Energy-dispersive X-ray fluorescence analysis of silicate rocks: comparisons with wavelength-dispersive performance

Abstract

The performance of routine energy-dispersive X-ray fluorescence (ED-XRF) analysis using direct tube excitation is compared with that of current wavelength-dispersive practice for the determination of both major and trace elements in silicate rocks. The influence of detector resolution is considered and a comparison is made between limits of determination, analysis times, instrumental precision and routine performance using data for typical wavelength-dispersive X-ray fluorescence (WD-XRF) techniques taken from the literature. It is shown that although ED-XRF limits of determination of the lighter major elements are inferior to those of WD-XRF data, analytical precisions at the levels normally encountered in silicate rocks are comparable. For the ED-XRF analysis of the heavier trace elements that are effectively excited by the silver X-ray tube used in this work (especially Rb, Sr, Y, Zr, Nb, Pb and Th) limits of determination, instrumental precision and routine analytical performance are equivalent to results obtained by WD-XRF. It is suggested that the over-all accuracy of either technique can be influenced significantly by uncertainties in the recommended values for international rock reference materials that are generally used to set up and/or test calibrations.