METHOD FOR THE DETERMINATION OF VITAMIN-K-1(20) IN HUMAN PLASMA BY STABLE-ISOTOPE DILUTION GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A method for the quantitative determination of vitamin K-1(20) (VK), a n essential cofactor in the carboxylation of clotting factors, is pres ented. The assay is based on gas chromatography/electron impact mass/s pectrometry. The preparation of deuterium-labelled vitamin K-1(20) for use as an internal standard is described. The method involves extract ion of Vg from human plasma and its derivatization to the heptafluorob utyryl ester after reduction of one carbonyl group with zinc. The dete ction limit was found to be 1.0 pg and the limit of quantitation 2.0 p g ml(-1) plasma. This permits the measurement of vitamin K-1(20) even in small quantities of plasma, which is highly desirable in investigat ions dealing with clotting abnormalities in neonates and infants.