Subcritical fluid extraction

Soil leachates were analyzed for ametryn, prometryn, and terbuthylazine using 85-pm polyacrylate and 100-pm PDMS SPME fibers.The results obtained 

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Extraction of stevia sweeteners from dried leaves can be accomplished with acetonitrile in the presence of calcium carbonate solution (116) or with boiling water adjusted to pH 9.0 (107). Ahmed and Dobberstein (117) extracted stevioside and rebaudioside A and C from dried leaves of S. rebaudiana in a micro-Soxhlet apparatus. They observed that chloroform/methanol provided the best results, compared to chloroform or to chloroform/methanol/water. Extraction of stevioside, rebaudioside A and C, and dulcoside A can also be performed by subcritical fluid extraction using C02 and methanol as a modifier. Such an extraction technique has been gaining popularity as an analytical tool because it is rapid, simple, and less expensive in terms of solvent cost (110). Beverages, tabletop sweeteners, beverages containing pulp, and candies are prepared as indicated in Sec. I.C (110,115,118). 

Supercritical fluid extraction [153,154], accelerated solvent extraction [68] and subcritical fluid extraction [107,155] have been studied. To reduce the equipment cost and the analysis time in the extraction process and sample preconcentration, a solid-phase microextraction method was proposed by Pawliszyn and coworkers [156-158]. 

Edder, R, Staub, C., Veuthey, J.L., Pierroz, I., Haerdi, W., Subcritical fluid extraction of opiates in hair of drug addicts, J. Chromatogr. B., 658, 75-86, 1994. 

A relatively new technique utilizing subcritical fluid extraction (SFE) was developed for the analysis of opioids in hair by Edder et al. Hair samples were washed. 

Edder P, Staub C, Veuthey JL, Pierroz I, Haerdi W. Subcritical-fluid extraction of opiates in hair of drugs addicts. J Chromatogr B 1994 658 75-86. 

Accelerated solvent extraction (ASE), focused microwave soxhiet extraction (FMSE), immuno affinity cleanup (im-Cu), liquid-liquid extraction (LLE), low-temperature lipid precipitation (LTLP), matrix solid-phase dispersion (MSPD), microwave-assisted extraction (MAE), nanofiltration (NF), pressurized fluid extraction (PEE), single drop microextraction (SOME), solid-phase extraction (SPE), solid-phase microextraction (SPME), steam distillation (SD), stir bar sorptive extraction (SBSE), surpercritical fluid extraction (SFE), subcritical fluid extraction (ScFE), supported liquid membrane extraction (SLME), ultra-sonication (US), size exclusion chromatography (SEC), liquid chromatography-fraction collection (LC)... 

A, acaricide AV, avicide I, insecticide F, fungicide H, herbicide GR, growth regulator N, nematocide R, rodenticide US, ultrasonication LLE, liquid-liquid extraction CU, cleanup ImCU, immuno cleanup SPE, solid-phase extraction MSPD, matrix solid-phase dispersion SBSE, stir bar sorptive extraction SD, steam distillation FMSE, focused microwave Soxhiet extraction PFE, pressurized fluid extraction ASE, assisted solvent extraction ScFE, subcritical fluid extraction SFE, supercritical fluid extraction SEC, size-exclusion chromatography LC, liquid chromatography (fraction collection) LTLP, low temperature lipid precipitation. 

Veggi, P. C., Cavalcanti, R. N. Meireles, M. A. A. (2014). Production of phenolic-rich extracts from Brazilian plants using supercritical and subcritical fluid extraction Experimental data and economic evaluation. Journal of Eood Engineering, 31, 96-109. DOI 10.1016//.jfoodeng. 2014.01.027. 

In liquid-solid extraction (LSE) the analyte is extracted from the solid by a liquid, which is separated by filtration. Numerous extraction processes, representing various types and levels of energy, have been described steam distillation, simultaneous steam distillation-solvent extraction (SDE), passive hot solvent extraction, forced-flow leaching, (automated) Soxh-let extraction, shake-flask method, mechanically agitated reflux extraction, ultrasound-assisted extraction, y -ray-assisted extraction, microwave-assisted extraction (MAE), microwave-enhanced extraction (Soxwave ), microwave-assisted process (MAP ), gas-phase MAE, enhanced fluidity extraction, hot (subcritical) water extraction, supercritical fluid extraction (SFE), supercritical assisted liquid extraction, pressurised hot water extraction, enhanced solvent extraction (ESE ), solu-tion/precipitation, etc. The most successful systems are described in Sections 3.3.3-3.4.6. Other, less frequently... 

