Supercritical fluid extraction (SFE) is a technique that adds a supercritical fluid of an extraction medium to a sample containing a constituent targeted for extraction, and it uses the difference in solubility compared with the extraction medium to carry out the extraction procedure. In particular, the method employing supercritical carbon dioxide as an extraction medium has a great many advantages and is thus used in a variety of fields. Extraction by means of supercritical carbon dioxide can be expected to improve efficiency, including shorter extraction times and simplified procedures, when compared with extraction techniques that employ organic solvents. At the same time, it offers easier solvent elimination and concentration procedures.

Furthermore, since its critical temperature is a low 31 C or so, it enables extraction at a near-room temperature state or in a carbon dioxide atmosphere devoid of oxygen. This makes it a technique that can be used for materials that exhibit temperature instability or constituents that are susceptible to oxidation. On top of all this, it has received a great deal of attention as an environmentally friendly extraction technique that does not use hazardous organic solvents, as has been advocated by the green chemistry movement in recent years.

Applications for SFE include the extraction of active constituents, including various flavors and medicinal constituents from natural products, docosahexaenoic acid (DHA), advanced unsaturated fatty acids and fatty esters such as eicosapentaenoic acid (EPA), fat-soluble vitamins, and pharmaceuticals, as well as the elimination of unwanted constituents, such as decaffeination and desolvation within tablets. It also can be applied to the preprocessing of analysis samples, including HPLC and GC.

Supercritical Fluid Extraction - Basic Configuration

The figure to the right shows the basic configuration and flow path of a supercritical carbon dioxide extraction system. In this system, a supercritical carbon dioxide pump, a modifier solvent transfer pump, an extraction vessel, thermostatic bath, and when necessary, a detector that monitors extraction and an automatic back-pressure regulation valve are connected to the downstream end. The extraction vessel can either be a column or cup-type vessel, depending on the state of the extraction sample, and it is also possible to select from a wide variety of volume types. Extraction parameters include pressure, temperature, and cosolvent typel/volume, and these parameters can be changed to set the optimal conditions.