Study of the Evaporation Mechanism of Impurity Elements in the Analysis of High-Purity Graphite Powder with Fluorine Additives by Arc Atomic Emission Spectrometry

The study examines the impact of chemically active fluorine-containing additives, namely AlF3, ZnF2, and SrF2, on the evaporation behavior of low- and medium-volatile impurity elements from a crater in a direct current arc electrode in the analysis of graphite powder. The results demonstrate that the use of AlF3 and ZnF2 significantly increases the intensity of spectral lines for the analyzed elements and shortens the time required for their complete evaporation from the electrode crater. Among the additives tested, zinc fluoride in a concentration of 5 wt % proved to be the most effective. The greatest increase in intensity was observed for low-volatile elements prone to carbide formation. The use of ZnF2 lowered the limits of detection for low- and medium-volatile elements in the graphite powder by direct arc atomic emission spectrometry by 2–3 orders of magnitude, reaching concentrations of n × 10–7 to n × 10–5 wt %. This approach improved the reproducibility of the results by a factor of 2 compared to the analysis of graphite powder without additives.