Semiconductor detector x-ray fluorescence spectrometry applied to environmental and biological analysis

The effective application of Si(Li) semiconductor X-ray detectors to the elemental analysis of trace impurities in environmental and biological specimens has required the improvement of existing systems. The use of low-background X-ray tubes for fluorescence excitation and the increased counting rate capability of the electronics have reduced counting times necessary for analysis. The presence of radiation-induced low-energy background in conventional detectors has been shown to be a major limiting factor in the detection sensitivity for trace element constituents in organic specimens. The use of guard-ring detector geometries has eliminated the cause of much of this background, and has reduced detection limits by approximately an order of magnitude. The practical detection of 0.1 ppm concentration achieved with these techniques has made energydispersive X-ray fluorescence a potent tool for the analysis of environmental and biological samples. A few examples have been chosen to emphasize particular advantages of the technique relative to alternative analytical methods. Examples include trace element determination in blood, air pollution particulate analysis, and studies of the influence of environment on the trace constituents of biological specimens.