Selective Separation of Tocopherol Homologues by Liquid-Liquid Extraction Using Ionic Liquids

Selective separation of tocopherol homologues was performed by liquid-liquid extraction, using ionic liquids (ILs) as extractants in the presence of diluent. The distribution coefficients and selectivities of tocopherols in the biphasic system were determined. A selectivity of delta-tocopherol to alpha-tocopherol up to 21.3 was achieved when using [bmim]Cl as extractant diluted by methanol. Considering the structural differences of tocopherols, tire separation mechanism based on the hydrogen-bonding interaction between IL's anion and the -OH group oil the tocopherols was proposed. The separation efficiency of IL was greatly affected by its anion, and followed the order [bmim]BF4 < [bmim]CF3SO3 < [bmim]Cl under tire same conditions, which is consistent with the ascending order of IL's hydrogen-bond basicity strengths.