Voltammetric Behavior and Determination of Tocopherol in Vegetable Oils at a Polypyrrole Modified Electrode

• Published in: Electroanalysis (New York, N.Y.) N.Y.), 2006-12, Vol.18 (23), p.2337-2342
• Main Authors: Li, Shu-Guo, Xue, Wen-Tong, Zhang, Hui
• Format: Article
• Language: English
• Subjects: Polypyrrole modified electrode; Tocopherols; Vegetable oil analysis; Voltammetry
• ISSN: 1040-0397; 1521-4109
• DOI: 10.1002/elan.200603663

The voltammetric behavior of α‐tocopherol in the presence of vegetable oil is studied at a polypyrrole modified Pt electrode in a 1,2‐dichloroethane‐ethanol medium with cyclic voltammetry. Cyclic voltammogram of α‐tocopherol showed a well‐defined oxidation peak; the peak potential shifting toward less positive and a much higher peak current obtained at a polypyrrole modified electrode than that obtained at the unmodified Pt electrode. An electroanalytical method for the determination of α‐tocopherol based on its electrochemical oxidation at the polypyrrole modified Pt electrode is developed. Using differential pulse voltammetry, the peak currents were found to increase linearly with the α‐tocopherol concentration over the range of 5.0 to 300 μM, with a sensitivity of 5.38×10−2 A L mol−1 and the limit of detection of 1.5 μM (S/N=3), the detection time being about 90 s for each assay. The interference of other synthetic antioxidants such as TBHQ, BHA and BHT to the analysis of α‐tocopherol was investigated. The developed method is applied to the quantification of tocopherols in six vegetable oils, showing that the results are in good agreement with those by HPLC method.