Supercritical Fluid Extraction (SFE)
SFE uses supercritical CO2, instead of organic solvents such as hexane and methylene chloride, to extract chemical compounds from a solid matrix (sometimes also from liquids). Near the critical point the density of a SCF is extremely sensitive to minor changes in temperature and pressure. Since the solvating power of a SCF is directly related to its density, selective extraction of the analyte of interest can be achieved by making slight changes in temperature and pressure and exploiting the differential solubility of analytes in the SCF. On the other hand, due to the higher diffusion coefficients in supercritical fluids, SFE is faster than liquid extraction. SFE is also a more efficient extraction method since the lower surface tension of supercritical fluids allows penetration into small pores of the solid matrix which are not accessible to liquids.