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A simple differential-pulse polarographic method has been developed for the determination of minoxidil in pharmaceutical dosage forms. The extracting solvent was methanol and the supporting electrolyte was 1.0 N sulphuric acid. An excellent linear relationship was obtained between the concentration and current peak height with a correlation coefficient of 0.999 9. Good agreement was obtained between results with the differential-pulse polarography method and those by the manufacturer's method of assay. There was no interference by the tablet excipients. In acid solution, a mechanism for reduction a t -1.2 V is proposed, which involves the transfer of four electrons as well as dehydration and deamination steps.

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A simple differential-pulse polarographic method has been developed for the determination of ketoprofen in dosage forms. Methanol was employed as the solvent for extracting the drug from the formulations, and Britton -Robinson buffer (pH 6.0) containing 5% V/Vmethanol was used as the supporting electrolyte. The EP occurs at -1.15 V. Results obtained by the proposed method are in excellent agreement with those provided by the manufacturer's laboratory. Commonly used tablet excipients and suppository bases were found not to interfere. A mechanism for the electrochemical reduction of ketoprofen at -1.25 V is proposed that involves the transfer of two electrons.

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