Supercritical CO, extraction

Raventos, M., Duarte, S. and Alarcdn, R., Application and possibilities of supercritical CO, extraction in food processing industry an overview. Food. Sci. Technol. Int., 8, 269, 2002. 

Dried muscle foods, supercritical CO extraction of lipids, 121,122r... 

Ultrasound-assisted leaching has also been used to extract natural compounds such as vitamins A, D and E from feeds [57], paclitaxel and related taxoids from leaf tissue of Taxus [58], opiates from hair samples [59] and antioxidants from rosemary [60]. Ultrasounds have so far had much more restricted application in this field than in the previous ones, possibly as a result of the technique being at a disadvantage with respect to alternatives such as microwave-assisted extraction [57] or supercritical CO, extraction [60]. 

As in other techniques, SF extracts are not always free of unwanted matrix components. A number of clean-up methods have been used with and after the extraction step to overcome this problem. Sample clean-up is mandatory with fat-soluble analytes. On the other hand, neat supercritical CO, extracts from environmental samples are often clean enough for direct injection into a gas chromatograph [17]. 

Supercritical CO. Extraction Results. The extent of lipid extraction from freeze dried algae was influenced by the total COj volume passed through the system, by the operating pressure, and by the ratio of non-polar to polar lipids present in the batches. 

Aresta, M. A. Dibenedetto M. Carone T. Colonna C. Fragale. Production of biodiesel from macroalgae by supercritical CO extraction and thermochemical liquefaction. Environ. Chem. Lett. 2005,3, 136-139. 

Dunford NT, Temelli F. 1997. Extraction Conditions and Moisture Content of Canola Flakes as Related to lipid Composition of Supercritical CO Extracts. Journal of Food Science 62(1) 155-159. 

Friedrich JP. 1984. Supercritical CO Extraction of Lipids from Lipid-Containing Materials,. US Patent 4,466,923. 

Supercritical fluid extraction — During the past two decades, important progress was registered in the extraction of bioactive phytochemicals from plant or food matrices. Most of the work in this area focused on non-polar compounds (terpenoid flavors, hydrocarbons, carotenes) where a supercritical (SFE) method with CO2 offered high extraction efficiencies. Co-solvent systems combining CO2 with one or more modifiers extended the utility of the SFE-CO2 system to polar and even ionic compounds, e.g., supercritical water to extract polar compounds. This last technique claims the additional advantage of combining extraction and destruction of contaminants via the supercritical water oxidation process."... 

Supercritical fluid extraction (SEE) is another modern separation technology usually employed to extract lipophilic compounds such as cranberry seed oil, lycopene, coumarins, and other seed oils. Anthocyanins generally and glycosylated anthocyanins in particular were considered unsuitable for SEE due to their hydrophilic properties, since SEE is applicable for non-polar analytes. However, a small amount of methanol was applied as co-solvent to increase CO2 polarity in anthocyanin extraction from grape pomace. New applications of SEE for anthocyanin purification have been reported for cosmetic applications from red fruits. ... 

Supercritical fluid extraction (SFE) is a technique in which a supercritical fluid [formed when the critical temperature Tf) and critical pressure Pf) for the fluid are exceeded simultaneously] is used as an extraction solvent instead of an organic solvent. By far the most common choice of a supercritical fluid is carbon dioxide (CO2) because CO2 has a low critical temperature (re = 31.1 °C), is inexpensive, and is safe." SFE has the advantage of lower viscosity and improved diffusion coefficients relative to traditional organic solvents. Also, if supercritical CO2 is used as the extraction solvent, the solvent (CO2) can easily be removed by bringing the extract to atmospheric pressure. Supercritical CO2 itself is a very nonpolar solvent that may not have broad applicability as an extraction solvent. To overcome this problem, modifiers such as methanol can be used to increase the polarity of the SFE extraction solvent. Another problem associated with SFE using CO2 is the co-extraction of lipids and other nonpolar interferents. To overcome this problem, a combination of SFE with SPE can be used. Stolker et al." provided a review of several SFE/SPE methods described in the literature. 

