X-Ray Fluorescence Spectroscopy for Laboratory Applications

Provides comprehensive coverage on using X-ray fluorescence for laboratory applications

This book focuses on the practical aspects of X-ray fluorescence (XRF) spectroscopy and discusses the requirements for a successful sample analysis, such as sample preparation, measurement techniques and calibration, as well as the quality of the analysis results.

X-Ray Fluorescence Spectroscopy for Laboratory Applications begins with a short overview of the physical fundamentals of the generation of X-rays and their interaction with the sample material, followed by a presentation of the different methods of sample preparation in dependence on the quality of the source material and the objective of the measurement. After a short description of the different available equipment types and their respective performance, the book provides in-depth information on the choice of the optimal measurement conditions and the processing of the measurement results. It covers instrument types for XRF; acquisition and evaluation of X-Ray spectra; analytical errors; analysis of homogeneous materials, powders, and liquids; special applications of XRF; process control and automation.

• An important resource for the analytical chemist, providing concrete guidelines and support for everyday analyses
• Focuses on daily laboratory work with commercially available devices
• Offers a unique compilation of knowledge and best practices from equipment manufacturers and users
• Covers the entire work process: sample preparation, the actual measurement, data processing, assessment of uncertainty, and accuracy of the obtained results

X-Ray Fluorescence Spectroscopy for Laboratory Applications appeals to analytical chemists, analytical laboratories, materials scientists, environmental chemists, chemical engineers, biotechnologists, and pharma engineers.

