supercritical fluids extraction

Supercritical Fluids                    Supercritical Fluids

                    Supercritical Fluids                   

The Supercritical Fluids Research group,

University of New South Wales, Sydney - Australia

To lead the way we consistently blaze new trails for others to follow

Professor Neil Foster, one of the Worlds most knowledgeable scientists in the fields of Supercritical Fluids research and development is at the helm and leads this dedicated and committed group of brilliant researchers and students.

The definition of a supercritical fluid usually begins with a phase diagram, which defines the critical temperature and pressure of a substance. (CO₂ ; T_c = 31.1 °C, P_c = 73.8 bar).
A supercritical fluid ( SCF ) is any compound at a temperature and pressure above the critical values. The critical temperature of a compound is defined as the temperature above which a pure, gaseous component cannot be liquefied regardless of the pressure applied. The critical pressure is then defined as the vapour pressure of the gas at the critical temperature. The temperature and pressure at which the gas and liquid phases become identical is the critical point. In the supercritical environment only one phase exists. The fluid, as it is termed, is neither a gas nor a liquid and is best described as intermediate to the two extremes. This phase retains the solvent power common to liquids as well as the transport properties common to gases.
Supercritical fluids can be used to extract analytes from samples. The main advantages of using supercritical fluids for extractions is that they are inexpensive, contaminant free, and less costly to dispose safely than organic solvents. Properties of supercritical fluids also provide some advantages for analytical extractions. Supercritical fluids can have solvating powers similar to organic solvents, but with higher diffusivities, lower viscosity, and lower surface tension. The solvating power can be adjusted by changing the pressure or temperature, or by adding modifiers to the supercritical fluid. A common modifier is methanol (typically 1-10%) which increases the polarity of supercritical CO₂.

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~ Last update 22nd. February 2007 ~

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