Extraction with Supercritical Fluids

ON-LINE COUPLING OF SUPERCRITICAL FLUID EXTRACTION WITH CAPILLARY ELECTRODRIVEN SEPARATION TECHNIQUES (SFE-CESTs)... 

X. Lou, H.-G. Janssen and C. A. Cramers, Investigation of pai ameters affecting the online combination of supercritical fluid extraction with capillai y gas cliromatogi aphy , J. Chromatogr. 750 215-226 (1996). 

M. C. Tavai es and P. M. Lan as, On-line coupling of supercritical fluid extraction with supera itical fluid cltromatogr aphy , 7. Braz. Chem. Soc. in press (2001). 

SFC-TLC is largely unexplored. Stahl [927] developed a device for supercritical fluid extraction with deposition of the fluid extracts on a moving TLC plate. Wunsche et al. [928] have described an automated apparatus for direct pSFC-TLC coupling. Compared to collecting the effluent from the SFC in decompression vessels, the direct deposition of the effluent on the TLC plate leads to significant losses of analytes. Multidimensional SFC has been reviewed [929]. 

One of the most studied technologies is supercritical fluid extraction with SC-CO2. The advantages of SC-CO2 include its low processing temperature, which minimizes thermal degradation the ease of separation with no solvent residue left in the final product and minimization of undesirable oxidation reactions. 

Ruiz del Castillo ML, Gomez-Prieto MS, Herraiz M and Santa-Maria G. 2003. Lipid composition in tomato skin supercritical fluid extracts with high lycopene content. J Am Oil Chem Soc 80(3) 271-274. 

Supercritical fluid extraction with carbon dioxide has been applied to the determination of polyaromatic hydrocarbons in soil. 

Von Bavel et al. [55] have developed a solid phase carbon trap (PX-21 active carbon) for the simultaneous determination of polychlorodibenzo-p-dioxins and polychlorodibenzofurans also polychlorobiphenyls and chlorinated insecticides in soils using superfluid extraction liquid chromatography for the final determination. Supercritical fluid extraction with carbon dioxide has been applied to the determination of dioxins in soil [114],... 

Snyder et al. [20] have compared supercritical fluid extraction with classical sonication and Soxhlet extraction for the extraction of selected pesticides from soils. Samples extracted with supercritical carbon dioxide modified with 3% methanol at 350atm and 50°C gave a =85% recovery of organochlorine insecticides including Dichlorvos, Endrin, Endrin aldehyde, p,p -DDT mirex and decachlorobiphenyl (and organophosphorus insecticides). 

Snyder et al. [94] compared supercritical extraction with classical sonication and Soxhlet extraction for the extraction of selected organophosphorus insecticides from soil. Samples extracted with supercritical carbon dioxide modified with 3% methanol at 350atm and 50°C gave a =85% recovery of Diazinon (diethyl-2-isopropyl-6-methyl-4-pyrimidinyl phosphorothiodate or 0,0 diethyl-0-(2-isopropyl-6-methyl-4-pyrimidyl) phosphorothioate). Ronnel (or Fenchlorphos) 0,0-dimethyl-0-2,4,5 trichlorophenol phosphorothiodate), Parathion ethyl (diethyl-p-nitrophenyl (phosphorothioate), Tetrachlorovinphos (trans,-2-chloro-l-(2,4,5 trichlorophenyl) vinyl (chlorophenyl-O-methylphenyl phosphorothioate) and Methiadathion. Supercritical fluid extraction with methanol modified carbon dioxide has been applied to the determination of organophosphorus insecticides in soil [260]. 

Steinheimer et al. [103] used supercritical fluid chromatography to extract Atrazine, diethyl Atrazine and Cyanazine from Canadian cornbelt soils by supercritical fluid extraction with carbon dioxide. 

The method based on immunosorbents coupled on-line with liquid chromatography-atmospheric pressure chemical ionization mass spectrometry [109], discussed in section 9.4.2.1, has been applied to the determination of substituted urea type herbicides. Supercritical fluid extraction with methanol modified carbon dioxide has been applied to the determinants of sulfonyl urea herbicides in soil [261],... 

Snyder et al. [23] compared supercritical fluid extraction with classical sonication and Soxhlet extraction from the analysis of selected insecticides in soils. 

Supercritical fluid extraction with C02 premixed with 3% methanol. 

Snyder JL, Grab RL, McNally ME, et al. 1992. Comparison of supercritical fluid extraction with classical sonication and soxhlet extractions for selected pesticides. Anal Chem 64 1940-1946. 

Supercritical fluid extractions with solid feed stocks are industrially carried out batchwise because of lack of equipment for feeding solid materials to a pressurized extractor. 

