For the determination of vitamin K1 an internal standard is added first. After a solid phase extraction on SPE-cartridges, the samples are precipitated. The supernatant is then extracted with an organic solvent and evaporated. After that the samples are re-suspended and injected into the HPLC system. A post-column reduction reactor reduces vitamin K and enables the measurement of vitamin K with a fluorescence detector. The isocratic separation at 30°C using a ``reverse phase'' column lasts 20 minutes. The chromatograms are recorded by a fluorescence detector. The quantification is performed by the delivered plasma calibrator; the concentration is calculated by the internal standard method via integration of the peak areas resp. heights. Sample Types: serum, plasma. Time: 10 minutes ? Vitamin K works as cofactor of an oxygen dependent carboxylase, which carboxylates specific glutamic acid residues in g-position. Because of that modification, blood clotting factors can be activated by cleavage. In bone metabolism the g-carboxylation enables osteocalcin to bind to hydroxyapatite of the bone matrix. Vitamin K can be stored only for a short time, whereby deficiency occur after a view days. A lack of vitamin K mainly manifests in clotting disorders. Beside this, disorders in bone metabolism caused by a deficient modification of osteocalcin have been reported. The Eagle Biosciences Vitamin K1 HPLC Assay kit makes it possible to determine the vitamin in an easy, fast and precise method. The kit includes all reagents for the preparation and separation of the samples with exception of the columns (IC2400rp) and the controls (IC2400ko).