Benefits of Supercritical Extraction Equipment Combined with Other Extraction Methods
I. Benefits of Supercritical Extraction Equipment Combined with Other Extraction Methods
Because of the inherent characteristics of high density, low viscosity and high diffusivity, supercritical fluid extraction (SFE) as a sample preparation and pretreatment technology has incomparable advantages compared with other classical methods. It can shorten the processing time by 1-2 orders of magnitude, avoid the use of a large number of toxic solvents and reduce the possibility of pollution. Sex. Supercritical extraction combined with other methods avoids the loss of sample transfer, which is of great significance to reduce human error and improve the sensitivity and accuracy of the method.
II. Principles of Supercritical Extraction Technology
Supercritical fluid extraction technology is a new separation technology in modern chemical separation. Supercritical CO2 extraction uses CO2 as solvent. The density and dielectric constant of CO2 fluid under supercritical condition are relatively high, and the solubility of the substance is very high. It changes sharply with the change of pressure and temperature. Therefore, it is not only the solubility of some substances. Degree is selective, and solvents and extracts are very easy to separate. The principle of supercritical CO2 fluid extraction (SFE) separation process is based on the relationship between the solubility of supercritical fluid and its density, that is, the influence of pressure and temperature on the solubility of supercritical fluid. In the supercritical state, the supercritical fluid is contacted with the substance to be separated, so that the components of sex, boiling point and molecular weight can be extracted selectively. Of course, the extracts obtained under different pressure ranges can not be single, but the optimum proportion of mixtures can be obtained under controlled conditions. Then supercritical fluids can be transformed into ordinary gases by means of decompression and heating, and the extracted substances can be completely or basically precipitated, thus achieving the purpose of separation and purification. The process of CO2 fluid extraction is a combination of extraction and separation.
3. Start-up sequence of supercritical fluid extraction equipment
1. After the power is connected, press the start power button.
2. Turn on the refrigeration switch and the water circulation switch at the same time.
3. To start heating, the heating switches of extraction cylinder, separation I, separation II and distillation column are switched on, and the respective thermometers are adjusted to their respective set temperatures.
4. After the freezer temperature drops to about 0 C, and the extraction, separation I and separation II temperatures are close to the set requirements, the following operations are carried out.
5. When refrigeration begins, the CO2 cylinder is put into the purifier, cold coil and storage tank through the valve, and CO2 is liquefied. The liquid CO2 is put into the extraction cylinder through the pump, mixer and purifier (the extraction cylinder has been filled with samples and the plug is closed). After equal pressure balance, the extraction cylinder is opened to empty the valve, and the residual air is slowly released, then the lower part is lowered. After partial pressure, close the vent valve.
6. Pressure: Pull the electrode point to the required pressure (upper limit), start the pump and press, when the pressure is close to the set pressure (about 1 MPa ahead), start to open the throttle valve behind the extraction cylinder.
7. After the extraction is completed, all kinds of heating cycle switches of refrigerators and pumps are closed, and then the main power supply switch is closed. The pressure in the extraction cylinder is put into the back separator or rectification column. After the pressure in the extraction cylinder and the back balance, the emptying valve is opened. After the extraction cylinder has no pressure, the extraction cylinder head is opened, and the material is extracted simply, and the whole extraction is completed. The fetching process is over.