[B._Beckhoff,_et_al.]_Handbook_of_Practical_X-Ray_(b-ok.org).pdf

With micro xrf not only the elemental composition of

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With micro-XRF, not only the elemental composition of a sample is accessible, but also the related spatial distribution. Furthermore, the use of synchrotron radiation extends the possibilities of micro-XRF with respect to the elemental range to light elements and increases both the elemental sen- sitivity and the spatial resolution. Another advantage of using synchrotron radiation is the possibility to combine micro-XRF with other microanalytical
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434 B. Kanngießer and M. Haschke methods. A first overview of micro-XRF techniques with the focus on micro- XRF at synchrotron sources can be found in the monograph by Janssens et al. [4]. This chapter focuses on laboratory units and their various applications. It delivers an overview on existing micro-XRF instruments and discusses the instrument components according to their practical relevance. Various fields of applications are also discussed giving an impression on the wide range of different analytical tasks that can be solved with a micro-XRF bench-top unit. The last part of this chapter describes the newest development in micro- XRF, which is the extension of micro-XRF into a depth-sensitive method. This results in a true three-dimensional analytical method. The new set-up is described for the laboratory as well as for the synchrotron source, and examples are given for both arrangements to demonstrate their application. This last part also serves as a transition to the following chapter by Simionovici and Chevallier in which the actual developments in micro-XRF at synchrotron sources are described. 7.1.2 General Description of Micro-XRF Laboratory Units There is a wide range of analytical methods available with which the chemical composition of a sample can be determined. They differ in the covered range of concentration and of elements, in information depth, in accuracy etc. But only a few of them are able to selectively analyse small sample areas. Table 7.1 provides a summary of the variety of analytical methods currently available for this purpose. Properties, such as the elemental range covered, together with the depth of the analysed sample volume are summarised for every method. The relation between the detectable concentration range and the spatial resolution is displayed in Fig. 7.1. Only the method with a spatial resolution better than 1 mm can be regarded as microanalytical method. From Fig. 7.1 Table 7.1. Analytical methods currently available for chemical composition together with their spatial resolution Method Elements Spatial resolution Sample quality AAS Li–U Solution ICP-OES Li–U Solution, slurry ICP-MS Li–U Solution LA-ICP-MS Li–U µ m Solids OES Li–U Solid (electrically conductive) GDS Li–U nm– µ m Solids WD-XRF Li–U µ m–mm Solids, liquids, powder ED-XRF Na–U µ m–mm Solids, liquids, powder Micro-XRF Na–U µ m–mm Solids, liquids, powder EPMA Be–U µ m Solid (electrically conductive) PIXE C–U nm– µ m Solids SIMS Li–U nm Solids AES B–U nm Solids
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Methodological Developments and Applications 435 100% 1000ppm 1ppm
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