Determination of liposoluble vitamins in cooked meals, milk and milk products by liquid chromatography

A method for the simultaneous determination of liposoluble vitamins in cooked meals was established. Saponification was performed with 50% (w/v) KOH at 80 °C, and ascorbic acid was added as antioxidant. The subsequent extraction was carried out with diethyl ether. This was followed by a liquid chromatographic separation on a reversed-phase C18 column with methanol–water (94:6, v/v) as the mobile phase. Retinyl acetate was used as the internal standard. The analytical parameters linearity, detection limit (0.19 and 8.33 μg/100 g for retinol and α-tocopherol, respectively), precision of the method (RSD=5.24 and 6.99% for retinol and α-tocopherol, respectively) and recovery assays (95.6 and 96.5% for retinol and α-tocopherol, respectively) show that the method studied is useful for measuring these compounds in foods and cooked meals.