Preface xvii

List of Abbreviations and Symbols xix

About the Authors xxiii

1 Introduction 1

2 Principles of X-ray Spectrometry 7

2.1 Analytical Performance 7

2.2 X-ray Radiation and Their Interaction 11

2.2.1 Parts of an X-ray Spectrum 11

2.2.2 Intensity of the Characteristic Radiation 13

2.2.3 Nomenclature of X-ray Lines 15

2.2.4 Interaction of X-rays with Matter 15

2.2.4.1 Absorption 16

2.2.4.2 Scattering 17

2.2.5 Detection of X-ray Spectra 20

2.3 The Development of X-ray Spectrometry 21

2.4 Carrying Out an Analysis 26

2.4.1 Analysis Method 26

2.4.2 Sequence of an Analysis 27

2.4.2.1 Quality of the Sample Material 27

2.4.2.2 Sample Preparation 27

2.4.2.3 Analysis Task 28

2.4.2.4 Measurement and Evaluation of the Measurement Data 28

2.4.2.5 Creation of an Analysis Report 29

3 Sample Preparation 31

3.1 Objectives of Sample Preparation 31

3.2 Preparation Techniques 32

3.2.1 Preparation Techniques for Solid Samples 32

3.2.2 Information Depth and Analyzed Volume 32

3.2.3 Infinite Thickness 36

3.2.4 Contaminations 37

3.2.5 Homogeneity 38

3.3 Preparation of Compact and Homogeneous Materials 39

3.3.1 Metals 39

3.3.2 Glasses 40

3.4 Small Parts Materials 41

3.4.1 Grinding of Small Parts Material 42

3.4.2 Preparation by Pouring Loose Powder into a Sample Cup 43

3.4.3 Preparation of the Measurement Sample by Pressing into a Pellet 44

3.4.4 Preparation of the Sample by Fusion Beads 48

3.4.4.1 Improving the Quality of the Analysis 48

3.4.4.2 Steps for the Production of Fusion Beads 49

3.4.4.3 Loss of Ignition 53

3.4.4.4 Quality Criteria for Fusion Beads 53

3.4.4.5 Preparation of Special Materials 54

3.5 Liquid Samples 55

3.5.1 Direct Measurement of Liquids 55

3.5.2 Special Processing Procedures for Liquid Samples 58

3.6 Biological Materials 58

3.7 Small Particles, Dust, and Aerosols 59

4 XRF Instrument Types 61

4.1 General Design of an X-ray Spectrometer 61

4.2 Comparison of Wavelength- and Energy-Dispersive X-Ray Spectrometers 63

4.2.1 Data Acquisition 63

4.2.2 Resolution 64

4.2.2.1 Comparison of Wavelength- and Energy-Dispersive Spectrometry 64

4.2.2.2 Resolution of WDS Instruments 66

4.2.2.3 Resolution of EDS Instruments 68

4.2.3 Detection Efficiency 70

4.2.4 Count Rate Capability 71

4.2.4.1 Optimum Throughput in ED Spectrometers 71

4.2.4.2 Saturation Effects in WDSs 72

4.2.4.3 Optimal Sensitivity of ED Spectrometers 73

4.2.4.4 Effect of the Pulse Throughput on the Measuring Time 74

4.2.5 Radiation Flux 75

4.2.6 Spectra Artifacts 76

4.2.6.1 Escape Peaks 76

4.2.6.2 Pile-Up Peak 77

4.2.6.3 Diffraction Peaks 77

4.2.6.4 Shelf and Tail 79

4.2.7 Mechanical Design and Operating Costs 79

4.2.8 Setting Parameters 80

4.3 Type of Instruments 80

4.3.1 ED Instruments 81

4.3.1.1 Handheld Instruments 82

4.3.1.2 Portable Instruments 83

4.3.1.3 Tabletop Instruments 84

4.3.2 Wavelength-Dispersive Instruments 85

4.3.2.1 Sequential Spectrometers 85

4.3.2.2 Multichannel Spectrometers 87

4.3.3 Special Type X-Ray Spectrometers 87

4.3.3.1 Total Reflection Instruments 88

4.3.3.2 Excitation by Monoenergetic Radiation 90

4.3.3.3 Excitation with Polarized Radiation 91

4.3.3.4 Instruments for Position-Sensitive Analysis 93

4.3.3.5 Macro X-Ray Fluorescence Spectrometer 94

4.3.3.6 Micro X-Ray Fluorescence with Confocal Geometry 95

4.3.3.7 High-Resolution X-Ray Spectrometers 96

4.3.3.8 Angle Resolved Spectroscopy – Grazing Incidence and Grazing Exit 96

4.4 Commercially Available Instrument Types 98

5 Measurement and Evaluation of X-ray Spectra 99

5.1 Information Content of the Spectra 99

