Behavior and Fractionation of Low-Volatile Impurities in a DC Arc in the Analysis of Zirconium by Atomic Emission Spectrometry

We studied the effect of chemically active fluorine-containing additives AlF3, BaF2, and ZnF2 on the character of evaporation of some low-volatile elements from a refractory matrix in the crater of a DC arc electrode in the analysis of zirconium by atomic emission spectrometry. The additives cause the formation of volatile fluorides of low-volatile elements and their fractional evaporation with respect to the base element evaporation. Impurity fluorides rapidly and completely evaporate during the first 30 s of arcing, and only after that the intensive evaporation of the base begins. Such fractionation increases significantly the intensity of the spectral lines of impurities, decreases the background intensity, and, consequently, improves the limits of determination of low-volatile elements in zirconium oxide. Zinc fluoride is the most effective of the studied additives. Using zinc fluoride, we lowered the limits of determination of low-volatile elements by two orders of magnitude compared to the limits of determination in zirconium oxide without additives and improved the reproducibility of the results of determinations.