Sample preparation for trace element analysis XLI : comprehensive analytical chemistry

Contents Contributors to Vol XLI . . . . . . . . . . . . . . . . . . . . . . vi Volumes in the Series . . . . . . . . . . . . . . . . . . . . . . . xiii Series Editor¡¯s Preface. . . . . . . . . . . . . . . . . . . . . . . xliii Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xliv Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xlvi Chapter 1. Sampling and sample preservation for trace element analysis . . . . . . . . . . . . . . . . . . . . . . . . 1 Byron Kratochvil 1.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Preliminary considerations . . . . . . . . . . . . . . . 2 1.2.1 Sampling variability . . . . . . . . . . . . . . . . . . . . . 2 1.2.2 Sampling strategies. . . . . . . . . . . . . . . 2 1.2.3 Uncertainties in sampling . . . . . . . . . . . 3 1.3 Types of samples . . . . . . . . . . . . . . . . . . . . 3 1.3.1 Judgment samples . . . . . . . . . . . . . . . 3 1.3.2 Random samples . . . . . . . . . . . . . . . . 4 1.3.3 Systematic samples . . . . . . . . . . . . . . . 4 1.3.4 Subsamples . . . . . . . . . . . . . . . . . . . 5 1.3.5 Composite samples . . . . . . . . . . . . . . . 5 1.4 Planning the sampling operation . . . . . . . . . . . . 5 1.4.1 Defining goals. . . . . . . . . . . . . . . . . . 5 1.4.2 Sampling plans . . . . . . . . . . . . . . . . . 6 1.5 Statistical sampling. . . . . . . . . . . . . . . . . . . 8 1.5.1 Introduction. . . . . . . . . . . . . . . . . . . 8 1.5.2 Minimum number of increments . . . . . . . . 8 1.5.3 Minimum size of increments in well-mixed particulate populations . . . . . . . . . . . . . 9 1.5.4 Sample increment size in segregated populations . . . . . . . . . . . . . . . . . . . 10 1.5.5 From where should increments be taken? . . . 11 1.5.6 Model-based sampling . . . . . . . . . . . . . 12 xv 1.5.7 Balancing economic factors and purpose of data collection against sample quality . . . . . . . . 13 1.6 Sample handling and preservation during collection, transport, and storage . . . . . . . . . . . . . . . . . 14 1.6.1 Handling and storage of samples . . . . . . . . 14 1.6.2 Sampling equipment . . . . . . . . . . . . . . 16 1.6.3 Sample containers . . . . . . . . . . . . . . . 16 1.7 Quality assurance in sampling [24,25] . . . . . . . . . 17 1.7.1 Overall objectives . . . . . . . . . . . . . . . . 17 1.7.2 Quality control . . . . . . . . . . . . . . . . . 17 1.7.3 Quality assessment . . . . . . . . . . . . . . . 17 1.8 Glossary. . . . . . . . . . . . . . . . . . . . . . . . . 18 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Selected bibliography . . . . . . . . . . . . . . . . . . . . . 21 Chapter 2. Sources of analyte contamination and loss during the analytical process . . . . . . . . . . . . . . . . . . . . . . . 23 Gunter Knapp and Peter Schramel 2.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 23 2.2 Contamination . . . . . . . . . . . . . . . . . . . . . 24 2.2.1 Materials . . . . . . . . . . . . . . . . . . . . 24 2.2.2 Reagents . . . . . . . . . . . . . . . . . . . . 27 2.2.3 Airborne particles. . . . . . . . . . . . . . . . 28 2.3 Losses. . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.4 Sampling . . . . . . . . . . . . . . . . . . . . . . . . 34 2.5 Storage . . . . . . . . . . . . . . . . . . . . . . . . . 35 2.6 Drying and homogenisation. . . . . . . . . . . . . . . 37 2.7 Dilution, dissolution and digestion . . . . . . . . . . . 39 2.8 Separation and preconcentration . . . . . . . . . . . . 41 2.9 Element measurement . . . . . . . . . . . . . . . . . 42 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Chapter 3. Calibration approaches for trace element determination 47 Douglas C. Baxter and Ilia Rodushkin 3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 47 3.2 Basic assumptions and some terminology . . . . . . . 48 3.3 Selection of the calibration approach . . . . . . . . . . 49 3.4 Statistical evaluation of recovery data . . . . . . . . . 