Square wave voltammetric determination of valproic acid in pharmaceutical Preparations

The electrochemical behavior of valproic acid (VAL) was investigated using square wave voltammetry, cyclic voltammetry, and sampled direct current polarography and a new square wave voltammetric method was developed for determination of VAL in pharmaceutical preparations. VAL showed two reduction peaks at about -0.2 V and -0.8 V vs. Ag/AgCl 3 M KCl with a hanging mercury drop electrode in 0.05 M pH 3.3 Britton-Robinson (BR) buffer. These peaks were named peak I and peak II, respectively. The types of limiting current of both peaks were determined as diffusion controlled based on cyclic voltammetry studies. A linear calibration graph was obtained in the range 1.46 x 10(-4)-1.0 x 10(-3) M. The limit of detection (LOD) and limit of quantification (LOQ) were 1.09 x 10(-4) M (21.05 mu g/mL) and 1.10 x 10(-4) M (144.20 mu g/mL), respectively. Recovery studies for the accuracy of the method were performed by adding known amounts of VAL and it was found to be 109.67 +/- 4.85%. The proposed method was successfully applied to pharmaceutical products on the market.