Differential determination of selenium(IV) and selenium(VI) in river waterby hydride generation inductively coupled plasma atomic emission spectrometry

Selenium(IV) and selenium(VI) in river water were determined differentially by hydride generation inductively coupled plasma atomic emission spectrome try. Selenium(IV) in the water was extracted with 4-nitro-o-phenylenediamin e into toluene as 4-nitropiazselenol. The extract was concentrated by evapo ration, decomposed with nitric and perchloric acids, and reduced with conce ntrated hydrochloric acid. The total selenium was determined by digesting t he water with nitric, sulfuric and perchloric acids and reducing the seleni um with concentrated hydrochloric acid. The interfering transition metals w ere eliminated by elution with Chelex 100 chelating resin. The siliceous re sidues deposited during the digestion were dissolved with hydrofluoric acid . The selenium(VI) content was estimated by subtracting the selenium(IV) co ntent from the total selenium. The detection limit (3 times the signal to n oise ratio) for both the total selenium and selenium(IV) with 500 ml water samples were 0.03 ng ml(-1). The relative standard deviations of the total selenium and selenium(IV) were 4.2 and 17.2%, respectively.