Determination of vitamin A and vitamin E esters in infant formulae and fortified milk powders by HPLC: Use of internal standardisation.

An HPLC method is described using normal phase conditions with an unbonded silica column to determine concentrations of supplementary vitamin A and vitamin E esters and β-carotene in infant formulae. The method utilises selective dual-channel fluoresence for vitamins A and E and visible absorbance for β-carotene. An attribute of the method is the use of retinol propionate, α-tocopheryl propionate and all-E-β-apo-8'-carotenoic acid ethyl ester internal standards to compensate for analytical variations associated with these labile vitamins.