Abstract: The voltammetric behavior of α-tocopherol in the presence of vegetable oil has been invetigated at a glass carbon electrode in a 1,2 dichloroethane-ethanol medium with cyclic voltammetry. Cyclic voltammogram of α-tocopherol showed a well-defined oxidation peak at 0.576 V, no cathodic peak observed. The oxidation process of the α-tocopherol is a typical diffusion-controlled current process. The optimum analytical parameters were obtained: the mixture of 1,2-dichloroethane and ethanol (1:3) as solvent, 0.05 mol/L LiClO4 and pH 3.0, the instrumental parameters: 10 mV/s of scan rate and 50 mV of pulse height. Using differential pulse voltammetry, the peak currents were found to increase linearly with the α-tocopherol concentration over the range of 5.0 to 350μmol/L, with a sensitivity of 1.852×10-8 A L/mol and the limit of detection of 1.5μmol/L (S/N=3), the detection time being 80 s for each assay. The interference of other synthetic antioxidants such as TBHQ, BHA and BHT to the analysis of α-tocopherol was studied. The developed method is applied to the quantification of α-tocopherol in four vegetable oils, showing that the results are in agreement with the results by HPLC method. It could be used as a simple, rapid and practical method for the quantification of tocopherols in vegetable oils without any sample pretreatment.

Key words: &alpha, -tocopherol； vegetable oil analysis； voltammetry； glass carbon electrode；