5.2 Procedural Steps to Execute a Measurement 101

5.3 Selecting the Measurement Conditions 102

5.3.1 Optimization Criteria for the Measurement 102

5.3.2 Tube Parameters 103

5.3.2.1 Target Material 103

5.3.2.2 Excitation Conditions 104

5.3.2.3 Influencing the Energy Distribution of the Primary Spectrum 105

5.3.3 Measurement Medium 107

5.3.4 Measurement Time 108

5.3.4.1 Measurement Time and Statistical Error 108

5.3.4.2 Measurement Strategies 108

5.3.4.3 Real and Live Time 109

5.3.5 X-ray Lines 110

5.4 Determination of Peak Intensity 112

5.4.1 Intensity Data 112

5.4.2 Treatment of Peak Overlaps 112

5.4.3 Spectral Background 114

5.5 Quantification Models 117

5.5.1 General Remarks 117

5.5.2 Conventional Calibration Models 118

5.5.3 Fundamental Parameter Models 121

5.5.4 Monte Carlo Quantifications 124

5.5.5 Highly Precise Quantification by Reconstitution 124

5.5.6 Evaluation of an Analytical Method 126

5.5.6.1 Degree of Determination 126

5.5.6.2 Working Range, Limits of Detection (LOD) and of Quantification 127

5.5.6.3 Figure of Merit 129

5.5.7 Comparison of the Various Quantification Models 129

5.5.8 Available Reference Materials 131

5.5.9 Obtainable Accuracies 132

5.6 Characterization of Layered Materials 133

5.6.1 General Form of the Calibration Curve 133

5.6.2 Basic Conditions for Layer Analysis 135

5.6.3 Quantification Models for the Analysis of Layers 138

5.7 Chemometric Methods for Material Characterization 140

5.7.1 Spectra Matching and Material Identification 141

5.7.2 Phase Analysis 141

5.7.3 Regression Methods 143

5.8 Creation of an Application 143

5.8.1 Analysis of Unknown Sample Qualities 143

5.8.2 Repeated Analyses on Known Samples 144

6 Analytical Errors 149

6.1 General Considerations 149

6.1.1 Precision of a Measurement 151

6.1.2 Long-Term Stability of the Measurements 153

6.1.3 Precision and Process Capability 154

6.1.4 Trueness of the Result 156

6.2 Types of Errors 156

6.2.1 Randomly Distributed Errors 157

6.2.2 Systematic Errors 158

6.3 Accounting for Systematic Errors 159

6.3.1 The Concept of Measurement Uncertainties 159

6.3.2 Error Propagation 160

6.3.3 Determination of Measurement Uncertainties 161

6.3.3.1 Bottom-Up Method 161

6.3.3.2 Top-Down Method 162

6.4 Recording of Error Information 164

7 Other Element Analytical Methods 167

7.1 Overview 167

7.2 Atomic Absorption Spectrometry (AAS) 168

7.3 Optical Emission Spectrometry 169

7.3.1 Excitation with a Spark Discharge (OES) 169

7.3.2 Excitation in an Inductively Coupled Plasma (ICP-OES) 170

7.3.3 Laser-Induced Breakdown Spectroscopy (LIBS) 171

7.4 Mass Spectrometry (MS) 172

7.5 X-Ray Spectrometry by Particle Excitation (SEM-EDS, PIXE) 173

7.6 Comparison of Methods 175

8 Radiation Protection 177

8.1 Basic Principles 177

8.2 Effects of Ionizing Radiation on Human Tissue 178

8.3 Natural Radiation Exposure 179

8.4 Radiation Protection Regulations 181

8.4.1 Legal Regulations 181

9 Analysis of Homogeneous Solid Samples 183

9.1 Iron Alloys 183

9.1.1 Analytical Problem and Sample Preparation 183

9.1.2 Analysis of Pig and Cast Iron 184

9.1.3 Analysis of Low-Alloy Steel 185

9.1.4 Analysis of High-Alloy Steel 187

9.2 Ni–Fe–Co Alloys 188

9.3 Copper Alloys 189

9.3.1 Analytical Task 189

9.3.2 Analysis of Compact Samples 189

9.3.3 Analysis of Dissolved Samples 189

9.4 Aluminum Alloys 191

9.5 Special Metals 192

9.5.1 Refractories 192

9.5.1.1 Analytical Problem 192

9.5.1.2 Sample Preparation of Hard Metals 192

9.5.1.3 Analysis of Hard Metals 193

9.5.2 Titanium Alloys 194

