Determination of antimony(iii) and total antimony by hydride generation atomic absorption spectrometry in samples of injectable drugs used for leishmaniasis treatment

Abstract

A procedure for the determination of Sb(III) and total Sb in commercial samples of injectable drugs based on pentavalent antimony was proposed. The drugs studied in this work are currently used for leishmaniasis treatment in many countries. Determination of Sb was performed by hydride generation atomic absorption spectrometry under controlled conditions for the reaction medium. The following parameters were investigated: type and concentration of acid, sodium tetrahydroborate concentration and purge time. The chosen conditions for Sb(III) were: 4% (m/v) citric acid, 1% (m/v) sodium tetrahydroborate and 10 s (a pre-reduction step was performed using 10% m/v KI in 0.2% m/v ascorbic acid solution). The same parameters for total Sb determination were: 0.5 mol l⁻¹ sulfuric acid, 4% (m/v) sodium tetrahydroborate and 10 s. Interference from As, Ni, Cu and Pb on the analytical signal for Sb(III) was also investigated. Two kinds of commercial drugs were analyzed. The trivalent Sb concentration varied from 1.7 to 3.1 mg l⁻¹, corresponding to 1.6 to 2.8% for the total Sb. Recovery tests for Sb(III) showed values varying from 98.9 to 101.9%. The characteristic mass for Sb(III) was 0.22 ng and the detection limit (3s) was about 1.5 ng (absolute). The main advantage of the proposed procedure is to allow the determination of Sb(III) in the presence of a large excess of pentavalent Sb (about 2000 ng).