Determination of alpha-tocopherol and alpha-tocopheryl acetate in diets of experimental animals : study of stability in the diets.

Abstract

A simple method is described which permits, avoiding saponification, a-tocopherol and cx-to:opheryl acetate measurement in semi-synthetic diets for experimental ao.imals by HPLC, with both UV and fluoresccn..:e detection. Phenyldodecane was chosen as internal standard with remarkable performances, an<l EDTA and BHT were added to prevent oxidation in aqueous and non-aqueous 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 redissolved with chloroform-methanol (1:1, v/v). validation parameters were studied between 25 ng and 6 µ,g for a-tocopherol and between 3 and 24.2 µ,g for a-tocopheryl acetate, which corresponds to the range of values in the existing diets. Results had correlation coefficients >0.99; recoveries >85%; R.S.D.<6%, so the method :s adequate to control vitamin E intake in animals as well as vitamin E stability in food during storage.