Differential-pulse polarographic determination of selenium species in contaminated waters

Selenium(IV), in the concentration range 2–100 μg l^?1 in contaminated waters, is determined by using the sensitive adsorption-controlled peak obtained by differential pulse polarography in dilute acid solution. Interfering heavy metals are removed on Chelex-100 resin. Selenium(VI) is not electroactive but can be determined after photolytic reduction in the absence of oxygen. Anion-exchange preconcentration is necessary if the total selenium is below the detection limit of 2 μg l^?1.