Gas-chromatographic determination of selenium in pure elemental arsenic and arsenic(III) oxide with 4-nitro-1,2-diaminobenzene

Abstract

A simple and practical method for the determination of very small amounts of selenium in elemental arsenic and arsenic(III) oxide is described. A mixture of 20 ml of fuming nitric acid and 5 ml of orthophosphoric acid dissolves up to 1 g of the arsenic sample and also oxidises the selenium quantitatively to the quadrivalent state. As the reaction of selenium(IV) with 4-nitro-1,2-diaminobenzene is scarcely interfered with by other elements, chemical separation from the matrix element is not necessary. The 5-nitropiaselenol formed in the reaction is extracted into toluene and determined by means of a gas chromatograph equipped with a sensitive electron-capture detector. No loss of selenium is observed following this treatment.