Extractive separation of selenium for atomic-absorption determination in purified sulfur

Abstract

The expanding use of sulfur in medicine, science and technology has tightened the requirements for the impurity composition, including the content of selenium in sulfur. Combined extraction-atomic absorption methods have been developed to determine selenium in purified sulfur. The possibility of using thiourea derivatives such as sodium diethyldithiocarbamate and diphenylthiocarbazone for the extraction of microgram amounts of selenium from sulfuric acid solutions was studied. Optimal conditions for the extraction of selenium from sulfate solutions are determined. Two procedures for selenium separation are proposed: extraction of selenium diethyldithiocarbamate with ethyl acetate from a solution of sulfuric acid with pH 3 or extraction of selenium dithizonate with chloroform from a 5.25 – 6.0 M sulfuric acid solution. The results of the extraction-atomic absorption determination of selenium in sulfur are compared for both procedures of selenium separation. The accuracy of the selenium determination in purified sulfur is confirmed by the method of varying sample weight. The optimal temperature-time parameters for the electrothermal atomic absorption determination of selenium are determined. The limit of selenium determination is 1 × 10–5 % wt. The values of sr in the range of selenium content 2 × 10–5 — 1 × 10–4 % wt. change from 0.10 to 0.12.