(265d) Selective Separation of Tocopherol Homologues by Liquid-Liquid Extraction Using Ionic Liquids: Effect of Diluent

Tocopherols are the main compositions of natural Vitamin E and can be extracted from vegetables and fruits as a mixture of four different homologues, viz. α-, β-, γ- and δ-tocopherol. Since α-tocopherol has been reported to possess the highest biological activity, there is a strong need to separate it from the other forms of tocopherol. The traditional chromatographic methods for this problem are almost only applied at a laboratory scale on account of the low capacity and the large consumption of absorbents and solvents. Therefore, novel methods for the effective separation of tocopherol homologues have been in great demand so far.

In the present work, selective separation of tocopherol homologues was performed by liquid-liquid extraction, using ionic liquids (ILs) as extractants. Because ILs are very viscous or even solid near room temperature, several molecular solvents as diluents were used. It was found that diluents had notable effects on the separation efficiency of α-tocopherol with the other homologues, both the kind of diluent and the concentration of IL could affect the distribution coefficients and selectivities of tocopherols. Satisfactory separation efficiency for tocopherols have been reached. For example, a selectivity of δ-tocopherol to α-tocopherol higher than 20 was achieved when using [bmim]Cl as extractant diluted by methanol.

To our best knowledge, the use of diluents was very few in the extraction researches about ILs as extractants until now, therefore we further investigated the several properties of the IL-diluent binary solutions which might make some sense to the extraction processes. Densities, viscosities, surface tensions as well as solvatochromic parameters were determined over different kinds of diluents and concentrations of ILs, and the liquid-liquid equilibrium was also investigated for the IL-diluent-solvent ternary systems.