PHASE-BEHAVIOR OF SOME PURE LIPIDS IN SUPERCRITICAL CARBON-DIOXIDE

The phase behavior of binary mixtures CO2-pure lipids has been determined in the pressure range 50-210 bar. Homologous series of glycerides with increasing carbon number and increasing polarity (tri-, di-, and monoglycerides) were investigated. All the systems except trilaurin-CO2 showed similar phase behavior concerning the three-phase line S-L1-V which was displaced towards higher temperature for larger and more polar lipids. For the trilaurin (the shortest triglyceride)-CO2 system, the three-phase line solid-liquid-vapor (S-L1-V) turned into a solid-liquid-liquid line (S-L1-L2) after passing through the quadruple point (S-L1-L2-V) from which also the S-L2 and L1-L2-V lines originate. All the lipids investigated showed a melting point depression of 15-25-degrees-C in the presence of carbon dioxide at high pressure.