Determination of (endogenous) vitamin K1 in human plasma by reversed-phase high-performance liquid chromatography using fluorometric detection after post-column electrochemical reduction. Comparison with ultraviolet, single and dual electrochemical detection.

A new method for the fluorometric detection of K1 and K2 vitamins using post-column electrochemical reduction is described. Dual electrochemical detection in the reduction/reoxidation mode for coulometric/coulometric as well as coulometric/amperometric detection appears to be more sensitive and selective towards the plasma background than simple reductive electrochemical detection, but fluorometric detection after coulometric reduction offers the best results. Combination of normal-phase chromatography and the described method is only possible if supporting electrolyte is added post-column, but leads to higher detection limits. This highly sensitive method is applied to the determination of vitamin K1 in human plasma samples.