ABSTRACT
X-ray fluorescence spectrometry (XRFS) is a technique for the determination of elemental abundances in samples that are normally presented for analysis in solid form (liquids can be analyzed directly as well, although such applications are not as common). The sample surface is excited by a primary beam of x-ray radiation. Provided they are sufficiently energetic, x-ray photons from this primary beam are capable of ionizing inner shell electrons from atoms in the sample, resulting in the emission of secondary x-ray fluorescence radiation of energy characteristic of the excited atoms. The intensity of this fluorescence radiation is measured with a suitable x-ray spectrometer and, after correction for matrix effects, can be quantified as the elemental abundance. The technique is notionally claimed to have the potential of determining all the elements in the periodic table from sodium to uranium to detection limits that vary down to the µg g−1 level. However, using specialized forms of instrumentation, this range may be extended for same sample types down to at least carbon, although with reduced sensitivity and with some care required in the interpretation of results, owing to the very small depth within the sample from which the analytical signal originates for this element. The technique is very well established and, in contrast to other common atomic spectrometry techniques, it is not usual to take the sample into solution before analysis. The preferred forms of sample preparation for quantitative analysis include a solid disk prepared by compressing powdered material, a glass disk prepared after fusion of a powdered sample with a suitable flux, loose powder placed in an appropriate sample cup, and dust analyzed in situ on the collection filter.