52 Contents xvi 3.5 Linear regression . . . . . . . . . . . . . . . . . . . . 55 3.5.1 Ordinary linear regression . . . . . . . . . . . 56 3.5.2 Weighted linear regression . . . . . . . . . . . 59 3.5.3 Linear regression for data with uncertainties in both variables. . . . . . . . . . . . . . . . . . 64 3.6 External calibration. . . . . . . . . . . . . . . . . . . 67 3.6.1 Estimating uncertainty . . . . . . . . . . . . . 68 3.6.2 Optimizing precision . . . . . . . . . . . . . . 70 3.6.3 Accounting for non-constant sensitivity . . . . 72 3.7 Method of standard additions. . . . . . . . . . . . . . 74 3.7.1 Estimating uncertainty . . . . . . . . . . . . . 75 3.7.2 Optimizing precision . . . . . . . . . . . . . . 76 3.7.3 Accounting for non-constant sensitivity . . . . 78 3.8 Internal standardization . . . . . . . . . . . . . . . . 79 3.8.1 Estimating uncertainty . . . . . . . . . . . . . 80 3.8.2 Optimizing precision . . . . . . . . . . . . . . 81 3.9 Isotope dilution . . . . . . . . . . . . . . . . . . . . . 81 3.9.1 Mass discrimination and detector dead time . . 85 3.9.2 Estimating uncertainty . . . . . . . . . . . . . 86 3.9.3 Optimizing precision . . . . . . . . . . . . . . 88 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 90 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 Chapter 4. Stated references for ensuring traceability of trace element analysis . . . . . . . . . . . . . . . . . . . . . . . . 93 Philippe Quevauviller 4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 93 4.2 Meaning of traceability for chemical measurements . . 94 4.3 SI units . . . . . . . . . . . . . . . . . . . . . . . . . 96 4.4 Documented standards . . . . . . . . . . . . . . . . . 96 4.5 Reference methods . . . . . . . . . . . . . . . . . . . 97 4.6 Reference materials. . . . . . . . . . . . . . . . . . . 99 4.6.1 The various categories of materials and related requirements . . . . . . . . . . . . . . . . . . 99 4.6.2 Production . . . . . . . . . . . . . . . . . . . 100 4.6.3 Methods used for material characterisation or certification . . . . . . . . . . . . . . . . . . . 102 xvii Contents 4.6.4 Use of reference materials . . . . . . . . . . . 102 4.6.5 Traceability of reference materials . . . . . . . 103 4.7 Specimen banking . . . . . . . . . . . . . . . . . . . 105 4.8 Proficiency testing . . . . . . . . . . . . . . . . . . . 105 4.9 Real-case achievement of traceability of trace element analysis . . . . . . . . . . . . . . . . . . . . 106 4.9.1 Total trace element determinations. . . . . . . 106 4.9.2 Operationally defined trace element determinations . . . . . . . . . . . . . . . . . 108 4.9.3 Determinations of chemical forms of elements . 110 4.10 Conclusions . . . . . . . . . . . . . . . . . . . . . . . 113 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 Chapter 5. Detection methods for the quantitation of trace elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 Les Ebdon, Andrew S. Fisher, Maria Betti and Maurice Leroy 5.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 117 5.2 Classical methods. . . . . . . . . . . . . . . . . . . . 117 5.3 Flame spectrometry. . . . . . . . . . . . . . . . . . . 118 5.3.1 Introduction. . . . . . . . . . . . . . . . . . . 118 5.3.2 Theory . . . . . . . . . . . . . . . . . . . . . 118 5.3.3 Instrumentation . . . . . . . . . . . . . . . . 119 5.3.4 Interferences and background correction techniques. . . . . . . . . . . . . . . . . . . . 121 5.3.5 Conventional nebulisation . . . . . . . . . . . 123 5.3.6 Alternative methods of sample introduction . . 127 5.4 Electrothermal AAS. . . . . . . . . . . . . . . . . . . 135 5.4.1 Introduction. . . . . . . . . . . . . . . . . . . 135 5.4.2 Conventional ET-AAS. . . . . . . . . . . . . . 136 5.4.3 Multi-element ET-AAS . . . . . . . . . . . . . 139 5.4.4 Chemical vapour generation.ET-AAS . . . . . 140 5.4.5 Speciation. . . . . . . . . . . . . . . . . . . . 