Standardless semi-quantitative analysis with WDS-EPMA

Abstract

A standardless semi-quantitative method for wavelength dispersive spectrometry (WDS) electron probe microbeam analysis was developed with a view to simplifying the analytical procedure required with this apparatus. Based on spectrum acquisition, this method is a way to obtain the sample composition in a short time with the advantages of the WDS system and maintaining reasonable accuracy. To this end, three specific algorithms were designed. The first algorithm was constructed to find automatically all the elements present in the sample and to select the appropriate X-ray line for each element. It needs to index automatically, with a good confidence level, all the peaks which are detected. The second was constructed to convert the X-ray peak area from the measured spectrum into X-ray peak intensity (normally used in WDS procedures) with a Gaussian function which is governed both by the characteristics of the crystal and by the X-ray line itself. This is essential to prevent any underestimation of the concentration due to the measurement of truncated peaks related to low sampling frequencies, and to improve the counting statistics by using all the information given by the spectrum. Finally, the sample composition was obtained with the calculation of the absolute intensity of the selected line which takes into account the spectrometer efficiency.