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Abstract
[Objectives] To make simultaneous determination of vitamin K1 (VK1 ) and vitamin K2 (VK2, mainly MK-4, MK-7 and MK-9) in milk and dairy products. [Methods] A high performance liquid chromatographic method was developed for the simultaneous determination of vitamin K1 (VK1 ) and vitamin K2 (VK2, mainly MK-4, MK-7 and MK-9) in milk and dairy products. After enzymatic digestion, the samples were extracted with hexane for VK1, MK-4, MK-7 and MK-9, subjected to gradient elution at excitation wavelength 243 nm and emission wavelength 430 nm, detected by high performance liquid chromatography with fluorescence detector and quantified by external standard method. [Results] The linearity of VK1, MK-4, MK-7 and MK-9 was good in the concentration range of 2.5 -1000 ng/mL with the correlation coefficients greater than 0.999; The relative standard deviations (RSD) of VK1, MK-4, MK-7 and MK-9 in milk powder, liquid milk and yogurt were 1.32%-5.05%, 1.10%-2.48% and 2.20%-3.47%, respectively; the recovery rates of VK1, MK-4, MK-7 and MK-9 at different levels in milk powder, liquid milk and yogurt were 81.1%-108%, 81.8%-103% and 82.1%-99.2%, respectively. [Conclusions] The method is rapid, accurate, reproducible and capable of simultaneous determination of VK1, MK-4, MK-7 and MK-9.