Abstract
A sensitive method for the selective determination of selenium(IV) and selenium(VI) in natural water using reversed-phase high-performance liquid chromatography with a spectrofluorometric detector has been developed. Selenium(IV) in 50ml of a natural-water sample was determined spectrofluorometrically after complexing with 2, 3-diaminonaphthalene (DAN) at a pH of 1, extracting the complex into 1ml of cyclohexane and injecting a 100-μl portion of the extract into a UNISIL ODS 5C18 column along with a mixture of cyclohexane and tetrahydrofuran (90/10, v/v) as a mobile phase. Selenium(VI) in the sample was first reduced to selenium(IV) at a temperature of 80°C for 60min with 2% (w/v) potassium bromide and 20μg/ml copper(II) in a 1.2M hydrochloric acid solution. The total inorganic selenium was then determined by the same treatment as mentioned for selenium(IV). The concentration of selenium(VI) was obtained by subtracting that of selenium(IV) from the total amount of selenium. For the purpose of eliminating interference, 2ml of a 0.1M EDTA-NaF solution was added to each sample. Absolute detection limits as high as 0.2ng and 0.3ng, respectively, were achieved for selenium(IV) and selemium(VI). For the determination of selenium in Tama river-water samples, the method gives average amounts for selenium(IV) and selenium(VI) as high as 25 and 127ng/l.
