Microwave is an electromagnetic wave with a frequency range between 300MHz and 300GHz. In a microwave oven, the microwave field is guided by microwaves emitted by a magnetron into a reflective cavity of the sample in the oven. In a microwave field, molecules in the sample undergo high-frequency vibrations, resulting in temperature rise and pressure changes, thereby achieving the effect of heating and removing substances from the sample.
Microwave extractor is a device that uses microwave technology for solvent-free extraction. Generally, a mobile phone or sleeve made of polytetrafluoroethylene material is used to surround the sample to prevent solvent gas crossover caused by sample evaporation and loss of sample products. The process principle of microwave extraction machine mainly includes the following three steps:
1. Absorption of microwave energy
In a microwave field, molecules in the sample will undergo high-frequency vibrations due to the polarization effect generated by the electric field, resulting in friction and collision between molecules. These frictions and collisions raise the temperature of the sample and promote a decrease in local gas partial pressure, thereby facilitating solute desorption.
2. Formation of solution
After the detached solutes are removed, they dissolve in the extracted solution. Solute ions and compounds can aggregate into small clusters and disperse during dissolution, forming a system that coexists with other solute molecules during extraction.
3. Recovery of extraction solution
The microwave radiation generated by the microwave extractor from the sample can accelerate the desorption of solutes in the sample and dissolve them as much as possible in the solution. When the sample is heated to a certain degree, the extraction solution begins to detach from the sample. At this point, distillation and other purification methods are used to recover the extract and obtain the desired target components.