141 5.5 Inductively coupled plasma-atomic emission spectrometry . . . . . . . . . . . . . . . . . . . . . . 142 5.5.1 Introduction. . . . . . . . . . . . . . . . . . . 142 5.5.2 Theory and interferences . . . . . . . . . . . . 142 xviii Contents 5.5.3 Instrumentation . . . . . . . . . . . . . . . . 143 5.5.4 Figures of merit. . . . . . . . . . . . . . . . . 152 5.6 Inductively coupled plasma-mass spectrometry . . . . 152 5.6.1 Introduction. . . . . . . . . . . . . . . . . . . 152 5.6.2 Theory . . . . . . . . . . . . . . . . . . . . . 153 5.6.3 Instrumentation . . . . . . . . . . . . . . . . 154 5.6.4 Different types of analysis . . . . . . . . . . . 156 5.6.5 Interferences . . . . . . . . . . . . . . . . . . 156 5.6.6 Sample introduction techniques . . . . . . . . 158 5.6.7 Figures of merit. . . . . . . . . . . . . . . . . 160 5.7 Atomic fluorescence spectrometry. . . . . . . . . . . . 160 5.7.1 Introduction. . . . . . . . . . . . . . . . . . . 160 5.7.2 Theory . . . . . . . . . . . . . . . . . . . . . 162 5.7.3 Instrumentation . . . . . . . . . . . . . . . . 162 5.7.4 Sample introduction . . . . . . . . . . . . . . 163 5.7.5 Interferences . . . . . . . . . . . . . . . . . . 163 5.7.6 Figures of merit. . . . . . . . . . . . . . . . . 163 5.8 Other atomic absorption, emission and fluorescence methods of detection . . . . . . . . . . . . . . . . . . 164 5.8.1 Microwave induced plasma . . . . . . . . . . . 164 5.8.2 Direct current plasma. . . . . . . . . . . . . . 165 5.9 Secondary ion mass spectrometry. . . . . . . . . . . . 165 5.9.1 Introduction. . . . . . . . . . . . . . . . . . . 165 5.9.2 Practical principles . . . . . . . . . . . . . . . 167 5.9.3 Sensitivity and quantification. . . . . . . . . . 168 5.10 Glow discharge mass spectrometry . . . . . . . . . . . 171 5.10.1 Introduction. . . . . . . . . . . . . . . . . . . 171 5.10.2 Glow discharge processes . . . . . . . . . . . . 173 5.10.3 Applications to trace element analysis . . . . . 175 5.11 X-ray fluorescence spectrometry . . . . . . . . . . . . 176 5.11.1 Introduction. . . . . . . . . . . . . . . . . . . 176 5.11.2 Instrumentation . . . . . . . . . . . . . . . . 177 5.11.3 Matrix effects . . . . . . . . . . . . . . . . . . 177 5.11.4 Quantitative and trace analysis . . . . . . . . 178 5.12 UV/Visible spectrophotometric and chemiluminescence techniques. . . . . . . . . . . . . . . . . . . . . . . . 179 5.12.1 UV/Visible spectrophotometric techniques . . . 179 xix Contents 5.12.2 Molecular fluorescence and chemiluminescence detection . . . . . . . . . . 181 5.13 Electrochemical methods . . . . . . . . . . . . . . . . 183 5.13.1 Differential pulse anodic stripping voltammetry 183 5.13.2 Cathodic and adsorptive stripping voltammetry 184 5.13.3 Ion selective electrodes . . . . . . . . . . . . . 185 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 DIGESTION AND EXTRACTION APPROACHES Chapter 6. Wet digestion methods . . . . . . . . . . . . . . . . . 193 Henryk Matusiewicz 6.1 Introduction and brief history . . . . . . . . . . . . . 193 6.2 Nomenclature. . . . . . . . . . . . . . . . . . . . . . 194 6.3 Bibliography . . . . . . . . . . . . . . . . . . . . . . 194 6.4 Reagents and vessel materials for wet digestion procedures . . . . . . . . . . . . . . . . . . . . . . . 195 6.5 Wet acid digestion (decomposition and dissolution) procedures . . . . . . . . . . . . . . . . . . . . . . . 199 6.5.1 Open systems . . . . . . . . . . . . . . . . . . 199 6.5.2 Closed systems . . . . . . . . . . . . . . . . . 203 6.5.3 Flow systems . . . . . . . . . . . . . . . . . . 210 6.5.4 Vapor-phase acid digestion (gas-phase reactions) 213 6.5.5 Efficiency of wet digestion (decomposition and dissolution) procedures . . . . . . . . . . . . . 216 6.5.6 Comparison of wet digestion techniques . . . . 219 6.5.7 Digestion systems (instrumentation, equipment, automation) . . . . . . . . . . . . 220 6.5.8 Safety of acid digestions (sample acid digestion safety). . . . . . . . . . . . . . . . . 