Indirect spectrophotometric determination of small amounts of selenium(IV)and arsenic(V) by simple extraction using flotation columns

A simple, rapid and selective procedure for the indirect spectrophotometric determination of Se(IV) and As(V) has been developed. It is based on the r eduction of Se(IV) to Se(0) and As(V) to As(III) with hydroiodic acid (KI HCl). The liberated iodine, equivalent to each analyte, is quantitatively extracted with oleic acid (HOL) surfactant. The iodine-HOL system exhibits its maximum absorbance at 435 nm. The different analytical parameters affec ting the extraction and determination processes have been examined. The cal ibration graphs were found to be linear over the ranges 5 - 120 and 0.25 - 20 ppm of Se(M and As(V), with lower detection limits of 2.5 and 0.15 ppm a nd molar absorptivities of I x 10(4) and 0.5 x 10(4) dm(3) mol(-1) cm(-1), respectively. Sandell's sensitivity was calculated to be 0.0078 and 0.0149 mug/cm(2) in the same order. The relative standard deviation for five repli cate analyses of 40 ppm Se(IV) and 4 ppm As(V) were 1.0 and 0.9%, respectiv ely. The proposed procedure in the presence of EDTA as a masking agent for foreign ions has been successfully applied to the determination of Se(IV) i n a reference sample and As(V) in copper metal, in addition to their determ ination in spiked and polluted water samples.