Investigations into mild conditions for reduction of Se(VI) to Se(IV) and for hydride generation in determination of selenium by direct current plasma atomic emission spectrometry

Alternatives to hydrochloric acid for the reduction of Se(VI) to Se(IV) (prereduction) were explored. Prereduction of Se(VI) in 0.1-1 M HCl and 0.1-3 M HBr as a function of NaBr concentration and time of boiling was investigated and conditions for mild prereduction of Se(VI) have been found. Minimum concentrations of sodium tetrahydroborate(III) and HCl for reduction of Se(IV) to Se(-II) in selenium hydride were found and minimum acid concentrations were determined. Prereduction of Se(VI) by the method involving optimum concentrations of 0.48 M HCl plus 1.4 M KBr was verified by comparison with the 5 M HCl reference method for determination of Se(VI) in Niagara River waters. (C) 1997 Elsevier Science B.V.