Determination of vitamin K in the edible part of fish by high-performance liquid chromatography

A highly sensitive high-performance liquid chromatography method for measuring endogenous phylloquinone (K-1) and several menaquinones (MK-4 to MK-10) in the edible part of fish was developed. The procedure consists of three chromatographic steps, a preliminary purification of crude lipid extracts on silica cartridges, a semipreparative stage using normal-phase HPLC, and a final analytical reversed-phase HPLC stage that uses postcolumn chemical reduction of the vitamin followed by fluorimetric detection. The accuracy of this method was evaluated by recovery experiments. The investigated fish included most of the important fish species consumed in Germany. Phylloquinone and MK-4 were the two dominant forms of vitamin K in fish. Relatively high concentrations were found in muscle of marine and freshwater fish with high fat content and in the liver of cod. Fish with low fat content contained only very small amounts. The main part of the vitamin K in fishery products like fish sticks and canned tuna in oil was of plant origin.