EX-SITU PORTABLE X-RAY FLUORESCENCE SPECTROMETRY FOR THE MAJOR ELEMENTS DETERMINATION IN SILICATE GEOLOGICAL SAMPLES USING MATRIX-MATCHING STANDARDS FOR CALIBRATION

Abstract

An ex-situ method for determining the major elements in the high silicate matrix using portable XRF spectrometry (pXRF) was developed. The calibration is based on the dilution of a matrix-matched certified reference material BCS-CRM No. 376/1 Potash Feldspar with analytical grade SiO₂. Significant correlation coefficients for linear regressions were obtained for all major oxides. This approach of instrument calibration has as the principal advantage the use of a single certified reference material, which reduce the cost of analysis. The limits of detection were evaluated from measurement of SiO₂ considered as blank. The method accuracy of the developed calibration was checked in the recovery study of two certified reference materials (BCS-CRM No. 309 Sillimanite and BCS-CRM No. 375/1 Soda Feldspar), with geological matrix, and the recoveries rate were in the range of 85 – 110 %. The relative expanded uncertainties (k = 2, P = 95%) calculated from CRM analysis were of 6.99% for Al₂O₃, 3.56% for Fe₂O₃, 4.82% for CaO and 4.31% for K₂O. The proposed methodology is a green analytical method, allowing fast and accurate analysis of geological samples without use of chemical reagents.