Determination of vitamin K1 in plasma by solid phase extraction and HPLC with fluorescence detection

We describe a procedure for quantification of vitamin K1 in human plasma by HPLC. Samples, enriched with a vitamin K derivative as internal standard, were deproteinized, purified on polymeric RP-SPE cartridges and injected into HPLC equipped with a post-column on-line zinc metal reactor and a fluorometric detector. Median level in blood donors (n = 87) was 1.967 nmol/L (0.93–4.01, 5th–95th percentiles), with a significant correlation between plasma levels and age (r = 0.276, p = 0.00958) and a lower (not significant) value in women than in men. This method, easy-to-handle and with a high throughput, can be used to identify covert states of vitamin K intake deficiency in patients thus at risk of alterations in blood clotting or bone mineralization.