original sample is in appropriate units The concentration of pentachlorophenol in the aqueous sample is 95.5 ppm, which is equivalent to 95.5 mg/mL or 95.5 mg/L Example 14.2 A soil sample was analysed for benzo(a)pyrene as follows An accurately weighed sample 2.1351 g was extracted The extract was quantitatively SOME NUMERICAL WORKED EXAMPLES 243 transferred to a volumetric flask (25 mL) and made up to volume with solvent A calibration plot was generated by diluting a 1000 mg/mL stock solutionof benzo(a)pyrene mLof the stock solutionwas placed ina 10 mL volumetric flask and made up to the mark with solvent (working solution) This solution was diluted to make the following standard solutions: Flask Extracted sample Benzo(a)pyrene working solution (mL) Final volume (mL) GC–MS (signal) 0.1 0.2 0.3 0.5 10 10 10 10 10 25 150 290 435 730 490 Plot a fully annotated calibration graph of signal response (y-axis) versus concentration (mg/mL) (x-axis) Then, determine the concentration of benzo(a)pyrene, in units of mg/mL, as determined from the graph Calculate the dilution/concentration factor and units of the sample extract Finally, determine the concentration of benzo(a)pyrene, in units of mg/kg, in the original sample Answer 14.2
Determine the concentration of the working solutions 0; 1; 2; and ppm:
Plot the calibration graph (concentration versus signal response) [Practical point: graph plotting can be done using either a suitable spreadsheet, for example Microsoft Excel, or on graph paper] 244 ENVIRONMENTAL TRACE ANALYSIS
Determine the best fit for the calibration data If we assume that a straight line graph is obtained then the following applies [Practical point: if using a suitable spreadsheet, for example Microsoft Excel, then this can be done by selecting ‘add trendline’ followed by ‘display equation on chart’ and ‘display r squared value on chart’ If using graph paper, manually plot the data points; then by using a ruler or flexi curve establish the best fit of the data points to each other Determine the intercept of the fitted line on the x-axis and calculate the slope of the line In either case you should now have the formula for a straight line equation that is y ẳ mx ỵ c, where y is the signal response, m is the slope of the graph, x is the concentration (in appropriate units) and c is the intercept of the line of best fit on the x-axis]
Calculate, using the equation y ¼ mx þ c, the concentration (in appropriate units) of the sample based on its generated signal response [Practical point: this can be done by re-arranging the equation y ẳ mx ỵ c such that the concentration of the sample, x, can be determined as follows: x ¼ (y  c)/m] x ¼ ðy  cÞ=m x ¼ ð490  0:81Þ=145:5 x ¼ 3:36 ppm or 3:36 mg=mL
Then, establish the dilution/concentration factor associated with the sample preparation (see Section 3.5) SOME NUMERICAL WORKED EXAMPLES 245 Dilution=concentration factor is ð25 mLị=2:1351 g ẳ 11:71 mL=g
Calculate the concentration (in appropriate units) based on the dilution/concentration factor (in appropriate units) multiplied by the sample concentration (in appropriate units) as determined from the calibration graph Concentration is 3:36 mg=mL  11:71 mL=g ¼ 39:3 mg=g
Finally, check that the reported concentration in the original sample is in appropriate units The concentration of benzo(a)pyrene in the soil sample is 39.3 mg/g, which is equivalent to 39.3 mg/kg Example 14.3 A 2.5324 g sample of contaminated soil was extracted in approximately 30 mL of nitric acid and made up to 100 mL in a volumetric flask with dilute acid This sample was analysed for Pb by FAAS and compared with values obtained from standard calibration solutions Construct an appropriately labelled calibration graph and determine the concentration of Pb in the soil sample (mg/kg) Standard calibration solutions (ppm) Absorbance 10 unknown 0.127 0.250 0.382 0.513 0.698 0.217 Answer 14.3
