Chemical Analysis: A Series of Monographs on

Analytical Chemistry and Its ApplicationsMark F. Vitha, Series Editor

Total-Relection X-ray Fluorescence Analysis and Related Methods

SECOND EDITION

REINHOLD KLOCKENKÄMPER ALEX VON BOHLEN

Total-Reflection X-RayFluorescence Analysisand Related Methods

CHEMICAL ANALYSIS

A SERIES OF MONOGRAPHS ON ANALYTICAL CHEMISTRYAND ITS APPLICATIONS

Series Editor

MARK F. VITHA

Volume 181

A complete list of the titles in this series appears at the end of this volume.

Total-Reflection X-RayFluorescence Analysisand Related Methods

Second Edition

Reinhold Klockenkämper

Alex von Bohlen

Leibniz-Institut für Analytische Wissenschaften – ISAS – e.V.

Dortmund and Berlin, Germany

Copyright 2015 by John Wiley & Sons, Inc. All rights reserved

Published by John Wiley & Sons, Inc., Hoboken, New JerseyPublished simultaneously in Canada

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in anyform or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise,except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, withouteither the prior written permission of the Publisher, or authorization through payment of theappropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers,MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests tothe Publisher for permission should be addressed to the Permissions Department, John Wiley &Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online athttp://www.wiley.com/go/permissions.

Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their bestefforts in preparing this book, they make no representations or warranties with respect to theaccuracy or completeness of the contents of this book and specifically disclaim any impliedwarranties of merchantability or fitness for a particular purpose. No warranty may be created orextended by sales representatives or written sales materials. The advice and strategies containedherein may not be suitable for your situation. You should consult with a professional whereappropriate. Neither the publisher nor author shall be liable for any loss of profit or any othercommercial damages, including but not limited to special, incidental, consequential, or otherdamages.

For general information on our other products and services or for technical support, please contactour Customer Care Department within the United States at (800) 762-2974, outside the UnitedStates at (317) 572-3993 or fax (317) 572-4002.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in printmay not be available in electronic formats. For more information about Wiley products, visit ourweb site at www.wiley.com.

Library of Congress Cataloging-in-Publication Data:

Klockenkämper, Reinhold, 1937- author.Total-reflection X-ray fluorescence analysis and related methods.—Second edition / Reinhold

Klockenkämper, Alex von Bohlen, Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V.,Dortmund und Berlin, Germany.

pages cmIncludes bibliographical references and index.

ISBN 978-1-118-46027-6 (hardback)1. X-ray spectroscopy. 2. Fluorescence spectroscopy. I. Bohlen, Alex von, 1954- author.II. Title.QD96.X2K58 2014543'.62–dc23

2014022279

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

CONTENTS

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 81.2.1 Retrospect on its Development 8

1.2.2 Relationship of XRF and TXRF 131.3 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 191.3.2.2 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 BendingMagnets 32

1.3.4.2 Radiation Power of a SingleElectron 35

1.3.4.3 Angular and SpectralDistribution of SR 36

1.3.4.4 Comparison with Black-BodyRadiation 42

1.4 Attenuation of X-Rays 441.4.1 Photoelectric Absorption 46

1.4.2 X-Ray Scatter 49

1.4.3 Total Attenuation 51

v

1.5 Deflection of X-Rays 531.5.1 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 661.5.3.2 Penetration Depth 67

1.5.4 Refraction and Dispersion 71References 74

CHAPTER 2 PRINCIPLES OF TOTAL REFLECTION XRF 79

2.1 Interference of X-Rays 802.1.1 Double-Beam Interference 80

2.1.2 Multiple-Beam Interference 842.2 X-Ray Standing Wave Fields 88

2.2.1 Standing Waves in Front of a ThickSubstrate 88

2.2.2 Standing Wave Fields Within a Thin Layer 94

2.2.3 Standing Waves Within a Multilayeror Crystal 100

2.3 Intensity of Fluorescence Signals 1002.3.1 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 1102.4 Formalism For Intensity Calculations 112

