A self-consistent mass absorption correction for silicate analysis by X-ray fluorescence

Abstract

Deviations from proportionality form the major source of error in X-ray fluorescent analysis. By careful preparation of the sample and equally careful operation of the spectrograph these deviations can be confined to inter-sample differences in total mass absorption. In order to eliminate or estimate these differences a variety of methods have been described; but none have found universal application. The method of a self-consistent mass absorption correction does not share the shortcomings of its predecessors. Without any pre-supposition regarding the over-all chemistry, an approximate composition of the unknown is first calculated by direct reference to a standard. Using this approximate composition the total mass absorption of the unknown is determined for each operational wavelength, and this information then used to make a more accurate estimate of the composition of the unknown. This more accurate estimate provides the means for determining a yet more accurate value for the total mass absorption at each wavelength. Thus, by an iterative process, a self-consistent chemical composition is obtained, and this value is then corrected for other deviations from proportionality by reference to a set of standards, using a quadratic regression relationship. Although this method has only been applied so far to whole rock analyses, its application could prove to be much more extensive, for the computer programme described is so constructed that, by a simple interchange of the matrix block and reference standards, analyses could be made within the entire range of the X-ray spectrum.