The determination of pentavalent antimony in sodium stibogluconate in a pharmaceutical formulation by flow injection analysis

Abstract

A flow injection analysis (FIA) procedure is described for the determination of pentavalent antimony (Sb 5+) in the drug, sodium stibogluconate, in a parenteral pharmaceutical formulation. The sample solution is injected directly into a carrier stream of iodide ion which is then mixed with an acid stream in situ. Sb 5+ is determined by the redox reaction with acidified iodide to liberate iodine, which is monitored spectrophotometrically at 350 nm. The closed conditions prevent interference from atmospheric oxygen and the rapid reaction time assists in minimizing interference from side reactions. The use of tartaric acid as a solvent for sample and standard solutions ensures obedience of Beer's law over the Sb 5+ concentration range 0.01–0.2% (w/v). The method is specific for the higher oxidation state in an ionic mixture of Sb 5+ and Sb 3+, and has been fully validated for use in a pharmaceutical preparation. Assuming absence of matrix interference it is applicable to Sb 5+ from other sources and should be applicable to other reducible ionic species.