2.4.1 A Thick and Flat Substrate 113

2.4.2 A Thin Homogeneous Layeron a Substrate 116

2.4.3 A Stratified Medium of Several Layers 120References 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 1303.2.1 Fine-Focus X-Ray Tubes 131

3.2.2 Rotating Anode Tubes 132

3.2.3 Air-Cooled X-Ray Tubes 1333.3 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

vi CONTENTS

3.4 The Beam Adapting Unit 1503.4.1 Low-Pass Filters 150

3.4.2 Simple Monochromators 155

3.4.3 Double-Crystal Monochromators 1573.5 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 1643.6.1 The Semiconductor Detector 165

3.6.2 The Silicon Drift Detector 167

3.6.3 Position Sensitive Detectors 1693.7 Wavelength-Dispersive Detection of X-Rays 173

3.7.1 Dispersing Crystals with SollerCollimators 176

3.7.2 Gas-Filled Detectors 178

3.7.3 Scintillation Detectors 1823.8 Spectra Registration and Evaluation 183

3.8.1 The Registration Unit 183

3.8.2 Performance Characteristics 185

3.8.2.1 Detector Efficiency 1853.8.2.2 Spectral Resolution 1883.8.2.3 Input–Output Yield 1943.8.2.4 The Escape-Peak

Phenomenon 197References 200

CHAPTER 4 PERFORMANCE OF TXRF AND GI-XRF

ANALYSES 205

4.1 Preparations for Measurement 2074.1.1 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 2164.1.3.2 Nanoliter Droplets by Capillaries 2174.1.3.3 Picoliter-Sized Droplets by Inkjet

Printing 2184.1.3.4 Microdispensing of Liquids

by Triple-Jet Technology 2204.1.3.5 Solid Matter of Different Kinds 220

CONTENTS vii

4.2 Acquisition of Spectra 2224.2.1 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 2274.2.3.2 Wavelength-Dispersive Mode 227

4.3 Qualitative Analysis 2284.3.1 Shortcomings of Spectra 228

4.3.1.1 Strong Spectral Interferences 2294.3.1.2 Regard of Sum Peaks 2354.3.1.3 Dealing with Escape Peaks 235

4.3.2 Unambiguous Element Detection 236

4.3.3 Fingerprint Analysis 2374.4 Quantitative Micro- and Trace Analyses 238

4.4.1 Prerequisites for Quantification 240

4.4.1.1 Determination of Net Intensities 2404.4.1.2 Determination of Relative

Sensitivities 2414.4.2 Quantification by Internal Standardization 244

4.4.2.1 Standard Addition for a SingleElement 245

4.4.2.2 Multielement Determinations 2464.4.3 Conditions and Limitations 248

4.4.3.1 Mass and Thickness of ThinLayers 249

4.4.3.2 Residues of Microliter Droplets 2514.4.3.3 Coherence Length of Radiation 252

4.5 Quantitative Surface and Thin-Layer Analysesby TXRF 2574.5.1 Distinguishing Between Types

of Contamination 257

4.5.1.1 Bulk-Type Impurities 2574.5.1.2 Particulate Contamination 2584.5.1.3 Thin-Layer Covering 2594.5.1.4 Mixture of Contaminations 259

4.5.2 Characterization of Thin Layers by TXRF 262

4.5.2.1 Multifold Repeated ChemicalEtching 262

4.5.2.2 Stepwise Repeated Planar SputterEtching 264

4.6 Quantitative Surface and Thin-LayerAnalyses by GI-XRF 267

viii CONTENTS

4.6.1 Recording Angle-Dependent IntensityProfiles 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 283References 284

CHAPTER 5 DIFFERENT FIELDS OF APPLICATIONS 291

5.1 Environmental and Geological Applications 2925.1.1 Natural Water Samples 292

5.1.2 Airborne Particulates 297

5.1.3 Biomonitoring 302

5.1.4 Geological Samples 3065.2 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 3155.3 Medical, Clinical, and Pharmaceutical

