Comparison of particle and photon excited X-ray fluorescence applied to trace element measurements of environmental samples

Abstract

The sensitivities of particle and photon excitation methods of X-ray fluorescence have been compared for the analysis of trace elements in environmental samples. The analysis sensitivity for comparing different methods of excitation has been shown to be proportional to the square root of the product of the peak to background ratio at the X-ray energy of interest and the peak to total ratio. The sensitivities possible with high energy alpha particle excitation are in the tens of ppm range while excitation by low energy proton, transmission tube X-rays and 100 mCi radioisotopic sources provide sensitivities in the 1 to 5 ppm range for environmental material in analysis times of about 10 min. Fifteen to twenty-five elements can be detected at the concentrations present in typical environmental samples with demonstrated quantitative techniques available for the measurement of 10 to 20 elements, depending on sample type. The results indicate that low energy proton excitation techniques do not exhibit analysis capabilities significantly different from those of photon excitation methods while high energy alpha excitation is not competitive.