A method for the determination of vitamin K in milk, milk powder and vegetable oil by high performance liquid chromatography

Depending on the capacity factors and resolutions of vitamin K, YMC-PACK A-314 was selected from several kinds of commercially prepared ODS columns, and ethanol-H2O (99: 1) was found to be most suitable mobile phase for this column. Vitamin K was extracted from liquid milk, whole milk powder and vegetable oil by using hexaneethyl ether (1: 1). Vitamin K was easily separated from fat by single. step silica gel column chromato. graphy eluted with hexane-ethyl ether (97: 3). Unsatisfactory extraction or separation of vitamin K was observed in th e case of formulated milk powder for infants. Therefore, hydrolysis of fat by lipase is required before HPLC determination of formulated milk powder for infants. Coefficients of variation were estimated as 9.2% for vitaminK1 and 4.8% for vitamin K2 in cow's raw milk, and recoveries were 97% for K1 and 94% for K2. Coefficients of variation for formulated milk powder for infants were estimated as 7.1%for vitamin K1 and 11.6% for vitamin K2, and recoveries were 95% both for K1 and K2. The detection limit of vitamin K1 or K2 was calculated as 0.2μg/l for liquid milk, 1μg/kg for whole milk powder, 2μg/kg for vegetable oil or 2.5μg/kg for formulated milk powder for infants.