Total-Reflection X-Ray Fluorescence Analysis and Related Methods

FOREWORD xiii ACKNOWLEDGMENTS xv LIST OF ACRONYMS xvii LIST OF PHYSICAL UNITS AND SUBUNITS xxii LIST OF SYMBOLS xxiii CHAPTER 1 FUNDAMENTALS OF X-RAY FLUORESCENCE 1 1.1 A Short History of XRF 2 1.2 The New Variant TXRF 8 1.2.1 Retrospect on its Development 8 1.2.2 Relationship of XRF and TXRF 13 1.3 Nature and Production of X-Rays 15 1.3.1 The Nature of X-Rays 15 1.3.2 X-Ray Tubes as X-Ray Sources 17 1.3.2.1 The Line Spectrum 19 1.3.2.2 The Continuous Spectrum 27 1.3.3 Polarization of X-Rays 29 1.3.4 Synchrotron Radiation as X-Ray Source 30 1.3.4.1 Electrons in Fields of Bending Magnets 32 1.3.4.2 Radiation Power of a Single Electron 35 1.3.4.3 Angular and Spectral Distribution of SR 36 1.3.4.4 Comparison with Black-Body Radiation 42 1.4 Attenuation of X-Rays 44 1.4.1 Photoelectric Absorption 46 1.4.2 X-Ray Scatter 49 1.4.3 Total Attenuation 51 1.5 Deflection of X-Rays 53 1.5.1 Reflection and Refraction 53 1.5.2 Diffraction and Bragg's Law 59 1.5.3 Total External Reflection 62 1.5.3.1 Reflectivity 66 1.5.3.2 Penetration Depth 67 1.5.4 Refraction and Dispersion 71 References 74 CHAPTER 2 PRINCIPLES OF TOTAL REFLECTION XRF 79 2.1 Interference of X-Rays 80 2.1.1 Double-Beam Interference 80 2.1.2 Multiple-Beam Interference 84 2.2 X-Ray Standing Wave Fields 88 2.2.1 Standing Waves in Front of a Thick Substrate 88 2.2.2 Standing Wave Fields Within a Thin Layer 94 2.2.3 Standing Waves Within a Multilayer or Crystal 100 2.3 Intensity of Fluorescence Signals 100 2.3.1 Infinitely Thick and Flat Substrates 102 2.3.2 Granular Residues on a Substrate 104 2.3.3 Buried Layers in a Substrate 106 2.3.4 Reflecting Layers on Substrates 108 2.3.5 Periodic Multilayers and Crystals 110 2.4 Formalism For Intensity Calculations 112 2.4.1 A Thick and Flat Substrate 113 2.4.2 A Thin Homogeneous Layer on a Substrate 116 2.4.3 A Stratified Medium of Several Layers 120 References 123 CHAPTER 3 INSTRUMENTATION FOR TXRF AND GI-XRF 126 3.1 Basic Instrumental Setup 128 3.2 High and Low-Power X-Ray Sources 130 3.2.1 Fine-Focus X-Ray Tubes 131 3.2.2 Rotating Anode Tubes 132 3.2.3 Air-Cooled X-Ray Tubes 133 3.3 Synchrotron Facilities 134 3.3.1 Basic Setup with Bending Magnets 136 3.3.2 Undulators, Wigglers, and FELs 137 3.3.3 Facilities Worldwide 139 3.4 The Beam Adapting Unit 150 3.4.1 Low-Pass Filters 150 3.4.2 Simple Monochromators 155 3.4.3 Double-Crystal Monochromators 157 3.5 Sample Positioning 160 3.5.1 Sample Carriers 161 3.5.2 Fixed Angle Adjustment for TXRF ("Angle Cut") 162 3.5.3 Stepwise-Angle Variation for GI-XRF ("Angle Scan") 162 3.6 Energy-Dispersive Detection of X-Rays 164 3.6.1 The Semiconductor Detector 165 3.6.2 The Silicon Drift Detector 167 3.6.3 Position Sensitive Detectors 169 3.7 Wavelength-Dispersive Detection of X-Rays 173 3.7.1 