Near real-time management of spectral interferences with portable X-ray fluorescence spectrometers: application to Sc quantification in nickeliferous laterite ores

Abstract

Since the development of portable X-ray fluorescence (pXRF) spectrometers, few studies have been conducted on the influence of spectral interferences between chemical elements. This study aims to improve the management of these interferences to obtain more reliable geochemical analyses. We specifically investigate Ca-related interferences on Sc analysis for the case of Ni-rich laterite samples using the Niton XL3t GOLDD + pXRF analyser. Three quantification methods were tested on 59 pelletized samples using the ‘Soil’ mode. The first, named ‘Manufacturer’, represents the elemental quantification directly provided by the device based on regions of interest and multilinear corrections of spectral interferences configured during the spectrometer design. The second, the ‘20 Cu’ method, is based on spectral fitting using the PyMCA software. The third, the ‘18 Fe’ method, combines spectral fitting with modified experimental conditions. For each, a quantification methodology was developed, establishing (i) Ca and Sc calibration lines and (ii) Ca/Sc threshold values delimiting fields of ‘reliable’, ‘to be confirmed’ and ‘unreliable’ measurements. The ‘20 Cu’ and ‘18 Fe’ methods greatly extend the ‘reliable measurements’ field concerning the Ca/Sc ratio compared to the ‘Manufacturer’ method. The ‘18 Fe’ method was also found to provide the most negligible measurement dispersion.Supplementary material: Figures A–F and Tables A and B are available at https://doi.org/10.6084/m9.figshare.c.5511838