Separation of Tocopheryl Acetate Isomers on Porous Graphitic Carbon

Vitamin E is a collective term for tocopherols and tocotrienols that includes isomers differing in the number and position of methyl substituents. An LC impurity method was required to determine the purity of RRR-alpha-tocopheryl acetate, especially with regard to the amounts of the beta- and gamma-isomers which have one fewer methyl substituents. Using the Hypercarb porous graphitic carbon column, a normal phase LC method was developed that separates alpha-, beta-, gamma-, and delta-tocopheryl acetates using a mobile phase of 25:85 (v/v) THF:hexane. The area response with detection at 205 nm is linear for column loadings of 0.006-10 mu g of alpha-tocopheryl acetate. It was also noted that SRR-alpha-tocopheryl acetate is partially resolved from RRR-alpha-tocopheryl acetate under these conditions.