PARTIAL MOLAR VOLUMES OF DHA AND EPA ESTERS IN SUPERCRITICAL FLUIDS

The critical loci and partial molar volumes at infinite dilution for solutes such as the ethyl and methyl esters of cis-4,7,10,13,16,19-docosahexaenoic acid (DHA) and the methyl ester of cis-5,8,11,14,17-eicosapentaenoic acid (EPA) in supercritical carbon dioxide were determined for a limited range of solute concentrations. The limits of miscibility of the esters in supercritical carbon dioxide were approximately 0.7 wt %. The results of the partial molar volume study exhibited large negative values in the highly compressible near-critical region. The Peng-Robinson and Soave-Redlich-Kwong equations of state were used to correlate the experimental data. These equations of state, although providing acceptable qualitative representations of the experimental data, were only semiquantitative in predictions of partial molar volumes.