Arc Atomic Emission Analysis of Rare Earth Metals and Their Oxides with Preliminary Sorption Concentration of Impurities

Resumo

This work investigates in analytical capacities of arc atomic emission analysis (AAEA) in determination of As, Bi, Sb, Cu, and Te in rare earth metals (REM) and their oxides after preliminary group concentration using S,N-containing heterochain polymer sorbent. The investigations have been carried out using a Grand-Extra high-resolution spectrometer developed by VMK-Optoelektronika (Russia). Sorption kinetics and impurity extraction rate as a function of solution acidity have been studied for a selection of conditions of sorption concentration. Aiming at optimization of arc atomic emission detection of As, Bi, Sb, Cu, and Te, various flowcharts of their sorption concentration and subsequent treatment of obtained concentrated product have been considered with addition of a collector at various sorption stages. Powdered graphite has been used in this work as a collector in analysis of rare earth oxides, which is attributed to the relative simplicity of its emission spectrum and versatility. Analytical conditions and spectrometer parameters affecting the analytical signal (sample weight and composition, shape and size of electrodes, current intensity and operating mode of generator, interelectrode distance, wavelengths of analytical lines) have been selected. The evaporation curves of detected impurities have been analyzed, and the exposure time of As, Bi, Sb, Cu, and Te in the obtained sorption concentrate has been determined. Accuracy of the results has been evaluated using reference samples and by comparisons between methods. The results have been used for development of arc chemical atomic emission analysis of yttrium, gadolinium, neodymium, europium, scandium, and their oxides in the concentration range of n × (10^–5–10^–2) wt %.