Direct determination of praziquantel in pharmaceutical formulations and human plasma by cathodic adsorptive stripping differential-pulse voltammetry.

The polarographic and cyclic voltammetric behaviour of praziquantel was studied in B.R. buffers of different pH values. Contradictory to that mentioned in a previously published work, praziquantel is an electro-active compound. Its polarogram exhibited a single 2-electron irreversible reduction wave in B.R. buffer of pH 5, the wave height decreased on the increase of pH till it disappeared in solution of pH >7. This wave was attributed to the reduction of the Cz.dbnd6;O double bond. The quantitative trace determination of bulk praziquantel was studied at a hanging mercury drop electrode by cathodic adsorptive stripping differential-pulse voltammetry. A fully validated sensitive procedure based on controlled adsorptive accumulation of the drug onto a HMDE was developed for its direct determination without derivatization. Accumulation of praziquantel was found to be optimized in 0.1 M Na(2)SO(4) solution as supporting electrolyte under the following conditions: accumulation potential, -1.2 V (vs. Ag/AgCl/KCl(s)); accumulation time, 30 s; scan rate, 10 mV/s and pulse height 100 mV. The proposed procedure was applied successfully for determination of praziquantel in its pharmaceutical formulations and human plasma. The mean recoveries of the drug were 98.85-99.42% and 99.12-100.47% with RSD of 0.49-0.95% and 0.45-0.52% in pharmaceutical formulations and human plasma, respectively. Limits of detection and quantitation of 1.14x10(-9) and 3.80x10(-9) M praziquantel, respectively, were achieved.