This document specifies a method for the quantitative determination of vitamin D2 and/or vitamin D3 in infant formula, and adult nutritionals in solid (i.e. powders) or liquid (i.e. ready-to-feed liquids and liquid concentrates) forms using liquid chromatography-mass spectrometry. The application range runs from 0,15 μg/100 g (limit of quantification) to 59 μg/100 g for vitamin D2 and from 0,25 μg/100 g to 65 μg/100 g for vitamin D3.