Determination of antibilharzial antimony compounds by direct current, differential pulse, square-wave and alternating current anodic stripping voltammetry

A simple, rapid and sensitive method has been developed for the determination of Sb(III) in five antimonial antibilharzial drugs using anodic stripping voltammetry. The method is based on the reduction of Sb(III) on the HMDE, followed by a selected mode of oxidative sweep, i.e. direct current, differential pulse, square-wave or first harmonic alternating current sweep, using 2 mol/L HCl as a supporting electrolyte. Voltammograms for various sample concentrations in the range 3-47 ppb Sb(III) were recorded and the respective calibration graphs constructed. To overcome the expected effect of adsorption of surface active organic compounds on the mercury drop, the standard addition technique of Sb2O3 solution was applied to calculate the recoveries of all the tested antimonials. The method gave reproducible results within 2% and the limit of detection for all measurement modes was 3 ppb. SW and AC modes seem to achieve lower detection limits than the other two modes. The four modes proved to be of equal accuracy and precision.