Applications 3175.3.1 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 Organsby a Microtome 322

5.3.3.2 Healthy and Cancerous TissueSamples 324

5.3.4 Medicines and Remedies 3275.4 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 DirectTXRF 340

CONTENTS ix

5.4.7.2 Contaminations Determinedby VPD-TXRF 342

5.4.8 Characterization of NanostructuredSamples 346

5.4.8.1 Shallow Layers by SputterEtching and TXRF 346

5.4.8.2 Thin-Layer Structures by DirectGI-XRF 347

5.4.8.3 Nanoparticles by TXRFand GI-XRF 354

5.5 Art Historical and Forensic Applications 3575.5.1 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 365References 367

CHAPTER 6 EFFICIENCY AND EVALUATION 383

6.1 Analytical Considerations 3846.1.1 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 3936.2 Utility and Competitiveness of TXRF

and GI-XRF 3976.2.1 Advantages and Limitations 398

6.2.2 Comparison of TXRF with Competitors 400

6.2.3 GI-XRF and Competing Methods 4096.3 Perception and Propagation of TXRF Methods 410

6.3.1 Commercially Available Instruments 410

6.3.2 Support by the International AtomicEnergy Agency 413

6.3.3 Worldwide Distribution of TXRF andRelated Methods 413

6.3.4 Standardization by ISO and DIN 417

6.3.5 International Cooperation and Activity 420References 424

CHAPTER 7 TRENDS AND FUTURE PROSPECTS 433

7.1 Instrumental Developments 4347.1.1 Excitation by Synchrotron Radiation 434

7.1.2 New Variants of X-Ray Sources 436

x CONTENTS

7.1.3 Capillaries and Waveguides for BeamAdapting 438

7.1.4 New Types of X-Ray Detectors 4427.2 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 4627.3 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-RayPhotoelectron Spectrometry 486

References 491

INDEX 501

CONTENTS xi

FOREWORD

This second edition of the first and only monograph on total reflection X-rayfluorescence (TXRF) is thoroughly revised and updated with important devel-opments of the last 15 years. TXRF is a universal and economic multielementmethod suitable for extreme micro- and trace analyses. Its unique and inherentfeatures are elaborated in detail in this excellent monograph. TXRF representsan individual method with its own history and special peculiarities in comparisonto other XRF techniques, and is well established within the community ofelemental spectroscopy. In particular, TXRF has been realized and understoodas a complementary rather than competitive instrument within the orchestra ofultramicro and ultratrace analytical instrumentation. In different round-robintests, TXRF demonstrated its performance quite well in comparison withmethods such as ET-AAS, ICP-OES, ICP-MS, RBS, and INAA.

Total reflection XRF is widely used in the analysis of flat sample surfacesand near-surface layers. Here, it may be applied as a nondestructive methodespecially suitable for the quality control of wafers in the semiconductorindustry. It can be used for the determination of impurities at the ultratracelevel and for mapping of the element distribution on flat surfaces. In addition tothe composition, the nanometer-thickness of thin layers can be determined bytilting the sample at grazing incidence. Direct density measurements are aspecial and unique feature of TXRF after sputter-etching.

The authors have built a successful and well established team in the field ofTXRF for about 25 years. In the first edition of this book, R. Klockenkämperdescribed the principles and fundamentals of TXRF, the performance ofanalyses, and its applications. After his retirement, he cooperated with A.von Bohlen in order to examine the latest developments and to place TXRF ina leading position of analytical atomic spectrometry.

Several new sections of this second edition demonstrate the essential pro-gress of TXRF. The new generation of silicon drift detectors, which are cooledthermo-electrically, is highlighted. About 80 synchrotron facilities around thewhole world are listed—with work places that are dedicated solely to TXRFoffering an extremely brilliant and tunable radiation. The previous fields ofapplications are enumerated and diversified, contamination control of wafers isshown to be standardized, and many new fields are represented especially inthe life sciences. Combinations of different methods of spectrometry, such asNEXAFS and XANES, with excitation under total reflection build a trend and

xiii

have been presented as future prospects. The worldwide distribution ofTXRF’s instrumentation and its different fields of applications are evaluatedstatistically.

