Supercritical fluid extraction solvents

Separation Techniques. Current methods for separating fatty acids are by solvent crystaUi2ation or by the hydrophili2ation process. Other methods that have been used in the past, or perhaps could be used in the future, are panning and pressing, solvent extraction, supercritical fluid extraction, the use of metal salts in assisting in separation, separations using urea complexes, and adsorption/desorption. 

Extraction of neonicotinoid residues from soil is much more difficult than their extraction from plant or water samples. Soil residues could exist as bound residue . Various extraction methods such as organic solvent extraction, supercritical fluid extraction (SEE), Soxhlet extraction and sonication have been used. Some extraction methods are described in the following. 

Extraction of solid samples Homogenization extractions Sonication extractions Microwave assisted extractions Soxhlet extractions Accelerated solvent extractions Supercritical fluid extractions Extraction of liquid samples Liquid-liquid extractions Solid phase extractions (SPE)... 

Extraction of phthalate esters from sohd samples is mostly performed by Soxhlet extraction or sonication. In addition, microwave assisted solvent extraction, supercritical fluid extraction, and ASE are used to extract phthalate esters from environmental solid matrices (see Table 28.8). 

See also Countercurrent Chromatography Solvent Extraction with a Helical Column. Extraction Solvent Extraction Principles Solvent Extraction Multistage Countercurrent Distribution Microwave-Assisted Solvent Extraction Supercritical Fluid Extraction. 

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... 

Saponins from plant materials can be extracted using different techniques and solvents. The conventional techniques for saponin extraction used soxhlet, liquid-liquid or solid-liquid extraction (Berhow et al. 2002 Hassan et al. 2010a, b). These methods consume a lot of solvent, time and may lead to potentially deleterious degradation of labile compounds (Kerem et al. 2005). Therefore, in recent years, new extraction techniques include accelerated solvent extraction, supercritical fluid extraction, solid-phase microextraction, sonication, extraction with supercritical or subcritical water, and microwave-assisted extraction have been developed and are considered to be more efficient than the conventional methods (Wu et al. 2001 Kerem et al. 2005 Ligor et al. 2005 Gii lii-Ustundag and Mazza 2007). Ultrasonication-assisted extraction of ginseng saponins was about three times faster than the liquid-liquid extraction and can be carried out at lower temperature (Wu et al. 2001). Kerem et al. (2005) reported that methanol- microwave assisted method to extract saponin of chiclqtea proved to be faster and more efficient than soxhlet extraction. 

Key words Traditional Chinese medicines. Extraction, Solvent extraction. Supercritical fluid extraction... 

Supercritical Fluid Extraction. Supercritical fluid (SCF) extraction is a process in which elevated pressure and temperature conditions are used to make a substance exceed a critical point. Once above this critical point, the gas (CO2 is commonly used) exhibits unique solvating properties. The advantages of SCF extraction in foods are that there is no solvent residue in the extracted products, the process can be performed at low temperature, oxygen is excluded, and there is minimal protein degradation (49). One area in which SCF extraction of Hpids from meats maybe appHed is in the production of low fat dried meat ingredients for further processed items. Its apphcation in fresh meat is less successful because the fresh meat contains relatively high levels of moisture (50). 

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... 

Sun M and Temelli F. 2006. Supercritical carbon dioxide extraction of carotenoids from carrot using canola oil as a continuous co-solvent. J Supercrit Fluids 37(3) 397-408. 

Vasapollo G, Longo L, Rescio L and Ciurlia L 2004. Innovative supercritical CO2 extraction of lycopene from tomato in the presence of vegetable oil as co-solvent. J Supercrit Fluids 29(1-2) 87-96. 

Other useful enriched natural materials such as paprika extract are predominantly produced through solvent-extraction methods using solvents or supercritical fluids like CO2. 

Besides solvent extraction, supercritical carbon dioxide has been applied to extract isoflavones (Rostagno et al., 2002). Due to the hydrophobicity of carbon dioxide, supercritical fluid extraction is more suitable for extracting nonpolar aglycones than polar glycosides of isoflavones, and may not be quantitative. 

