Determination of Tocopherol Using Reduced Graphene Oxide-Nafion Hybrid-Modified Electrode in Pharmaceutical Capsules and Vegetable Oil Samples

Abstract

The Nafion/graphene nanocomposite electrodes showed excellent electrochemical reactivity toward the oxidation of alpha-tocopherol, which permitted the highly sensitive detection of alpha-tocopherol. The optimal experimental conditions for the oxidation of alpha-tocopherol were achieved in acetone/acetate buffer solution and acetone/room temperature ionic liquid solution. The oxidation peak current of alpha-tocopherol was also a linear relationship in the concentration range 0.5-90 mu M with a detection limit of 0.06 mu M in both the solvent systems. The electrode reaction of alpha-tocopherol (TOH) is an irreversible process which occurs readily in the presence of water in the solvent. Regarding analyte response, the acetone/acetate systems gave a higher analyte response than the acetone/room temperature ionic liquid systems. Ascorbic acid in less than 2000-fold excess does not interfere. Moreover, the hybrid electrode surface has very good reproducibility and stability. The sensing procedures were applied to the quantification of the alpha-TOH in different pharmaceutical formulations and vegetable oil samples. In addition, the developed method can be applied for the determination of alpha-TOH in alpha-TOH-beta-carotene (ATBC) drinks.