Another processing procediue that could involve supercritical fluid extraction with CO2 is the preparation of flavor concentrates from meat lipids for use in mixtures of other natural precursors for the preparation of tynthetic meat flavor additives that serve bofii as antioxidants that prevent warmed-over flavor (WOF) in cooked meat diuing storage and enhance the flavor of the natural products. 

For sample preparation, isolation and separation traditional methods like distillation (e.g. essential oil content of raw materials) or Soxhlet extraction are still in use. Beyond that, more recent methods are employed, for example supercritical fluid extraction with liquid carbon dioxide. 

Hartonen K, Bowadt S, Hawthorne SB, et al. 1997. Supercritical fluid extraction with solid-phase trapping of chlorinated and brominated pollutants from sediment samples. J Chromatogr A 774(l-2) 229-242. 

Solid-phase extractions can reduce solvent consumption in analytical chemistry. For example, a standard procedure approved by the U.S. Environmental Protection Agency for the analysis of pesticides in wastewater requires 200 mL of dichloromethane for the liquid-liquid extraction of 1 L of water. The same analytes can be isolated by solid-phase extraction on C g-silica disks. The pesticides are recovered from the disks by supercritical fluid extraction with C02 that is finally vented into a small volume of hexane. This one kind of analysis can save 10s kg of CH2C12 per year.24... 

JM Snyder, JW King, MA Jackson. Analytical supercritical fluid extraction with lipase catalysis conversion of different lipids to methyl esters and effect of moisture. J Am Oil Chem Soc 74 585-588, 1997. 

M. Ashraf-Khorassani, M. Barzegar and Y. Yamini, On-line coupling of supercritical fluid extraction with high performance liquid chromatography , J. High Resolut. Chromatogr. 18 472-476 (1995). 

Applications of supercritical fluid extraction and headspace analysis are, however, now creeping in. Thus supercritical fluid extraction with carbon dioxide-methanol has been used to extract 2,4-chlorophenol from crops [231 ], sulfonylurea herbicides from plants [161], and organophosphorus pesticides from fruit and vegetables [226]. 

Supercritical fluid extraction with carbon dioxide has been shown to be an excellent alternative to conventional solvent extraction for the removal of hydrocarbon pollutants from solid samples [4-7]. It is fast ( 30 minutes), nonpolluting, and relatively simple to implement. Additionally, recent work has shown that (supercritical fluid extraction using carbon dioxide is generally applicable to soil samples that have been contaminated with petroleum hydrocarbons ranging from those found in gasoline to those in medium crude oil (i.e., < C30) hydrocarbons) [8-10]. 

Combination of static subcritical water extraction and solid-phase microextraction Comparison of CHC1F2, N2O and CO2 extractants. CHC1 F2 gave highest recovery, methanol-modified CO2 gave 90% recovery Combination of supercritical fluid extraction with off-line Fourier transform infrared spectroscopy... 

McNally and Wheeler [364] used supercritical fluid extraction coupled to supercritical fluid chromatography to determine sulfonylurea herbicides in soil. Klatterback et al. [365,366] used supercritical fluid extraction with methanol-modified carbon dioxide followed by high-performance liquid chromatography with UV detection to determine sulfonylurea herbicides obtained on a Cis solid-phase extraction disc. Alternatively the determination was carried out by gas chromatography of the dimethyl derivatives of the sulfonylurea herbicides, employing an electron capture or a NP detector on the gas chromatograph. 

K. Jinno and M. Saito, Coupling of supercritical fluid extraction with chromatography, Anal. Sci., 7 361 (1991). 

X. Chaudot, A. Tambute and M. Caude, Comparison of supercritical fluid extraction with solvent sonication for chemical warfare agent determination in alkyd painted plates, J. High Resolut. Chromatogr., 21, 457-463 (1998). 

Supercritical fluid extraction with carbon dioxide has long been proposed as a method for the cleanup of soils, sediments and sludges that are contaminated Avith toxic substances. An attractive feature of this process is that very little solvent residue remains in the processed... 

Extraction can be carried out in several ways, including cold-pressing at temperatures not exceeding 45°C, pressing at higher temperatures, and/or solvent extraction. Solvent extraction is not favored for high-quality gourmet oils. Supercritical fluid extraction with carbon dioxide is an acceptable possibility, but there is no evidence that this technique is widely used for this purpose. A further possibility is to use enzymes to break down cell walls followed by extraction under the mildest possible conditions. 

Fig. 2 Gas chromatogram (BCD) resultant from the analysis of captafol residues in tomato, after supercritical fluid extraction with neat CO2 without further cleanup.

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