Caffeine is a naturally occurring substance found in the leaves, seeds, or fruits of more than 60 plants. These include coffee and cocoa beans, kola nuts, tea leaves, guarana (Paulinia cupana) and Paraguay tea. Thus it is present naturally in many beverages, such as coffee, tea, and cola drinks, or is added in small amounts (up to 200 ppm) in some soft drinks and in foods such as chocolate. Caffeine is obtained by solvent or supercritical fluid extraction from green coffee beans, mainly during the preparation of decaffeinated coffee. 

U. Ullsten and K. E. Markides, Automated on-line solid phase adsorption/supercritical fluid extraction/supercritical fluid chromatography of analytes from polar solvents , J. Micmcolumn Sep. 6 385-393 (1994). 

This chapter covers techniques for the extraction of semivolatile organics from solid matrices. The focus is on commonly used and commercially available techniques, which include Soxhlet extraction, automated Soxhlet extraction, ultrasonic extraction, supercritical fluid extraction (SFE), accelerated solvent extraction (ASE), and microwave-assisted extraction (MAE). The underlying principles, instrumentation, operational procedures, and selected applications of these techniques are described. In a given application, probably all the methods mentioned above will work, so it often boils down to identifying the most suitable one. Consequently, an effort is made to compare these methodologies. 

Supercritical fluid extraction Supercritical fluid extraction (SFE) uses compressed gas as the extraction medium and circumvents some of the problems associated with the use of classical separation techniques involving organic solvents. This technique combines features of distillation (i.e., separation because of differences in component volatiles) and liquid extraction (i.e., separation of components that exhibit little difference in their relative volatilities or that are thermally labile). A number of gases, when compressed isothermally at a temperature greater than their critical temperature and to pressures greater than their critical pressure, exhibit an enhanced solvating power (136), which has been known since the nineteenth century (137, 138), but its actual applications did not come to practice until the late twentieth century. 

Sample preparation represents a formidable challenge in the chemical analysis of the real-world samples. Not only is the majority of total analysis time spent in sample preparation, but also it is the most error-prone, least glamorous, and the most labor-intensive task in the laboratory. The components to be separated from the matrix are usually taken up with an auxiliary substance such as a carrier gas, an organic solvent, or an adsorbent. These separation processes can be regarded as extraction procedures (i.e., liquid-liquid extraction, liquid-solid extraction, Soxhlet extraction, solid-phase extraction, supercritical fluid extraction, solid-phase microextraction, etc.). 

The impact of the extraction conditions using various solvents on the recoveries has never been studied in detail, and the results have never been compared. The introduction of modern extraction methods, such as microwave-assisted extraction, supercritical fluid extraction, and solid-phase extraction, probably will improve the efficiency of extraction, even in the instance of unstable pigments and pigment mixtures. The majority of TLC separations were carried out on traditional silica layers. As the chemical structures and, consequently, the retention characteristics of pigments are highly different, a wide variety of eluent systems has been employed for their separation, consisting of light petroleum, ethyl formate, ethyl acetate, benzene, toluene, chloroform, methanol, n-butanol, formic or acetic acid, and so forth. 

Membrane filtration is a widely used but narrowly understood technique for sample preparation in chemical analysis. This section has the goal of providing some basic information to aid in the use of filtration tools with drug impurities. Many of the common sample preparation approaches described elsewhere in this chapter, such as liquid extraction, supercritical fluid extraction, and accelerated solvent extraction are effective at removing the dissolved analytes of interest from the matrix while leaving behind many poorly soluble or insoluble matrix components. In contrast, filtration is designed to remove these suspended particles from the extract prior to subsequent analytical steps. Unfiltered samples can destroy the performance of a downstream analytical technique such as HPLC or optical spectroscopy.68,69... 

Miege, C., Dugay, J., and Hennion, M.-C., Optimization and validation of solvent and supercritical-fluid extractions for the trace-determination of polycyclic aromatic hydrocarbons in sewage sludges by liquid chromatography coupled to diode-array and fluorescence detection, J. Chromatogr. A, 823, 219-230, 1998. 

Saim, N., Dean, J. R., Abdullah, M. P., and Zakaria, Z., Extraction of polycyclic aromatic hydrocarbons from contaminated soil using Soxhlet extraction, pressurized and atmosphereic microwave-assisted extraction, supercritical fluid extraction and accelerated solvent extraction,... 

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