Reverse phase high pressure liquid chromatographic determination of vitamin D in fortified milk.

Vitamin D was determined in commercially fortified milk, using reverse phase high pressure liquid chromatography (HPLC). The milk sample was saponified at room temperature and cleaned up on an alumina column to remove cholesterol and carotenes. The sample was then chromatographed in an HPLC system on a 0.26 X 25 cm ODS-HC-Sil-X-1 column using methanol-acetonitrile (1+1) as the mobile phase. For 6 milk samples, the recovery of added vitamin D using this procedure was 92%.