Chemical reduction system for the detection of phylloquinone (vitamin K1) and menaquinones (vitamin K2). 
Both isocratic and gradient elution systems for fluorometric detection of K vitamins after post-column reduction with zinc metal to their hydroquinones are described.  The reaction detection system for K vitamins (phylloquinone and menaquinones) in liquid chromatography is based on reduction of K vitamins to their corresponding hydroquinones with zinc metal in the presence of zinc ions.  It was found that 95% of the injected quinones (K vitamins) could be reduced to their corresponding hydroquinones with zinc metal compared to 60% reduction for electrochemical detectors.  Menaquinones could be detected down to 100 pg with relative ease during gradient elution.