Separation of vitamin E on a 100-Å phenogel column

The effect of π-electrons and hydroxyl group on the separations of vitamin E on a swellingcontrolled polystyrene-divinylbenzene (Phenogel) column using toluene/isooctane as the mobile phase was investigated. The effect of the π-electrons was demonstrated in the baseline separation of α-tocopherol and α-tocotrienol on a 100-Å Phenogel column. In addition, baseline separation of α-, (β- + γ-)- and δ-tocopherol could be achieved on this column. The separation mechanism of these isomers are due to the difference in the interactions between the hydroxyl group on the chromanol ring of each tocopherol and the gel matrix caused by the steric hindrance of methyl group(s). It was concluded that solutes of the same molecular size but different in the polar groups could be separated on a high performance size-exclusion chromatography by controlling the swelling of the gel matrix via modification of the mobile phase.