This articulate monograph on TXRF with several color pictures providesfundamental and valuable help for present and future users in the analyticalcommunity. Many disciplines, such as geo-, bio-, material-, and environmentalsciences, medicine, toxicology, forensics, and archaeometry can profit from themethod in general and from this outstanding monograph in particular.

Geesthacht, May 2014 PROF. DR. ANDREAS PRANGE

Helmholtz-Zentrum Geesthacht

Institute for Coastal Research

Head of the Department for

Marine Bioanalytical Chemistry

xiv FOREWORD

ACKNOWLEDGMENTS

The authors are grateful to all the colleagues of our TXRF community for theirlaborious and important investigations and for manifold publications that buildthe basis of this monograph. Special thanks go to the attendees of the lastconference on TXRF, who took part in the survey described in Chapter 6.

We also wish to thank Mrs. Maria Becker for carefully adapting the firstedition in a readable word document, and for the diligent compilation of allreferences and all the data of synchrotron beamlines. Furthermore, we thankour former colleague Prof. Dr. Joachim Buddrus for proofreading chemicalterms and formulas. Scientific and technical assistance of the Leibniz-Institutfür Analytische Wissenschaften – ISAS – e.V., represented by members of theExecutive Board, Prof. Dr. Albert Sickmann and Jürgen Bethke, is gratefullyacknowledged. ISAS in Dortmund is supported by the Bundesministerium fürBildung und Forschung (BMBF) of Germany, by the Ministerium für Innova-tion, Wissenschaft und Forschung of North Rhine-Westphalia, and by theSenatsverwaltung für Wirtschaft, Technologie und Forschung, Berlin.

It is a pleasure for the authors to thank our friend Prof. Dr. Andreas Prangefor providing a felicitous and penetrative foreword. The authors are alsoobliged to the publishers John Wiley and particularly to Bob Esposito andMichael Leventhal for their reliable assistance, and to Dr. Mark Vitha for hisgreat care in editing the manuscript. We also pay tribute to the printers for theexcellence of their printing, especially to our project manager, Ms. ShikhaPahuja, for the diligent organization.

xv

LIST OF ACRONYMS

AC Alternating current

ADC Analog-to-digital converter

AFM Atomic force microscopy

AITR Attenuated internal total reflection

ALS Amyotrophic Lateral Sclerosis

AMC Adiabatic microcalorimeter

ANNA Activity of Excellence and Networking for Nano-and Microelectronics Analysis

