Supercritical fluid extraction with chromatography

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

Analytical Supercritical Fluid Extraction and Chromatography Supercritical fluids, especially CO9, are used widely to extrac t a wide variety of solid and hquid matrices to obtain samples for analysis. Benefits compared with conventional Soxhlet extraction include minimization of solvent waste, faster extraction, tunabihty of solvent strength, and simple solvent removal with minimal solvent contamination in the sample. Compared with high-performance liquid chromatography, the number of theoretical stages is higher in... 

B. Wenclawiak (Ed.), Analysis with Supercritical Fluids Extraction and Chromatography, Springer-Verlag, Berlin (1992). 

Henry, M.C. andYonker, C.R., Supercritical fluid chromatography, pressurized hquid extraction, and supercritical fluid extraction. Anal. Chem., 78, 3909, 2006. Wenclawiak, B., Ed., Analysis with Supercritical Fluids Extraction and Chromatography, Springer Verlag, Berlin, 1992. 

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],... 

As discussed in section 5.6.1.4 a solid phase carbon trap has been used in conjunction with supercritical fluid extraction liquid chromatography for the simultaneous determination of organochlorine insecticides, polychlorobiphenyls, polychlorodibenzo-p-dioxins and polychlorodibenzofurans in soils [19]. 

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],... 

B. WENCLAWIAK, "Analysis with Supercritical Fluids Extraction and Chromatography", Springer-Verlag, Heildeberg, 1992. 

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). 

X. Lou, H.-G. Janssen and C. A. Cramers, Investigation of parameters affecting the online combination of supercritical fluid extraction with capillary gas chromatography , J. Chromatogr. 750 215-226 (1996). 

E. S. Francis, M. Wu, P. B. Farnsworth and M. L. Lee, Supercritical fluid extraction/gas chromatography with thermal desorption modulator interface and nitro-specific detection for the analysis of explosives , J. Microcolumn Sep. 7 23 -28 (1995). 

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. 

Oudsema, J.W. and Poole, C.F. (1992) On-line supercritical fluid extraction and chromatography of organotins with packed microbore columns and formic acid modified carbon dioxide. Fresenius J. Anal. Chem., 344, 426-434. 

Solubility Parameters of the Most Common Fluids for Supercritical Fluid Extraction and Chromatography Solubility Parameters of Supercritical Fluids Solubility Parameters of Liquid Solvents Instability of Modifiers Used with Supercritical Fluids... 

The following table provides the solubility parameters, 8, for the most common fluids and modifiers used in supercritical fluid extraction and chromatography. The data presented in the first table are for carrier or solvent supercritical fluids at a reduced temperature, T of 1.02 and a reduced pressure, P of 2. These values were calculated with the equation of Lee and Kesler.1 2 The data presented in the second table are for liquid solvents that are potential modifiers.3... 

In this table, we provide solubility parameters for some liquid solvents that can be used as modifiers in supercritical fluid extraction and chromatography. The solubility parameters (in MPa1/2) were obtained from reference 3, and those in cal1/2cm 3/2 were obtained by application of Equation 4.1 for consistency. It should be noted that other tabulations exist in which these values are slightly different, since they were calculated from different measured data or models. Therefore, the reader is cautioned that these numbers are for trend analysis and separation design only. For other applications of cohesive parameter calculations, it may be more advisable to consult a specific compilation. This table should be used along with the table on modifier decomposition, since many of these liquids show chemical instability, especially in contact with active surfaces. 

V. J. Krukonis, Processing with supercritical fluids, overview and applications, in B. A. Charpentier and M. R. Sevenants, eds.. Supercritical Fluid Extraction and Chromatography, Techniques and Applications, Amer. Chem. Soc., Washington, D. C., 1988, pp. 26 3. 

The combination of supercritical fluid chromatography and supercritical fluid extraction with standard GC and LC techniques offers an attractive extension to conventional procedures (Greibrokk 1992), and this will probably receive increased attention in the analysis of samples containing a large number of components. 

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. 

Off-line supercritical fluid extraction, ultrasonic supercritical fluid extraction, and on-line supercritical fluid extraction-gas chromatography methodologies that have been developed specifically for analytical sample preparation and analysis are described. These methods offer the potential for extraction rate increases of over an order of magnitude, and are compatible with online analysis which provides the basis for automated sample preparation and analysis. These methods are particularly useful for small sample sizes or trace levels of analytes, and have been demonstrated to operate quantitatively. Combined ultrasonic supercritical fluid extraction can further enhance extraction rates from macro-porous materials by inducing convection through internal pores. The apparatus and instrumentation are described in detail and several examples are presented illustrating the applicability of these methodologies. 

Off-line supercritical fluid extraction, simultaneous ultrasonic supercritical fluid extraction, and on-line supercritical fluid extraction-gas chromatography have been described. These analytical supercritical fluid extraction methods provide the potential for very rapid extraction rates and compatibility with on-line analytical methods. Extraction rate increases of over an order of magnitude compared to Soxhlet methods have been demonstrated and even greater increases seem feasible. Optimization of fluid solvating conditions also provides the potential for selective fractionation of specific analytes. The application of ultrasound during supercritical fluid extraction provides an efficient... 

There are many literature reports on industrial uses of supercritical fluids, and many patents have been issued for various uses of supercritical fluids as solvents in extraction processes. Randall (1) prepared an excellent review on the uses and patents issued up to 1982 in the area of supercritical fluid extraction and chromatography. Many of these applications deal with natural products such as flavors, fragrances, oils and fats, or the removal of unwanted components from natural materials such as caffeine from coffee or tea and nicotine from tobacco. 

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