Uncertainties in electron probe microanalysis

We determined uncertainties for WDS-EPMA (wavelength-dispersive X-ray spectroscopy – electron probe microanalysis) data using the globally accepted ISO/GUM (International Standards Organization/Guide to the Expression of Uncertainty in Measurement). For each calculation, such as the current drift correction and deadtime correction that precede the calculation of a k-value (net corrected X-ray counts of unknown/net corrected X-ray counts of standard), uncertainties were calculated from contributing factors and combined until a final combined standard uncertainty for the k-value was calculated. Our example used data from the analysis of the Ge Lα X-ray line in a SiGe alloy. Additional contributions to uncertainties in EPMA results, such as the matrix correction procedure and mass absorption coefficients (MACs) are considered. All statistical calculations used in the process of arriving at the combined uncertainty are included, and the basic steps of the ISO/GUM are described.