X-ray fluorescence analysis

Abstract

X-ray fluorescence analysis (XRF) is a powerful analytical technique for the qualitative and quantitative determination of chemical elements in a sample. The operating principle of XRF is based on the irradiation of the sample with ionizing radiation, thus inducing excited states of the atoms in the analyte. The response of the atoms during the de-excitation process is the emission of X-rays having well defined energies or wavelengths characteristic for an element. (The characteristic energies of many elements of the Periodic Table can be found in Table 8A.I in the Appendix.) Complementary to the emission of characteristic X-rays is the emission of Auger electrons, which is the dominant process for light elements. The term ‘fluorescence’ expresses the analogy with the excitation of atoms during irradiation with ultraviolet (UV) radiation or by thermal excitation of the optical states by a flame and emission of fluorescence light in the visible regime. The identification by the color of the emitted radiation is accomplished by an optical spectroscope. As humans are not able to ‘see’ X-rays, sophisticated detectors are necessary to detect the characteristic lines of the elements.