Rapid supercritical extraction process

Poco JF, Coronado PR, Pekala RW, Hrubesh LW (1996) A rapid supercritical extraction process for the production of silica aerogels. Mater Res Soc Symp Proc 431 297-302... 

Gross J, Corrmado PR, Hmbesh LW (1998) Elastic properties of silica aerogels from a new rapid supercritical extraction process. J Non-Cryst Solids 225 282-286... 

Scherer GW, Gross J, Hmbesh LW, Coronado PR (2002) Optimization of the rapid supercritical extraction process fm a ogels. J Non-Cryst SoUds 311 259-272... 

IF Poco, PR Coronado, RW Pekala, LW Hrubesh, A Rapid Supercritical Extraction Process for the Production of Silica Aerogels MRS Apr 8-12 1996 Spring Meeting... 

Gross J., Coronado P.R., Hrubesh L.W. Elastic properties of silica aerogels from a new rapid supercritical extraction process. J. Non-Cryst. Solids. 1998 225 282-286 Hench L.L. Use of drying control chemical addition (DCC As) in controlling sol-gel processing. In Science of Ceramic Chemical Processing, L.L. Hench, D.R. Ulrich, eds. New York John Wiley, 1986, pp. 52-64... 

Supercritical Extraction. The use of a supercritical fluid such as carbon dioxide as extractant is growing in industrial importance, particularly in the food-related industries. The advantages of supercritical fluids (qv) as extractants include favorable solubiHty and transport properties, and the abiHty to complete an extraction rapidly at moderate temperature. Whereas most of the supercritical extraction processes are soHd—Hquid extractions, some Hquid—Hquid extractions are of commercial interest also. For example, the removal of ethanol from dilute aqueous solutions using Hquid carbon dioxide... 

Roth, T B, Anderson, A M, Carroll, M K (2008) Analysis of a rapid supercritical extraction aerogel fabrication process Prediction of thermodynamic ctmditions during processing. J Ntm-Cryst Sohds 354(31) 3685-3693. 

Anderson, A M, Wattley, C W, Carroll, M K (2009) Srhca aerogels prepared via rapid supercritical extraction Effect of process variables on aerogel properties. J Ntm-Cryst Sohds, 355(2) 101 108. 

The number of reports on on-line TLC analysis of extracts is quite limited. Stahl [16,29] described a device for supercritical extraction with deposition of the fluid extract on to a moving TLC plate. On-line SFE-TLC provides rapid and simple insight into the extraction performance. Its strength is that the extract is deposited on a plate, which means that detection is a static process. Limitations of SFE-TLC are that quantification is difficult, and that the stability of components on the support material or in the presence of oxygen may be a problem. For additives in beverages (such as benzoic... 

Extraction with supercritical CO2 is a technical process of increasing importance. It provides a mild and rapid technique for the extraction of low- or medium-polarity substances. Supercritical CO2 is used for supercritical fluid extraction (SFE) in important technical processes such as the decaffeination of coffee and the extraction of hops, as well as the extraction of naturally occurring compounds from biomaterials. As many applications are performed in the pharmaceutical, polymer, environmental and nutritional fields, direct on-line SFE-NMR would be an ideal tool to monitor the various extraction processes. 

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. 

The coefficient of sell-diffusion does not appear to have an anomaly near the critical point. For the engineer, however, the mutual dift usion coefficient is the more important property. The binary dilfusion coefficient approaches zero at the mixture critical point ("critical slowing-down"). In dilute mixtures, however, the decrease of the binary dilfusion coefficient is not seen until the critical line is approached very closely. For many practical purposes, such as supercritical extraction and chromatography, the mixture is dilute, and it can be assumed that the coefficient of binary diffusion is intermediate between that in the vapor and that in the liquid. Since the diffusion coefficient decreases roughly inversely proportional to the density, dilfusion in supercritical solvents is much more rapid than in liquid solvents, thus increasing the speed of diffusion-controlled chemical processes. 

Supercritical fluid extraction, offers also some desirable advantages including processing at low temperature, recovery of a solvent-free extract, and rapid extraction. However, very limited studies have been published on the use of supercritical fluids for the isolation of corticosteroids from biological samples. A combination of supercritical fluid extraction and liquid chromatography has been employed for the detection of dexamethasone residues in bovine tissues (448). 

An alternative to supercritical fluid extraction is to use a classical solvent combined with microwaves. In a pressurised environment, this can be an efficient and rapid process for the treatment of samples. 

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