Dispersing Crystals with Soller Collimators 176 3.7.2 Gas-Filled Detectors 178 3.7.3 Scintillation Detectors 182 3.8 Spectra Registration and Evaluation 183 3.8.1 The Registration Unit 183 3.8.2 Performance Characteristics 185 3.8.2.1 Detector Efficiency 185 3.8.2.2 Spectral Resolution 188 3.8.2.3 Input-Output Yield 194 3.8.2.4 The Escape-Peak Phenomenon 197 References 200 CHAPTER 4 PERFORMANCE OF TXRF AND GI-XRF ANALYSES 205 4.1 Preparations for Measurement 207 4.1.1 Cleaning Procedures 207 4.1.2 Preparation of Samples 211 4.1.3 Presentation of a Specimen 215 4.1.3.1 Microliter Sampling by Pipettes 216 4.1.3.2 Nanoliter Droplets by Capillaries 217 4.1.3.3 Picoliter-Sized Droplets by Inkjet Printing 218 4.1.3.4 Microdispensing of Liquids by Triple-Jet Technology 220 4.1.3.5 Solid Matter of Different Kinds 220 4.2 Acquisition of Spectra 222 4.2.1 The Setup for Excitation with X-Ray Tubes 222 4.2.2 Excitation by Synchrotron Radiation 225 4.2.3 Recording the Spectrograms 226 4.2.3.1 Energy-Dispersive Variant 227 4.2.3.2 Wavelength-Dispersive Mode 227 4.3 Qualitative Analysis 228 4.3.1 Shortcomings of Spectra 228 4.3.1.1 Strong Spectral Interferences 229 4.3.1.2 Regard of Sum Peaks 235 4.3.1.3 Dealing with Escape Peaks 235 4.3.2 Unambiguous Element Detection 236 4.3.3 Fingerprint Analysis 237 4.4 Quantitative Micro- and Trace Analyses 238 4.4.1 Prerequisites for Quantification 240 4.4.1.1 Determination of Net Intensities 240 4.4.1.2 Determination of Relative Sensitivities 241 4.4.2 Quantification by Internal Standardization 244 4.4.2.1 Standard Addition for a Single Element 245 4.4.2.2 Multielement Determinations 246 4.4.3 Conditions and Limitations 248 4.4.3.1 Mass and Thickness of Thin Layers 249 4.4.3.2 Residues of Microliter Droplets 251 4.4.3.3 Coherence Length of Radiation 252 4.5 Quantitative Surface and Thin-Layer Analyses by TXRF 257 4.5.1 Distinguishing Between Types of Contamination 257 4.5.1.1 Bulk-Type Impurities 257 4.5.1.2 Particulate Contamination 258 4.5.1.3 Thin-Layer Covering 259 4.5.1.4 Mixture of Contaminations 259 4.5.2 Characterization of Thin Layers by TXRF 262 4.5.2.1 Multifold Repeated Chemical Etching 262 4.5.2.2 Stepwise Repeated Planar Sputter Etching 264 4.6 Quantitative Surface and Thin-Layer Analyses by GI-XRF 267 4.6.1 Recording Angle-Dependent Intensity Profiles 268 4.6.2 Considering the Footprint Effect 270 4.6.3 Regarding the Coherence Length 272 4.6.4 Depth Profiling at Grazing Incidence 274 4.6.5 Including the Surface Roughness 283 References 284 CHAPTER 5 DIFFERENT FIELDS OF APPLICATIONS 291 5.1 Environmental and Geological Applications 292 5.1.1 Natural Water Samples 292 5.1.2 Airborne Particulates 297 5.1.3 Biomonitoring 302 5.1.4 Geological Samples 306 5.2 Biological and Biochemical Applications 307 5.2.1 Beverages: Water, Tea, Coffee, Must, and Wine 308 