Polarographic and voltammetric determination of chlorhexidine in pharmaceutical preparations

Direct-current polarography (DCP) involving sampled current measurement, differential pulse polarography (DPP), square-wave voltammetry (SWV) and cyclic voltammetry (CV) with a controlled-growth mercury drop electrode (CGMDE) were used to determine chlorhexidine (ChH). The DCP method was used to study wave height and wave potential in relation to pH of the solution over a range 1-11. Optimum measurement parameters and supporting electrolyte compositions were established. The currents observed with the mercury electrodes were found to be diffusion and irreversible. By using the adsorptive SWV, SWV and DPP methods, current intensity was found to vary linearly with ChH concentration over the ranges 40-100 ng ml(-1), 0.25-20 mu g ml(-1), and 25-100 mu g ml(-1), respectively. The DPP and SWV methods were adapted for the determination of chlorhexidine in the solid substance, in eye drops and in contact-lens preservation solutions (by the standard-addition technique). A statistical analysis of the analytical results showed both methods to be characterized by satisfactory accuracy and precision (RSD 0.87% and 1.19%, respectively).