High-performance liquid chromatographic assay of vitamin K in human serum.

A sensitive combined adsorption and reversed-phase high-performance liquid chromatographic procedure is described that permits the determination of endogenous vitamin K1 levels in serum. The separation of vitamin K1 (cis- + trans-isomers), vitamin K1 epoxide and the menaquinones MK-2, MK-4 and MK-9 by adsorption, reversed-phase and cyano-bonded phase chromatography is discussed. The methodology was further developed for the quantitative measurement of vitamin K1 in human serum. Concentrations as low as 500 pg/ml in serum could be detected. The identity of the vitamin K1 peak was confirmed by UV absorption spectrophotometry and re-chromatography. The method has been applied to the determination of serum levels in normal healthy individuals and patients treated with vitamin K1.