PGSS Particles from Gas-Saturated

Although most of the applications of supercritical particle formation are known in the pharmaceutical industry, some examples can be found with foodstuff. Cocoa butter a relatively high value product has been successfully micronised using the PGSS (particles from gas-saturated solutions) process [4], In this paper we will investigate the production of fine cocoa butter crystals in order to use them for the seeding of chocolate. 

A new developed process PGSS (Particles from Gas Saturated Solutions) was applied for generation of powder from polyethyleneglycols. Principle of PGSS process is described and phase equilibrium data for the binary systems PEG-CO2 for the vapour-liquid and the solid-liquid range are presented in a master diagram . The influence of the process parameters on particle size, particle size distribution, shape, bulk density and crystallinity is discussed. 

Several new processes for formation of solid particles with defined particle size and particle size distribution using supercritical fluids were developed in the past years. Examples are crystallisation from supercritical fluids, rapid expansion of supercritical solutions (RESS), gas antisolvent recrystallisation (GASR), and PGSS (Particles from Gas Saturated Solutions)-process [1,2]. 

PGSS = particles from gas-saturated solution (gaseous CO2 is dissolved in a melted drug and the gas-saturated solution is expanded). 

PGSS Particles from gas-saturated solutions or suspensions achieved by dissolving a supercritical fluid into a liquid substrate, or a solution of the substrates in a solvent, or a suspension of the substrate(s) in a solvent followed by rapid depressurization of this mixture through a nozzle causing the formation of solid particles or liquid droplets... 

Weidner E, Knez Z Novak Z. PGSS (particles from gas-saturated solutions) a new process for powder generation. Proceedings of the 3rd International Symposium on Supercritical fluids, ISASF 1994 229. 

One of the interesting apphcations where scC02-processing of polymeric materials is beneficial is the method of PGSS (Particles from Gas Saturated Solution). PGSS is a technique able to form polymer/active compound foams, solid particles, or droplets [160]. The principle of the technique is for CO2 to form a gas-saturated solution/suspension which may then be foamed or passed through a nozzle to produce sohd particles or droplets. The technique is suited to thermally labile components, since the process is undertaken at near ambient temperature. Control of particle size has been achieved by the introduction of N2 back-pressure in the collection chamber, as demonstrated by Hao et al. [161] with poly(DL-lactic acid). The PGSS method has been shown to enhance the dissolution characteristics of nifedipine from PEG 400 [162, 163]. 

D. PGSS — Particles from Gas-Saturated Solutions/Suspensions. 652... 

In a relatively new process for production and fractionation of fine particles by the use of compressible media - the PGSS process (Particles from Gas-Saturated Solutions) - the compressible medium is solubilized in the substance which has to be micronized [58-61]. Then the gas-containing solution is rapidly expanded in an expansion unit (e.g., a nozzle) and the gas is evaporated. Owing to the Joule-Thomson effect and/or the evaporation and the volume-expansion of the gas, the solution cools down below the solidification temperature of the solute, and fine particles are formed. The solute is separated and fractionated from the gas stream by a cyclone and electro-filter. The PGSS process was tested in the pilot- and technical size on various classes of substances (polymers, resins, waxes, surface-active components, and pharmaceuticals). The powders produced show narrow particle-size distributions, and have improved properties compared to the conventional produced powders. 

Particles from gas-saturated solutions (or suspensions) (PGSS) SCF is dissolved in liquid product or solution in solvent, followed by rapid depressurization. 

In both processes of depressurization crystallization, namely, particles from gas-saturated solutions (PGSS) and rapid expansion from supercritical solutions (RESS), the solid solute and the SCF solvent constitute the binary system. Supersaturation is attained as a result of a drastic reduction of solubility by rapid depressurization, and subsequently the two-phase (S-V) system is formed. The process chosen depends on the solubility of the solid solute and its melting point. 

Kikic I, Lora M, Bertucco A. Thermodynamic analysis of three phase equilibria in binary and ternary systems for applications in rapid expansion of a supercritical solution (RESS) particles from gas-saturated solutions (PGSS) and supercritical antisolvent (SAS). Ind Eng Chem Res 1997 36 5507-5515. 

PARTICLES FROM GAS-SATURATED SOLUTIONS (PGSS) AND RELATED METHODS... 

Mandel FS, Don Wang J, Me Hugh MA. Pharmaceutical material production via supercritical fluids employing the technique of particles from gas saturated solutions (PGSS). Proceedings of the 7th Meeting on Supercritical Fluids, Antibes, France, 2000 1 35-46. 

Formation of Particles from Gas Saturated Solution (PGSS)... 

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