Boundaries in chromatography and extraction are blurring, as evident from the relation between GC, SFC and HPLC, the use of superheated/subcritical water for extraction and chromatography, and the role of enhanced fluidity solvents and pressurised fluid extractions [2]. Extraction is an extreme form of chromatography. Separation science recognises that there is unity in the... 

Although SFC fills a niche in what can be considered as a continuum of separation eluents from gases to liquids, it cannot claim a unique status subcritical water extraction (SWE, cf. Section 3.4.3) and pressurised fluid extraction (PFE, cf. Section 3.4.6) are other examples of eluents where altering the conditions cause a useful change in the solvation properties. 

S.B. Hawthorne, C.B. Grabanski, E. Martin and D.J. Miller, Comparison of Soxhlet extraction, pressurized liquid extraction, supercritical fluid extraction and subcritical water extraction for environmental solids recovery, selectivity and effects on sample matrix. J. Chromatogr.A 892 (2000) 421 133. 

Solvent extraction Microwave extraction Solid phase microextraction Subcritical water extraction Subcritical water extraction Supercritical fluid extraction... 

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... 

Chloropyritos metabolite Supercritical fluid extraction and subcritical water extraction [530]... 

For purposes of comparison, some supercritical fluid extraction processes have been calculated in which the extract is separated at the subcritical pressure p = 60 bar (Process 4). Such a process corresponds to that in Fig. 1 with the difference that a pump is employed to increase the pressure from state 1 to state 2, since the CO2 is cooled down to 17°C after separation, i.e. is present in the liquid state before the pressure is increased. Even for the most favourable variant with K = 0.062 DM/kg hop extract, the operating costs for this process are significantly higher than for processes employing supercritical separation. They can be reduced significantly by heat recovery with a heat pump as published by Sievers and Eggers 3. ... 

In this project, the feasibility of catalyst regeneration by supercritical fluid extraction was studied. A spent catalyst from an industrial naphtha hydrotreater was extracted with tetrahydrofuran, pyridine, carbon dioxide, and sulfur dioxide under subcritical and supercritical conditions. The coke reduction and changes in the catalyst pore characteristics were measured and to a limited extent the catalyst activity was evaluated. It is shown that by supercritical extraction, the coke content of spent hydrotreating catalysts can be reduced and the catalyst pore volume and surface area can be increased. 

Supercritical fluids, most commonly carbon(IV) oxide, occasionally modified by a small addition of a polar solvent (methanol, acetonitrile, or water). Supercritical fluid extraction (SEE) uses water as the most popular additive, because increasing the temperature from 50 to 400 °C at a pressure exceeding the critical level makes it possible to achieve transition of extractant from the subcritical to the supercritical state and leaching of the compoimds in the order of polar to moderately polar [86]. 

Since 1929, polychlorinated biphenyls (PCBs) have been produced and used as heat-transfer, hydraulic, and dielectric fluids. Because of their chemical and physical stability, PCBs have been found in many environmental samples. Generally, PCBs have been analyzed by GC with electron-capture detection. There are many reports on subcritical and supercritical fluid extraction of PCBs, but only a few on supercritical fluid separation of PCBs. 

Most of the data available in the literature are for subcritical conditions. Corrosion studies of iron alloys in supercritical water have not been reported. For supercritical fluid extraction and corrosion studies, a supercritical fluid reactor system for temperatures up to 530 C and pressures up to 300 atm was constructed. This system was used to determine the electrochemical behavior of type 304 stainless steel (304 S.S.), 316 S.S., 1080 carbon steel (1080 C.S.), and pure iron in supercritical water. 

King JW, Grabiel RD, Wightman JD. Subcritical water extraction of antho-cyanins from fruit berry substrates. In Brunner G, ed. Proceedings of the 6th International Symposium on Supercritical Fluids— Vol. 1, 2003 409-418. 

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