This leads to the application aspects often not being understood very well. Consequently, the analytical results are accepted without scrutinizing the influence of sample state, preparation methods, and measurement parameters. This becomes especially true because complete results are often available as the outcome of an instrumental analysis and their quality cannot be correctly comprehended.
In order to assure the quality of the applications and their results, the analyst must critically question all aspects of the test method. For this purpose, a basic understanding of the influences of sample condition, preparation methods, measurement parameters, and evaluation models used on the quality of the analytical result is imperative.
Therefore, we are deliberately focusing on the daily laboratory work with commercially available instruments. On the other hand, the interesting but not routine applications of the method utilizing synchrotron radiation excitation are not addressed. Nevertheless, methodical developments obtained on a synchrotron are often incorporated into laboratory analysis, such as micro-X-ray fluorescence (μ-XRF) or applications with grazing beam geometry. However, this book treats only laboratory applications. If any of these newly developed methods have been implemented into special laboratory instruments these are also presented as examples.
Despite the focus on the various applications, a brief introduction to the fundamentals of X-ray spectrometry and a comprehensive presentation of the basic steps for a complete analysis are required in order to be able to relate in the following discussion of the individual applications.
The book therefore starts with a discussion of the analytical capability of X-ray spectrometry in Chapter 2. The most important relations that describe the generation of the characteristic radiation are presented, and the individual steps in the execution of an analysis follow, along with a brief characterization of their influence on the analysis result. Deeper descriptions of the physical bases are comprehensively given in other publications (e.g. Erhardt 1989; Hahn-Weinheimer et al. 2012; van Grieken and Markowicz 2002; Beckhoff et al. 2006).
In Chapter 3, the various sample preparation procedures typical for X-ray spectrometry are presented and their influence on the precision and trueness of the analyses is discussed. Even though the sample preparation is generally regarded as being very simple for XRF, it is important to carry it out carefully, appropriate to the expectations of the analysis result.
In Chapter 4, the different types of X-ray spectrometers are discussed. On the one hand, the general differences and application characteristics of wavelength-dispersive and energy-dispersive instruments are examined; on the other hand, the different instrument types as well as the instruments currently available on the market are presented.
In Chapter 5, the essential steps for the measurement of a spectrum are reviewed, in particular, the optimum selection of the measurement parameters and the steps for the evaluation of the measured data. The first step is the determination of the intensities of the fluorescence peaks, where different procedures are used for wavelength- and energy-dispersive spectrometers. Then quantification models and factors concerning the consideration of matrix interaction, both in the analysis of homogeneous samples and in the characterization of layers, are presented. Here, a comprehensive and detailed description of the theory of X-ray spectrometry is not required, since a series of detailed papers are available (see, for example, Hahn-Weinheimer et al. 2012; Jenkins et al. 1981; Lachance and Claisse 1994; Mantler 2006) and only very few new ideas have been added in the last few years. In this chapter, further possibilities for the evaluation of spectra are presented, in which the individual spectral components are not considered separately, but the spectrum as a whole is evaluated by means of chemometric methods.
Chapter 6 is devoted to the discussion of the classification, determination, and evaluation of errors. The achievable analytical precision of XRF is determined by the errors. In addition to the traditional treatment of errors with the Gaussian error model, the principle of measurement uncertainty is also discussed. This chapter is intended to qualify the expectations of an analytical result.
In Chapters 7 and 8, a brief comparison is made with other element analysis methods, in particular atomic absorption and emission spectrometry as well as mass spectrometry. The fundamentals of radiation protection when dealing with X-ray radiation, in particular when carrying out X-ray analysis experiments, are compiled as well.
Based on these fundamentals, various applications of XRF, which have been used already over a long time period or were introduced recently, are presented and discussed. The presentation here is carried out according to the different sample qualities or according to the analytical question.
Typical XRF applications are discussed first. Chapter 9 discusses the analysis of homogeneous solid samples, such as various metallic materials, glasses, or plastics. Chapter 10 describes the investigation of powdered samples, such as geological samples, soil, building materials, slags, and dusts.
In Chapter 11, the different possibilities for analyzing liquids are presented, either by direct analysis or, for example, by different enrichment procedures to answer specific analytical questions. Applications with total reflection XRF (TXRF) are dealt with in Chapter 12. Here, in addition to ultra-trace analyses of liquids the analysis of very small sample quantities is the focus.
Descriptions of the analysis of nonhomogeneous materials cover a wide range of analytical questions. This concerns inhomogeneities normal to the sample surface, i.e. the characterization of layered materials (Chapter 14) along with their different applications, as well as inhomogeneities in the sample plane and the analysis of irregularly shaped samples (Chapter 15). In this case, only small sample areas are to be analyzed, which means a point analysis has to be carried out. This is important when identifying particles or inclusions as also when analyzing inhomogeneous materials.
Handheld instruments are increasingly being used for element analysis. Based on this fact, the applications that up to now have been typical for this instrument technology are presented in Section 15.4. It was possible to increase the efficiency of this type of instruments significantly in recent years due to the miniaturization of all hardware assemblies. In this way, their range of measurement applications could be expanded continuously. An important factor for that expansion is the possibility for “on-site” analysis, i.e. materials for analysis are no longer required to be taken to a laboratory. However, the quality of the analyses is not as high, mainly because of a very simplified or even completely missing sample preparation, undefined sample geometry, or contamination in the measuring environment.
A further important field of application of spatially resolved analysis, the determination of element distributions, is dealt with in Chapter 16. This method allows not only the analysis of small areas on structured materials, but also the investigation of their element distributions and therefore their more detailed characterization. Presentation of the examples for the distribution analysis is carried out according to the different analytical tasks. For example, the analysis of geological samples and of electronic assemblies as well as homogeneity tests of reference samples is presented.
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