Separation of vegetable oil triglycerides by subcritical fluid chromatography with octadecyl packed columns and CO2/modifier mobile phase

The separation of triglycerides (TGs) was studied by subcritical fluid chro matography (SubFC) with octadecyl packed columns and C02/modifier mobile ph ases. Two detection systems (UV and ELSD) were used. In the first part systematic experiments were carried out for studying the retention behavior of characteristic triglycerides. This was done by analys ing a simple vegetable oil (argan), which contains triglycerides differing by the methylene group number (between P and S) or by the unsaturation numb er (between O, L and Ln). The selectivity calculations from these selected triglycerides have enabled better modeling of the effect of chromatographic parameters on separation (modifier nature and percentage, temperature, and oulet pressure). Following eluotropic strength or specific interaction mod ifications, polar modifiers (methanol and acetonitrile) improve the selecti vity between the selected pairs of triglycerides. An increase in these sele ctivities also occurs when the temperature decreases, but the effect of pre ssure on the separation is almost negligible. In a second part, the final optimization was studied. Since polyfunctional octadecyl bonded silica fails to separate one of these pairs, a monofunctio nal one was chosen. An improved isocratic separation was achieved with seve n coupled columns (Hypersil ODS) and with a modifier mixture (ACN/MeOH/CO2) . The analysis time was 65 minutes. Applied to complex samples, rapeseed, t hese conditions enabled separation of numerous compounds in comparison to R PLC.