Matrix corrections for energy dispersive X-ray fluorescence analysis of environmental samples with coherent/incoherent scattered X-rays.

A numerical method is given for computing matrix effects in relatively thick (63 mg/cm/sup 2/), pelletized homogeneous or particulate samples of biological and environmental origin. The method relies on estimating an approximate light element (Z less than or equal to 13) content of the sample from the coherent and incoherent scatter peaks after they have been corrected for absorption and for scattering from the heavy elements (Z greater than 13). The total sample absorption due to both light and heavy elements is computed by an iterative procedure which yields self-absorption corrections with a relative precision of several percent. Enhancement and particle size effects are also computed in the iterative procedure on the same basis as the absorption corrections. Since the corrections are based on a thin sample x-ray calibration, repeated calibrations for specific sample types are avoided. The method yields matrix corrected quantities of 24 elements from 1024 channels of raw data in approximately 20 to 50 s (5 to 15 iterations) using a 24K, PDP-15 computer.