Determination of alpha-tocopherol and alpha-tocopheryl acetate in diets ofexperimental animals - Study of stability in the diets

A simple method is described which permits, avoiding saponification, alpha- tocopherol and alpha-tocopheryl acetate measurement in semi-synthetic diets for experimental animals by HPLC, with both UV and fluorescence detection. Phenyldodecane was chosen as internal standard with remarkable performance s, and EDTA and BHT were added to prevent oxidation in aqueous and non-aque ous phases respectively. The mobile phase was methanol-water (94:6, v/v) at a flow-rate of 2 ml/min. Samples were homogenized and extracted twice with n-hexane by probe sonication. Extracts were evaporated to dryness and redi ssolved with chloroform-methanol (1:1, v/v). Validation parameters were stu died between 25 ng and 6 mu g for alpha-tocopherol and between 3 and 24.2 m u g for alpha-tocopheryl acetate, which corresponds to the range of values in the existing diets. Results had correlation coefficients >0.99; recoveri es = 85%; R.S.D.<6%, so the method is adequate to control vitamin E intake in animals as well as vitamin E stability in food during storage. (C) 1999 Elsevier Science EV All rights reserved.