Abstract

The term 'X-ray fluorescence analysis' (XRF) refers to the measurement of characteristic fluorescent emission resulting from the deexcitation of inner shell vacancies produced in the sample by means of a suitable source of radiation. For a particular energy (wavelength) of fluorescent light emitted by a sample, the number of photons per unit time (generally referred to as peak intensity or count rate) is related to the amount of that analyte in the sample. The counting rates for all detectable elements within a sample are usually calculated by counting, for a set amount of time, the number of photons that are detected for the various analytes' characteristic X-ray energy lines. It is important to note that these fluorescent lines are actually observed as peaks with a semi-Gaussian distribution because of the imperfect resolution of modern detector technology. Therefore, by determining the energy of the X-ray peaks in a sample’s spectrum, and by calculating the count rate of the various elemental peaks, it is possible to qualitatively establish the elemental composition of the samples and to quantitatively measure the concentration of these elements. XRF is an analytical method to determine the chemical composition of all kinds of materials. The materials can be in solid, liquid, powder, filtered or other form. XRF can also sometimes be used to determine the thickness and composition of layers and coatings. The method is fast, accurate and non-destructive, and usually requires only a minimum of sample preparation. Applications are very broad and include the metal, cement, oil, polymer, plastic and food industries, along with mining, mineralogy and geology, and environmental analysis is of water and waste materials. XRF is also a very useful analysis technique for research and pharmacy. For routine XRF analysis, two major approaches are distinguishable based on the type of detector used to measure the characteristic X-ray emission spectra. Wavelength dispersive X-ray fluorescence (WDXRF) analyses depend upon the use of diffracting crystal to determine the characteristic wavelength of the emitted X-rays. Energy dispersive X-ray fluorescence (EDXRF) employs detectors that directly measure the energy of the X-rays by collecting the ionization produced in suitable detecting medium.

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