Spectrophotometric determination of selenium with 2-mercaptobenzothiazole

Abstract

A rapid, sensitive and selective spectrophotometric method has been developed for the determination of micro amounts of selenium. This method is based on the absorptiometric measurement of the stable yellow colour formed by the reaction of selenium(IV) with 2-mercaptobenzothiazole in strong hydrochloric acid solution (more than 6·5 M). At 370 mµ, Beer's law is obeyed from 1 to 7 µg of selenium per ml, the optimum range being from 3 to 6 µg. The sensitivity and molar absorptivity at 370 mµ are 0·008 µg per cm² and 9480, respectively. The yellow product conforms to a stoicheiometry of 1:4 between selenium and the ligand. A 10 to 12-fold excess of tellurium(IV) can be tolerated. Interference by iron(III) and copper(II) are eliminated by extraction. The method has been successfully applied to the determination of selenium in various samples.