SEPARATION OF TIN FROM WATER AND SEA-WATER BY FLOTATION AND THE DETERMINATION OF TIN BY ATOMIC-ABSORPTION SPECTROPHOTOMETRY FOLLOWING STANNANE GENERATION

A method is described for the separation and determination of sub-microgram levels of tin in water. A submicrogram amount of tin(II, 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 dodecyl sulfate and small air bubbles, and then separated and dissolved in 2 ml of 6 M hydrochloric acid and diluted to 10 ml with water. Finally, the tin content is determined by the generation of stannane, using sodium borohydride as a reductant, followed by atomic absorption spectrophotometry with a long absorption cell (60 × 1.2 cm i.d.). This separation technique has also been successfully applied to the determination of sub-microgram amounts of tin in natural sea-water. The time required for the pre-concentration of tin from a 1000-ml volume of solution is about 15 min per sample after 15 min of stirring.