APS Advanced photon source or American Physical Society

ASTM American society for testing and materials

ATI Atom institute

AXIL Analytical X-ray analysis by iterative least squares

BB Black body

BCR Breakpoint cluster region (protein or gene) or

British Chemical Standard - Certified reference material

BESSY Berliner Elektronen Speicherring Gesellschaftfür Synchrotronstrahlung

BRM Blank reference material

CAS Chemical Abstracts Services

CCD Charge-coupled device

CHA Concentric hemispherical analyzer

CHESS Cornell high-energy synchrotron source

CMA Cylindrical mirror analyzer

CMOS Complementary metal oxides

CMOS Complementary metal oxides semiconductor

CRM Certified reference material

CVD Chemical vapor deposition

CXRO Center for X-ray Optics and Advanced Light Source

DC Direct current

xvii

DCM Double-crystal monochromator

DESY Deutsches Elektronen Synchrotron

DIN Deutsches Institut für Normung

DMM Double multilayer monochromator

DORIS Doppel Ring Speicher

EDS Energy-dispersive spectrometry or spectrometer

EDTA Ethylene-diaminetetraceticacid

EPMA Electron probe microanalysis

ESCA Electron spectroscopy for chemical analysis

ET-AAS Electrothermal atomic absorption spectrometry

EXAFS Extended X-ray absorption fine structure

FAAS Flame atomic absorption spectrometry

FCM Four-crystal monochromator

FEL Free-electron laser

FET Field effect transistor

FPS Flat panel sensor

FT-IR Fourier transform-infra red

FWHM Full width at half maximum

GC-MS Gas chromatography-mass spectrometry

GeLi Ge(Li) detector; Germanium drifted with Lithium ions

GE-XRF Grazing exit X-ray fluorescence

GF-AAS Graphite furnace-atomic absorption spectrometry

GI-XRD Grazing incidence X-ray diffractometry

GI-XRF Grazing incidence X-ray fluorescence

GIE-XRF Grazing incidence/exit X-ray fluorescence

GLP Good laboratory practice

HASYLAB Hamburger Synchrotron Strahlungslabor

HOPG Highly ordered (oriented) pyrolytic graphite

HPGe HPGe detector; high-purity Germanium

HPLC High-performance liquid chromatography

HS Humic substances

IAEA International Atomic Energy Agency

IC Integrated circuit

ICDD International Centre for Diffraction Data

ICP Inductively coupled plasma

ICP-MS Inductively coupled plasma-mass spectrometry

ICP-OES Inductively coupled plasma-optical emission spectrometry

IDMS Isotope dilution-mass spectrometry

xviii LIST OF ACRONYMS

IEEE Institute of Electrical and Electronics Engineers

IFG Institut für Geräteentwicklung

IMEC Interuniversity Microelectronics Center

INAA Instrumental neutron activation analysis

IR Infrared

IRMM Institute of Reference Materials and Measurements

ISO International Standard Organization

ITRS International Technology Roadmap for Semiconductors

IUPAC International Union for Applied Chemistry

JCPDS Joint Committee on Powder Diffraction Standards

JFET Junction Gate FET

KFA Kernforschungsanlage

LED Light emitting diode

LINAC Linear accelerator

MBI Max-Born Institut

MCA Multichannel analyzer

MRI Magnetic resonance imaging

MRT Magnetic resonance tomography

NEXAFS Near extended X-ray absorption fine structure

NIES National Institute for Environmental Studies

NIST National Institute of Standards and Technology

NSF Nephrogenic Systemic Fibrosis

NSLS National Synchrotron Light Source

PES Photoelectron spectrometry

PGM Plane grating monochromator

PIN Positive-intrinsic-negative

PIXE Proton or particle induced X-ray emission

PMM Primary methods of measurement

PTB Physikalisch-Technische Bundesanstalt

PVD Physical vapor deposition

QM Quality management

QXAS Quantitative X-ray analysis system

RBS Rutherford backscattering spectrometry

RMS Root mean square (of the mean squared deviations)

