XRF Facilities

An XRF facility usually consists of a primary radiation source, a detector, an electronics system, and sometimes an optics system. Various XRF 

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Quantitative XRF analysis has developed from specific to universal methods. At the time of poor computational facilities, methods were limited to the determination of few elements in well-defined concentration ranges by statistical treatment of experimental data from reference material (linear or second order curves), or by compensation methods (dilution, internal standards, etc.). Later, semi-empirical influence coefficient methods were introduced. Universality came about by the development of fundamental parameter approaches for the correction of total matrix effects... 

Principles and Characteristics Particle-induced X-ray emission spectrometry (PIXE) is a high-energy ion beam analysis technique, which is often considered as a complement to XRF. PIXE analysis is typically carried out with a proton beam (proton-induced X-ray emission) and requires nuclear physics facilities such as a Van der Graaff accelerator, or otherwise a small electrostatic particle accelerator. As the highest sensitivity is obtained at rather low proton energies (2-4 MeV), recently, small and relatively inexpensive tandem accelerators have been developed for PIXE applications, which are commercially available. Compact cyclotrons are also often used. 

Two different experiments have been performed at ID18F (p-XRD and p-XRF) and ID21 (p-XRF and p-XANES) beamlines at the ESRF (European Synchrotron Radiation Facilities, Grenoble, France). 

Because of the gradual loss of neutron irradiation facilities (and the general public unpopularity of nuclear sciences), NAA is being slowly replaced by other techniques, chiefly ICP-OES, and more recently ICP MS, which has comparable sensitivity. It has, consequently, become necessary to carry out research comparing these techniques since there is a need to know how compatible ICP data are with the vast databanks (such as the Aegean databank discussed above) of NAA. This has included comparison of NAA with ICP OES on bone (Akesson et al. 1994) XRF and NAA on ceramics (Garcia-Heras et al. 2001) NAA, XRF, ICP-OES, and ICP MS on ceramics... 

Analytical techniques used for clinical trace metal analysis include photometry, atomic absorption spectrophotometry (AAS), inductively coupled plasma optical emission (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS). Other techniques, such as neutron activation analysis (NAA) and x-ray fluorescence (XRF), and electrochemical methods, such as anodic stripping voltammetry (ASV), are used less commonly For example. NAA requires a nuclear irradiation facility and is not readily available and ASV requires completely mineralized solutions for analysis, which is a time-consuming process. 

Since XRF results are also influenced by sample density, the sample conditioning system may also require facilities for temperature and pressure regulation. This obviously adds to the cost of an on-stream system compared to an equivalent at-plant or laboratory based system. 

Abbreviations AES, Auger emission spectrometry CRM, Certified reference material DL, Detection limit ED, Energy dispersive ESRF, European Synchrotron Radiation Facility EXAES, Extended X-ray absorption fine structure NEXAFS, Near edge X-ray absorption fine structure PCI, Phase contrast imaging RM, Reference material SR, Synchrotron radiation SRM, Standard reference material TXRF, Total reflection X-ray fluorescence XANES, X-ray absorption near edge structure XAS, X-ray absorption spectrometry XDM, X-ray diffraction microscopy XFCT, X-ray fluorescence computerized microtomography XPEEM, X-ray photoelectron microscopy XPS, X-ray photoelectron spectrometry XRD, X-ray diffraction XRF, X-ray fluorescence... 

Experimental (dots) and simulated (solid curve) synchrotron radiation-X-ray fluorescence (SR-XRF) spectra obtained for the NIST SRM 1577b bovine liver standard, corresponding to 21 keV excitation at the European Synchrotron Radiation Facility (ESRF) ID18F end-station (Adapted from Vincze et al. 2004)... 

In principle. X-ray fluorescence (XRF) per se is an atomic analytical technique, rather than a nuclear one, since it is based on electron transitions outside atomic nucleus. However, XRF is often defined as a nuclear-related technique, as frequently mentioned in many technical documents issued by the International Atomic Energy Agency, mainly because XRF is used where there are radioactive isotopic sources or accelerators, and even in large synchronous radiation facilities. Further, the detection of X-rays almost always needs nuclear radiation detectors, like Si(Li) or other planar detectors. 

Process control in today s highly automated production facilities is strongly dependent upon fast, precise and accurate chemical analysis, and XRF has been found to be widely applicable in the metal industries. XRF of metallic samples includes several solvable problems, especially in the areas of sample preparation and modelling calculations to convert intensities into concentration data. In general, metallic samples do not need complicated sample preparation, but the analytical information is derived from a volume close to the surface which must be polished. XRF is applied to various kinds of alloys, such as Na-Mg alloys, and Al, Ti, ferrous, Ni, Cu, Zr, W and Au alloys, bronzes... 

The advantages of expressing the results of XRF measurements in mgl/gr thyroid tissue instead of total iodine have been extensively discussed by Leisner during the symposium held in Brussels in September 1982 and alluded to in Chapter VIII of this monograph. It seems nevertheless that from the point of view of clinical applications, the choice is essentially a question of available facilities Indeed, as a whole, comparable results in differential diagnosis and follow-up of patients have been obtained with both modes of expression.. An unexpensive approach such as described in Chapter IV might be a practical solution. 

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