Determination of small amounts of antimony in organic matter

Abstract

Methods for determining antimony in the range 0.05–0.5 µg in samples of organic matter have been examined. Several techniques for determining antimony in solution (after oxidation of organic matter) were considered, and of these only hydride generation followed by atomic-absorption spectrometry with atomisation in a heated tube offered sufficient sensitivity and accuracy for solutions containing 50 ng ml^–1 of antimony.

The most satisfactory method for the oxidation of organic matter was to use sulphuric and nitric acids; the use of perchloric acid was shown to lead to low recoveries of antimony from samples of grass. It was also shown that the antimony must be in an oxidation state of three for successful atomic-absorption measurement; this was achieved by use of sulphite at the end of wet oxidation, and addition of sodium iodide before the atomic-absorption spectrometric measurement. An Appendix describes the recommended method; collaborative studies of the method as applied to samples of grass with and without added antimony, and to Standard Biological Kale, gave satisfactory results, with relative standard deviations of 5–9% and 29%, respectively.