THE DETERMINATION OF TOCOPHEROLS IN VEGETABLE-OILS BY SQUARE-WAVE VOLTAMMETRY

Square-wave voltammetry (SWV) has been applied to the determination of tocopherol concentrations in eight vegetable oils: canola, corn, olive, peanut, safflower, sesame, soybean, and sunflower. This technique has a lower limit of detection and somewhat better resolution than differential-pulse voltammetry (DPV) and is significantly faster than both DPV and high-performance liquid chromatography (HPLC), the technique most often used for tocopherol determinations. The tocopherols are oxidized at a stationary glassy carbon electrode as its potential is scanned from 0.40 to 1.00 V vs Ag/AgCl at a rate of 20 mV/s. The currents that arise from these oxidations are directly proportional to the tocopherols' concentrations. A standard addition method is used to determine the tocopherol contents of the oils listed. Under the conditions employed, the limit of detection is 10 mg/L tocopherol in oil.