FLOTATION SEPARATION AND ATOMIC-ABSORPTION SPECTROMETRIC DETERMINATION OF SELENIUM(IV) IN WATER

A method is described for the flotation and determination of sub-microgram levels of selenium(IV) in water. Selenium(IV) in a 1000-mL sample of water is coprecipitated with iron(III) hydroxide at pH 4.0 ± 0.2. The precipitate is floated with the aid of sodium lauryl sulfate and small air bubbles, then separated and dissolved in 4 M hydrochloric acid and diluted to 10 mL. Finally the selenium content is determined by generation of hydrogen selenide using sodium borohydride as a reductant and subsequent atomic absorption spectrophotometry with a long absorption cell (60 × 1.2 cm i.d.). Selenium(IV) at the levels of 0.4 hq and 0.8 µg added to water (1000 mL) and to seawater could be determined with a recovery of above 97% and with a relative standard deviation within 2%. The time required for the pre-concentration of selenium(IV) from a 1000-mL volume of solution was about 30 min per sample. © 1979, American Chemical Society. All rights reserved.