Determine the concentration of the working solutions Information is already provided in the table i:e: 0; 2; 4; 6; and 10 ppm:
Plot the calibration graph (concentration versus signal response) [Practical point: graph plotting can be done using either a suitable spreadsheet, for example Microsoft Excel, or on graph paper] 246 ENVIRONMENTAL TRACE ANALYSIS
Determine the best fit for the calibration data If we assume that a straight line graph is obtained then the following applies [Practical point: if using a suitable spreadsheet, for example Microsoft Excel, then this can be done by selecting ‘add trendline’ followed by ‘display equation on chart’ and ‘display r squared value on chart’ If using graph paper, manually plot the data points; then by using a ruler or flexi curve establish the best fit of the data points to each other Determine the intercept of the fitted line on the x-axis and calculate the slope of the line In either case you should now have the formula for a straight line equation, that is y ¼ mx þ c, where y is the signal response, m is the slope of the graph, x is the concentration (in appropriate units) and c is the intercept of the line of best fit on the x-axis]
Calculate, using the equation y ẳ mx ỵ c, the concentration (in appropriate units) of the sample based on its generated signal SOME NUMERICAL WORKED EXAMPLES 247 response [Practical point: this can be done by re-arranging the equation y ẳ mx ỵ c such that the concentration of the sample, x, can be determined as follows: x ¼ (y  c)/m] x ¼ y  cị=m x ẳ 0:217 ỵ 0:013ị=0:068 x ẳ 3:38 ppm or 3:38 mg=mL
Then, establish the dilution/concentration factor associated with the sample preparation (see Section 3.5) Dilution=concentration factor is 100 mL=2:5324 g ¼ 39:5 mL=g
Calculate the concentration (in appropriate units) based on the dilution/concentration factor (in appropriate units) multiplied by the sample concentration (in appropriate units) as determined from the calibration graph Concentration is 3:38 mg=mL  39:5 mL=g ¼ 133:5 mg=g
Finally, check that the reported concentration in the original sample is in appropriate units The concentration of Pb in the contaminated soil sample is 133.5 mg/g, which is equivalent to 134 mg/kg Example 14.4 A 1.0500 g sample of tea leaves was digested in approximately 30 mL of nitric acid and made up to 100 mL in a volumetric flask This sample was analysed for manganese by flame atomic absorption spectroscopy and compared with values obtained for standard calibration solutions The results are shown in the table below Standard calibration solutions (mg/mL) Absorbance 10 Unknown sample 0.145 0.289 0.397 0.586 0.740 0.265 248 ENVIRONMENTAL TRACE ANALYSIS Plot a fully annotated calibration graph of signal response (y-axis) versus concentration (mg/mL) (x-axis) Then, determine the concentration of Mn, in units of mg/mL, as determined from the graph Calculate the dilution/concentration factor and units of the sample extract Finally, determine the concentration of Mn, in units of %w/w, in the original tea sample Answer 14.4
Determine the concentration of the working solutions Information is already provided in the table that is 0, 2, 4, 6, and 10 ppm
Plot the calibration graph (concentration versus signal response) [Practical point: graph plotting can be done using either a suitable spreadsheet, for example Microsoft Excel, or on graph paper]
Determine the best fit for the calibration data If we assume that a straight line graph is obtained then the following applies [Practical point: if using a suitable spreadsheet, for example Microsoft Excel, then this can be done by selecting ‘add trendline’ followed by ‘display equation on chart’ and ‘display r squared value on chart’ If using graph paper, manually plot the data points; then by using a ruler or flexi curve establish the best fit of the data points to each other Determine the intercept of the fitted line on the x-axis and calculate the slope of the line In either case you should now have the formula for a straight line equation, that is y ¼ mx þ c, where y is the signal response, m is the slope of the graph, x is the SOME NUMERICAL WORKED EXAMPLES 249 concentration (in appropriate units) and c is the intercept of the line of best fit on the x-axis]
