The spectrophotometric determination of antimony in water, effluents, marine plants and silicates

Abstract

A spectrophotometric procedure is described for the determination of antimony in natural waters (including sea water and effluents), algae and silicates. After a preliminary oxidative digestion for waters, or acid attack for algae and silicates, the element is quantitatively coprecipitated at pH 5.0 with hydrous zirconium oxide. The precipitate is dissolved in acid, and, after reduction with titanium(III) chloride, antimony is oxidized to antimony(V) with sodium nitrite. The ion pair of the SbCl 6 - ion with crystal violet is extracted with benzene and its absorbance is measured at 610 nm (molar absorptivity 74,000 l mol -1 cm -1). Extraction with toluene causes some loss of sensitivity. The detection limit is 0.005 μg l -1; relative standard deviations are 0.5% and 1.1% for spiked distilled water (0.5 μg l -1) and sea water (0.26 μg l -1), respectively. A wide range of anions and cations cause no interference at levels many times those in natural waters. The technique can be adapted for application to marine algae and silicates; relative standard deviations are 1.8% and 2% for samples of Pelvetia canaliculata (0.19 μg Sb g -1) and a Pacific Ocean red clay (1.08 μg Sb g -1), respectively. Results for the U.S. Geological Survey Standard rocks GSP1 (2.7 ppm) and DTS1 (0.53 ppm) are in good agreement with those of earlier workers.