Normal-phase high-performance liquid chromatography of tocopherols and tocotrienols. Comparison of different chromatographic columns.

Natural vitamin E is composed of eight different vitamers (alpha-, beta-, gamma- and delta-tocopherols and alpha-, beta-, gamma- and delta-tocotrienols). As these eight vitamers have different antioxidant and biological activities, it is necessary to have quantitative data on each substance separately. The aim of this study was to find universal HPLC columns for the separation of all eight components and to test if a few columns of the same material (different batches) will give reproducible results. Normal-phase HPLC separations of vitamin E compounds in a prepared mixture (containing oat extracts, palm oil and tocopherol standards) were tried on six silica, three amino and one diol columns. As shown by calculations of retention factors (k), separation factors (alpha), numbers of theoretical plates (N) and resolutions (Rs), the best separations were obtained on three silica columns and two amino columns using 4 or 5% dioxane in hexane as the mobile phase as well as on a diol column using 4% tert.-butyl methyl ether in hexane as the mobile phase.