Evaluation of rapid polarographic method for determining tocopherols in vegetable oils and oil-based products

A polarographic procedure for the determination of the tocopherols in vegetable oils was compared to a conventional gas-liquid chromatographic procedure. The polarographic method is 2-3 times more precise and more rapid, which is an important advantage for monitoring the nutritional value of processing conditions of vegetable oil-based products. Attempts to establish the validity of apparently slightly higher values for alpha- and gamma-tocopherols obtained by polarography has implicated the gas chromatography or derivative formation rather than the extensive prior manipulation of the sample for chromatography as the source of error. Essentially the same results were obtained for alpha-tocopherol, regardless of the technique used. However, more variable results which were product dependent were obtained for gamma- and delta-tocopherols when gas-liquid chromatography was used.