9.5.3 Solder Alloys 194

9.6 Precious Metals 195

9.6.1 Analysis of Precious Metal Jewelry 195

9.6.1.1 Analytical Task 195

9.6.1.2 Sample Shape and Preparation 196

9.6.1.3 Analytical Equipment 197

9.6.1.4 Accuracy of the Analysis 198

9.6.2 Analysis of Pure Elements 198

9.7 Glass Material 199

9.7.1 Analytical Task 199

9.7.2 Sample Preparation 200

9.7.3 Measurement Equipment 202

9.7.4 Achievable Accuracies 202

9.8 Polymers 203

9.8.1 Analytical Task 203

9.8.2 Sample Preparation 204

9.8.3 Instruments 205

9.8.4 Quantification Procedures 205

9.8.4.1 Standard-Based Methods 205

9.8.4.2 Chemometric Methods 206

9.9 Abrasion Analysis 209

10 Analysis of Powder Samples 213

10.1 Geological Samples 213

10.1.1 Analytical Task 213

10.1.2 Sample Preparation 214

10.1.3 Measurement Technique 215

10.1.4 Detection Limits and Trueness 215

10.2 Ores 216

10.2.1 Analytical Task 216

10.2.2 Iron Ores 216

10.2.3 Mn, Co, Ni, Cu, Zn, and Pb Ores 217

10.2.4 Bauxite and Alumina 218

10.2.5 Ores of Precious Metals and Rare Earths 219

10.3 Soils and Sewage Sludges 221

10.3.1 Analytical Task 221

10.3.2 Sample Preparation 221

10.3.3 Measurement Technology and Analytical Performance 222

10.4 Quartz Sand 223

10.5 Cement 223

10.5.1 Analytical Task 223

10.5.2 Sample Preparation 224

10.5.3 Measurement Technology 225

10.5.4 Analytical Performance 226

10.5.5 Determination of Free Lime in Clinker 227

10.6 Coal and Coke 227

10.6.1 Analytical Task 227

10.6.2 Sample Preparation 228

10.6.3 Measurement Technology and Analytical Performance 229

10.7 Ferroalloys 230

10.7.1 Analytical Task 230

10.7.2 Sample Preparation 230

10.7.3 Analysis Technology 232

10.7.4 Analytical Performance 234

10.8 Slags 235

10.8.1 Analytical Task 235

10.8.2 Sample Preparation 235

10.8.3 Measurement Technology and Analytical Accuracy 236

10.9 Ceramics and Refractory Materials 237

10.9.1 Analytical Task 237

10.9.2 Sample Preparation 237

10.9.3 Measurement Technology and Analytical Performance 238

10.10 Dusts 239

10.10.1 Analytical Problem and Dust Collection 239

10.10.2 Measurement 242

10.11 Food 242

10.11.1 Analytical Task 242

10.11.2 Monitoring of Animal Feed 243

10.11.3 Control of Infant Food 244

10.12 Pharmaceuticals 245

10.12.1 Analytical Task 245

10.12.2 Sample Preparation and Analysis Method 245

10.13 Secondary Fuels 246

10.13.1 Analytical Task 246

10.13.2 Sample Preparation 247

10.13.2.1 Solid Secondary Raw Materials 247

10.13.2.2 Liquid Secondary Raw Materials 249

10.13.3 Instrumentation and Measurement Conditions 250

10.13.4 Measurement Uncertainties in the Analysis of Solid Secondary Raw Materials 251

10.13.5 Measurement Uncertainties for the Analysis of Liquid Secondary Raw Materials 252

11 Analysis of Liquids 253

11.1 Multielement Analysis of Liquids 254

11.1.1 Analytical Task 254

11.1.2 Sample Preparation 254

11.1.3 Measurement Technology 254

11.1.4 Quantification 255

11.2 Fuels and Oils 255

11.2.1 Analysis of Toxic Elements in Fuels 256

11.2.1.1 Measurement Technology 256

11.2.1.2 Analytical Performance 258

11.2.2 Analysis of Additives in Lubricating Oils 258

11.2.3 Identification of Abrasive Particles in Used Lubricants 260

11.3 Trace Analysis in Liquids 261

11.3.1 Analytical Task 261

11.3.2 Preparation by Drying 261

11.3.3 Quantification 262

11.4 Special Preparation Techniques for Liquid Samples 263

11.4.1 Determination of Light Elements in Liquids 263

11.4.2 Enrichment Through Absorption and Complex Formation 264

12 Trace Analysis Using Total Reflection X-Ray Fluorescence 267

