3.1 Analysis of mixed tocopherols
As shown in Fig 2a, the components of mixed tocopherols are four kinds
of tocopherol monomers and some impurities with a less polarity than
α-tocopherol. And we all know that the mixed tocopherols are mainly
obtained by molecular distillation under reduced pressure and high
temperature after esterification of fatty acids, triglyceride and
crystallization of sterols (Ito et al. 2007). After comparison with the
standard substances, we speculated that the impurities may be fatty acid
methyl ester. The four tocopherols and impurities are thereby separated
in the following order: δ-T, (β + γ)-, α-tocopherol and impurities with
increasing Rf values: 0.69, 0.79, 0.90, 0.95, this order showed that the
polarity of our target γ- tocopherol is between δ- and α-tocopherol. In
order to obtain the high-purity target γ-tocopherol, we have to remove
not only impurities, but also α- and δ-tocopherol, so it is difficult to
separate target substance for the reasons given above. The total
tocopherol content in mixed tocopherol was 91.62%, with the contents of
α-, β-, γ- and δ- tocopherol were 7.17%, 1.47%, 60.04% and 24.41%,
respectively. And the impurities were around 6.91%.