A New Calibration Methodology for Quantitative Elemental Analysis of Zeolite Compounds through WD-XRF

Considering the growing need for rapid and accurate analysis of zeolites, X-Ray Fluorescence (XRF) spectrometry is a suitable technique for fast analysis without the need for extensive sample preparation. Due to the interaction between the emission of secondary fluorescent radiation and the sample matrix, there is no simple proportion between the intensity of X-ray fluorescence and the content of elements, mainly when the matrix contains heavy elements. The matrix effects cannot be reduced or omitted during sample treatment except for the fusion method which is destructive and time-consuming. Consequently, perfect matching between standards and samples, and adjusting the calibration based on Certified Reference Materials (CRMs) with a matrix quite similar to the test sample are required. Since zeolites are very diverse and CRMs for these materials are not readily available, the semi-quantitative method with low precision and accuracy is inevitably used. The present study describes an innovative XRF calibration method using validated samples and an inert binder, to make some matrix-matched standard samples according to the principles of Green Sample Preparation (GSP). Due to the use of solid-solid sample preparation, the Weighted Least-square linear Regression (WLR) model was applied for the authentic quantitative multi-elemental analysis. Moreover, the effect of the particle size, spectral line interferences, and moisture content of the samples on the accuracy of XRF was assessed. This method was adapted to determine five major elements, including Al, K, Na, Si, and La, in the most common type of zeolites like A, Y, and X. Variations represented that the limits of quantification were 0.20%, 0.18%, 0.31%, 0.16%, and 0.010%, respectively.