Thermal chromatography

Besides simple alkyl-substituted sulfoxides, (a-chloroalkyl)sulfoxides have been used as reagents for diastereoselective addition reactions. Thus, a synthesis of enantiomerically pure 2-hydroxy carboxylates is based on the addition of (-)-l-[(l-chlorobutyl)sulfinyl]-4-methyl-benzene (10) to aldehydes433. The sulfoxide, optically pure with respect to the sulfoxide chirality but a mixture of diastereomers with respect to the a-sulfinyl carbon, can be readily deprotonated at — 55 °C. Subsequent addition to aldehydes afforded a mixture of the diastereomers 11A and 11B. Although the diastereoselectivity of the addition reaction is very low, the diastereomers are easily separated by flash chromatography. Thermal elimination of the sulfinyl group in refluxing xylene cleanly afforded the vinyl chlorides 12 A/12B in high chemical yield as a mixture of E- and Z-isomers. After ozonolysis in ethanol, followed by reductive workup, enantiomerically pure ethyl a-hydroxycarboxylates were obtained. 

We report here the results of our recent studies of poly(alkyl/arylphosphazenes) with particular emphasis on the following areas (1) the overall scope of, and recent improvements in, the condensation polymerization method (2) the characterization of a representative series of these polymers by dilute solution techniques (viscosity, membrane osmometry, light scattering, and size exclusion chromatography), thermal analysis (TGA and DSC), NMR spectroscopy, and X-ray diffraction (3) the preparation and preliminary thermolysis reactions of new, functionalized phosphoranimine monomers and (4) the mechanism of the polymerization reaction. 

Butenes were subjected to photosensitized reaction with molecular oxygen in methanol. 1-Butene proved unreactive. A single hydroperoxide, l-butene-3-hydroperoxide, was produced from 2-butene and isolated by preparative gas chromatography, Thermal and catalyzed decomposition of pure hydroperoxide in benzene and other solvents did not result in formation of any acetaldehyde or propionaldehyde. The absence of these aldehydes suggests that they arise by an addition mechanism in the autoxidation of butenes where they are important products. l-Butene-3-hydroperoxide in the absence of catalyst is converted predominantly to methyl vinyl ketone and a smaller quantity of methyl vinyl carbinol —volatile products usually not detected in important quantities in the autoxidation of butene. 

For the analyses discussed here, we have used Gas Chromatography-Thermal Energy Analysis (GC-TEA ) and/or High Pressure Liquid Chromatography-Thermal Energy Analysis (HPLC-TEA). The TEA has been used as the detector... 

His interests have included such areas of analytical chemistry as separation science, supercritical fluid extraction, chromatography, thermal analysis, and mathematical analysis of the chemical data (chemometrics). 

Belcher, R., Majer, J. R., Stephen, W. I., Thomson, I. J., Uden,P. C. The gas chromatography, thermal analysis and mass spectrometry of fluorinated lead (3-diketones. Determination of traces of lead by the intergrated ioncurrent technique. Anal. Chim. Acta 50, 423 (1970). 

Table 2. Applications of gas chromatography-thermal energy analyser (GC-TEA) to explosive analysis...

Supercritical fluid chromatography-thermal energy analyser Supercritical fluids are produced by heating a gas above its critical temperature or compressing a liquid above its critical pressure. In SFC, the sample is carried through a separating column by a supercritical fluid (typically C02) that is used as mobile... 

Soot samples were obtained by use of a nitrogen-quench, porous-walled probe and Nucleopore filters (7). Gas phase hydrocarbons were collected by the porous probe as batch samples and analyzed by standard FID gas chromatography. Thermal measurements included gas temperature by radiation-corrected bare wire thermocouple, and soot temperature by Kurlbaum reversal (9, 10) and two color pyrometry (11). 

MEVIS/IPM, membrane inlet mass spectrometry/isotope pairing method TCD, gas chromatography-thermal conductivity detector AIT, acetylene inhibition technique IPM, isotope pairing method with isotope ratio mass spectrometry MIMS, membrane inlet mass spectrometry Stoichiometery, benthic flux DICiDIN stoichiometry MIMS + N03, membrane inlet mass with N03 amendment 15N2 production, 15N03 or 15NH4 conversion to 15N2. 

