Supercritical water extractions extract composition

Conversions between 42-68% were obtained for supercritical water extraction of Victorian brown coals at 380°C and 22MPa, considerably higher than using toluene under the same conditions. The conversions obtained with a bituminous and a sub-bituminous coal were much lower. Pressure had a marked effect on both the conversion and the extract composition, whereas temperature had only a slight effect. Considerably higher conversions were achieved using dilute sodium hydroxide rather than water. The composition of the products is discussed. 

Bergeron, C. et al.. Comparison of the chemical composition of extracts from Scutellaria lateriflora using accelerated solvent extraction and supercritical fluid extraction versus standard hot water or 70% ethanol extraction, J. Agric. Food Chem., 53, 3076, 2005. 

Other extraction methods used in the lipid extraction include supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE). With SEE, good extraction yields have been obtained for nonpolar lipids including ester-ified fatty acids, acylglycerols, and unsaponifiable matter. However, complex polar lipids are only sparingly soluble in supercritical carbon dioxide alone and polar modifiers, such as methanol, ethanol, or even water is required to improve the extraction of polar lipids (10). SFE has been used for the extraction of lipids especially from various food matrices, such as different nuts, edible oils, and seeds (11). The recoveries of lipids in SFE were on the same levels than with conventional solvent extraction methods (12,13), no significant differences between the fatty acids extracted were observed. PLE has also been used in lipid extraction, although only in very few applications (14). The elevated temperatures used in PLE can cause alteration of the lipid composition. 

The second example W demonstrates two stage extraction using dry CO2 followed by wet CO2. Cinnamon Is extracted at 300 BAR and 55 C. This first stage occurs with dry CO2 to remove the essential oils responsible for the aroma and odor of the spice. The second extraction, using supercritical CO2 saturated with water, extracts the flavor components. The fractions can be used separately or recombined to the desired composition. 

The committee also believes that commercially available hazardous waste incinerators should be suitable for final treatment of neutralents, although test burns may be necessary. Some neutralents are high in sodium, which tends to shorten the life of the refractory brick used to line incinerators, but wastes of similar composition have been treated satisfactorily. Commercial hazardous waste facilities are available that offer other technologies that might be better for aqueous wastes. These technologies include biological treatment, supercritical fluid extraction (not to be confused with supercritical water oxidation, discussed later in this chapter) followed by incineration of the smaller volume of extracted organics, and chemically based proprietary processes. 

Apart from these techniques, supercritical fluids extraction (SEE) is the preferred technique in many areas of active compounds extraction. However, in what concerns to flavonoids, its utility is highly influenced by the matrix s composition. For example, in the case of isolation of non-polar flavonoid aglycones by SEE, when compared with classical techniques, SEE provided identical or sometimes better results. Nevertheless, when water-soluble glycosides are considered, the use of SEE results in considerably different yields.Still, the use of aqueous methanol constitutes a useful and balanced extraction solvent that allows the extraction of both aglycones and flavonoid glycosides, depending on the conditions used, such as time and temperature, among others. Other reported solvents used for extraction are acetone, ethanol, and dimethyl sulfoxide (DMSO), with... 

This review focuses on the extraction of lipids from plant and muscle tissues using supercritical CO2 with an emphasis on the effect of structural and compositional differences as well as C02/lipid/protein/water interactions. The effect of moisture content ranging from 3-20% in oilseeds to 3-64% in muscle tissues on hpid and water extractability and residual proteins is demonstrated. 

The chemical composition of the matrix can have either a positive or a negative effect on the results obtained by SFE. One of the most important parameters influencing the extraction is the degree of humidity of the sample. For example, it is generally admitted that a partial dehydration of the sample allows for a faster extraction. Indeed, hydrophylic matrices have a tendency of preventing contact between the supercritical fluid and the analyte. This is particulary true for the extraction of drugs from skin tissue. In specific cases, however, the presence of water can, on the contrary, improve the rate of extraction by acting as an "internal cosolvent."... 

One of new trends today in sol-gel chemistry is the use of supercritical carbon dioxide as a solvent during sol-gel polymerization or for extraction of the resulting product. The initial aUcoxysilane is mixed with anhydrous 99% HCO2H and sol-gel polymerization of the mixture is then carried out in supercritical CO2 in an autoclave (40°C, 41.4-55.2 MPa). Gel formation proceeds over 12h and then CO2 is slowly removed (8 h). This procedure favors for the formation of highly porous monolithic composites with the mesopore and macropore architectures. Components that sharply enhance the ability of Si02 to adsorb water may also be introduced at the stage of formation. For example, selective water adsorbents, such as CaCl2 and LiBr, bind up to 53 wt% of H20. " " ... 

The variability of the composition of an EO is also impacted by the choice of the method of extraction of EOs. One characteristic of EOs is the volatility of their compounds which allows them to be easily extracted by water vapors, in contrast to fixed lipid oils and essences (concrete, absolute, oleoresins, and resinoids) which are extracted by solvents and alcohol. Guenther [9] distinguished three kinds of water and steam distillation methods for obtaining essential oils. These methods are far more restrictive than more recent extraction and separation methods which are mentioned in the European Pharmacopoeia [10] using supercritical fluids, steam distillation, dry distillation, or mechanical cold pressing of plants. 

PMMA- and poly(a-methyl-st)rrene)-PI block copolymer [9,10] blend solution containing polyurethane and PAA [11] and polyacrylamide- and PMMA-grafted PI [12]. They have achieved 10-30% decrease in a dielectric constant of polyimide films, and low-fc porous films ( fc 2.2) have been provided. Also, other methods, such as using water droplets and LiCl crystal as templates, and extracting a porogen polymer from composite PI film by supercritical CO2, have been known [47-49]. On the other hand, we have obtained ultralow-fc porous films by depositing porous PI MPs onto substrates [18,20]. 

Hops are extracted with a mixture of water and an organic solvent (e. g., alcohol, diethylether), giving extracts of varying compositions. Recently, a hops extraction process using supercritical carbon dioxide has become important. 

Given the concerns about the use of toxic organic solvents in food chemistry, many new techniques have been developed to overcome or minimize this problem. For instance, environmentally clean extraction techniques, such as those based on the use of compressed fluids (pressurized liquids, PLE supercritical fluids, SFE and subcritical water, SWE or PHWE), are widely used as alternatives to conventional procedures, such as solid—liquid extraction (SEE), liquid—liquid extraction (LLE), and the like. These alternative processes have in common the use of lower amount of solvents (from hundred milliliters to few milliliters), the lack of toxic residues, higher efficiency extraction (in terms of yields and energy used), and the improved selectivity of the process. SFE has been used in food analysis as a sample preparation technique, mainly for lipophilic compounds, while PLE has been extensively used for many compositional food applications, because the selectivity of this technique... 

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