Plasma
vitamin K1 (
phylloquinone) determination is commonly used for the diagnosis of
vitamin K deficiency in patients suffering from
lipid malabsorption. Moreover, current evidence that adequate
vitamin K intake, and correspondingly adequate plasma
vitamin K1 concentration, could also be of importance in relation to bone and
brain diseases emphasizes the need to improve the current analytical methods. We developed a liquid chromatography coupled to tandem mass spectrometry method using a stable
isotope ring-D4-labeled internal standard of
vitamin K1 and operating in the multiple reaction monitoring mode by the selection of a precursor and product
ions. The atmospheric pressure chemical ionization (APCI) method was shown to be more sensitive than electrospray ionization. After a single-step extraction with
cyclohexane, chromatographic separation was performed on a C18 column with an isocratic mobile phase. The linearity was up to 5400ng/L, and the limit of detection was 14ng/L. Intra- and interrun precision were 2.4% and 8.3%, respectively, for the lower limit of the reference range. Recovery was better than 98%. The method is simple and reliable, allowing accurate
vitamin K1 measurement in plasma samples from healthy subjects and patients suffering from
vitamin K deficiency.