The molecule of α-tocopherol is characterised by three chiral centres (C-2, C-4', C-8') which yield eight optically active stereoisomers. The two compounds of the highest biological activity and the greatest practical significance are the naturally occurring RRR-α-tocopherol and the synthetic all-rac-α-tocopherol, which is a mixture of the following stereoisomers: SSR, SSS, SRS, SRR, RSS, RRS, RRR, RSR.

Most pharmaceutical products whose composition includes vitamin E contain racemic α-tocopherol or its esters (mostly acetate). It is therefore important to determine stereoisomeric purity of the pharmaceutical products containing this compound.

Previous papers describe methods of determination of the stereoisomers of α-tocopherol in biological material.

The aim of our study was to separate all-rac-α-tocopherol into individual stereoisomers in pharmaceutical products containing dl-α-tocopherol acetate.

We performed hydrolysis of dl-α-tocopherol acetate to α-tocopherol, followed by precolumn derivatisation of the standard and the pharmaceutical products with dimethyl sulphate. Derivatisation was performed to change the polarity of the analyte. We then separated the resulting methyl derivatives of α-tocopherol by HPLC, yielding 5 peaks corresponding to the 2S (SRS+SSR+SSS+SRR) and RSS, RRS, RRR, RSR stereoisomers. We then collected the 2S stereoisomer fraction with a fraction collector and analysed it by gas chromatography.

The combining of the two chromatography techniques (HPLC with GC) allowed us to separate α-tocopherol derivatives (α-TMe) into 8 stereoisomers. HPLC additionally enabled unequivocal identification of these stereoisomers. Our results confirm the correct selection of raw materials used for the manufacture of the pharmaceutical products we investigated.

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