DETERMINATION OF SELENIUM(IV) IN SEAWATER BY GAS CHROMATOGRAPHY AFTER COPRECIPITATION WITH HYDROUS IRON(III) OXIDE.

Selenium(IV) concentration in seawater was determined by gas chromatography with electron capture detection after coprecipitation with hydrous iron(III) oxide. Quantitative precipitation of Se(IV) was obtained at pH 5. 0. Following a brief, 15 min, stirring and settling period, the coprecipitate was filtered and dissolved in hydrochloric acid. Selenium was derivatized to 5-nitroplazselenol, extracted into toluene and introduced into the chromatograph. The detection limit was 1 pg injected or 5 ng of Se/L of seawater using a 200-mL sample. The precision was 6% at the 0. 025 mu g of Se/L level