Supercritical fluid extraction derivatization

FIG. 17 Ion pair/supercritical fluid extraction (SFE) and derivatization gas chromatography-mass-spectrometry (GC-MS). 

Starting with a description of the analytical challenge in Chapter 19, the third part, which is devoted to analytical attitudes, proceeds with a detailed description in Chapter 20 of modern sample preparation procedures including solid-phase extraction, matrix solid-phase dispersion, use of restricted-access media, supercritical fluid extraction, and immunoaffinity cleanup. Flexible derivatization techniques including fluorescence, ultraviolet-visible, enzymatic, and photochemical derivatization procedures are presented in Chapter 21. 

Analytes can be separated from complex matrices by sample preparation techniques that include liquid extraction, supercritical fluid extraction, and solid-phase extraction. Dilute ionic analytes can be preconcentrated by adsorption onto an ion-exchange resin. Nonionic analytes can be concentrated by solid-phase extraction. Derivatization transforms the analyte into a more easily detected or separated form. 

Several researchers have combined the separating power of supercritical fluid chromatography (SFC) with more informative spectroscopic detectors. For example, Pinkston et. al. combined SFC with a quadrupole mass spectrometer operated in the chemical ionization mode to analyze poly(dimethylsiloxanes) and derivatized oligosaccharides (7). Fourier Transform infrared spectroscopy (FTIR) provides a nondestructive universal detector and can be interfaced to SFC. Taylor has successfully employed supercritical fluid extraction (SFE)/SFC with FTIR dectection to examine propellants (8). SFC was shown to be superior over conventional gas or liquid chromatographic methods. Furthermore, SFE was reported to have several advantages over conventional liquid solvent extraction (8). Griffiths has published several... 

Field, J.A., D.J. Miller, T.M. Field, S.B. Hawthorne, and W. Giger. 1992. Quantitative determination of sulfonated aliphatic and aromatic surfactants in sewage sludge by ion-pair/supercritical fluid extraction and derivatization gas chromatography / mass spectrometry. Anal. Chem. 64, 3161-3167. 

Cai, Y., Alzaga, R. and Barjona, J.M. (1994) In situ derivatization and supercritical fluid extraction for the simultaneous determination of butyltin and phenyltin compounds in sediment. Anal. Chem., 66, 1161-1167. 

In situ derivatization reactions prior to SFE with C02 Sequential supercritical fluid extraction (SSFE) for estimating the availability of PAHs in a sohd... 

Chlorinated phenolic compounds in air-dried sediments collected downstream of chlorine-bleaching mills were treated with acetic anhydride in the presence of triethylamine. The acetylated derivatives were removed from the matrix by supercritical fluid extraction (SEE) using carbon dioxide. The best overall recovery for the phenolics was obtained at 110°C and 37 MPa pressure. Two SEE steps had to be carried out on the same sample for quantitative recovery of the phenolics in weathered sediments. The SEE unit was coupled downstream with a GC for end analysis . Off-line SEE followed by capillary GC was applied in the determination of phenol in polymeric matrices . The sonication method recommended by EPA for extraction of pollutants from soil is inferior to both MAP and SEE techniques in the case of phenol, o-cresol, m-cresol and p-cresol spiked on soil containing various proportions of activated charcoal. MAP afforded the highest recoveries (>80%), except for o-cresol in a soil containing more than 5% of activated carbon. The SEE method was inefficient for the four phenols tested however, in situ derivatization of the analytes significantly improved the performance . 

Wang SM, Giang YS, Ling YC. Simultaneous supercritical-fluid extraction and chemical derivatization for the gas chromatographic-isotopic dilution mass spectrometric determination of amphetamine and methamphetamine in urine. J Chromatogr B 2001 759 17-26. 

Extraction with HCl/toluene, derivatization with NaBEt4, capillary GC followed by FPD Supercritical fluid extraction (COj and methanol), Grignard derivatization, capillary GC followed by FPD... 

Analysis of chlorophenolic compounds in sediment samples has been carried out by in situ acetylation followed by solvent extraction (Xie et al. 1985) or by combined supercritical fluid extraction with carbon dioxide and derivatization (Lee et al. 1992). 

Hawthorne, S.B., D.J. Miller, D.E. Nivens, and D.C. White. 1992. Supercritical fluid extraction of polar analytes using in situ chemical derivatization. Anal. Chem. 64 405-412. 

Lee, H.-B., T.E. Peart, and R.L. Hong-You. 1992. In situ extradion and derivatization of pentachlorophenol and related compounds from soils using a supercritical fluid extraction system. J. Chromatogr. 605 109-113. 