221 6.6 Conclusions and future trends . . . . . . . . . . . . . 224 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 Chapter 7. Dry ashing . . . . . . . . . . . . . . . . . . . . . . . 235 Michel Hoenig 7.1 General considerations . . . . . . . . . . . . . . . . . 235 7.2 Why dry ashing? . . . . . . . . . . . . . . . . . . . . 238 7.3 Oxidation process and dissolution of the residue . . . . 240 Contents xx 7.3.1 Particular case of plant matrices . . . . . . . . 243 7.4 Methodology . . . . . . . . . . . . . . . . . . . . . . 244 7.4.1 Heating devices . . . . . . . . . . . . . . . . . 244 7.4.2 Ashing vessels . . . . . . . . . . . . . . . . . 245 7.4.3 Influence of the sample composition . . . . . . 246 7.4.4 Operating modes for environmental samples . . 246 7.5 Particular cases of arsenic and selenium . . . . . . . . 248 7.5.1 Ashing aids . . . . . . . . . . . . . . . . . . . 250 7.5.2 What to do? . . . . . . . . . . . . . . . . . . . 251 7.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . 253 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 Chapter 8. Microwave based extraction . . . . . . . . . . . . . . 257 Edward E. King and David Barclay 8.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 257 8.2 Brief history of industrial microwave devices. . . . . . 257 8.3 Microwave theory . . . . . . . . . . . . . . . . . . . . 258 8.4 Microwave laboratory equipment. . . . . . . . . . . . 263 8.4.1 Magnetron . . . . . . . . . . . . . . . . . . . 264 8.4.2 Power application. . . . . . . . . . . . . . . . 267 8.4.3 Waveguide . . . . . . . . . . . . . . . . . . . 267 8.4.4 Microwave cavity . . . . . . . . . . . . . . . . 267 8.4.5 Reflected energy . . . . . . . . . . . . . . . . 267 8.4.6 Mode stirrer and turntables . . . . . . . . . . 268 8.4.7 Microwave compatible materials . . . . . . . . 269 8.5 Vessels . . . . . . . . . . . . . . . . . . . . . . . . . 270 8.5.1 Materials . . . . . . . . . . . . . . . . . . . . 271 8.5.2 Structural components . . . . . . . . . . . . . 272 8.5.3 Safety . . . . . . . . . . . . . . . . . . . . . . 272 8.5.4 Closed vessels. . . . . . . . . . . . . . . . . . 273 8.5.5 Vent and reseal vessels . . . . . . . . . . . . . 274 8.5.6 Open vessels . . . . . . . . . . . . . . . . . . 274 8.6 Control systems. . . . . . . . . . . . . . . . . . . . . 275 8.6.1 Power/time . . . . . . . . . . . . . . . . . . . 275 8.6.2 Pressure. . . . . . . . . . . . . . . . . . . . . 275 8.6.3 Temperature . . . . . . . . . . . . . . . . . . 278 xxi Contents 8.6.4 Power optimization feedback . . . . . . . . . . 280 8.7 Methodology . . . . . . . . . . . . . . . . . . . . . . 281 8.7.1 Pressurized closed vessel extractions . . . . . . 282 8.7.2 Atmospheric open vessel extractions . . . . . . 283 8.8 Sample types . . . . . . . . . . . . . . . . . . . . . . 285 8.8.1 Inorganic . . . . . . . . . . . . . . . . . . . . 285 8.8.2 Leaches and other partial extractions . . . . . 286 8.8.3 Complete dissolutions . . . . . . . . . . . . . . 287 8.8.4 High-temperature extractions . . . . . . . . . 288 8.8.5 Complex sequential extractions. . . . . . . . . 290 8.8.6 Organic . . . . . . . . . . . . . . . . . . . . . 291 8.8.7 Carbohydrates . . . . . . . . . . . . . . . . . 292 8.8.8 Proteins . . . . . . . . . . . . . . . . . . . . . 293 8.8.9 Fats, oils, and waxes . . . . . . . . . . . . . . 294 8.9 Advanced applications . . . . . . . . . . . . . . . . . 297 8.9.1 Clean chemistry. . . . . . . . . . . . . . . . . 297 8.9.2 Concentration/evaporation . . . . . . . . . . . 297 8.10 Conclusions . . . . . . . . . . . . . . . . . . . . . . . 298 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 299 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 Chapter 9. Fusion and fluxes . . . . . . . . . . . . . . . . . . . 301 Fernand Claisse 9.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 301 9.2 Fusion in lithium borates . . . . . . . . . . . . . . . . 301 9.2.1 General . . . . . . . . . . . . . . . . . . . . . 