Liquid solvent extraction

The liquid-liquid (solvent) extraction is based on the extraction of various ions into either an organic or aqueous phase according to the complex ion structure. The structure of the complex ions generally depends on the solution parameters and, first and foremost, on the acidity of the aqueous solution. At... 

Liquid (solvent) extraction is not the only way of sample preparation, but stands along with various forms of heat extraction (headspace, thermal desorption, pyrolysis, etc.) and with laser desorption techniques. 

SFE instrument development has greatly been stimulated by the desire of the Environmental Protection Agency (EPA) to replace many of their traditional liquid-solvent extraction methods by SFE with carbon dioxide. In the regulatory environment, EPA and FDA approved SFE and SFC applications are now becoming available. Yet, further development requires interlaboratory validation of methods. Several reviews describe analytical SFE applied to polymer additives [89,92,324]. 

Kirschner et al. [358] have observed a lower percent finish-on-yarn (FOY) for SFE as compared to solvent extraction of various fibre/textile matrices. This is rationalised as organic solvents tend to extract components from a matrix more vigorously than scCC>2 and thus remove more of the oligomer and organic components present in the fibre. SFE is a potentially softer extraction technique since it removes less of the polymer from the fibre matrix than liquid solvent extraction. 

A schematic diagram of the liquid solvent extraction process is illustrated in Figure 1. Where the production of liquid hydrocarbons is the main objective an hydrogenated donor process solvent is used, whereas in the production of needle coke this is not necessary and a coal derived high boiling aromatic solvent may be used (e.g. anthracene oil). An essential economic requirement of the process is that a high extraction yield of the coal is obtained and this will depend upon the coal used and the digestion conditions. 

LSE [Liquid solvent extraction] A coal liquifaction process, under development in 1990 by British Coal, at Point of Ayr, North Wales. The coal is dissolved in a coal-derived hydrocarbon solvent and then catalytically hydrocracked. 

Liquid-liquid solvent extraction, 21 399 Liquid lithium, 15 131 Liquid low density polyethylene, 20 205 Liquid lubricants, for extreme environments, 15 256 Liquid lubricated system, coefficient of friction in, 15 209 Liquid magnesium, 15 336 Liquid manometers, 20 646-647 Liquid MDI, 25 462. See also MDI [4,4 -methylenebis(phenyl isocyanate)] Liquid melamine resins, 15 773 Liquid membrane extraction, 10 766 Liquid membranes, 15 800, 814-815 supported, 16 28... 

Much of the current interest in using analytical-scale SFE systems comes from the need to replace conventional liquid solvent extraction methods with sample preparation methods that are faster, more efficient, have better potential for automation, and also reduce the need for large volumes of potentially hazardous liquid solvents. The need for alternative extraction methods is emphasized by current efforts to reduce the use of methylene chloride as an extraction fluid for environmental sample preparation [158]. The potential for applying SFE to a wide variety of environmental and biological samples for both qualitative and quantitative analyses is widely described in reviews [159-161] and the references therein. Analytical-scale SFE is most often applied to relatively small samples (e.g., several grams or less). 

On-line supercritical fluid extraction/GC methods combine the ability of liquid solvent extraction to extract efficiently a broad range of analytes with the ability of gas-phase extraction methods to rapidly and efficiently transfer the extracted analytes to the gas chromatograph. The characteristics of supercritical fluids make them ideal for the development of on-line sample extraction/gas chromatographic (SFE-GQ techniques. SFE has the ability to extract many analytes from a variety of matrices with recoveries that rival liquid solvent extraction, but with much shorter extraction times. Additionally, since most supercritical fluids are converted to the gas phase upon depressurization to ambient conditions, SFE has the potential to introduce extracted analytes to the GC in the gas phase. As shown in Fig. 13.8, the required instrumentation to perform direct coupling SFE-GC includes suitable transfer lines and a conventional gas chromatograph [162,163]. 

Liquid-liquid solvent extraction is the most important process used to separate the rare earths today. 

Among the separation techniques, liquid-liquid (solvent) extraction is one of the best-known, well-established, versatile, and easy to use. However, traditional extraction employs conventional organic solvents immiscible with water, which are typically volatile, flammable, and health hazardous. This makes extraction inappropriate for modern and future environmental-friendly technologies and analysis processes. Another problem with conventional solvents is that their number is rather limited, so it may be difficult to find fhe solvenf ideally suifed for a particular application (even considering solvent mixtures). 

