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

✍ Scribed by Shu-Guo Li; Wen-Tong Xue; Hui Zhang

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 163 KB
• Volume: 18
• Category: Article
• ISSN: 1040-0397
• DOI: 10.1002/elan.200603663

✦ Synopsis

The voltammetric behavior of a-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 a-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 a-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 a-tocopherol concentration over the range of 5.0 to 300 mM, with a sensitivity of 5.38 Â 10 À2 A L mol À1 and the limit of detection of 1.5 mM (S/N ¼ 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 a-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.