Supercritical Fluid Extraction For Fine Particles
Super Critical Fine Particles Equipment
The supercritical powder preparation technology is a new method for preparing ultrafine particles. Compared with the conventional method, the preparation condition is mild, and does not need to be in contact with a solvent, and the generated particles have small particle size and uniform distribution, and are sensitive to heat sensitivity. The miniaturization of oxidized bioactive substances is particularly suitable, and thus has become one of the research hotspots.
At present, supercritical technology is used to prepare ultrafine particles, which can be divided into supercritical solution rapid expansion method (RESS) and supercritical fluid solvent method (SAS) according to the experimental principle, and SAS is further divided into liquid batch mode according to the operation mode (liquid batch). Operation), gas batch operation and continuous operation.
The RESS method uses supercritical fluid as the solvent of the drug, and requires the solubility of the drug in the high-pressure supercritical fluid to be large. When the supercritical fluid in which the drug is dissolved is suddenly reduced to the normal pressure room temperature, the drug is restored to the ordinary gas state, and the solubility of the drug is drastically decreased. The dissolved drug is rapidly nucleated and precipitated in a supersaturated state to form fine particles.
Studies have shown that the main factors affecting the physical properties such as particle size and morphology include the solubility of the drug in the supercritical fluid, the nozzle diameter, the pressure temperature of the particle forming kettle, the decompression and expansion phase transition path, and nozzle clogging and particle polymerization.
The GAS rule uses supercritical fluid as an anti-solvent for drugs. It requires the drug to be insoluble or very low in solubility in the supercritical fluid. The drug is first dissolved in a common organic solvent (the solvent must be dissolved in the supercritical fluid) and then mixed with the supercritical fluid. At this time, the solvent density is drastically reduced, the solvency of the drug is rapidly lowered, and the drug solution is actually supersaturated, resulting in crystallization of particles.
Studies have shown that the main factors affecting the physical properties such as particle size and morphology include the solubility of the drug in organic solvents, the degree of insolubility of the drug in the supercritical fluid, the degree of swelling of the drug in the organic solvent, and the ratio of the organic solvent to the supercritical fluid. The pressure temperature of the particle forming kettle, the phase transition path of the particle nucleation process, and the like.
Supercritical fluid deposition is new developing techonlogy. Through reducing the pressure of the supercritical solution, high saturation degree can be reached in very short time.
Then, ultrafine particlescan be precipitated uniformly because this process is conducted in quasi-uniform media. the size and size distribution of the particle can be controlled easily.
Thus supercritical deposition technique is a new promising technology for producing ultrafine particles. Currently several different supercritical fluid models have been raised, such as: GAS, SAS, SESS,SEDS, PGSS, etc