Use of supercritical fluid extraction

Alzaga R, Bayona JM, Barcelo D. Use of supercritical fluid extraction for pirimi-carb determination./. Agric. Food Chem. 1995 43 395 400. 

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]. 

Wong, D.C.L. van Compemolle, R. Nowlin, J.G. O Neal, D.L. Johnson, G.M. Use of supercritical fluid extraction and fast ion bombardment mass spectrometry to identify toxic chemicals from a refinery effluent adsorbed onto granular activated carbon. Chemosphere 1996, 32, 621. 

The adaptation of supercritical fluid extraction (SFE) in routine residue and metabolism analysis as well as other extraction/separation laboratories and applications has been slow. This is despite the demonstrated feasibility of using SFE for the removal of sulfonylureas, phenylmethylureas and their metabolites from soil and plant materials (1-2), as well as widespread demonstrated use of supercritical fluid extraction for other applications (3-6). The reason for this is simple. Although automated, SFE extraction apparatus typically only analyzes a single sample at a time. The technique could not compete effectively with the productivity of an experienced technician performing many sample extractions simultaneously. In essence, with a one vessel automated supercritical fluid extractor, operator attendance is high and throughput is about the same or even less than current conventional liquid-liquid and solid-liquid extraction techniques. 

Facchetti S, Larsen B (1994), Fresenius J. Anal. Chem. 348 159-163. Use of supercritical fluid extraction in the analysis of polychlorinated dibenzodioxins and dibenzofurans"... 

Lindstrdm G, van Bavel B, Karlsson MJL, Rappe C, Hardell L (1995), Organohalogen Compounds 23 27-30. The use of supercritical fluid extraction (SFE) as a sample preparation method in the analyses of PCDD, PCDF and PCB in human tissue", Eds. Dioxin 95 Secretariat, Edmonton, Kanada ISBN 3-928379-13-5... 

Preparing the sample is a key step in all biological analyses, and hair analysis is no exception to this rule. Over the last ten years, there has been an ever increasing interest in the use of supercritical fluid extraction (SFE) as an alternative to traditional methods of preparing samples. The driving force behind this development is, without doubt, the need for a simple, rapid, automated, and selective method which should also be environmentally friendly. In this context, the use of supercritical fluids fulfills these conditions, due to their unique physicochemical properties. The following is a list of advantages ... 

The use of supercritical-fluid-extraction techniques in the fractionation of polysiloxanes has been demonstrated by the data presented. The poly-dispersities of the fractions were comparable with those generally attainable only by anionic-polymerization techniques, with which the incorporation of two functional groups is often difficult to attain. The ability to isolate these well-defined fractions will lead to important fundamental studies on structure-property relationships in multiphase copolymer systems. 

Karlsson L, Torstensson A, Taylor LT. The use of supercritical fluid extraction for sample preparation of pharmaceutical formulations. J Pharm Biomed Anal 1997 Feb 15(5) 601-611. 

Ibanez E, Cifuentes A, Crego AL, Senorans FJ, Cavero S, Reglero G. Combined use of supercritical fluid extraction, micellar electrokinetic chromatography and reverse phase high performance liquid chromatography for the analysis of antioxidants from rosemary Rosmarinus officinalis L.). J Agric Food Chem 2000 48 4060-4065. 

Euerby MR, Lewis RJ, Nichols SC. Preliminary investigations into the use of supercritical-fluid extraction to extract a novel corticosteroid (tipredane INN) from rodent diet. Anal Proc 1991 28 287-289. 

Allen DL, Oliver JS. The use of supercritical-fluid extraction for the determination of amphetamines in hair. Forensic Sci Int 2000 107 191-199. 

Howard AL, Shah MC, Ip DP, Brooks MA, Strodelll JTB, Taylor LT. Use of supercritical-fluid extraction for sample preparation of sustained-release felo-dipine tablets. J Pharm Sci 1994 83 1537-1542. 

For the extraction process, the use of supercritical fluids extraction in adequate equipment improves the quality of the extraction. The most often used technique for separation is the chromatographic technique.196 HPLC... 

McDowell and Metcalfe proposed the use of supercritical fluid extraction (SEE) with ultra high purity CO2 as supercritical fluid for the extraction of phthalate esters from sediment samples. Extracts were collected by bubbling the vented gas through 12 ml hexane, and solvent... 

