Submitted to: Canadian Society of Chemistry Conference
Publication Type: Abstract Only
Publication Acceptance Date: 6/5/1997
Publication Date: N/A
Technical Abstract: Supercritical fluid extraction (SFE) is becoming widely applicable for the analysis of trace compounds in food samples. The extracts from SFE of lipid rich food samples usually need to undergo a cleanup step to remove their excess lipid content before chromatographic analysis is applied. In this study, the solubility of lipids (using soybean oil as a model system for lipids) in binary carbon dioxide gas mixtures was measured at selected temperatures and pressures while simultaneously measuring the composition and density of the gas mixtures. It was found that the lipid solubility can be significantly reduced when carbon dioxide/helium or carbon dioxide/nitrogen gas mixtures are used. The experimental results indicate that the significant drop of solute solubility in carbon dioxide/helium mixtures cannot be explained by a reduction in the fluid density of the binary mixture. Hildebrand solubility parameter was used for characterizing the solvation power of the gas mixtures and provided a better understanding of lipid solubility trend in such mixtures. At the molecular level, the reduced solubility in binary carbon dioxide gas mixtures may involve a disruption of the solvent (carbon dioxide) shell around the dissolved solute. The above results have allowed the use of carbon dioxide/nitrogen gas mixtures for the selective extraction of pesticide residues in poultry fat. With proper control of the ratio of carbon dioxide/nitrogen, quantitative recoveries of pesticides have been achieved with limited coextraction of lipids, thus eliminating the time consuming cleanup step required before chromatographic analysis.