Analysis of plant oils by subcritical fluid chromatography using pattern fitting

A new method for analyzing plant oils was developed, which allows determination of fatty acid (FA) and triglyceride (TG) compositions of oils directly from their chromatograms without complete separation and peak identification. TGs of oils were separated by subcritical fluid chromatography using an octadecyl-silica column, carbon dioxide mobile phase and flame ionization detector. Observed chromatograms were compared with simulated ones, which were generated using FA compositions and predicted retentions of TGs on the assumption that FAs are combined with glycerol at random. FA compositions were determined by minimizing the differences between observed and simulated chromatograms through trial and error. Compared with GC analysis, relative errors of calculated FA compositions were less than 10% for main components (mol fraction>0.2). However, cocoa butter presented large errors even for main components because of the selective bonding of FAs to glycerol. Application of this method to the analysis of blended oils was also demonstrated, where FA compositions and mixing ratio were determined.