ROI Region of interest

RSD Relative standard deviation

SAXS Small angle X-ray scattering

SD Standard deviation, absolute value

LIST OF ACRONYMS xix

SDD Silicon drift detector

SDi Strategic Directions International

SEM Scanning electron microscopy

SGM Spherical grating monochromator

SiLi Si(Li) detector; Silicium drifted with Lithium ions

SIMS Secondary ion mass spectrometry

SOP Standard operating procedure

SPM Suspended particulate matter

SQUID Superconducting quantum interference device

SR Synchrotron radiation

SRM Standard reference material

SSD Solid-state detector

SSRL Stanford Synchrotron Radiation Laboratory

STJ Superconducting tunnel junction

STM Scanning tunneling microscope or microscopy

SW Standing wave

TDS Total dissolved solids

TES Transition edge sensor

TR Total reflection

TRIM Transport and range of ions in matter

TR-XPS Total reflection XPS

TR-XRD Total reflection XRD

TR-XRR Total reflection XRR

TXRF Total reflection X-ray Fluorescence

UCS Ultra-Clean Society

UHV Ultra-high-vacuum

ULSI Ultra-large-scale integration

UPS Ultraviolet photoelectron spectrometry

USB Universal serial bus

UV Ultraviolet

VAMAS Versailles Project on Advanced Materials and Standards

VLSI Very-large-scale integration

VPD Vapor-phase decomposition

WDS Wavelength-dispersive spectrometry or spectrometer

XAFS X-ray absorption fine structure

XANES X-ray absorption near-edge structure

XPS X-ray photoelectron spectrometry

XRD X-ray diffractometry

xx LIST OF ACRONYMS

XRF X-Ray fluorescence

XRR X-ray reflectometry

XSW X-ray standing waves

Chemical Compounds

APDC Ammonium pyrrolidine dithiocarbamate

DNA Deoxyribonucleic acid

h-BN hexagonal form of boron-nitride

HMDTC Hexamethylene-dithiocarbamate

mQC murine Glutaminyl cyclase

MIBK Methyl isobutyl ketone

NaDBDTC Sodium dibutyldithiocarbamate

PEDOT:PSS Polyethylenedioxythiophene: Polystyrene sulfonate

PEG Polyethylene glycol

PFA Polyfluoroalkoxy (polymers)

PEI Polyethylenimine

PEO Polyethylene oxide

PP Polypropylenes

PTFE Polytetrafluoro-ethylenes

PMMA Polymethyl methacrylate

RNA Ribonucleic acid

ROS Reactive oxygen species

TEAB Triethylamine boraneTMAB Trimethylamine borane

TMB Trimethylborazine

LIST OF ACRONYMS xxi

LIST OF PHYSICAL UNITS AND SUBUNITS

A ampere

a year (annum)

°C °Celsius or centigrade

C coulomb

cm centimeter

d day

eV electronvolt

F farad

ft foot

GHz gigahertz

GeV giga-electronvolt

g gram

h hour or hecto

hPa hectopascal

Hz hertz

in inch

J joule

K kelvin

keV kilo-electronvolt

kg kilogram

km kilometer

kPa kilopascal

kV kilovolt

kW kilowatt

l liter

m meter or milli

mA milliampere

MeV mega-electronvolt

min minute

ml milliliter

mm millimeter

mol mole

mrad milliradian

N newton

nl nanoliter

nm nanometer

Pa pascal

pl picoliter

rad radian

rpm revolutions per minute

s second

sr steradian (squared radian)

T tesla

V volt

W watt

kΩ kiloohm

μl microliter

μrad microradian

Ω ohm

% per cent (10�2)

‰ per mill (10�3)

ppm parts per million (10�6)

ppb parts per billion (10�9)

ppt parts per trillion (10�12)

xxii

LIST OF SYMBOLS

Symbols for Physical Quantities (in general they are unambiguous; in excep-tional cases their meaning becomes clear by their individual context; for adetailed definition and distinction they can have indices)

α Glancing angle of incident primary beam

αcrit Critical angle of total reflection

αd glancing angle determined by the detector’s field of vision

αf Sommerfeld’s fine structure constant or glancing angle determinedby the footprint

αk glancing angles of Kiessig maxima

β Imaginary component of refractive index or ratio of electronvelocity and light velocity or take-off angle of the fluorescenceradiation

γ Lorentz factor

δ Decrement or real component of refractive index (or sometimesdifference)

Δ Path difference or interval

ε Efficiency of a detector

ζ Vertical coherence length

η Efficiency

θ Polar angle of an electron’s position (in plane of the orbit)

Θ Tilt angle around horizontal x-axis (corresponds to α)

λ Wavelength

λC Compton wavelength

λcut Longest wavelength of radiation refracted at a given angle

μ/ρ Total mass-absorption coefficient

ν Frequency or index

ξ Horizontal coherence length

ρ Density of an element or material

ρm Radius of curvature of the circular electron orbit

xxiii

σ Shielding constant or roughness

σ/ρ Mass-scatter coefficient or cross-section of X-ray scattering

τ Dead time

τdead Dead-time or shaping time

τ/ρ Photoelectric mass-absorption coefficient

υ Phase velocity or velocity of light in a medium

φ Phase difference

Φ Angle of rotation around vertical z-axis or work function ofa spectrometer

χ Tilt correction around horizontal y-axis

ψ Azimuthal angle of an electron’s position (vertical to the orbit)

