Quantitation of trans-vitamin K1 in small serum samples by off-line multidimensional liquid chromatography.

A sensitive high-performance liquid chromatography method for vitamin K1 using normal-phase fractionation was updated in order to cope with the limited volume of blood samples obtained from newborns. The method combines sample clean-up, normal-phase fractionation with reversed-phase chromatography using post-column electrochemical reduction and fluorescence detection. It was possible to measure vitamin K1 concentration in at least 0.2 ml of (potentially lipemic) serum even at a level of 0.3 nmol/l. The normal-phase method was compared to the updated method. The updated method shows about a twenty-fold lower limit of detectability than the previously described method.