Residual solvents in biodegradable microparticles. Influence of process parameters on the residual solvent in microparticles produced by the aerosol solvent extraction system (ASES) process.

Different batches of microparticles were produced by the aerosol solvent extraction system (ASES) utilizing the extraction properties of supercritical carbon dioxide. Using a central composite design, the influence of production conditions such as spraying rate of the polymer solution and pump rate of the circulating carbon dioxide phase, on the characteristics of microparticles was studied. The experiments were carried out with regard to the residual solvent in the particles, the residual methylene chloride in the carbon dioxide flow of the ASES, the particle size, the morphology, and the yield. The results showed an influence of the pump rate of carbon dioxide on the yield, on the residual solvent in the microparticles, and on the circulating carbon dioxide. There was no major influence of the production conditions on the size and morphology of the microparticles, indicating that the ASES process seems to be a precipitation process.