Ψ Angle of deflection

ω Angular frequency (Larmor frequency) or fluorescence yield

Ω Solid angle

a Distance or period or axis or acceleration of a particle or latticeconstant

A Atomic mass of an element or absorption or ordinate offset or

detector area

b Axis or constant of Wien’s displacement law or lattice constant

B Slope of calibration straight line or absolute sensitivity or magneticfield strength

c Concentration or molar ratio of an element in a sample or latticeconstant

cA Area related mass of an element (area density)

cv Volume concentration of an element

c0 Light velocity in vacuo

C Particular constant

Cm Material constant determining αcrit

d Thickness of a sample or a particular layer or interplanar spacingof a Bragg crystal

D Dead-time loss or thickness of a stack of layers

e Elementary charge of a single electron or energy necessary for aspecial atomic reaction

E Energy of photons or amplitude of the electric field strength or

energy of radiation

Ebinding Binding energy of an electron within an atom

Ecrit Characteristic (central) photon energy of synchrotron radiation

Ecut Cut-off energy of refraction

Eel Kinetic energy of an electron (beam energy)

xxiv LIST OF SYMBOLS

Ekin Kinetic energy of a particle

Emin Minimum photon or electron energy required or critical excitationenergy

Emax Maximum photon or electron energy accepted or photon energyfor maximum brilliance

f Absorption jump factor or frequency or length of the footprint orparameter of fading

F Fano factor or Lorentz force or formfactor (fading coherence)

g Relative emission rate

h Planck’s constant or height

h̵ Planck’s constant over 2π

h, k, l Miller indices

i Current or index

I Intensity or current

j index

k Particular constant or Boltzmann’s constant or order of Kiessigmaxima

K Calibration constant or Bessel function or undulatorparameter

l Length

L Distance of two points

m Matrix element or mass or order of Bragg’s reflection

M Matrix, two-dimensional

M molar mass of ions or atoms

n Count rate or refractive index or number density

N Number of photons or layers or oscillations or net intensity

NA Avogadro’s constant

P Level of significance or probability or electrical power

q Charge of a particle

Q Auxiliary quantity of mass absorption

r Radius or distance from the origin or absorption jump ratio

rel Classical electron radius

R Reflectivity

Ra average roughness

R∝

Rydberg’s constant

S Relative spectral sensitivity or Poynting vector

t Time or live time or thickness of a layer or student factor

T Acquire time or transmissivity or tilt center or temperature

U Voltage

LIST OF SYMBOLS xxv

υ Small volume

V Volume

υ/V Dilution factor

w Width or spiked volume

wbeam beam width

W Radiant energy or window distance

x Lateral movement or axis

X Addenda of trinomial expression of fluorescence intensity

y Lateral movement or axis

z Depth in a sample normal to its surface or vertical shift

zn Penetration depth of radiation in a sample normal to its surface

Z Atomic number of a chemical element

zfade damping constant of fading

xxvi LIST OF SYMBOLS

CHAPTER

1

FUNDAMENTALS OF X-RAY FLUORESCENCE

1.1 A Short History of XRF 2

1.2 The New Variant TXRF 8

1.2.1 Retrospect on its Development 81.2.2 Relationship of XRF and TXRF 13

1.3 Nature and Production of X-Rays 15

1.3.1 The Nature of X-Rays 151.3.2 X-Ray Tubes as X-Ray Sources 171.3.3 Polarization of X-Rays 291.3.4 Synchrotron Radiation as X-Ray Source 30

1.4 Attenuation of X-Rays 44

1.4.1 Photoelectric Absorption 461.4.2 X-Ray Scatter 491.4.3 Total Attenuation 51

1.5 Deflection of X-Rays 53

1.5.1 Reflection and Refraction 531.5.2 Diffraction and Bragg’s Law 591.5.3 Total External Reflection 621.5.4 Refraction and Dispersion 71

X-ray fluorescence (XRF) is based on the irradiation of a sample by a primaryX-ray beam. The individual atoms hereby excited emit secondary X-rays thatcan be detected and recorded in a spectrum. The spectral lines or peaks of sucha spectrum are similar to a bar-code and are characteristic of the individualatoms, that is, of the respective elements in the sample. By reading a spectrum,the elemental composition of the sample becomes obvious.