301 9.3 The key to successful fusion beads . . . . . . . . . . . 305 9.3.1 The concept of ¡°neutrality¡± . . . . . . . . . . . 305 9.3.2 The optimal flux and crystallization . . . . . . 306 9.3.3 Cracking of fused beads . . . . . . . . . . . . . 307 9.3.4 Loss and retention of sulfur. . . . . . . . . . . 308 9.4 Application to trace element analysis. . . . . . . . . . 308 9.4.1 Maximizing X-ray intensities . . . . . . . . . . 308 9.4.2 Minimizing background. . . . . . . . . . . . . 309 9.5 Features of fusion for trace elements . . . . . . . . . . 309 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 310 xxii Contents Chapter 10. Supercritical fluid extraction . . . . . . . . . . . . . 313 Roberto Alzaga, Sergi D©¥¢¥ez and Josep M. Bayona 10.1 Properties of supercritical fluids . . . . . . . . . . . . 313 10.2 Instrumentation . . . . . . . . . . . . . . . . . . . . 316 10.2.1 Experimental solubility measurements. . . . . 318 10.3 SFE of trace elements. . . . . . . . . . . . . . . . . . 318 10.3.1 Ligand solubility in SFs. . . . . . . . . . . . . 326 10.3.2 Complex.SF solubility . . . . . . . . . . . . . 328 10.3.3 SFE process. . . . . . . . . . . . . . . . . . . 328 10.4 Organometallic compounds . . . . . . . . . . . . . . . 332 10.4.1 Organotin compounds. . . . . . . . . . . . . . 332 10.4.2 Organomercury compounds . . . . . . . . . . . 338 10.4.3 Organolead compounds . . . . . . . . . . . . . 339 10.4.4 Arsenic compounds . . . . . . . . . . . . . . . 339 10.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . 339 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Chapter 11. Accelerated solvent extraction of organometallic and inorganic compounds . . . . . . . . . . . . . . . . . . . 343 John L. Ezzell 11.1 Accelerated solvent extraction as a sample preparation technique . . . . . . . . . . . . . . . . . 343 11.1.1 Introduction. . . . . . . . . . . . . . . . . . . 343 11.1.2 Basic principles of ASE operation. . . . . . . . 344 11.1.3 ASE instrumentation . . . . . . . . . . . . . . 345 11.1.4 ASE methods development . . . . . . . . . . . 346 11.1.5 Application areas . . . . . . . . . . . . . . . . 349 11.1.6 Summary . . . . . . . . . . . . . . . . . . . . 351 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 352 Chapter 12. Sonication as a sample preparation method for elemental analysis . . . . . . . . . . . . . . . . . . . . . . . 353 Kevin Ashley 12.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 353 12.2 Methodological considerations . . . . . . . . . . . . . 354 12.3 Historical background . . . . . . . . . . . . . . . . . 357 xxiii Contents 12.4 Applications.sonication and sample preparation . . . 358 12.4.1 Environmental analysis. . . . . . . . . . . . . 358 12.4.2 Industrial hygiene . . . . . . . . . . . . . . . 360 12.4.3 Biological tissues and fluids. . . . . . . . . . . 363 12.4.4 Other applications . . . . . . . . . . . . . . . 364 12.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . 366 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 Chapter 13. Solid phase microextraction as a tool for trace element determination . . . . . . . . . . . . . . . . . . . . . 371 Zolta¢¥n Mester and Ralph Sturgeon 13.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 371 13.2 General description of solid phase microextraction . . . 373 13.2.1 Extraction modes . . . . . . . . . . . . . . . . 373 13.2.2 Coatings. . . . . . . . . . . . . . . . . . . . . 375 13.3 Solid phase microextraction: step-by-step method development. . . . . . . . . . . . . . . . . . . . . . . 375 13.3.1 Extraction mode selection. . . . . . . . . . . . 375 13.3.2 Fiber coating selection . . . . . . . . . . . . . 376 13.3.3 Derivatization method selection . . . . . . . . 376 13.3.4 Optimization of desorption conditions . . . . . 376 13.3.5 Sample volume optimization . . . . . . . . . . 376 13.3.6 Optimization of the extraction time. . . . . . . 377 13.3.7 Optimization of extraction conditions. . . . . . 