12.1 Special Features of TXRF 267

12.2 Sample Preparation for TXRF 269

12.3 Evaluation of the Spectra 271

12.3.1 Spectrum Preparation and Quantification 271

12.3.2 Conditions for Neglecting the Matrix Interaction 272

12.3.3 Limits of Detection 273

12.4 Typical Applications of the TXRF 274

12.4.1 Analysis of Aqueous Solutions 274

12.4.1.1 Analytical Problem and Preparation Possibilities 274

12.4.1.2 Example: Analysis of a Fresh Water Standard Sample 275

12.4.1.3 Example: Detection of Mercury in Water 277

12.4.2 Analysis of the Smallest Sample Quantities 278

12.4.2.1 Example: Pigment Analysis 278

12.4.2.2 Example: Aerosol Analysis 279

12.4.2.3 Example: Analysis of Nanoparticles 279

12.4.3 Trace Element Analysis on Human Organs 280

12.4.3.1 Example: Analysis of Blood and Blood Serum 280

12.4.3.2 Example: Analysis of Trace Elements in Body Tissue 282

12.4.4 Trace Analysis of Inorganic and Organic Chemical Products 283

12.4.5 Analysis of Semiconductor Electronics 284

12.4.5.1 Ultra-Trace Analysis on SiWafers with VPD 284

12.4.5.2 Depth Profile Analysis by Etching 285

13 Nonhomogeneous Samples 287

13.1 Measurement Modes 287

13.2 Instrument Requirements 288

13.3 Data Evaluation 290

14 Coating Analysis 291

14.1 Analytical Task 291

14.2 Sample Handling 292

14.3 Measurement Technology 293

14.4 The Analysis Examples of Coated Samples 294

14.4.1 Single-Layer Systems: Emission Mode 294

14.4.2 Single-Layer Systems: Absorption Mode 297

14.4.3 Single-Layer Systems: Relative Mode 298

14.4.3.1 Analytical Problem 298

14.4.3.2 Variation of the Specified Working Distance 298

14.4.3.3 Sample Size and Spot Size Mismatch 299

14.4.3.4 Non-detectable Elements in the Layer: NiP Layers 300

14.4.4 Characterization of Ultrathin Layers 302

14.4.5 Multilayer Systems 304

14.4.5.1 Layer Systems 304

14.4.5.2 Measurement Technology 305

14.4.5.3 Example: Analysis of CIGS Solar Cells 305

14.4.5.4 Example: Analysis of Solder Structures 306

14.4.6 Samples with Unknown Coating Systems 307

14.4.6.1 Preparation of Cross Sections 308

14.4.6.2 Excitation at Grazing Incidence with Varying Angles 309

14.4.6.3 Measurement in Confocal Geometry 311

15 Spot Analyses 313

15.1 Particle Analyses 313

15.1.1 Analytical Task 313

15.1.2 Sample Preparation 314

15.1.3 Analysis Technology 315

15.1.4 Application Example:Wear Particles in Used Oil 315

15.1.5 Application Example: Identification of Glass Particles by Chemometrics 316

15.2 Identification of Inclusions 318

15.3 Material Identification with Handheld Instruments 318

15.3.1 Analytical Tasks 318

15.3.2 Analysis Technology 319

15.3.3 Sample Preparation and Test Conditions 320

15.3.4 Analytical Accuracy 320

15.3.5 Application Examples 321

15.3.5.1 Example: Lead in Paint 321

15.3.5.2 Example: Scrap Sorting 321

15.3.5.3 Example: Material Inspection and Sorting 322

15.3.5.4 Example: Precious Metal Analysis 322

15.3.5.5 Example: Prospecting and Screening in Geology 323

15.3.5.6 Example: Investigation of Works of Art 323

15.4 Determination of Toxic Elements in Consumer Products: RoHS Monitoring 324

15.4.1 Analytical Task 324

15.4.2 Analysis Technology 325

15.4.3 Analysis Accuracy 327

15.5 Toxic Elements in Toys: Toys Standard 328

15.5.1 Analytical Task 328

15.5.2 Sample Preparation 328

15.5.3 Analysis Technology 330

16 Analysis of Element Distributions 331

16.1 General Remarks 331

16.2 Measurement Conditions 332

16.3 Geology 333

16.3.1 Samples Types 333

16.3.2 Sample Preparation and Positioning 333

16.3.3 Measurements on Compact Rock Samples 334

