This document specifies a method for the determination of vitamin C (L-ascorbic acid) present in all forms of infant and adult formulas (powders, ready-to-feed liquids and liquid concentrates), using (ultra) high performance liquid chromatography with ultraviolet detection (U)HPLC-UV. The application range runs from 2,5 mg/100 g (limit of quantification) to 50 mg/100 g expressed in the product as consumed. The method is able to distinguish between D-ascorbic acid (isoascorbic- or erythorbic acid) and L-ascorbic acid.