Analysis of vitamin K by directry coupled supercritical fluid extraction/supercritical fluid chromatography.

Abstract

We have already reported the new double-stage separation method which combines supercritical fluid. extraction (SFE) directly with supercritical fluid chromatography (SFC). The new SFE/SFC method incorporates SFE as the first separation step and SFC as the second separation step. This arrangement allows the analyst to apply raw and solid samples directly to the system. In addition, the use of SFE/SFC enables true SFC which is not affected by the solvent, that often plays a role of modifier only for early eluting peaks, used for dissolving samples. Here, application of this method to the analysis of vitamin Ks is described. A solution of vitamins K1, K2 and K3 were dried on a piece of filter paper, then applied to the SFE/SFC system. Stopped-flow extraction was performed at 40 °C with 200 bar pressure for 2.5 min, then the extract was directly introduced into the SFC system. All the three vitamins were completely separated on a silica gel column within 4.5 min using supercritical carbon dioxide (2.0 1 /min) with acetonitrile (0.1 ml/ min) as a modifier. The relative standard deviation of the retention times was less than 2.0% for ten consecutive runs.