Determination of majority elements and minorities in Cuban zeolites using X-Ray Fluorescence

Abstract

The pharmaceutical industry establishes very precise requirements in relation to the quality of the raw materials it uses. The analytical control of Cuban zeolites used as raw material in the pharmaceutical industry includes procedures for the determination of major, minor and potentially toxic trace elements. The experimental conditions for the determination by X-Ray Fluorescence of oxides of major elements (SiO₂, Al2O₃) and minor elements (MgO, CaO, TiO2, Fe₂O₃, ZnO and K₂O) in natural and activated Cuban zeolites were adjusted according to the needs of the industry. The samples were mixed with starch as a binder and boric acid was used as a support for the preparation of the tablets. A sequential wavelength dispersion spectrometer with a Cr tube and flow detector was used, making the measurements under vacuum conditions. The Lucast-Tooth and Price models were used to correct the calibration and to calculate the concentrations. The preparation of the tablets was found to be repeatable. The procedure was validated using a reference sample of natural zeolite and also comparing the results by additionally analyzing an unknown sample by Flame Atomic Absorption Spectroscopy. Ti was determined colorimetrically as a comparison method. The proposed procedure is exact, precise and the working intervals for each element in the natural and activated zeolites were established. Large amounts of samples can be analyzed with rapid preparation and low consumption of reagents and standards.