Billedeau SM, Thonpson HC Jr, Miller BJ, et al. 1986. Volatile N-nitrosamines in infant pacifiers sold in the United States as determined by gas chromatography/thermal energy analysis. J Assoc Off Anal Chem 69 31-... 

Products were collected and weighed to determine a mass balance. Except for two experiments, in which the volume of gases exceeded the capacity of the gas collection system and the last portion was vented, the mass balance ranged from 95 to 98% ( 14). We measured C, H, N, and acid-evolved CO2 content for all retorted shales and for some burnt shales from the cracking experiments. Oils were analyzed for C, H, and N. Gases were analyzed by gas chromatography (thermal conductivity detector for h2> CO2 N2, and CH4 flame ionization detector for... 

Maddock, J. Lewis, P.A. Woodward, A. Massey, P.R. Kennedy, S. Determination of isosorbide dinitrate and its mononitrate metabolites in human plasma by high-performance liquid chromatography-thermal energy analysis. J.Chromatogr., 1983, 272, 129-136... 

Mola, M., G. Lionetti, and A. Nunziata Determination of tobacco specific nitrosamines in mainstream smoke by gas chromatography-thermal energy analysis 57th Tobacco Science Research Conference, Program Booklet and Abstracts, Vol. 57, Paper No. 10, 2003, p. 23. 

Theiler, R., K. Sato, T. Aspelund, and A. Miller Inhibition of A-nitrosamine formation in a cured ground pork belly model system J. Food Sci. 49 (1984) 341-344. Thompson, H.C. Jr, S.M. BUledeau, B.J. Miller, E.B. Hansen Jr, J.P. Freeman, and M.L. Wind Determination of A-nitrosamines and A-nitrosamine precursors in rubber nipples from baby pacifiers by gas chromatography thermal energy analysis J. Toxicol. Env. Hlth. 13 (1984) 615-632. 

The simple broad-band irradiation with a medium-pressure mercury lamp delivers, after chromatography, thermal isomerisation and purification, chole-calciferol in a yield of only 9 %, based on 7-dehydrocholesterol. The greatest losses result fi"om the formation of tachysterol3 (Fig. 7.44). [93]... 

NPYR, N-nitrosopyrrolidine NPRO, N-nitrosoproline NTHZ, N-nitroso-thiazolidine NPIP, N-nitrosopiperidine NDEA, N-nitrosodiethyl-amine GC-TEA, gas chromatography - thermal energy analyzer NMOR, N-nitrosomorpholine NDPA, N-nitrosodipropylamine. 

As is the case with all detectors for gas chromatography, thermal control of a FID is an important requirement. The block enclosing the detector should be heated above the temperature of the column to avoid the condensation of sample components in the transfer lines and jet. In addition, the temperature must be... 

As in gas chromatography, thermal degradation of components can occur in GCMS. This degradation is frequently catalyzed by active sites somewhere in the chromatographic system. 

Keywords SIC nanowires. Formation mechanism. Gas chromatography. Thermal evaporation... 

Both infrared and Raman spectroscopy are extremely powerful analytical techniques for both qualitative and quantitative analysis. However, neither technique should be used in isolation, since other analytical methods may yield important complementary and/or confirmatory information regarding the sample. Even simple chemical tests and elemental analysis should not be overlooked and techniques such as chromatography, thermal analysis, nuclear magnetic resonance, atomic absorption spectroscopy, mass spectroscopy, ultraviolet and visible spectroscopy, etc., may all result in useful, corroborative, additional information being obtained. 

ASTM F 151-97. Standard test method for residual solvents in flexible barrier materials. Withdrawn 2004. ISO 17052-07. Rubber, raw — Determination of residual monomers and other volatile low-moleoular-mass compounds by capillary gas chromatography — Thermal desorption (dynamic headspace) method. 

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