[Determination of retinol and alpha-tocopherol in milk and milk products using high-pressure liquid chromatography after saponification in serum vials].

An improved procedure is described for the determination of retinol and alpha-tocopherol in milk and dairy products using high-pressure liquid chromatography (HPLC). Samples are saponified in sealed 10-ml serum vials in the absence of oxygen, cooled and neutralized by injecting glacial acetic acid into the system. Retinyl acetate and 5,7-dimethyltocol respectively are used as the internal standards. The solution is extracted with hexane and the organic phase is cleaned up on a sodium sulphate/aluminium oxide column. The solution is evaporated under vacuum and dissolved in ethanol for HPLC analysis. A short reversed-phase column packed with RP-18, using methanol as the eluent, allows fast separations of both the vitamins.