Super-critical fluid extraction

Fig. 4.3-33. SITEC super-critical fluid extraction small-scale plant [50].

SPE), super critical fluid extraction (SEE), or matrix solid-phase dispersion (MSPD). The preferred approach is determined according to the nature of the plant matrix and the number and chemical properties of analyzed phenolic acids. 

Jimenez-Carmona MM, Tena MT, Luque de Castro MD. lon-pair-super-critical fluid extraction of clenbuterol from food samples. J Chromatogr A 1995 711 269-276. 

Several plastic toys were analyzed for their DEHP content by supercritical fluid extraction followed by GC analysis [67]. DEHP recoveries obtained after super-critical fluid extraction were considerably better than those obtained with soxhlet extraction. The results showed that PVC toys normally contained rather high DEHP concentrations. In another study, 72 toys from 17 countries were analyzed for the composition and 64 of these toys contained PVC [68]. Almost all of the soft toys contained 10-40 wt.% of phthalates, the most common phthalates being diisononyl phthalate (DINP) and DEHP. Shaking... 

Super critical fluid extraction enlarges the range of solvents. Using super critical carbon dioxide has the advantage that the final extract is automatically concentrated to dryness. The polarity of supercritical carbon dioxide is rather low therefore, small amounts of methanol are added as modifier to increase the polarity of the extractant. The solvents also have a large penetrating power because of their low viscosity. The invention of ASE has reduced the interest in SFE due to the more versatile applicability and robustness of ASE. 

Ramsay, M.E., Hsu, J.T., Novak, R.A. and Reightler, W.J. (1991) Processing rice bran by super critical fluid extraction. Food Technol., 45, 98-104. 

Early studies involved pyrolysis of this residue and revealed the presence of aromatic ring systems such as benzene, naphthalene, their alkyl derivatives as well as higher aromatic hydrocarbons. Today, GC-MS analyses of super-critical fluid extracts of hydrous pyrolysates (77), Ha-pyrolysis products (72) as well as solid-state C-NMR spectroscopy (75) of meteorite organic residues are applied to provide insight into the structure of the macromolecular carbon. Most recent, hydrothermal treatment (300 °C at 10 MPa) of demineralized lOM of the Murray meteorite has yielded in the release of a wide variety of carboxylic acids and heteroaromatic compounds including C3-C17 alkyl carboxylic acids and N-, O-and S-containing hydroaromatic and aromatic compounds (74). 

Current trends have been to accelerate the extraction of pesticides from the sample matrix by accelerated solvent extraction (ASE) or pressurized solvent extraction (PSE), microwave-assisted solvent extraction (MASE), and super critical fluid extraction (SEE). 

Morello, M.J., Isolation of aroma volatiles from an extruded oat ready-to-eat-cereal comparison of distillation-extraction and super critical fluid extraction, in Thermally Generated Flavors, T.H. Parhment, M.J. Morello, R.J. McGorrin, Eds., Amer. Chem. Soc., Washington, D.C., 1994, p. 95. 

Rahuni, P. Dettman, H. Gentzis, T. Chung, K. Nowlan, V. Upgrading chemistry of Athabasca bitumen fractions derived by super critical fluid extraction. Presented at the 47 CSChE conference, Edmonton, Alberta, Canada, October 5-8,1997. 

One active area is in using super-critical fluids (SCFs) as a reaction medium. While the usefulness of SCFs as an extraction solvent, a cleaning solvent or in analytical methodologies has been well-established, the use of super-critical carbon dioxide as well as other SCF s is a far less explored area of research. There have been recent successes documented in the use of SCFs as a reaction medium for polymerization reactions (25), free-radical transformations (26), and in certain cat ytic transformations (27). 

A recent development in liquid-liquid extraction has been the use of supercritical fluids as the extraction-solvent. Carbon dioxide at high pressure is the most commonly used fluid. It is used in processes for the decaffeination of coffee and tea. The solvent can be recovered from the extract solution as a gas, by reducing the pressure. Super critical extraction processes are discussed by Humphrey and Keller (1997). 

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