Calculate, using the equation y ẳ mx ỵ c, the concentration (in appropriate units) of the sample based on its generated signal response [Practical point: this can be done by re-arranging the equation y ẳ mx ỵ c such that the concentration of the sample, x, can be determined as follows: x ¼ (y  c)/m] x ¼ y  cị=m x ẳ 0:265 ỵ 0:007ị=0:073 x ẳ 3:73 mg=mL
Then, establish the dilution/concentration factor associated with the sample preparation (see Section 3.5) Dilution=concentration factor is 100 mL=1:0500 g ¼ 95:24 mL=g
Calculate the concentration (in appropriate units) based on the dilution/concentration factor (in appropriate units) multiplied by the sample concentration (in appropriate units) as determined from the calibration graph Concentration is 3:73 mg=mL  95:24 mL=g ¼ 355:2 mg=g
Finally, check that the reported concentration in the original sample is in appropriate units The concentration of Mn in the tea sample is 355.2 mg/g, which is equivalent to 355.2 mg/kg or 0.036%w/w Index 4-methylpentan-2-one 82 8-hydroxyquinoline 83 ball mill 51 biogenic (sources) 145 abscissa (axis) accelerated solvent extraction (ASE) 91, 206 accuracy 21 acetic acid extraction 65, 76, 199 acetonitrile-hexane partition (cleanup) 154 acid digestion 53, 55 acid-alkaline partition (clean-up) 153 alkaline decomposition (clean-up) 154 alumina 152 ammonium nitrate extraction 66, 76 ammonium pyrrolidine dithiocarbamate (APDC) 82 anthropogenic (sources) 42, 145 ashing 53 ashing aid 53 atmospheric precipitation 81 atomic absorption spectroscopy (AAS) 157, 158 atomic emission spectroscopy (AES) 157, 163 atomic fluorescence spectroscopy (AFS) 158, 167 atomic spectroscopy 157 auger 39 calcium chloride extraction 66, 76 calibration (graph) 24, 240, 243, 245, 248 Carboflow1 103 cation-exchange (resin) 83 ceramic dosimeter 143 certified reference material (CRM) 30, 197 chelation extraction 82 chelation ion exchange 83 Chelex-100 83 chemcatcher 141 CISED method 69 column chromatography (clean-up) 152 concentration factor 27 coning and quartering 40 contaminant–receptor–pathway 221, 224 contaminant (distribution) 37 Contaminated Land Exposure Assessment (CLEA) 230 continuous extraction 119 co-precipitation 84 COSHH critical point 105 Environmental Trace Analysis: Techniques and Applications, First Edition John R Dean Ó 2014 John Wiley & Sons, Ltd Published 2014 by John Wiley & Sons, Ltd 252 decomposition (techniques) 53 derivatization (for GC) 178 desk top study 37, 220 detailed quantitative risk assessment (DQRA) 219, 231 diethylenetriaminepentaacetic acid (DTPA) extraction 66, 76 dilution factor 27 diphenylthiocarbazone 82 discontinuous extraction 117 distribution coefficient 115 dithizone 83 drinking water 81 dry ashing 53 dynamic headspace (DHS) 131, 215 earthworms 72 emulsion (formation) 119 energy-dispersive (EDXRF) 173 Environment Agency (England and Wales) 217 error 21 estuarine water 81 ethylenediaminetetraacetic acid (EDTA) extraction 65, 75, 199 exchangeable fraction 202 extract clean-up 149 Fed Organic Estimation human Simulation Test (FOREhST) 108, 112 flame photometry 163 Florisil 152 flux 54 Fourier transform infra-red (FTIR) 188 fusion 54 gas chromatography (GC) 176 gas-blow down (evaporation) 149 gastric ỵ intestinal extraction 72 gastric extraction 71 gel permeation chromatography (cleanup) 153 Generic Assessment Criteria (GAC) 230 Generic Quantitative Risk Assessment (GQRA) 219, 225 good laboratory practice grinding (sample) 51 groundwater 81 INDEX hazard