Gas chromatography of retinol and alpha-tocopherol without derivatization.

An improved gas chromatographic method for the analysis of retinol and alpha-tocopherol in biological samples is described. The use of cold on-column injection in combination with wall coated open tubular column gas chromatography eliminates thermal decomposition of vitamin A and yields efficient separations of fat-soluble vitamins (A, D2, D3, and E) without derivatization. Peak tailing was judged to be minimal. Vitamins were quantified by flame ionization detection responses down to 3.5 ng injected, and their identities were confirmed using gas chromatography-mass spectrometry. Extracts of biological samples were saponified, and sterols were removed using digitonin-impregnated celite chromatography before analysis by gas chromatography and gas chromatography-mass spectrometry. Recoveries of vitamins from a test diet ranged from 89 to 103%.