5.2.2 Vegetable and Essential Oils 312 5.2.3 Plant Materials and Extracts 312 5.2.4 Unicellular Organisms and Biomolecules 315 5.3 Medical, Clinical, and Pharmaceutical Applications 317 5.3.1 Blood, Plasma, and Serum 317 5.3.2 Urine, Cerebrospinal, and Amniotic Fluid 320 5.3.3 Tissue Samples 322 5.3.3.1 Freeze-Cutting of Organs by a Microtome 322 5.3.3.2 Healthy and Cancerous Tissue Samples 324 5.3.4 Medicines and Remedies 327 5.4 Industrial or Chemical Applications 329 5.4.1 Ultrapure Reagents 330 5.4.2 High-Purity Silicon and Silica 331 5.4.3 Ultrapure Aluminum 332 5.4.4 High-Purity Ceramic Powders 334 5.4.5 Impurities in Nuclear Materials 336 5.4.6 Hydrocarbons and Their Polymers 336 5.4.7 Contamination-Free Wafer Surfaces 338 5.4.7.1 Wafers Controlled by Direct TXRF 340 5.4.7.2 Contaminations Determined by VPD-TXRF 342 5.4.8 Characterization of Nanostructured Samples 346 5.4.8.1 Shallow Layers by Sputter Etching and TXRF 346 5.4.8.2 Thin-Layer Structures by Direct GI-XRF 347 5.4.8.3 Nanoparticles by TXRF and GI-XRF 354 5.5 Art Historical and Forensic Applications 357 5.5.1 Pigments, Inks, and Varnishes 357 5.5.2 Metals and Alloys 361 5.5.3 Textile Fibers and Glass Splinters 363 5.5.4 Drug Abuse and Poisoning 365 References 367 CHAPTER 6 EFFICIENCY AND EVALUATION 383 6.1 Analytical Considerations 384 6.1.1 General Costs of Installation and Upkeep 384 6.1.2 Detection Power for Elements 385 6.1.3 Reliability of Determinations 388 6.1.4 The Great Variety of Suitable Samples 391 6.1.5 Round-Robin Tests 393 6.2 Utility and Competitiveness of TXRF and GI-XRF 397 6.2.1 Advantages and Limitations 398 6.2.2 Comparison of TXRF with Competitors 400 6.2.3 GI-XRF and Competing Methods 409 6.3 Perception and Propagation of TXRF Methods 410 6.3.1 Commercially Available Instruments 410 6.3.2 Support by the International Atomic Energy Agency 413 6.3.3 Worldwide Distribution of TXRF and Related Methods 413 6.3.4 Standardization by ISO and DIN 417 6.3.5 International Cooperation and Activity 420 References 424 CHAPTER 7 TRENDS AND FUTURE PROSPECTS 433 7.1 Instrumental Developments 434 7.1.1 Excitation by Synchrotron Radiation 434 7.1.2 New Variants of X-Ray Sources 436 7.1.3 Capillaries and Waveguides for Beam Adapting 438 7.1.4 New Types of X-Ray Detectors 442 7.2 Methodical Developments 445 7.2.1 Detection of Light Elements 445 7.2.2 Ablation and Deposition Techniques 449 7.2.3 Grazing Exit X-Ray Fluorescence 452 7.2.4 Reference-Free Quantification 459 7.2.5 Time-Resolved In Situ Analysis 462 7.3 Future Prospects by Combinations 463 7.3.1 Combination with X-Ray Reflectometry 464 7.3.2 EXAFS and Total Reflection Geometry 466 7.3.3 Combination with XANES or NEXAFS 468 7.3.4 X-Ray Diffractometry at Total Reflection 480 7.3.5 Total Reflection and X-Ray Photoelectron Spectrometry 486 References 491 INDEX 501