Title : A Novel Approach to Calibration Methodology of WD_XRF Applied in Elemental Analysis of Zeolite Compounds and FCC samples with High Accuracy and Precision
Abstract:
X-ray Fluorescence spectrometry (XRF) is offered in terms of quantitative, fast, and reliable analysis in a wide range of mineral compounds. The intensity of the fluorescence X-ray radiation emitted from the analyte is used for the quantitative analysis of elements in the sample. However, there is no simple proportion between the intensity of X-ray fluorescence and concentration of each elements, due to the interaction between the emission of secondary fluorescent radiation and the sample matrix, especially when the matrix contains heavy elements. While matrix effects cannot be reduced or omitted during sample pretreatment, perfect matching between standards and samples, and adjusting of the calibration based on standard reference materials (CRMs) with a matrix quite similar to the test sample are required for better estimates. The present paper describes an innovative XRF calibration method using validated samples and an inert binder to make some matrix-matched standard samples. The uncertainty-weighted least-square linear regression (UWLR) model was applied for the authentic quantitative multi-elemental analysis. Moreover, the effect of the parameters such as particle size, spectral line interferences, and moisture content of the samples on the accuracy of XRF was assessed. This evaluated method was adapted to determine five major elements, including Al, K, Na, Si, and La in the most common type of synthetic zeolites and Fluid catalytic cracking (FCC) samples like A, Y, and ZMS-5. Variations represented that the limits of detection were 0.20%, 0.12%, 0.31%, 0.18%, and 0.10%, respectively which computed from statistical analyses of duplicate sample aliquots, with RSD <2% for most elements mentioned above, and RSD < 5% for Na. Analytical accuracies were verified by Inductively Coupled Plasma Spectroscopy (ICP) measurements and classical analysis with reliable ASTM test methods.
WD-XRF analysis, Calibration method, Zeolite sample, UWLR model, Fluid catalytic cracking,
- With large-scale mineral concentrating operations, the trustworthy analysis will play a major part in the development of automatic control systems. X-ray Fluorescence spectrometry (XRF) is applied for simultaneous multi-elemental analysis in a wide variety of mineral compounds without dissolution, digestion, and destruction of the samples and usually requires only a minimum of sample preparation. Previous studies indicated that WD-XRF quantitative analysis is carried out by the calibration curve method and is strongly common for measuring raw mineral compounds. This technique requires its methods to be calibrated using Standard Reference Materials (SRMs), Certified Reference Materials (CRMs), and Geochemical Reference Materials (GRMs). While, This work is devoted to the novel calibration method of WD_XRF for improving the accuracy of quantitative determinations of elements, based on the in-house standards of different types of zeolite samples.
- Since the calibration strategy in X-ray fluorescence spectroscopy is depending on the sample preparation, and in pressed pellets particle size, water content, and matrix effects are the main interference factors for multi-element analysis, it can be applied the CRM samples. The advantage of the methodology adopted in this article is to have valid calibration coefficients able to ensure good results of accuracy for wide compositional spectrum. Furthermore, it is not to be underestimated the fact that the empirical coefficients, which account for the matrix effects, are obtained on in-house standards, consisting of chemicals and mixtures of them. We have developed UWLR model for the calibration methodology for the first time using in-house zeolite samples. The advantage of this method is its ability to compete with CRM samples.
