EVALUATION OF AN HPLC METHOD FOR THE DETERMINATION OF PHYLLOQUINONE (VITAMIN-K-1) IN VARIOUS FOOD MATRICES

The amount of phylloquinone (vitamin K-1) in five different foods was determined by applying a highly sensitive HPLC method that incorporates postcolumn chemical reduction of the quinone followed by fluorescence detection of the hydroquinone form of the vitamin. After initial extraction in 2-propanol and hexane, the food extracts were purified by solid-phase extraction (SPE) on silica gel and analyzed by HPLC or, depending on the matrix, further purified using liquid-phase reductive extraction or reversed-phase SPE on C-18. Intra- and interday precision of the assay ranged from 6.6 to 13.6%; The between sample coefficient of variation in the phylloquinone content of 10 random bulk samples ranged from 7.8 to 44.6%, depending on the food item analyzed. In addition,endogenous dihydrophylloquinone was identified in foods containing hydrogenated oils, although its biological activity is unknown.