A supercritical fluid extraction (SFE) method for analysis of CO2 extractables in cranberry seeds was investigated. The SFE operating conditions were optimized to maximize the extraction yields. Extraction yields obtained by SFE were comparable to conventional Soxhlet extraction. The extracts were derivatized and then analyzed by GC-MS. The extracts obtained via hexane and CO2 mostly contained methylated fatty acids. Linoleic acid and palmitic acid were the major compounds extracted. 

Ashraf-Khorrasani, M. Ude M. Doane-Weideman, T. Tomczak, J. Taylor, L. T. "Comparison of Gravimetry and Hydrolysis/ Derivatization/ Gas Chromatography-Mass Spectrometry for Quantitative Analysis of Fat from Standard Reference Infrnt Formula Powder Using Supercritical Fluid Extraction", J. Agric. Food Chem., 2002,50,1822. 

Hills et al. (1991) applied simultaneous supercritical fluid extraction to roasted coffee beans. This technique can be used with or without a derivatizing reagent In a dissociative mechanism, the adsorbed analyte must first desorb from a matrix active site and be dissolved in the supercritical fluid and then react to form the less polar derivative, which favors solvation in the supercritical carbon dioxide. In the associative mechanism, derivatization occurs while the analyte is adsorbed on the active site of the matrix. Reaction with the adsorbed analyte results in the desorption of the non-polar derivative into the supercritical fluid . Thus 2-hexenedioic acid (E.49) was identified for the first time as a native compound (without the use of a derivatizing agent). Benzenic and furanic compounds and caffeine were also identified. 

Ca. 3.5 g sediment were extracted by supercritical fluid extraction (CO2 and 20% methanol) after HCl addition. The extraction recovery for TBT (verified with a TBT-spiked sediment) was (82 + 6)%. Grignard derivatization was performed, using 2 mol L EtMgCl in tetrahydrofuran. Separation was by CGC (column of 30 m length, internal diameter of 0.25 mm, DB-5 as stationary phase, 0.1 pm film thickness He as carrier gas at 2 mL min injector temperature at 40 °C column temperature ranged from 40 to 290 °C). Detection was FPD (temperature of 225 °C). Calibration was carried out with butyltin chloride calibrants calibration graph and standard additions of tripropyltin as internal standard. 

See also. Clinical Analysis Sample Handling. Derivatization of Analytes. Extraction Solvent Extraction Principles Supercritical Fluid Extraction Solid-Phase Extraction. Lipids Overview. 

Derivatization may, in certain cases, be effected within the injection port of a GC-MS system. An ion pair/supercritical fluid extraction and injection port derivatization process has been presented as a method for the quantitative determination of aromatic and aliphatic sulfonated surfactants in sewage sludge by GC-MS with SIM (Figure 2). 

See also Atomic Absorption Spectrometry Principles and Instrumentation. Atomic Emission Spectrometry Inductively Coupled Plasma. Cosmetics and Toiletries. Derivatization of Analytes. Electrophoresis Is-otachophoresls. Environmental Analysis. Enzymes Overview. Extraction Supercritical Fluid Extraction Solid-Phase Extraction Solid-Phase Microextraction. Ion Exchange Ion Chromatography Applications. Liquid Chromatography Reversed Phase Liquid Chromatography-Mass Spectrometry. Nuclear Magnetic Resonance Spectroscopy - Applicable Elements Carbon-13 Phosphorus-31. Perfumes. 

Given the variety of explosives, it is no surprise that chromatography is central to their analysis. Techniques that are or have been used include TLC, GC, HPLC, ion chromatography, CE, MEKC, supercritical fluid extraction, and size exclusion chromatography. Samples can be prepared for chromatographic analysis with simple solvents using water, acetone, and the like. SPME is also used to preconcentrate samples, particularly when the explosives must be extracted from an aqueous environment. SPME can be adapted to HPLC to avoid thermal degradation issues that commonly arise in explosives. Another approach is to derivatize the explosives directly on the fiber such that the derived substance can be analyzed by means of GC. ... 

While liquid-liquid, headspace, and sorbent-based extractions are perhaps the most commonly nsed and pnbhshed sample preparation techniqnes for GC, there are numerous additional techniques to consider. While we do not attempt to fully describe every technique that has ever been nsed, the techniques described below are certainly of importance in the arsenal of sample preparation techniques for GC. These include supercritical-fluid extraction, accelerated solvent extraction, microwave-assisted extraction, pyrolysis, thermal desorption, and membrane-based extractions, pins comments on antomation and derivatization. 

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