Electrochemical study of spiramycin and its determination in pharmaceutical preparation

Spiramycin (SPY) is a medium-spectrum antibiotic with high effectiveness against Gram-positive bacteria. The voltammetric behaviour of spiramycin was studied using differential pulse polarography (DPP) and square wave polarography (SWP). The drug in Britton-Robinson buffer (pH 11.5) is reduced at - 1.45 V, giving rise to a well-defined cathodic peak using hanging mercury drop electrode (HMDE) versus Ag/AgCl electrode. This peak is attributed to the reduction of the aldehyde group. The results proved that the reduction of SPY is an irreversible diffusion-controlled process. The diffusion current-concentration relationship was shown to be rectilinear over the range of 20-80 and 0.8-80 µg ml(-1) using DPP and SWP modes, respectively, with detection limit of 8.5 µg ml(-1) (1.01 × 10(-5) M) and 0.46 µg ml(-1) (5.46 × 10(-7) M) for DPP and SWP modes, respectively. A mechanism is postulated for the reduction of SPY. The proposed techniques were successfully applied to the determination of the studied compound either in pure form or in its formulation.