Adsorptive stripping voltammetric quantification of the antipsychotic drug clozapine in bulk form, pharmaceutical formulation and human serum at a mercury electrode.

Using the cyclic voltammetry technique and the Britton-Robinson buffer (pH 2-10) as a supporting electrolyte, clozapine was found to reduce at the hanging mercury drop electrode in a single two-electron irreversible step corresponding to reduction of the azomethine group of the seven-member heterocyclic ring. Based on the interfacial adsorptive character of clozapine onto the hanging mercury drop electrode, a validated square-wave adsorptive cathodic stripping (SWAdCS) voltammetric procedure was described for the quantification of bulk clozapine with limits of detection and quantitation of 4.5 x 10(-10) and 1.5 x 10(-9) M, respectively. The proposed procedure was successfully applied to the quantification of the drug in pharmaceutical formulation (Leponex) and human serum without the necessity for samples' pretreatment or any time-consuming extraction or evaporation steps prior to the analysis. The limits of detection and quantitation of clozapine in spiked human serum were found to be 1 x 10(-9) and 3.3 x 10(-9) M, respectively. The proposed procedure for quantification of clozapine in bulk form, tablets and human serum has the advantage of being simple, rapid, sensitive, precise and inexpensive compared to most of the reported methods.