Supercritical extraction is to contact the supercritical fluid with the substance to be separated in the supercritical state, so that it can selectively extract the components of polarity, boiling point and molecular weight in sequence. Then, the supercritical fluid is turned into an ordinary gas by means of decompression and temperature increase, and the extracted substance is completely or basically precipitated, so as to achieve the purpose of separation and purification.

The common supercritical extraction agent is carbon dioxide. Supercritical extraction has been widely used in the pharmaceutical and food industry, especially in traditional Chinese medicine and plant extraction, such as the purification of flavonoids, terpenoids, lipids and other substances. Compared with other separation processes, it has many advantages, such as low operating temperature, which has great advantages for the separation of heat-sensitive substances (active ingredients or drugs, etc.); secondly, there are extractants (such as carbon dioxide) that are non-toxic and harmless , Has no effect on the human body and the environment. The current shortcomings are higher requirements for equipment and higher initial investment.