Difficult separations can often be effected by liquid-liquid solvent extraction, which depends on differences in the distribution of solute species between two immiscible or partially immiscible phases.4,9 For a solute species A, this distribution is governed by the Nemst partition law... 

The role of the slag in what is in effect liquid-liquid solvent extraction is, once again, crucial in the removal of unwanted material such as iron compounds. 

Liquid-liquid solvent extraction processes using aqueous glycols and improved contacting means (1952)... 

R Marsili, D Callahan. Comparison of a liquid solvent extraction technique and supercritical fluid extraction for the determination of a- and /8-carotene in vegetables. J Chromatogr Sci 31 422-428, 1993. 

Phospholipid-derived fatty acids are often used to identify bacteria by capillary GC analysis after liquid solvent extraction, concentration steps, and chemical derivatization to their methyl esters. Our initial investigations attempted to extract the intact phospholipids, but no significant recoveries were achieved using pure C02. Even if SFE conditions were developed that could extract intact phospholipids, an additional derivatization step would be required before GC analysis of the fatty acid components. For these reasons, chemical derivatization/SFE was investigated in an effort to eliminate the lengthy conventional liquid solvent extractions as well as to combine (and shorten) the extraction and derivatization steps. The derivatization/SFE procedure was performed on samples of whole bacteria using 0.5 mL of 1.5% TMPA in methanol. The static derivatization step was performed for 10 minutes at 80°C and 400 atm C02, followed by dynamic SFE for 15 minutes at a flow rate of ca. 0.5 mL/min of the pressurized C02. Extracts were collected in ca. 3 mL of methanol and immediately analyzed by capillary GC without any further sample preparation. 

Several researchers have combined the separating power of supercritical fluid chromatography (SFC) with more informative spectroscopic detectors. For example, Pinkston et. al. combined SFC with a quadrupole mass spectrometer operated in the chemical ionization mode to analyze poly(dimethylsiloxanes) and derivatized oligosaccharides (7). Fourier Transform infrared spectroscopy (FTIR) provides a nondestructive universal detector and can be interfaced to SFC. Taylor has successfully employed supercritical fluid extraction (SFE)/SFC with FTIR dectection to examine propellants (8). SFC was shown to be superior over conventional gas or liquid chromatographic methods. Furthermore, SFE was reported to have several advantages over conventional liquid solvent extraction (8). Griffiths has published several... 

Leaching Solid Liquid Liquid solvent Extraction of sucrose from sugar beets with hot water... 

Supercritical fluid extraction(SFE) combined with five types of bioassay tests is extensively applied to explore some bioactive substances from thirty types of natural resources available in Korean peninsula. To evaluate comparatively the economic viability of the SFE, organic liquid solvent extraction(LSE) with n-hexane, chloroform and methanol was also performed. To characterize the extracts, GC and HPLC are employed. Also, the column chromatography is used to isolate some target compounds from the total extracts. For all the samples, the optimum SFE condition for each sample which gives maximum yield and cytotoxicity were discussed. 

To figure out comparatively whether the SFE is advantageous or not, the traditional Soxhlet organic liquid solvent extraction(LSE) with n-hexane, chloroform and methanol was carried out. Also, simple but reliable in vitro bioactivity tests were established and applied to the extracts. The bioassays... 

Calculations of multicomponent liquid-liquid equilibrium are needed in the design of liquid (solvent) extraction systems. Since these operations take place considerably below the bubble point, it is not necessary to consider the equilibrium-vapor phase. The equations to be solved are ... 

Bromoform is used as a chemical intermediate in the synthesis of organic chemicals and pharmaceuticals. It is used as an ingredient in fire-resistant chemicals and as an industrial solvent in liquid-solvent extractions. Bromoform is used in polymer reactions and in the vulcanization process for rubber. Bromoform is also used for medicinal purposes as a sedative, an-titussive, and antiseptic. 

The process consists of liquid-liquid solvent extraction of trivalent actinides and/or lanthanides from a dilute acid or salt solution in which the anion can be either nitrate or chloride. 

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