A new system for spectrophotometric determination of trace amounts of selenium

Abstract

A simple and selective spectrophotometric method for the determination of trace amounts of selenium(IV) is described based on the oxidation of phenylhydrazine-<i style="">p</i>-sulphonic acid and coupling reactions. Selenium(IV) oxidizes phenylhydrazine-<i style="">p</i>-sulphonic acid into its diazonium salt in an acid medium. The diazonium salt is then coupled with acetylacetone or ethylacetoacetate in an alkaline medium, which gives azo dyes with absorption maximum at 490 or 470 nm, respectively. The method obeys Beer’s law in the concentration range of 0.5-20 μg mL^-1 of selenium with phenylhydrazine-<i style="">p</i>-sulphonic acid-acetylacetone and 1-24 μg mL^-1 of selenium with phenylhydrazine-<i style="">p</i>-sulphonic acid-ethylacetoacetate couples. The molar absorptivity, Sandell’s sensitivity of the systems with phenylhydrazine-<i style="">p</i>-sulphonic acid-acetylacetone and phenylhydrazine-<i style="">p</i>-sulphonic acid-ethylacetoacetate couples were found to be 1.02<img src='/image/spc_char/cross.gif' border=0>10⁴ Lmol^-1cm^-1, 7.69<img src='/image/spc_char/cross.gif' border=0>10^-3μg cm^-2 and 1.18<img src='/image/spc_char/cross.gif' border=0>10⁴L mol^-1cm^-1, 6.67<img src='/image/spc_char/cross.gif' border=0>10^-3μg cm^-2, respectively. The developed method has been successfully applied for the determination of selenium in plant material, water and soil samples.