Anal. Chem. 2008, 80, 4421–4454 X-ray Spectrometry Kouichi Tsuji* Department of Applied Chemistry, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka, 558-8585, Japan Kazuhiko Nakano Inovation Plaza Osaka, Japan Science and Technology Agency (JST), 3-1-10 Technostage, Izumi, Osaka, 594-1144 Japan Hisashi Hayashi Department of Chemical and Biological Sciences, Faculty of Science, Japan Women’s University, 2-8-1 Mejirodai, Bunkyo-ku, 112-8681, Japan Kouichi Hayashi Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan Chul-Un Ro Inha University, 253 Yonghyun-dong, Nam-gu, Incheon, 402-751, Korea Review Contents electron probe microanalysis (EPMA), total reflection X-ray Overview 4421 fluorescence (TXRF), particle-induced X-ray emission (PIXE) Detection 4422 analysis, and X-ray absorption spectrometry (XAS). Finally, dif- Instrumentation and X-ray Optics 4428 ferent applications in each subfield of XRS are described. Since Quantification and Fundamental Data 4432 X-ray Imaging 4435 the previous review, the sections of µ-XRF and 3D-XRF are newly Total Reflection X-ray Fluorescence Analysis 4438 introduced. Electron Probe Microanalysis 4440 An international group of scientists published two overviews Particle-Induced X-ray Emission 4441 on XRS (1, 2)intheJournal of Analytical Atomic Spectrometry Micro X-ray Fluorescence Analysis 4442 X-ray Absorption Spectrometry 4443 covering the period 2006-2007 in the principal field of XRS Applications 4444 analytical spectroscopic methods and instruments. These review Sample Preparation 4444 articles involve all the important sections of XRS in nine chapters: ED-XRF 4445 Micro-XRF 4445 reviews, instrumentation, spectrum analysis, matrix correction and TXRF 4446 calibration, X-ray optics and microfluorescence, synchrotron EPMA 4447 radiation, TXRF, portable and mobile X-ray fluorescence (XRF), PIXE 4448 and online XRF and applications. In the present review, we use a XAS 4449 Standards 4450 different method of classifying the information published in the Literature Cited 4451 literature during the 2006-2007 period: detection, instrumentation (except detectors) and optics, quantification models and related OVERVIEW fundamental data, tomography and holography methods as In this review, we focus on the most significant and essential primary tools of X-ray imaging, TXRF, EPMA, PIXE, XAS, and a progress in X-ray spectrometry (XRS) published during the period final chapter that reviews the application of these methods in 2006-2007 covering the following topics: developments and geology, environmental research, industry, biology, and medicine. - improvements in the detection performance and instrumentation Two practically useful books were published in 2006 2007. of X-ray techniques and X-ray optics, new quantification models The handbook entitled Practical X-ray Fluorescence Analysis was in X-ray spectra and data evaluation, micro-X-ray fluorescence (µ- edited by five famous German researchers (3). Following the XRF) including 3D-XRF, imaging techniques such as tomography historical progress of XRF, the basic and recent developments in and holography methods for 2D or 3D imaging of microstructures, X-ray sources, X-ray optics, and X-ray detectors are described. Quantification, specimen preparation, and special configurations, * To whom correspondence should be addressed. such as TXRF and micro-XRF, and their applications in environ- 10.1021/ac800678s CCC: $40.75 2008 American Chemical Society Analytical Chemistry, Vol. 80, No. 12, June 15, 2008 4421 Published on Web 05/24/2008 mental science, geology, metallurgy, archeology, and forensic will acquire more interest in the future. Besides X-ray imaging investigations were introduced with 385 figures and 53 tables. detectors such as CCD X-ray detectors, the development of Especially, the chapter “Methodological Developments and Applica- microcalorimeters will also probably open a new phase for XRS. tions” including many recent results with pictures, drawings, and A joint mission (Suzaku) between NASA (U.S.A.) and ISAS/JAZA more than 900 literature references is judged quite valuable to (Japan) (9) has planned the development of a high-resolution researchers in XRF field. Another useful book was written by Ide- microcalorimeter array, which covers the energy band from 0.3 Ektessabi (4). In the book entitled Applications of Synchrotron to 10 keV with a nearly constant energy resolution of 6 eV and a Radiation, Microbeams in Cell Microbiology and Medicine,the peak effective area of 200 cm2 at 1.5 keV. Further developments author describes the fundamentals and applications of synchrotron will be required for practical use, not only for physical and radiation (SR) in certain aspects of cell microbiology, specifically