Material is dissolved in a dense gas and sprayed into a low pressure chamber thorugh nozzle. Precipitation occurs due to the high reduction in termperature and solvation power of scCO2 as it transits to the vapour phase.

 

 

Dense gas is dissolved in a solid material which melts. Precipitation is induced by spraying the gas saturated solution via a nozzle into al ow pressure chamber. Depressurization results in a temperature quench whereby the previously melted phase solidifies.

 

 

A batch precipitation technique that uses near critical or supercritical fluid anit-solvents to precipitate solutes from solution. The GAS process was originally developed by Gallagher et al. (1989) and has since been shown to have application in the crystallisation of drugs, polymeric microspheres explosives, and the purification of organic acids. Operating pressures of GAS processing are comparatively lower than other processes and supercritical conditions are not required.

 

This dense gas precipitation technique injects miscible anti-solvent in a liquid phase solution to cause the volumetric expansion and therefore decrease in solvent power of that phase. As the anti-solvent has no affinity for the solute, the solvent power of the solvent is a unique function of its density, or the intermolecular distances between the solvent molecules. Therefore at a critical anti-solvent concentration or expanded volume the solution becomes saturated. At higher anti-solvent concentrations precipitation of the solute results. After the precipitation phase the product is filtered and washed at the same pressure, whilst the solvent is in expanded state, to prevent re-dissolution into the solvent. Therefore the nature of the final precipitate which is determined by the volumetric expansion rate is a function of the pressurisation rate, temperature and the type of solvent and anti-solvent used.

 

This research has been motivated by the need to refine the mode of delivery and therefore the effectiveness of therapeutic compounds. Many modern drug administration techniques make use of controlled release systems that are able to more closely  model the natural release of a drug. Controlled release processes may simply involve drug modifications to delay or enhance chemical diffusion through membranes or even the encapsulation of the active component in a microporous or bioerodible solid such as polymer.

 

 

 

Material is dissolved in an organic solution and sprayed into a chamber containing a high pressure dense gas, cuasing particles to precipitate.

 

 

Similar to the GAS and the ASES processes, ARISE process uses the antisolvent abilities of a dense gas such as CO2 to effect the precipitation of solutes from their dissolved forms. The ARISE process eliminates the use of capillary nozzles for solution atomization and is able to effect precipitation over a much larger volume.