Simultaneous liquid chromatographic determination of vitamins A, E and β-carotene in common dairy foods

Abstract Milkfat was extracted quantitatively from dairy foods and the vitamins A, E and β-carotene in the extract were analysed by normal phase high performance liquid chromatography (HPLC) using a silica column, a fluorescence detector and a UV/visible detector. Products such as butter and anhydrous milkfat were dissolved simply in hexane, whereas milk and milk powders underwent a Rose-Gottlieb fat extraction prior to HPLC analysis. The extraction method used was superior to commonly used saponification procedures in terms of speed as well as reduced loss and isomerization of the vitamin components in the food, because the chemical form of the vitamin is not changed to a less stable form such as retinol during extraction. The individual geometrical isomers of vitamin A, which possess different in vivo vitamin activities, were uniquely identified and quantified. Recovery studies showed satisfactory results for all three vitamins. The simultaneous nature of the assay allowed the estimation of the total vitamin A activity of the food because both vitamin A and pro-vitamin A (β-carotene) were quantified. The single extraction and single HPLC analysis used for the three vitamins made the method well suited for routine work.