[Determination of vitamin K in animal foods]

To establish a high performance liquid chromatography method with fluorescence detection for a variety of vitamin K and to assess the content of vitamin K in animal foods.

Animal foods were hydrolyzed by 0.2 g lipase and 0.1 g protease in pH 8 for 4 hours, extracted with isooctane followed by rotary evaporation and reconstitution. The mobile phase was 900 mL methanol and 100 mL tetrahydrofuran which contained 5 mmol glacial acetic acid, 11 mmol zinc chloride and 6 mmol anhydrous sodium acetate. The content of vitamin K_1, menaquinone-4(MK-4), and menaquinone-7(MK-7)were separated on Atlantis T3 column(4.6 mm×250 mm, 5 μm)by high-performance liquid chromatography. The fluorescence detector was set at a wavelength of 320 nm for excitation and 410.3 nm for emission.

The linear range of the method was 0.01-0.40 μg/mL, and coefficient of determination was > 0.999. The spiked recoveries were 84.4%-124.2% with relative standard deviation was <6%(n=6). MK-4 was the main form of vitamin K in pork and chicken. The highest content of vitamin K_1 was found in beef, and MK-7 could be detected in aquatic products.

The proposed method is successfully applied for the determination of vitamin K in animal foods. A variety of vitamin K are distributed differently in distinct animals.