The solvent strength of supercritical fluid depends on the temperature and pressure of the extraction. Using this feature, simply change the pressure and temperature of fluid in the extraction, can the different components of the samples according to the size of the solubility in the fluid, successively extracted, weak polar material extraction, first under low pressure with the increase of pressure, larger and larger molecular weight of the material and the basic properties, so the supercritical extraction under the booster program, can get different extraction components, can also have the effect of separation.

Temperature changes in the density of extraction solvent and solute the vapor pressure of the two factors, the low temperature zone (still above the critical temperature), temperature to reduce the fluid density, and solute the vapor pressure increases, therefore, the solution ability of extracting agent temperature can make the solute precipitation from fluid extraction agent, and further raise the temperature to high temperature, although further reduce the density of the extractant, but increased solute steam pressure, increased volatility, instead, not only will not reduce the extraction rate has a tendency to increase.

In addition to pressure and temperature, the solute solubility of supercritical fluid can be changed by adding a small amount of other solvents. The mechanism of action is not yet fully understood. Generally, the amount of addition is no more than 10%, and the polar solvent methanol, isopropanol, etc. are the majority. The application of supercritical extraction technology can be extended to more polar compounds by adding a small amount of polar solvent. Articles come from the Internet

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