PCA Precipitation with Compressed

Abbreviations ASES, aerosol solvent extraction system BSA, bovine serum albumin PCA, precipitation with compressed antisolvent PLA, polylactic acid PLGA poly(lactic-co-glycolic acid) PMMA, poly(methyl methacrylate) PPG, poly(propylene glycol) RESS, rapid expansion of supercritical solution TFE, 2,2,2-trifluoroethanol. 

Abbreviations A, acetone ASES, aerosol solvent extraction system DM, dichloromethane DMF, A/,A/-dimethyl-formamide E, ethanol GAS, gas antisolvent process H, hexane HYAFF-11, hyaluronic acid benzylic ester I, isopropanol PAN, polyacrylonitrile PCA, precipitation with compressed antisolvent PCL, polycaprolactone PHB, poly(p-hydroxybutyric acid) PLA, polylactic acid PLGA, poly(lactic-co-glycolic acid) SAS, supercritical antisolvent process SEDS, solution enhanced dispersion by supercritical fluids TFE, 2,2,2-trifluoroethanol Triblock polymer, p poly(L-lactide-CO-D,L-lactide-co-glycolide)(62.5 1 2.5 25). 

Abbreviations PLA, polylactic acid PCA, precipitation with compressed antisolvent GAS, gas antisolvent DMSO dimethyl sulfoxide. 

If the OS-HC solution is injected into the vessel already pressurized with the SCF, this is called PCA (Precipitation with compressed antisolvent). Note that the OS is completely vaporized into the supercritical phase during injection and the specific amount of SCF required to get precipitation is much larger than in GAS (SAS) batch. Therefore, PCA is more useful during development than production. 

PCA [Precipitation with a compressed anti-solvent] A process for making a solid with unusual morphology by spraying a solution of it into a supercritical fluid. The process resembles spray drying into a supercritical fluid. Used for making microspheres, microporous fibers, and hollow microporous fibers. 

Precipitation inhibitors, dispersants contrasted, 3 686 Precipitation leachate procedure, synthetic, 25 868-869 Precipitation reactions, for niobium and tantalum determination, 27 142-143 Precipitation reagents, protein, 22 133 Precipitation with compressed antisolvent (PCA) process, 24 17, 18 Precipitator dust, in phosphorus manufacture, 19 12 Precipitators, electrostatic, 23 180 Precision agriculture, 23 328 26 269-270 Precision measurement techniques, noble gases in, 27 370 Precision scales, 26 245 Preconcentration, of uranium ores, 25 401 Pre-crosslinked polychloroprene grades, 19 852... 

Gas anti-solvent processes (GASR, gas anti-solvent recrystallization GASP, gas antisolvent precipitation SAS, supercritical anti-solvent fractionation PCA, precipitation with a compressed fluid anti-solvent SEDS, solution-enhanced dispersion of solids) differ in the way the contact between solution and anti-solvent is achieved. This may be by spraying the solution in a supercritical gas, spraying the gas into the liquid solution. 

Supercritical drying and particle formation processes are also important areas in SCCO2 based materials chemistry. Some of the particle processing methods available, such as precipitation with compressed antisolvent (PCA), are shown schematically in Chapter 9. 

Gas antisolvent processes can be performed in a semicontinuous mode. In this case the solution and the antisolvent are continuously introduced in the system until the desired amount of the product is formed. The introduction of the solution is then stopped and the DG flux extracts the residual solvent from the system. The system is then depressurized to enable collection of the product. The solution is generally introduced through an atomization nozzle that favors the prompt expansion of the solution and the formation of small particles. Different process configurations have been utilized, i.e., co- and countercurrent introduction of the solution and antisolvent fluxes and various nozzles have been designed. The process is referred to by different acronyms such as ASES (aerosol solvent extraction system), SAS (supercritical antisolvent), SEDS (solution enhanced dispersion by supercritical fluids), PCA (precipitation with a compressed fluid antisolvent), GASR (gas antisolvent recrystallization), GASP (gas antisolvent precipitation). 

As described in Chapter 3, several SCF techniques are available for the preparation of drug delivery systems. These include rapid expansion of supercritical solutions (RESS), gas antisolvent recrystallization (GAS), supercritical antisolvent recrystallization (SAS), supercritical antisolvent with enhanced mass transfer (SAS-EM), solution-enhanced dispersion by supercritical fluids (SEDS), supercritical fluid nucleation (SFN), precipitation with compressed antisolvent (PCA), and aerosolized supercritical extraction of solvents (ASES). While RESS and SFN involve the expansion of a supercritical fluid solution of a drug to form drug particles, GAS, SAS, SAS-EM, SEDS, PCA, and ASES use a supercritical fluid as an antisolvent to precipitate particles of a drug dissolved in an organic solvent (5). General RESS and GAS processes are further elaborated in Sections 1.1.1 and 1.1.2. 

Several processes utilizing supercritical fluids for materials processing have been reported in the literature although their commercial use is not well documented. Among the well-known processes are rapid expansion of supercritical solutions (RESS) (Phillips and Stella, 1993), the gas antisolvent process (GAS) (Yeo et al., 1993), aerosol solvent extraction system (ASES) (Bleich and Muller, 1996), a precipitation with compressed antisolvent process (PCA) (Brennecke, 1996), and solution-enhanced dispersion by supercritical fluids (SEDS) (Samp et al., 2000). The first four processes are for products that are soluble in the supercritical fluid or in an organic solvent. Biomolecules such as proteins or nucleic acids cannot be dissolved, and for such processes... 

In the second method the solution is sprayed through a nozzle into compressed carbon dioxide the process is termed as precipitation with compressed antisolvent (PCA) [33] and liquid or supercritical antisolvents can be employed. In the case of continuous flow of the solution and of the antisolvent the process is termed also as aerosol solvent extraction system (ASES) [34], in the case of countercurrent flow and supercritical antisolvent precipitation (SAS) in the case of co-current flow [35]. 

There have been several reviews of RESS over the past decade, with the most comprehensive being the 1991 work of Tom and Debenedetti (7), as it discusses both theory and experimental work in detail. An updated review of their modeling work was presented 2 years later (8). In more recent years, reviews have become more general, discussing RESS as one of several alternatives for processing materials with supercritical fluids (9-11). Such a development is, of course, not surprising, as many of the other techniques (such as supercritical antisolvent (SAS) and precipitation with compressed antisolvent (PCA) processes) have been developed to overcome one of the disadvantages of RESS, namely, the limited solubility of many materials in supercritical carbon dioxide. 

PRECIPITATION WITH A COMPRESSED FLUID ANTISOLVENT (PCA), A SUPERCRITICAL ANTISOLVENT (SAS), AND THE AEROSOL SOLVENT EXTRACTION SYSTEM (ASES) PROCESSES... 

Dozens of drugs have been recrystallized by means of the precipitation with a compressed fluid antisolvent (PCA) and the supercritical antisolvent (SAS) and aerosol solvent extraction system (ASES) processes. 

The organic-C02 interface plays a central role in physical particle formation processes including rapid expansion from supercritical solution (RESS), precipitation with a compressed antisolvent (PCA, also called SAS... 

---