A sensitive method for the selective determination of selenium(I V) and seleniutn(VI) in natural water using reversed-phase high-performance liquid chromatography with a spectrofluorometric detector has been developed. Selenium(IV) in 50 ml of a natural-water sample was determined spectrofluorometrically after complexing with 2,3-diaminonaphthalene (DAN) at a pH of 1, extracting the complex into 1 ml 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 60 min with 2% (w/v) potassium bromide and 20 ng/ml copper(II) in a 1.2 M 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, 2 ml of a 0.1 M EDT A-NaF solution was added to each sample. Absolute detection limits as high as 0.2 ng and 0.3 ng, 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 127 ng/1.
ASJC Scopus subject areas
- Analytical Chemistry