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.

Thermal conditions during deformation of partially molten crust from TitaniQ geothermometry: rheological implications for the anatectic domain of the Araçuaí belt, eastern Brazil

“…These constraints require a compromise between X-ray line, peak counting statistics, background subtraction, electron beam size, beam drift, quantification uncertainty, stray radiation and sample damage. In order to find the optimum balance, recent developments in microanalysis, such as spectrum simulation and X-ray emission modeling (Fournier et al, 1999;Kalfoun et al, 2002a, b), were taken into account. Traces of titanium in quartz are relatively easy to identify, but care must be taken against sample damage and Bremsstrahlung fluorescence (braking radiation) of Ti atoms in close proximity to rutile (Wark and Watson, 2006), ilmenite and biotite.…”

Fast and accurate expression for the Voigt function. Application to the determination of uranium M linewidths

“…Although the pseudo-Voigt function has largely been used as an approximated expression to depict the characteristic line profiles [1,2], it may lead to discrepancies too large in some cases. Fig.…”

“…Due to the lack of a closed-form expression for the Voigt function, the pseudo-Voigt function is a usual approach in X-ray spectroscopy [1][2][3][4]. This function is a linear combination of a Gaussian and a Lorentzian.…”

An Expert System for EPMA

“…A standardless semiquantitative method for EPMA using WD spectrometers was developed with a view to simplifying the analytical procedure required with this apparatus [4]. A standardless semiquantitative method for EPMA using WD spectrometers was developed with a view to simplifying the analytical procedure required with this apparatus [4].…”