Determination of endogenous vitamin K (phylloquinone and menaquinone-n) in plasma by high-performance liquid chromatography using platinum oxide catalyst reduction and fluorescence detection

Abstract

A sensitive method for the determination of endogenous phylloquinone (PK) and menaquinones (MK-3 to MK-10) by high-performance liquid chromatography using a hydrogen gas saturated mobile phase with fluorescence detection after post-column reduction by a platinum oxide catalyst column has been developed. The detection limits were 25 pg (injected amount) for PK and MK-3 to MK-5, 60 pg for MK-7 and 150 pg for MK-10. The detection limits with 1 ml of plasma were 0.1 ng ml^–1 for PK, MK-4 and MK-5. The levels of PK and MK-4 to MK-8 in healthy human plasma (n= 5) were 2.94, 0.32, 0.92, 0.26, 3.82 and 0.26 ng ml^–1, respectively; those in healthy human milk (n= 5) were 2.3, 1.54, 0.58, 0.12, 0.80 ng ml^–1 and undetectable, respectively.