Supercritical fluid extraction-liquid chromatography

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]. 

D. Supercritical-Fluid Extraction-Liquid Chromatography Assays... 

Vela, N.P. and Caruso, J.A. (1996) Trace metal speciation via supercritical fluid extraction-liquid chromatography-inductively coupled plasma mass spectrometry. /. Anal. At. 

Shimmo, M., A. Piia, K. Hartonem, et al. 2004. Identification of organic compounds in atmospheric aerosol particles by on-line supercritical fluid extraction-liquid chromatography-gas chromatography-mass spectrometry./. Chromatogr. A 1022 151-159. 

Roston, D.A. Sun, J.J. Collins, P.W. Perkins, W.E. Tremont, S.J. Supercritical fluid extraction-liquid chromatography method development for a polymeric controlled-release drug formulation. J. Pharm. Biomed. Anal. 1995, 13 (12), 1513-1520. 

Shimmo, M., Adler, H., Hyotylainen, T., Hartonen, K., Kulmala, M., and Riekkola, M. L., Analysis of particulate polycyclic aromatic hydrocarbons by on-line coupled supercritical fluid extraction-liquid chromatography-gas chromatography-mass spectrometry, Atmos. Environ., 36, 2985-2995, 2002. 

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... 

The single largest use of ammonia is its direct apphcation as fertdizer, and in the manufacture of ammonium fertilizers that have increased world food production dramatically. Such ammonia-based fertilizers are now the primary source of nitrogen in farm soils. Ammonia also is used in the manufacture of nitric acid, synthetic fibers, plastics, explosives and miscellaneous ammonium salts. Liquid ammonia is used as a solvent for many inorganic reactions in non-aqueous phase. Other apphcations include synthesis of amines and imines as a fluid for supercritical fluid extraction and chromatography and as a reference standard in i N-NMR. 

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. 

KE Lainta, CM Wai, CR Yonker, RD Smith. Extraction of metal ions from liquid and solid materials by supercritical carbon dioxide. Anal Chem 64 2875-2878, 1992. Y Lin, NG Smart, CM Wai. Supercritical fluid extraction and chromatography of metal chelates and organometaUic compounds. Trends Anal Chem 14 123-133, 1995. 

Unfortunately, not much experimental work has been carried out on the combination of Supercritical fluid extraction and liquid chromatography systems (43, 44). One of the reasons for this arises from the difficulties in achieving compatibility between the extraction solvent and the FC mobile phase. Baseline perturbations have been... 

Y. Hirata and Y. Okamoto, Supercritical fluid extraction combined with microcolumn liquid chromatography for the analysis of polymer additives , J. Microcolumn Sep. 1 46-50(1989). 

One example of normal-phase liquid chromatography coupled to gas chromatography is the determination of alkylated, oxygenated and nitrated polycyclic aromatic compounds (PACs) in urban air particulate extracts (97). Since such extracts are very complex, LC-GC is the best possible separation technique. A quartz microfibre filter retains the particulate material and supercritical fluid extraction (SPE) with CO2 and a toluene modifier extracts the organic components from the dust particles. The final extract is then dissolved in -hexane and analysed by NPLC. The transfer at 100 p.1 min of different fractions to the GC system by an on-column interface enabled many PACs to be detected by an ion-trap detector. A flame ionization detector (PID) and a 350 p.1 loop interface was used to quantify the identified compounds. The experimental conditions employed are shown in Table 13.2. 

Henry, M.C. and Yonker, C.R., Supercritical fluid chromatography, pressurized liquid extraction, and supercritical fluid extraction. Anal. Chem., 78, 390, 2006. 

High performance liquid chromatography (HPLC) has been by far the most important method for separating chlorophylls. Open column chromatography and thin layer chromatography are still used for clean-up procedures to isolate and separate carotenoids and other lipids from chlorophylls and for preparative applications, but both are losing importance for analytical purposes due to their low resolution and have been replaced by more effective techniques like solid phase, supercritical fluid extraction and counter current chromatography. The whole analysis should be as brief as possible, since each additional step is a potential source of epimers and allomers. 

Foreign uranium resources, 17 522 Foreman and Veatch cell, 9 664 Forensic analysts, certification of, 12 95 Forensic biology, 12 102-104 Forensic chemistry, 12 89-104 physical evidence in, 12 90-95 Forensic laboratories, local and state, 12 98 Forensics, liquid chromatography applications, 6 465 Forensic science laboratories, 12 95 Forensic science, supercritical fluid extraction in, 24 14 Forensic testing, 12 95-104 Forensic toxicology, interpretation of results in, 12 98... 

Reindt and Hoffler [50] optimized parameters in the supercritical fluid extraction of polyaromatic hydrocarbons from soil. These workers used carbon dioxide -8% methanol for extraction and obtained 88-101% recovery of polyaromatic hydrocarbons in the final high-performance liquid chromatography. 

Fernandez et al. [9] used supercritical fluid extraction combined with ion pair liquid chromatography to determine quaternary ammonium in digested sludges and marine sediments. Carbon dioxide modified with 30% methanol was used as the extractant at an operating pressure of 380atm. Between 0.2 and 3.7g kg-1 surfactant was found in Swiss works effluent sludges, determined with a relative standard deviation of 7%. 

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],... 

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],... 

Supercritical fluid extraction followed by high-performance liquid chromatography-mass spectrometry has been used to determine Atrazine and its metabolites in soil [22],... 

Spell JC, Srinivasan K, Stewart JT, Bartlett MG. 1998. Supercritical fluid extraction and negative ion electrospray liquid chromatography tandem mass spectrometry analysis of phenobarbital, butalbital, pentobarbatal and thiopentoal in human serum. Rapid Commun Mass Spectrom 12 890. 

CZE = capillary zone electrophoresis EC = electrochemical detector GC = gas chromatography HCD = Hall conductivity detector HPLC = high performance liquid chromatography IDMS = isotope dilution mass spectrometry MS = mass spectrometry RSD = relative standard deviation SEE = supercritical fluid extraction SPE = solid phase extraction UV = ultraviolet absorbance detection... 

Tire aqueous or organic extract obtained at this point may be a very dilute solution containing interfering compounds and making it difficult to determine trace level concentrations of the analyte(s) of interest. To reduce interferences and concentrate the analyte(s), the primary sample extract is furiher subjected to various types of sample cleanup procedures such as conventional liquid-liquid partitioning, solid-phase extraction, matrix solid-phase dispersion, online trace enrichment, liquid chromatography, online dialysis and subsequent trace enrichment, and supercritical fluid extraction. In most cases some of Urese procedures are used in combination to obtain highly purified extracts. 

The primary sample extract is subsequently subjected to cleanup using several different approaches including conventional liquid-liquid partitioning, solid-phase extraction, liquid chromatography, immunoaffinity chromatography, and supercritical fluid extraction cleanup. In some instances, more than one of these purification procedures can be applied in combination for better results. 

Supercritical fluid extraction, offers also some desirable advantages including processing at low temperature, recovery of a solvent-free extract, and rapid extraction. However, very limited studies have been published on the use of supercritical fluids for the isolation of corticosteroids from biological samples. A combination of supercritical fluid extraction and liquid chromatography has been employed for the detection of dexamethasone residues in bovine tissues (448). 

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