16.3.3.1 Sum Spectrum and Element Distributions 334

16.3.3.2 Object Spectra 335

16.3.3.3 Treatment of Line Overlaps 336

16.3.3.4 Maximum Pixel Spectrum 339

16.3.4 Thin Sections of Geological Samples 340

16.4 Electronics 342

16.5 Archeometric Investigations 344

16.5.1 Analytical Tasks 344

16.5.2 Selection of an Appropriate Spectrometer 346

16.5.3 Investigations of Coins 347

16.5.4 Investigations of Painting Pigments 349

16.6 Homogeneity Tests 350

16.6.1 Analytical Task 350

16.6.2 Homogeneity Studies Using Distribution Analysis 351

16.6.3 Homogeneity Studies Using Multi-point Measurements 352

17 Special Applications of the XRF 355

17.1 High-Throughput Screening and Combinatorial Analysis 355

17.1.1 High-Throughput Screening 355

17.1.2 Combinatorial Analysis for Drug Development 357

17.2 Chemometric Spectral Evaluation 358

17.3 High-Resolution Spectroscopy for Speciation Analysis 361

17.3.1 Analytical Task 361

17.3.2 Instrument Technology 361

17.3.3 Application Examples 362

17.3.3.1 Analysis of Different Sulfur Compounds 362

17.3.3.2 Speciation of Aluminum Inclusions in Steel 363

17.3.3.3 Determination of SiO2 in SiC 365

18 Process Control and Automation 367

18.1 General Objectives 367

18.2 Off-Line and At-Line Analysis 369

18.2.1 Sample Supply and Analysis 369

18.2.2 Automated Sample Preparation 371

18.3 In-Line and On-Line Analysis 376

19 Quality Management and Validation 379

19.1 Motivation 379

19.2 Validation 380

19.2.1 Parameters 384

19.2.2 Uncertainty 385

Appendix A Tables 387

Appendix B Important Information 419

B.1 Coordinates of Main Manufacturers of Instruments and Preparation Tools 419

B.2 Main Suppliers of Standard Materials 422

B.2.1 Geological Materials and Metals 422

B.2.2 Stratified Materials 423

B.2.3 Polymer Standards 424

B.2.4 High Purity Materials 424

B.2.5 Precious Metal Alloys 425

B.3 Important Websites 425

B.3.1 Information About X-Ray Analytics and Fundamental Parameters 425

B.3.2 Information About Reference Materials 426

B.3.3 Scientific Journals 427

B.4 Laws and Acts, Which Are Important for X-Ray Fluorescence 427

B.4.1 Radiation Protection 427

B.4.2 Regulations for Environmental Control 428

B.4.3 Regulations for Performing Analysis 428

B.4.4 Use of X-ray Fluorescence for the Chemical Analysis 428

B.4.4.1 General Regulations 428

B.4.4.2 Analysis of Minerals 429

B.4.4.3 Analysis of Oils, Liquid Fuels, Grease 430

B.4.4.4 Analysis of Solid Fuels 432

B.4.4.5 Coating Analysis 433

B.4.4.6 Metallurgy 433

B.4.4.7 Analysis of Electronic Components 434

References 435

Index 453 

Michael Haschke, PhD, has been working in the product management of various companies for more than 35 years where he was responsible for the development and introduction to market of new x-ray fluorescence techniques, mainly in the field of energy-dissipative spectroscopy. 

Jörg Flock, PhD, is Head of the Central Laboratory of ThyssenKrupp Stahl AG and well-versed with different analytical techniques, in particular with x-ray fluorescence spectroscopy. He has extensive practical experience in using this technique for the analysis of samples with different qualities and the interpretation of the acquired results. 

Michael Haller has been using X-rays as an analytical tool for over thirty years, first in X-ray crystallography, then later in the development and application of polycapillary X-ray optics. Further he has developed new applications for coating thickness instruments. In 2018 he became co-owner of CrossRoads Scientific, a company specializing in the development of analytical X-ray software.