Vitamin E is an essential vitamin that functions as a chain-breaking antioxidant in the body by preventing the spread of free-radical reactions. For the nutritional purpose, vitamin E activity is defined as being limited to the 2R-stereoisomeric forms of alpha-tocopherol.(1) Depending on the stereoisomeric forms of alpha-tocopherol, or the source of the alpha-tocopherol, different conversion factors are used in calculating the vitamin E activities in foods and dietary supplements. (1, 2) So far, there is no established standard method for the determination of the stereoisomers of alpha-tocopherol, recordkeeping of the source of the alpha-tocopherol is required for the estimation of the vitamin E activity in foods or dietary supplement.(2) There is a need for an routine analytical method to verify the form of the alpha-tocopherol in foods and dietary supplements.
Separation of the eight stereoisomers of alpha-tocopherol is a complicated process. Normal phase liquid chromatography has been partially successful in separating the stereoisomers using chiral columns. (3) Up to five peaks can be separated for a racemic-alpha-tocopherol, which could be used to verify the source of the alpha-tocopherol, since the natural source only has one stereoisomeric form, the RRR-alpha-tocopherol. The main drawback of the NPLC chiral separation is the long run time. Ultra performance convergence chromatography has been successful in the chiral separation. Much shorter run time is often achieved in UPCC for chiral separations. Here the application of the UPCC to the chiral separation of alpha-tocopherol has been exploited.
