Voltammetric determination of α-tocopheryl acetate in pharmaceutical dosage forms

A simple and rapid voltammetric method has been developed for the quantitative determination of alpha-tocopheryl acetate (alpha-TOAc) in pharmaceutical preparations. Studies with linear scan (LSV), square-wave (SQWV) and differential pulse voltammetry (DPV) were carried out using platinum microelectrodes. A well-defined, irreversible oxidation wave/peak was obtained at 1.30 V (vs. Ag/AgCl reference electrode.) The use of SQWV or DPV technique provides a precise determination of alpha-tocopheryl acetate using the multiple standard addition method. The statistical parameters and the recovery study data clearly indicate good reproducibility and accuracy of the method. Accuracy of the results assessed by recovery trials was found within the 99.3% to 103.5%, and 99.1% to 101.4%, for SQWV and DPV, respectively. The quantification limits for the both voltammetric techniques were found to be 6 x 10(-5) M (SQWV) and 7 x 10-5 M (DPV). Analysis of the authentic samples containing alpha-TOAc showed no interference with common additives and excipients, such as unsaturated fatty acids (co-formulated as glycerine esters) and vitamin A (as retinol or beta-carotene). The method proposed does not require any pretreatment of the pharmaceutical dosage forms. A gas chromatography determination of alpha-TOAc in real samples was also performed for comparison.