J.E. Cox, and D. Hoffmann The use of supercritical fluid extraction for the analysis of tobacco-specific V-nitrosamines in tobacco and in tobacco smoke CORESTA 1992 Symp., Jerez de la Frontera, Spain, CORESTA Inf. Bull., 1992 Spec. Edition Paper STIO, 84. 

The third instrumental approach is the use of supercritical fluid extraction (SEE). A supercritical fluid is a substance at a temperature and pressure above the critical point for the substance. (You may want to review phase diagrams and the critical point on the phase diagram in your general chemistry text.) Supercritical fluids are more dense and viscous than the gas phase of the substance but not as dense and viscous as the hquid phase. The relatively high density (compared with the gas phase) of a supercritical fluid allows these fluids to dissolve nonvolatile organic molecules. Carbon dioxide, CO2, has a critical temperature of 31.3°C and a critical pressure of 72.9 atm this temperature and pressure are readily attainable, making supercritical CO2 easy to form. Supercritical CO2 dissolves many organic compormds, so it can replace a variety of common solvents supercritical... 

When smokeless powder is suspected as having been used in a pipe bomb, the inside surface of the pipe is swabbed, rinsed, or, more effectively, the pipe fragments are sonicated with methylene chloride. The extract is filtered and concentrated by slow evaporation. The extract is examined by GC-TEA or LC-TEA or using an electrochemical detector to detect NG indicative of double-base powder. Similarly, GC-MS may be used for detection of NG with good sensitivity and excellent selectivity. The use of supercritical fluid extraction (SEE) has been used to extract smokeless powders and residues but the equipment cannot accommodate bulky fragments such as pipe fragments. 

The use of supercritical fluid extraction (SEE) as an extraction technique is related to the unique properties of the supercritical fluid. These fluids have a low viscosity, high diffusion coefficients, low toxicity, and low flammability, all clearly superior to the organic solvents used in SPE extraction. The most common fluid used is carbon dioxide. SEE extractions of sediment samples have shown recoveries of >95% for all the individual PCBs. The separation of PCDDs from PCBs and chlorinated benzenes is difficult because of their similar solubility. An interesting development is the use of fat retainers. Samples, mixed in different weight ratios with, e.g., silica/silver nitrate 10% or basic alumina, can be placed in 7 ml extraction cells. The analytes are recovered by elution with 1.5-1.8 ml of hexane. With the correct fat-silica ratios and SEE conditions, no additional cleanup procedure is necessary for GC with an electron-capture detector (ECD). One drawback of SEE may be that the methods developed are valid for a specific matrix, but as soon as, e.g., the fat content of a biota sample or the type of lipids changes, the method has to be adapted. SEE is relatively complicated compared to other extraction techniques. In addition, the cell volumes are small, which limits the sample intake, and, with that, the detection limits. Einally, some reliable types of SEE equipment have recently been withdrawn from the market. This will have a substantial negative effect on the use of SEE in the near future. 

Use of supercritical fluid extraction (SFE), for a more effective separation of products from ILs Continuous bicycUc process of extraction of sulphur-containing aromatic compounds (SAs) from diesel fuel and gasoline with ionic liquids and reextraction of SAs from ILs with supercritical carbon dioxide (scCOj)... 

Recently, there has been an increasing interest in the use of supercritical fluid extraction (SEE) with carbon dioxide (CO2) as a solvent. This process uses the properties of gases above their critical points to extract selective soluble components from a raw material. Carbon dioxide is an ideal solvent for the extraction of natural products because it is nontoxic, nonexplosive, readily available, and easy to remove from extracted products [3,6]. SFE has the abihty to use low temperatures, leading to less deterioration of the thermally labile components in the extract. In addition, SFE is typically carried out in the absence of air which also ensures minimal alteration of the active ingredients and preservation of the curative properties [46, 47]. SC CO2 is generally efficient in the purification and fractionation of hydrophobic compounds, such as flavonoids and cinnamic acid derivatives from plant matrixes [49]. 

Glazkov, I.N. et al.. Gas-chromatographic determination of organic compounds in water with the use of supercritical fluid extraction, /. Anal. Chem., 59, 1085, 2004. 

One attractive approach in this context is the use of supercritical fluid extraction (SEE) with carbon dioxide as the supercritical fluid, which can provide a fast and efficient extraction of a wide range of compounds. SEE has been shown as an excellent extraction system of different matrixes [16-26]. 

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