Such an XRF analysis reaches near-surface layers of only about 100 μmthickness but generally is performed without any consumption of the sample.The method is fast and can be applied universally to a great variety of samples.Solids can be analyzed directly with no or only little sample preparation. Apartfrom the light elements, all elements with atomic numbers greater than 11(possibly greater than 5) can be detected. The method is sensitive down to themicrogram-per-gram level, and the results are precise and also accurate ifmatrix-effects can be corrected.

Total-Reflection X-ray Fluorescence Analysis and Related Methods, Second Edition.Reinhold Klockenkämper and Alex von Bohlen.© 2015 John Wiley & Sons, Inc. Published 2015 by John Wiley & Sons, Inc.

1

For these merits, XRF has become a well-known method of spectrochemicalanalysis. It plays an important role in the industrial production of materials, inprospecting mineral resources, and also in environmental monitoring. Thenumber of spectrometers in use is estimated to be about 15 000 worldwide. Ofthese, 80% are working in the wavelength-dispersive mode with analyzingcrystals; only 20% operate in the energy-dispersive mode, mainly with Si(Li)detectors, and recently with Si-drift detectors. At present, however, energy-dispersive spectrometers are four times more frequently built than wavelength-dispersive instruments due to the advantage the former provides in fastregistration of the total spectrum.

A spectrum originally means a band of colors formed by a beam of light asseen in a rainbow. The Latin word “spectrum” means “image” or “apparition.”The term was defined scientifically as a record of intensity dependent on thewavelength of any type of electromagnetic radiation. The “intensity” is to beinterpreted as a number of photons with particular photon energy. Today, aspectrum can also be a record of a number of ions according to their atomicmass or it can demonstrate the number of electrons in dependence of theirelectron energy. The visual or photographic observation of such a spectrum iscalled spectroscopy. The term is deduced from the Greek verb “σκoπειν,” whichmeans “to observe” or “to look at.” On the other hand, “μετρω” in Greekmeans “to measure” so that spectrometry is a quantitative photoelectricexamination of a spectrum.

1.1 A SHORT HISTORY OF XRF

The foundations of spectrochemical analysis were laid by R.W. Bunsen, achemist, and G.R. Kirchhoff, a physicist. In 1859, they vaporized a salt in aflame and determined some alkaline and alkaline-earth metals by means of anoptical spectroscope. Today, optical atomic spectroscopy has developed avariety of new analytical techniques with high efficiency, such as atomicabsorption spectroscopy (AAS) with flames (FAAS) or electrothermal fur-naces (ET-AAS), and the inductively coupled plasma technique (ICP) com-bined with atomic emission or mass spectrometry (ICP-AES and ICP-MS).These techniques do entail some consumption of the sample, but they arehighly suitable for ultratrace analyses of solutions.

Nearly 40 years after the discovery by Bunsen and Kirchhoff, in 1895,Wilhelm Conrad Röntgen (Figure 1.1) discovered a remarkable, invisible, andstill unknown radiation, which he called X-rays. This name has been adopted inthe English-speaking areas; only in German-speaking parts is the radiationcalled “Röntgenstrahlen” in his honor [1]. In 1901, Röntgen was awarded thefirst Nobel Prize in Physics. The great potential of X-rays for diagnosticpurposes in medicine and dentistry was immediately recognized worldwide.Furthermore, different researchers clarified the fundamentals of X-ray spec-troscopy and developed the methods of XRF (X-ray fluorescence) and XRD

2 FUNDAMENTALS OF X-RAY FLUORESCENCE