Quantification in XRF analysis of intermediate-thickness samples

In recent years, a number of approaches have been developed for quantitation in x-ray fluorescence (XRF) analysis of intermediate-thickness samples whose mass per unit area m fulfills the relation mthin < m < mthick where mthin and mthick are the values of mass per unit area for thin and thick samples. Intermediate samples can be preferable to thick specimens because remaining uncertainties about mass attenuation coefficients have a smaller effect on the analysis results, less material is required, the sensitivity is more favorable for low-Z elements, and secondary enhancement effects are less important. Historically, the oldest correction method applied in quantitative XRF analysis of intermediate-thickness samples is the emission-transmission method in which the specific x-ray intensities from a sample are measured successively with and without a target positioned adjacent to the back of the sample in a fixed geometry. To avoid many additional measurements that are inevitable in the emission-transmission method, some alternative correction procedures based on the use of scattered primary radiation were recently developed. The underlying principles as well as the ranges of applicability and the limitations of the correction procedures applied to XRF analysis of intermediate-thickness samples are outlined here