377 13.3.8 Determination of the linear dynamic range. . . 378 13.3.9 Selection of the calibration method . . . . . . . 378 13.3.10 Precision of the method . . . . . . . . . . . . . 379 13.3.11 Automation of the method . . . . . . . . . . . 379 13.4 Solid phase microextraction for speciation analysis . . 380 13.4.1 Volatile metal species.gas chromatographic determination. . . . . . . . . . . . . . . . . . 380 13.5 Solid phase microextraction as an investigative tool . . 388 13.6 Limitations of solid phase microextraction . . . . . . . 388 13.7 Isotope dilution calibration in combination with solid phase microextraction. . . . . . . . . . . . . . . . . . 389 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 390 xxiv Contents Chapter 14. Solid-phase extraction . . . . . . . . . . . . . . . . 393 Vale¢¥rie Camel 14.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 393 14.2 Theory . . . . . . . . . . . . . . . . . . . . . . . . . 393 14.2.1 Presentation of the technique. . . . . . . . . . 394 14.2.2 Operation . . . . . . . . . . . . . . . . . . . . 400 14.2.3 Advantages of the technique . . . . . . . . . . 403 14.3 Step-by-step method development guide . . . . . . . . 410 14.3.1 Selection of solid sorbent . . . . . . . . . . . . 410 14.3.2 Influential parameters . . . . . . . . . . . . . 432 14.4 Applications of SPE to the determination of some trace elements . . . . . . . . . . . . . . . . . . . . . 439 14.4.1 Chromium. . . . . . . . . . . . . . . . . . . . 439 14.4.2 Iron . . . . . . . . . . . . . . . . . . . . . . . 443 14.4.3 Mercury. . . . . . . . . . . . . . . . . . . . . 445 14.4.4 Selenium . . . . . . . . . . . . . . . . . . . . 445 14.4.5 Tin . . . . . . . . . . . . . . . . . . . . . . . 445 14.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . 450 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 451 Chapter 15. Chelation solvent extraction for separation of metal ions . . . . . . . . . . . . . . . . . . . . . . . . . . . 459 Hideyuki Itabashi and Taketoshi Nakahara 15.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 459 15.2 Theoretical considerations . . . . . . . . . . . . . . . 460 15.2.1 General principles . . . . . . . . . . . . . . . 460 15.2.2 Preconcentration of metal ions . . . . . . . . . 465 15.2.3 Mutual separation of metal ions . . . . . . . . 467 15.2.4 Speciation of metal ions in natural water. . . . 472 15.3 Adsorption of metal ions using chelating resins . . . . 474 15.3.1 General principles . . . . . . . . . . . . . . . 475 15.3.2 Features of some chelating resins . . . . . . . 475 15.4 Application of chelation to sample preparation for trace metal analysis. . . . . . . . . . . . . . . . . . . 477 15.4.1 Procedure for the extraction of metal ions from natural waters. . . . . . . . . . . . . . . 477 xxv Contents 15.4.2 Procedure for the extraction of metal ions from high-purity materials and inorganic solid samples . . . . . . . . . . . . . . . . . . 488 15.4.3 Procedure for the extraction of metal ions from biological samples . . . . . . . . . . . . . 490 15.4.4 Procedure for the speciation of metal ions in natural waters . . . . . . . . . . . . . . . . . 491 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 492 Chapter 16. Cryogenic trapping for speciation analysis . . . . . . 495 Marie-Pierre Pavageau, Eva Krupp, Alberto de Diego, Christophe Pe¢¥cheyran and Olivier F.X. Donard 16.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 495 16.2 Definition of volatile species . . . . . . . . . . . . . . 502 16.3 Physico-chemical principles and processes associated with cryofocusing . . . . . . . . . . . . . . . . . . . . 504 16.4 Analytical constraints. . . . . . . . . . . . . . . . . . 509 16.4.1 Removal of CO2 . . . . . . . . . . . . . . . . . 510 16.4.2 Water removal . . . . . . . . . . . . . . . . . 512 16.5 Sample preservation and stability . . . . . . . . . . . 517 16.6 Instrumentation for cryogenic trapping and selected applications. . . . . . . . . . . . . . . . . . . . . . . 