Author: Mazen H. Hanna

Publisher:

Published: 1995

Total Pages: 238

ISBN-13:

A novel apparatus and methods of controlled particle formation from supercritical fluids are proposed. A solution of the material of interest is fed together with a fluid (e.g. CO2) above its critical point through a concentric nozzle into a high pressure vessel. The temperature and pressure of the vessel are controlled by a thermocouple and an automated back pressure regulator respectively. The supercritical fluid disperses, mixes and rapidly extracts the solvent leading to formation of particulate products. The products are retained in the high pressure vessel by a particle retention device. The supercritical solution (i.e. the supercritical fluid and the solvent) emerging from the back pressure regulator is allowed to expand so that the solvent may separate from the gas, and both are recycled. By changing the working conditions of pressure, temperature and flow rate of the solution to the supercritical fluid, it is possible to control the size, shape and morphology of the products - increase of the pressure and/or flow rate of the supercritical fluid led to a decrease in particle size. Products prepared by this new technique include, drug materials, inorganics, polymers, carbohydrates and proteins. Microparticulate products of the drug salmeterol xinafoate exhibit narrow size distribution, batch-to-batch consistency, high degree of crystallinity, enhanced chemical and polymorphic purity, low dynamic bulk density, undetectable amounts of residual solvent content and are free flowing with low dispersion energy due to lack of static charge. This new method of preparation of particles from supercritical fluids has potential applicatlon to industrial particle formation processing avoiding problems of conventional crystallisation procedures.