Development of vitamin K analysis method using column switching high-performance liquid chromatography method and analysis results of various food items for vitamin K content

In this study, we developed a column-switching high-performance liquid chromatography (HPLC) method with fluorescence detection for the analysis of vitamin K. Column-switching is accomplished by changing the direction of flow using a switching valve with a set time program. Using this method, three vitamin K, phylloquinone (PK), menaquinone-4 (MK-4), and menaquinone-7 (MK-7), were separated and identified with high sensitivity, and impurities were eliminated. This method was used to determine the vitamin K content in meat, fish meat, snails, bivalves, sea urchins, seaweeds, vegetables, tea, soy products, milk products, and supplements. The results showed that chicken showed the highest content of MK-4 (15.35 ± 0.35 μg/100 g), matcha showed the highest content of PK (3069.66±80.10 μg/100 g), and dried natto showed the highest content of MK-7 (3997.57±79.42 μg/100 g). This method can also be used to analyze vitamin K in supplements and pharmaceuticals. The results of this study revealed that different manufacturers add different types of vitamin K to their commercial supplements and infant formulas. The developed method provides highly reproducible and quantitative results and allows for the rapid analysis of the three vitamin K types. Thus, the method developed in this study may aid the sequential analysis of vitamin K in different samples to assess food nutrients.