520 16.6.1 Cryosampler for determination of industrial and environmental VMCs . . . . . . . . . . . 520 16.6.2 Cryogenic trapping for speciation analysis . . . 523 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 529 Chapter 17. Biotrapping as an alternative to metal preconcentration and speciation . . . . . . . . . . . . . . . . 533 Yolanda Madrid and Carmen Ca¢¥mara 17.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 533 17.2 General characteristics of biological substrates. . . . . 535 17.2.1 Algae . . . . . . . . . . . . . . . . . . . . . . 535 17.2.2 Bacteria. . . . . . . . . . . . . . . . . . . . . 536 17.2.3 Fungi . . . . . . . . . . . . . . . . . . . . . . 537 xxvi Contents 17.3 Uptake mechanisms . . . . . . . . . . . . . . . . . . 538 17.4 Working procedures. . . . . . . . . . . . . . . . . . . 541 17.4.1 Immobilisation . . . . . . . . . . . . . . . . . 541 17.5 Applications. . . . . . . . . . . . . . . . . . . . . . . 546 17.5.1 Analytical applications . . . . . . . . . . . . . 546 17.5.2 Technological applications . . . . . . . . . . . 556 17.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . 557 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 557 Chapter18 Membrane extraction . . . . . . . . . . . . . . . . . . . . . 559 Jan A ¢ª ke Jo¡§nsson and Lennart Mathiasson 18.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 559 18.2 Membrane extraction techniques . . . . . . . . . . . . 559 18.2.1 Supported liquid membrane extraction (SLM) . 560 18.2.2 Microporous membrane liquid liquid extraction (MMLLE) . . . . . . . . . . . . . . 565 18.3 Chemical principles for metal extraction . . . . . . . . 566 18.4 Properties of membrane extraction . . . . . . . . . . . 566 18.4.1 Clean-up and selectivity . . . . . . . . . . . . 567 18.4.2 Enrichment . . . . . . . . . . . . . . . . . . . 568 18.4.3 Automation and unattended operation . . . . . 569 18.4.4 Solvent consumption . . . . . . . . . . . . . . 570 18.5 Experimental set-up . . . . . . . . . . . . . . . . . . 570 18.5.1 Flow systems for membrane extraction. . . . . 570 18.5.2 How to set up a membrane extraction experiment for metal ions. . . . . . . . . . . . 571 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 574 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 574 Chapter 19. Derivatization and vapor generation methods for trace element analysis and speciation . . . . . . . . . . . . . 577 Yong Cai 19.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 577 19.2 Theory . . . . . . . . . . . . . . . . . . . . . . . . . 578 19.2.1 Grignard reactions . . . . . . . . . . . . . . . 578 19.2.2 Hydride generation . . . . . . . . . . . . . . . 579 xxvii Contents 19.2.3 Aqueous derivatization with tetraalkyl (aryl)borates . . . . . . . . . . . . . . . . . . 580 19.3 Method development . . . . . . . . . . . . . . . . . . 583 19.3.1 Grignard reactions . . . . . . . . . . . . . . . 583 19.3.2 Aqueous derivatization . . . . . . . . . . . . . 584 19.4 Applications. . . . . . . . . . . . . . . . . . . . . . . 585 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 590 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 590 Chapter 20. Laser ablation sampling . . . . . . . . . . . . . . . 593 Richard E. Russo and David P. Baldwin 20.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 593 20.2 Experimental system . . . . . . . . . . . . . . . . . . 594 20.3 Ablation detection systems . . . . . . . . . . . . . . . 599 20.4 Calibration . . . . . . . . . . . . . . . . . . . . . . . 601 20.5 Fractionation . . . . . . . . . . . . . . . . . . . . . . 603 20.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . 604 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 606 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 606 Chapter 21. Flow injection techniques for sample pretreatment . . 611 Zhao-Lun Fang 21.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 611 21.1.1 General . . . . . . . . . . . . . . . . . . . . . 