The differentiation and assay of vitamins D2 and D3 by gas-liquid chromatography

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Abstract
A method is described for the differentiation and determination of as little as 0.2[mu]g. of vitamins D2 by gas-liquid chromatography. The vitamins are converted by treatment with anatomy trichloride into isovitamins D2 and D3, which show single, separate peaks on gas-liquid chromatography, unlike the unmodified vitamins, which give twin peaks due to the formation of pyro and isopyro derivatives. Since isovitamins D2 and D3 remain together in all steps of the procedure except during gas-liquid chromatography, one may be used as an internal standard for the other. The use of an internal standard reduces the importance of loss during sample preparation and increases precision. The application of the method to biological materials is demonstrated.