headspace extraction 128 high performance liquid chromatography (HPLC) 182 hydrofluoric acid 56 hydromatrix 98 hydrophilic (compounds) 116 hydrophobic (compounds) 116 inductively coupled plasma (ICP) 164 inductively coupled plasma mass spectrometry (ICP-MS) 168, 227 infra-red (IR) spectroscopy 188 in-situ clean-up 97 In-situ PFE absorbent 96 In-situ SFE absorbent 96 in-vitro gastrointestinal extraction 70, 77, 108, 204 ion chromatography 175 ion exchange (resin) 83 ion exchange (SPE) 122 ion-exchange chromatography (cleanup) 153 light sensitive compounds 48 limit of detection (LOD) 27 limit of quantitation (LOQ) 27 linear dynamic range 26 liquid phase microextraction 139 liquid-liquid extraction (LLE) 82, 115, 116 liquid-liquid microextraction 139 liquid-phase microextraction 139 liquid-solid extraction 85 man-made (sources) 145 mass concentration 23 mass spectrometry (MS) 168, 186, 188 matrix solid phase dispersion (MSPD) 107 membrane enclosed-sorptive coating (MESCO) 143 membrane extraction 140 methyl isobutyl ketone (MIBK) 82 micro organism degradation 48 microextraction in a packed syringe (MEPS) 137 microwave (digestion) 53, 58, 198, 227 INDEX microwave-assisted extraction (MAE) 100 microwave-assisted organic extraction 100 microwave-assisted solvent extraction (MASE) 100 molar concentration 23 mortar and pestle 51 muffle furnace 53 natural (sources) 42, 145 needle trap device (NTD) 139 non-passive sampling 42 normal phase (SPE) 121 oral bioaccessibility testing 204 ordinate (axis) oxidizable fraction 204 oxine 82 partition chromatography (cleanup) 153 passive sampling 42 phase diagram 104 phase ratio 130 photochemical degradation 48 photoionization detector (PID) 193 physiologically based extraction test (PBET) 70, 108, 204 pilot study 38 polar organic chemical integrative sampler (POCIS) 141 pollutant linkage 224 portable calorimetry 189 portable GC-MS 195 portable IR spectroscopy 192 portable Raman spectroscopy 193 portable techniques 189 portable X-ray fluorescence 189 precision 22 preliminary risk assessment 219 preservation techniques 47, 48 pressurised fluid extraction (PFE) 91, 206 pressurised liquid extraction 91, 206 purge and trap (extraction) 127 quality assurance 29 quality assurance scheme 29 253 random error 21 reducible fraction 203 regression 24 remediation 232 repeatability 22 reproducibility 22 reversed phase (SPE) 121 risk risk assessment rotary-film evaporation 150 rovap 150 salting out 120, 129 sample oxidation 48 sampling 37 selective PFE 97 semi-permeable membrane (SPM) 140 sequential extraction 67, 77, 201 shake-flask extraction 89 SI derived units 12 SI units 12 signal-to-noise ratio 27 significant figures 8, silica gel 152 simulated bile fluid 72, 79, 109, 114 simulated duodenal fluid 72, 78, 109, 113 simulated gastric fluid 71, 72, 78, 109, 113, 210 simulated saliva fluid 71, 72, 77, 109, 112 single drop microextraction (SDME) 139 single extraction 64, 199 site investigation 225 sodium diethyldithiocarbamate 83 sodium nitrate extraction 66, 76 Soil Guideline Values (SGVs) 230 solid phase extraction (SPE) 109, 115,120, 210 solid phase microextraction (SPME) 115, 132, 211 solvent evaporation 149 solvent microextraction 139 sonic bath 90 sonic probe 90 Soxhlet extraction 86 254 soxtec extraction 87 spatial variation 41 standard addition (method) 25 static headspace (SHS) 131 stir-bar sorptive extraction (SBSE) 135, 143 stock solution 21, 23 storage (sample) 45 storage container 45 sulfated ashing 53 sulfur (clean-up) 154 supercritical fluid extraction (SFE) 103 surface water 81 systematic error 22 Systeme International d’Unites (SI) 12 INDEX temporal variation 41 thermal desorption 147 ultrasonic extraction 90 uncertainty 22 unified bioaccessibility method (UBM) 71, 77, 112 waste water 81 wavelength-dispersive (WDXRF) 173 WeflonTM 103 X-ray diffraction (XRD) 176 X-ray fluorescence (XRF) spectroscopy 173