611 21.1.2 General features of flow injection on-line sample pretreatment systems. . . . . . . . . . 612 21.1.3 Classification of FI sample pretreatment systems. . . . . . . . . . . . . . . . . . . . . 612 21.1.4 Principles and general guidelines for the development of FI systems . . . . . . . . . . . 613 21.1.5 Practical hints for manipulation of FI equipment 614 21.2 FI liquid.liquid extraction systems. . . . . . . . . . . 615 21.2.1 Introduction. . . . . . . . . . . . . . . . . . . 615 21.2.2 Apparatus for FI liquid.liquid extraction . . . 617 21.2.3 Guidelines for the development of FI liquid.liquid extraction systems . . . . . . . . 623 21.2.4 Typical manifolds for FI liquid.liquid extraction 624 21.3 FI solid phase extraction systems. . . . . . . . . . . . 626 Contents xxviii 21.3.1 Introduction. . . . . . . . . . . . . . . . . . . 626 21.3.2 Sorption media for FI solid phase extraction . . 627 21.3.3 Guidelines for the development of FI solid phase extraction systems . . . . . . . . . . . . 629 21.3.4 Typical manifolds for FI solid phase extraction . 630 21.4 FI vapor generation systems . . . . . . . . . . . . . . 635 21.4.1 Introduction. . . . . . . . . . . . . . . . . . . 635 21.4.2 Gas.liquid separators for FI vapor generation . 635 21.4.3 Guidelines for development of FI vapor generation systems . . . . . . . . . . . . . . . 636 21.4.4 Typical FI manifolds for VG-AAS. . . . . . . . 638 21.5 FI gas diffusion systems . . . . . . . . . . . . . . . . 641 21.5.1 General . . . . . . . . . . . . . . . . . . . . . 641 21.5.2 Gas-diffusion separators . . . . . . . . . . . . 641 21.5.3 Typical FI manifolds for gas-diffusion separation and preconcentration . . . . . . . . . . . . . . 642 21.6 FI on-line sample digestion . . . . . . . . . . . . . . . 643 21.6.1 Introduction. . . . . . . . . . . . . . . . . . . 643 21.6.2 FI on-line sample digestion systems for AAS . . 644 21.6.3 FI digestion systems coupled to VG-AAS . . . . 644 21.6.4 FI systems for digestion of solid samples in AAS 645 21.6.5 FI pretreatment systems with on-line photo-oxidation by UV irradiation . . . . . . . 646 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 646 Chapter 22. Automation of sample preparation . . . . . . . . . . 649 Maria Dolores Luque de Castro and Jose Luis Luque Garc©¥¢¥a 22.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 649 22.1.1 Generalities. . . . . . . . . . . . . . . . . . . 649 22.1.2 Principal shortcomings in automating sample preparation . . . . . . . . . . . . . . . . . . . 650 22.1.3 Batch versus serial approaches to automated sample preparation . . . . . . . . . . . . . . . 651 22.1.4 Bar codes: a necessary tool in automating routine analyses . . . . . . . . . . . . . . . . 652 22.2 Automation of liquid sample preparation. . . . . . . . 653 xxix Contents 22.2.1 Continuous systems. . . . . . . . . . . . . . . 653 22.2.2 Discontinuous approaches . . . . . . . . . . . 656 22.3 Automation of solid sample preparation . . . . . . . . 659 22.3.1 One-step approaches to automation and acceleration of solid sample preparation . . . . 659 22.3.2 Direct solid sampling . . . . . . . . . . . . . . 660 22.4 Robotics . . . . . . . . . . . . . . . . . . . . . . . . . 660 22.4.1 Workstations, robots, modules and peripherals. 662 22.4.2 The role of robots in the analytical process . . . 670 22.4.3 Analytical scope of robotics for sample preparation . . . . . . . . . . . . . . . . . . . 674 22.5 Advantages and disadvantages of automation of sample preparation. . . . . . . . . . . . . . . . . . 676 22.6 Future prospects . . . . . . . . . . . . . . . . . . . . 677 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 678 MATRICES Chapter 23. Sample preparation for crude oil, petroleum products and polymers . . . . . . . . . . . . . . . . . . . . . . . . . 683 Robert I. Botto 23.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . 683 23.1.1 Nature of petroleum crude, produc