The development of energy dispersive x-ray spectrometry (EDS) has had a profound impact on the methodology of quantitative x-ray microanalysis of thick specimens (i.e., thickness≫ electron range) as performed in electron beam instruments. By equipping the scanning electron microscope (SEM) with EDS, quantitative x-ray microanalysis has become commonly available to a wide range of users, at least some of whom have only a modest background in analytical science. An important aspect of the development of quantitative analysis by EDS has been the extensive analytical experience gained during the development of the electron probe microanalyzer (EPMA) equipped with wavelength dispersive x-ray spectrometers (WDS). The critical measurement step for quantitative WDS analysis was recognized to be the determination of the “k-value”:

k = Iunk / Istd (1)

where I is the measured characteristic intensity of a specific x-ray peak, corrected for background and peak overlaps, for both the unknown and the standard.