Quantitative x‐ray fluorescence analysis. Theory and practice of the fundamental coefficient method

Abstract

AbstractThe object of this paper is to outline the principle of the fundamental influence coefficient method and emphasize its utilization for the accurate x‐ray fluorescence analysis of compact or diluted specimens.For any given composition, effective coefficients, as defined by Tertian's identities, can be derived from the calculation of the theoretical fluorescence intensities, as used in the fundamental parameter approach. The importance of a careful selection of theoretical data is underlined. These include the fundamental parameters, i.e. essentially the mass absorption coefficients and the excitation factors, and the instrumental characteristics, namely the spectral intensity distribution of the x‐ray tube and the geometric factor of the spectrometer. All of these data are still under investigation and the accuracy of their determination is being assessed. The effective coefficients are inserted in a comparison standard algorithm, a practice which compensates for the residual uncertainties affecting some of the parameters. In fact, and in terms of concentration ranges, the compensation limits are fairly large and can be extended, if necessary, by recurrence procedures. A special correction algorithm, similar to the basic one, but based on ‘modified’ coefficients, is used for the analysis of diluted specimens. A suitable computer program and its accessories are defined and their use is illustrated by a variety of practical applications including the analysis of stainless steels, high‐temperature alloys, non‐ferrous alloys (bronzes) and, as an example of fused specimens, cement. The characteristic of the fundamental coefficient method is that it combines the theoretical exactness of the fundamental parameter approach with the flexibility of the usual Lachance‐Traill formulation, thus allowing any given analytical problem, whether complex or comparatively simple, to be studied and solved in agreement with the actual degree of difficulty and the accuracy required.