ISO 20633:2015 specifies a method for the simultaneous quantitative determination of vitamin E (a-tocopherol and a-tocopheryl acetate) and vitamin A (13-cis and all-trans isomers of retinyl palmitate and retinyl acetate) present in all forms of infant and adult formulas (powders, ready-to-feed liquids and liquid concentrates).
Retinol is not used for fortification purposes and therefore is not addressed in this method. The innate amount in products is insignificant.
Stereoisomers of vitamin E, a-tocopherol and a-tocopheryl acetate, are not differentiated in this method.