Skip to main content
ARS Home » Research » Publications at this Location » Publication #60966
Title: MOLECULAR SELECTIVITY IN SFE

Author
item King, Jerry
item Jackson, Michael
item Snyder, Janet
item Taylor, Scott
item MONTANARI, LUIGI - UNIV DI PERUGIA, ITALY

Submitted to: European Symposium on Supercritical Fluid Chromatography and Extraction
Publication Type: Abstract Only
Publication Acceptance Date: 9/8/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The extraction of specific molecular compounds by SFE can only be affected in certain cases where cohesional energy densities and/or molecular weights of the target analytes differ significantly. Definite examples can be cited where the composition of the substance extracted are covered by the above criteria, but often the converse is true where the selectivity of SFE must be enhanced by several techniques. These may include density-based fractionation, separation according to characteristic threshold pressures, analyte segregation via sorbents, the use of different extraction fluids, SFC coupled with SFE, and specific reactions to enhance extraction specificity. Large differences in solute polarity have been exploited to separate triglycerides from phospholipids (PL) and to effectively fractionate specific PLs from each other according to their relative polarity. Neat fluids used in conjunction with specific adsorbents have proven to be useful SF-analogs to normal phase chromatographic cleanup schemes; however, the power of this approach is enhanced considerably by adjusting the eluent strength of SC-CO2 via addition of cosolvents. An example of this principle is the fractionation of cholesterol from coextracted fat/oil using an amino-bonded silica-based sorbent and methanol-laced CO2 in the extraction cell. Reaction chemistry can also be used to increase molecular specificity in SFE. Conversion to FAMES is accomplished over a non-specific lipase catalyst, placed ahead of the sample in the extraction cell. The esterification reaction is rapid, quantitative, and specific for hydrolyzed fatty acid moieties, thereby providing a fat-specific assay method.