astronomical studies but also for material and chemical studies. nondestructive elemental analyses, chemical-state analyses, and High-gain free-electron lasers (FELs) are being developed as imaging of the elements within a cell. The high brilliance and extremely bright sources. Huang and Kim (10) reviewed the basic energy variability of the SR X-ray beam are especially useful for theory of high-gain FELs. They discussed both shortening the XRF and X-ray absorption fine structure (XAFS) in the research X-ray pulse lengths and increasing the coherence of the source. areas of biology and medicine. The authors expected that the theoretical formula would progress TXRF is now a well-established technique especially for in achieving X-ray FELs and improve their performance. Gaffney applications in the field of semiconductors. Two excellent review and Chapman (11) reviewed atomic-resolution images of materials articles were recently published. Wobrauschek (5) described the with X-ray free electron lasers during chemical reactions. They fundamentals of TXRF in the laboratory and the SR facility, discussed recent advances in ultrafast X-ray lasers, femtosecond concerning the theory of the total reflection phenomenon, ap- X-ray scattering for the study of structural dynamics, and coherent plications in chemical analysis and wafer surface analysis, instru- X-ray imaging with atomic resolution. The same topic is reviewed mentation, quantification, SR-TXRF, and X-ray absorption near- in the section X-ray Imaging in the present review. edge structure (XANES) measurement in TXRF geometry. In The number of papers concerned with biological and environ- addition, he clearly discussed the drawbacks of TXRF concerning mental applications of XRS is increasing. Thus, we will review only the preparation of clean sample carriers and quantification. two such papers here, although they will also be reviewed in the Another TXRF review article, especially SR-TXRF, was written by section of Applications. Carvalho et al. (12) investigated the trace Streli (6). Recent TXRF applications for environmental, medical, elements in cancerous tissues in healthy humans using several biological, polymer, and archeological samples were reviewed with XRS techniques such as energy dispersive X-ray fluorescence (ED- over 80 references. XRF), TXRF, SR-XRF, and PIXE. They measured several tissue samples, including breast, lung, serum, intestine, prostate, and One of the research trends in XRF is micro-XRF analysis. To uterus. They mentioned that all XRS techniques showed good obtain detailed chemical information regarding advanced materials agreement, although some differences in detection limits or and environmental and biological samples, XRF analysis at analytical performance were found. TXRF gave more sensitive localized regions has been required. Therefore, many papers on results for light elements, while ED-XRF had advantages for the micro-XRF and synchrotron radiation-assisted X-ray fluorescence detection of heavier elements. Osan et al. (13) applied X-ray (SR-XRF) have been published. On the other hand, electron microanalytical methods, such as near edge X-ray absorption fine probes produce characteristic X-rays in a small region of only a structure (NEXAFS), TXRF, and EPMA, for determination of few micrometers. Therefore, EPMA is a useful technique for nitrogen and sulfur compounds in Antarctic fine aerosol particles. micro-X-ray analysis of especially light elements, although the It was possible to quantify the molar ratio of ammonium and sample must be placed in a high vacuum. However, a strong nitrate based on linear combinations of standard reference spectra continuum background is usually observed in the EPMA spec- of (NH ) SO and NaNO . Single-particle analytical results obtained trum. Thus, Haschke et al. (7) attached micro-X-ray beam 4 2 4 3 by low-Z particle EPMA supported results obtained by TXRF- equipment to the vacuum chamber of a SEM, to utilize advantages NEXAFS. provided by both micro-XRF and EPMA at the same time. In this system, excitations by both X-rays and electrons are possible. The DETECTION authors discussed quantification for X-ray analysis in both excita- Cryogenic detectors operating at very low temperature offer tion processes. Another recent trend in XRS research is medical energy resolution with an order of magnitude higher than applications and development of X-ray imaging techniques. The conventional, semiconductor-based, energy-dispersive detectors, development of X-ray detectors is critically required for X-ray such as Si or Ge detectors. The energy resolution of the cryogenic imaging. Hoheisel (8) authored an excellent review article on detector is currently 2-4 eV, which is comparable