Phenols supercritical fluid extraction

Llompart MP, Lorenzo RA, Cela R, Li K, Belanger JMR, Pare JRJ. Evaluation of supercritical fluid extraction, microwave-assisted extraction and sonication in the determination of some phenolic compounds from various soil matrices. J. Chro-matogr. A 1997 774 243-251. 

The microwave assisted extraction for organic compounds including polyaromatic hydrocarbons, phenols and organochlorine insecticides, described in section 11.1.8 [25] has been applied to sediments. The application of supercritical fluid extraction to the determination of various insecticides in soils described in section 11.1.7 [23] has been applied to river sediments. 

The first use of supercritical fluid extraction (SFE) as an extraction technique was reported by Zosel [379]. Since then there have been many reports on the use of SFE to extract PCBs, phenols, PAHs, and other organic compounds from particulate matter, soils and sediments [362, 363, 380-389]. The attraction of SFE as an extraction technique is directly related to the unique properties of the supercritical fluid [390]. Supercritical fluids, which have been used, have low viscosities, high diffusion coefficients, and low flammabilities, which are all clearly superior to the organic solvents normally used. Carbon dioxide (C02, [362,363]) is the most common supercritical fluid used for SFE, since it is inexpensive and has a low critical temperature (31.3 °C) and pressure (72.2 bar). Other less commonly used fluids include nitrous oxide (N20), ammonia, fluoro-form, methane, pentane, methanol, ethanol, sulfur hexafluoride (SF6), and dichlorofluoromethane [362, 363, 391]. Most of these fluids are clearly less attractive as solvents in terms of toxicity or as environmentally benign chemicals. Commercial SFE systems are available, but some workers have also made inexpensive modular systems [390]. 

Supercritical Fluid Extraction of Phenols from Water... 

M. H. Liu, S. Kapila, K. S. Nam and A. A. Elseewi, Tandem supercritical fluid extraction and liquid chromatography system for determination of chlorinated phenols in solid matrices ,/. Chromatogr. 639 151-157 (1993). 

Supercritical fluid extraction has been applied to extract phenolic acids from a variety of plant samples. It uses high-pressure to force carbon dioxide to be a mixture of liquid and gas phases, which is called a supercritical fluid. The liquid and gas phase mixture of carbon dioxide can more readily permeate the sample matrix than only the gas phase of carbon dioxide. The compounds solublized in the liquid phase of carbon dioxide are extracted from the sample matrix and collected after they elute from the outlet of the system. The biggest advantage of supercritical fluid extraction is that there is no, or less, organic solvent involved in the extraction, due to the use of carbon dioxide supercritical fluid as the major solvent.. The carbon dioxide readily evaporates as gas phase at the system outlet. Thus, unlike other solvent extraction methods, there is no evaporation step for the extraction, making this an environmentally friendly method. However, the system is much more expensive and delicate than the other novel technology extraction... 

Sample handling strategies for the determination of plant phenols in food and plant material have been reviewed [42]. Attention was paid to hydrolysis, liquid extraction, solid-phase extraction (SPE), and supercritical-fluid extraction. 

Sometimes, for solid and semisolid samples, the above-referenced methods were not suitable the extraction times were very long, with consequent chemical modifications and appearance of artifacts. Supercritical fluid extraction provides a good recovery of phenolics. The extraction behavior of phenolics has been delineated, using supercritical carbon dioxide and either sand or an inert support as sample matrix. ... 

Chlorinated phenolic compounds in air-dried sediments collected downstream of chlorine-bleaching mills were treated with acetic anhydride in the presence of triethylamine. The acetylated derivatives were removed from the matrix by supercritical fluid extraction (SEE) using carbon dioxide. The best overall recovery for the phenolics was obtained at 110°C and 37 MPa pressure. Two SEE steps had to be carried out on the same sample for quantitative recovery of the phenolics in weathered sediments. The SEE unit was coupled downstream with a GC for end analysis . Off-line SEE followed by capillary GC was applied in the determination of phenol in polymeric matrices . The sonication method recommended by EPA for extraction of pollutants from soil is inferior to both MAP and SEE techniques in the case of phenol, o-cresol, m-cresol and p-cresol spiked on soil containing various proportions of activated charcoal. MAP afforded the highest recoveries (>80%), except for o-cresol in a soil containing more than 5% of activated carbon. The SEE method was inefficient for the four phenols tested however, in situ derivatization of the analytes significantly improved the performance . 

Iron, titanium, and zirconium salts can be substituted for the chromium ones.146 Vegetable tannins, such as 4.20 can also be used, but they slow down the tanning process. Similar phenols can be found in the residue from tea leaves left after the manufacture of instant tea. Perhaps, they could be used in making leather to eliminate or reduce the amount of another waste product. Getting reagents to penetrate the hide is a problem. Newer methods, such as ul-trasonication and supercritical fluid extraction, may help reduce the time required to make leather, so that these alternative-tanning agents can be used instead of the chromium. 

For biological evaluation larger quantities of component phenols and their constituents may be required and where different components such as alkylresorcinols and anacardic acids co-occur, an initial solvent separation may prove desirable. Mild extraction methods, such as supercritical fluid extraction with carbon dioxide, [1,219,220], followed by phase separation [221], preparative TLC [222], or column chromatography [223] may be valuable for complex mixtures. 

Wong, J. M., Li, Q. X., Hammock, B. D. and Seiber, J. N., Method for the analysis of 4-Nitro-phenol and parathion in soil using supercritical fluid extraction and immunoassay, J. Agric. Food Chem., 39, 1802-1807, 1991. 

Fung, Y.S. and Long, Y.H., Determination of phenols in soil by supercritical fluid extraction-capillary electrochromatography, J. Chromatogr. A, 907, 301, 2001. 

Most of the extraction techniques of phenolic compounds from vegetables are based on ultrasound-assisted extraction (UAE) [27,44,45], In addition, other techniques have been successfully applied to the pretreatment of phenolic compounds in fruits and vegetables, including pressurized liquid extraction (PLE) [46], solid-phase extraction (SPE) [47], supercritical fluid extraction (SFE) [48], microwave-assisted extraction (MAE) [49], rotary shaker-assisted extraction (RAE), [50] and QuEChERS (acronym of quick, easy, cheap, effective, rugged and safe) [51], as can be observed in Tables 16.3 and 16.4. In some cases, an acid treatment [52] was applied to hydrolyze the glycosides in order to determine the content of free and conjugated flavonoids as aglycons. 

Phenols are an important group of phytochemicals with significant health beneficial effects. Extraction of phenols firom the biological sources is a growing field of interest and is an integrated part of analytical methods. Some of the common methods of extraction of phenolic compounds are solvent extraction, accelerated solvent extraction, supercritical fluid extraction, ultrasonic extraction, and microwave extractimi. Separation is the next important step of analytical methods, which is done to separate the required phenolic components from the unwanted part of the extract. In case of phenols, methods such as... 

Le Floch F, Tena MT, Rios A, Valcarcel M (1998) Supercritical fluid extraction of phenol compounds from olive leaves. Talanta 46(5) 1123—1130... 

Supercritical fluid extraction (SFE) has been used mostly in environmental analysis [129,205] for the extraction of nonpolar organic pollutants from solid samples, for example, sediments. The technique has abo been used together with SPE dbks (silica Cis, polymeric, and ion exchanger disks) for the extraction of phenols from water samples followed by GC-MS [206]. After adsorbing the phenols onto the SPE disk, they are eluted with a supercritical fluid (carbon dioxide). 

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