Determination of arsenic in selenium metal or in the presence of high levels of selenium by hydride generation atomic absorption spectrometry

Abstract

Selenium(IV) interferes strongly in the determination of arsenic by hydride generation atomic absorption spectrometry. The interference occurs in the gas phase in the heated quartz cell. Selenium(VI) is only very slightly reduced to hydrogen selenide by sodium tetrahydroborate(III), so arsenic at levels below 1 p.p.m. could be determined in analytical-reagent grade selenium metal by oxidising selenium(IV) to selenium(VI). The oxidation was performed using potassium permanganate in sulphuric acid medium immediately before the determination of arsenic as arsenic(V). The same procedure was applied to the determination of arsenic in geochemical samples that had been synthetically enriched with selenium(IV) to high levels. The mechanism of the interference is considered.