Supercritical fluid extraction (SFE) is generally used for the extraction of selected analytes from solid sample matrices, but applications have been reported for aqueous samples. In one study, recoveries of 87-100% were obtained for simazine, propazine, and trietazine at the 0.05 ug mL concentration level using methanol-modified CO2 (10%, v/v) to extract the analytes, previously preconcentrated on a C-18 Empore extraction disk. The analysis was performed using LC/UV detection. Freeze-dried water samples were subjected to SFE for atrazine and simazine, and the optimum recoveries were obtained using the mildest conditions studied (50 °C, 20 MPa, and 30 mL of CO2). In some cases when using LEE and LC analysis, co-extracted humic substances created interference for the more polar metabolites when compared with SFE for the preparation of the same water sample. ... 

To date most of the work which has been done with supercritical fluid extraction has concentrated on the extraction of analytes from solid matrices or liquids supported on an inert solid carrier matrix. The extraction of aqueous matrices presents particular problems [276-278]. The co-extraction of water causes problems with restrictor plugging, column deterioration, and phase separation if a nonpolar solvent is used for sample collection. Also, carbon dioxide isay have limited extraction efficiency for many water soluble compounds. 

Vasapollo G, Longo L, Rescio L and Ciurlia L 2004. Innovative supercritical CO2 extraction of lycopene from tomato in the presence of vegetable oil as co-solvent. J Supercrit Fluids 29(1-2) 87-96. 

Another supercritical C02 extraction method employed vegetable oil as co-solvent. Sun-dried tomatoes (50 per cent moisture content) were further dried at 70°C and 20mbar for 70-80h. The final product, containing about 6 per cent moisture, was ground to a particle size of 1 mm. 

New Fluorinated Hydroxamic Acid Reagents for the Extraction of Metal Ions With Supercritical CO°2 (Glennon et al., 1997)... 

Figure 3. Solubilities of hyoscyamine (I) and scopolamine (2) free bases in supercritical CO, [39]. Reprinted from J. Chromatogr. A, 863, Y. H. Choi et al., Strategies for supercritical fluid extraction of hyoscyamine and scopolamine salts using basified modifiers, 47-55 (1999), with permission from Elsevier Science.

Although there were some differences on the effects of temperature and pressure according to each particular compound, the free bases of hyoscyamine (1), scopolamine (2), and pseudoephedrine (6) were all found to be highly soluble in supercritical CO,. However, the hydrochloride salts of these compounds were scarcely extracted by pure CO, under any conditions employed. These results were consistent with preliminary evidence indicating that these alkaloids are not extracted from plant materials by pure CO,. This means that the alkaloids in living cells in the plant are not in the form of their free bases but rather as water-soluble salts in the cell vacuole [40]. Therefore, it was necessary to develop a procedure to enhance the solubilities of alkaloidal salts in CO,. 

Fernandez, P., A. Alder, and W. Giger. 1993. Quantitative determination of cationic surfactants in sewage sludges and sediments by supercritical fluid extraction and HPLC applying postcolumn ion-pair extraction. Presentation at the American Chemical Society Meeting, Denver, CO, March 28-April 2, 1993. 

This is true even if it is capable of dissolving the solutes. Supercritical solvents such as N2O and CHC1F2 are more efficient in extracting polar compounds, but their routine use is uncommon due to environmental concerns. The extraction efficiency of polar compounds by C02 can be improved by the addition of small quantities (1 to 10%) of polar organic solvents, referred to as modifiers. This is a common practice in SFE. Table 3.4 lists some common modifiers for supercritical CO 2. 

In another method, developed by Jacobucd and co-workers (9), alcohol is removed by supercritical CO2 extraction in a semi-continuous system. 

In general, the extraction process must be streamlined to reduce solvent consumption since removal of solvents can represent a major bottleneck. Additionally, the extraction method chosen should support the first step of fractionation for library generation. Supercritical fluid extraction (SFE) represents an efficient extraction method in terms of low solvent consumption and extraction speed. Supercritical fluids exhibit high diffusivity with low viscosity and low surface tension they can readily permeate biomass matrices and solvate molecules, including drug-like compounds, leading to efficient extractions. The addition of small amounts of organic co-solvents may enhance... 

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