GDMS Analysis Of Calcium Carbonate Naturaly Doped By REE, Phospates And Other Impurities

Abstract

A mathematical model was developed for calculation of types and intensities of molecular interferences and simulation of mass-spectra at GDMS analysis of non-conducting samples with the use of a secondary cathode. An improved design of the cell with Ta-secondary cathode were suggested enhancing the matrix to tantalum ion current ratio and sensitivity of the analysis in ca. 1.5 orders of magnitude. The model have been used for interpretation of complicate mass-spectra of calcium carbonate naturally doped with REE, phosphates and other impurities. Comparison calculated and experimental mass-spectra of VG9000 instrument demonstrates good agreement and allows select the most suitable isotopes and rejecting wrong molecular peaks. It have been shown that electrons in glow discharge plasma have different temperatures in different zones that reveals itself as separate Boltzmann populations of ionization levels for molecules, metal atoms and argon atoms/ions. Calcium carbonate is widely used for many application including as precursor for nano-hydroxyapatite synthesis. Calcium carbonate was precipitated from natural mine waters and was used as model object having high number of various impurities allowing to investigate the impact of complicate molecular ions, determine necessary resolving power of the GD-instruments to meet required detection limit.