Polarographic behavior and determination of finasteride

The polarographic behavior of finasteride at the dropping mercury electrode (DME) was studied adopting direct current (DC(t)), alternating current (AC(t)) and differential-pulse polarography (DPP) modes. In Britton-Robinson buffer (BRb), finasteride exhibited cathodic waves over the pH range 6-12. At pH 10, a well-defined cathodic wave was obtained. The latter could be characterized as being irreversible, diffusion-controlled and partially affected by adsorption phenomenon. The number of electrons involved in the reduction process was accomplished and a proposal of the electrode reaction was presented. The current-concentration plots were rectilinear over the ranges 8-40 and 2-30 microg ml(-1) using DC(t) and DPP modes, respectively. The minimum delectability was 0.2 microg ml(-1) (5.4 x 10(-7) M), for the latter. The proposed method was successfully applied to the determination of finasteride in its commercial capsules and the results obtained were in good agreement with those given with a reference method.