Gas chromatographic studies

Silyl Ethers. The preparation of per- O-trimethyl silyl ethers of sucrose is generally achieved by reaction with chi orotrimethyl sil ane and/or hexamethyldisila2ane in pyridine (25,26). However, this reaction is not selective and in general per-trimethyl silyl ethers are only used as derivatives for gas chromatographic studies. 

Machado and coworkers53 studied the products produced in the radiolysis of DMSO and found the formation of a product which absorbs at 252-262 nm, absorption which is known to be that of dimethyl disulfide. Gas chromatographic studies show the formation... 

L. Castellani, P. Ferrantelli, M. Sinibaldi, G. Vigliano, Identification of Proteinaceous Adhesives in the Wooden Backing of Piero della Francesca s Painting Pala of Saint Bernardino a Gas Chromatographic Study, Journal of Cultural Heritage, 2, 209 215 (2001). 

Renner, G. Gas chromatographic studies of chlorinated phenols, chlorinated anisoles, and chlorinated phenylacetates, Toxicol Environ. Chem., 27 217-224, 1990. 

Patil SA, Shinde VM. 1989. Gas chromatographic studies on the biodegradation of nitrobenzene and... 

Brooks, C.J.W. and Homing, E.C., Gas chromatographic studies of catecholamines, tryptamines, and other biological amines, Anal. Chem., 36, 1540, 1964. 

Betts, T.J., Charmaine, M.M. and Tassone, A.I. (1991) Use of a liquid crystal stationary phase at temperatures below its melting point for the gas chromatographic study of some volatile oil constituents, journal of Chromatography A 547, 335-344. 

Brixins, L. and Treiber, H. (1974) Comparative gas chromatographic studies on the fatty acid composition of lard and goose dipping. Fette Seif. Anstrichm., 76, 83-86. 

However, we will later discuss Eq. (9) again for the determination of London dispersive force of the surface dynamics in the gas chromatographic study. 

The rate of derivatization of different compounds varies when trimethylsilyl derivatives are prepared (Lundquist and Kirk 1971). Another complication arises from the fact that enolization and subsequent formation of enol derivatives occur during the derivatization treatment (Lundquist and Kirk 1971). Ketol la (Fig. 6.1.1), for example, has been shown to give rise to three different derivatives (Fig. 6.1.3) (Lapierre et al. 1983a). One approach for overcoming these difficulties consists of derivatization under mild conditions in combination with a gas chromatographic study of the rate of derivatization (Lundquist and Kirk 1971, Pometto and Crawford 1985). A second solution to this problem consists of performing the silylation under conditions that secure complete derivatization and analysis of all types of derivatives formed (Lapierre et al. 1983a). The latter principle has been adopted in the preferred acidolysis procedure. 

A gas chromatographic study (Carrott and Sing, 1990) of the adsorption of a series of hydrocarbons (C2-C6) by the AMOCO AX21 carbon has revealed some unusual features. Thus, values of the height equivalent to a theoretical plate (HETP) over the range 90-l20°C were found to be independent of both the adsorptive and the temperature. Furthermore, over the range of gas flow rate studied, only the initial section of the Van Deemter plot could be observed (in contrast to the behaviour of other microporous carbons). At present, the explanation for this behaviour is not entirely... 

Galin, M. Rupprecht, M. C., "Gas Chromatographic Study of the Interactions in Styrene-Dimethylsiloxane Block Copolymers and Blends," Macromolecules, 12, 506 (1979). 

S. J. Evans, P. J. Haines and G. A. Skinner, Pyrolysis-gas-chromatographic study of a series of polyester thermosets. J. Anal. Appl. Pyrolysis, 55, 13-58, (2000). 

To be amenable to investigation by gas chromatography, metal compounds must be volatile and thermally and solvolytically stable at the temperatures necessary for reasonably rapid elution. Many metal chelates of / -diketones have been found to possess these properties and have been successfully chromatographed. Until recently, however, almost all gas chromatographic studies had been limited to complexes of the transition and representative elements because of the paucity of volatile, thermally stable, lanthanide compounds. 

Other techniques have begun to be used more often in structural studies. Immunological precipitation has been used to identify structural attributes of gums by their similarity to virus sheath polysaccharides (8). Gas chromatographic studies have made use of methylated (23), acetyl-ated (16), formylated, trifluoroacetylated, and trimethylsilylated derivatives (19,24). 

Dutt MC, Lo DS-T, Ng DLK, Woo S-O. Gas chromatographic study of the urinary codeine-to-morphine ratios in controlled codeine consumption and in mass screening for opiate drugs. JChromatogr 1983 267 117-24. 

Reprinted from Talanta, 25 (10), Steffen A, Bachmann K, Gas chromatographic study of volatile oxides I, 551-556, 1978, with permission from Elsevier. 

To diminish any eventual residual adsorptive activity of the support that may still be present after deactivation by acid and alkaline washing, and by chemical procedures, Bohemen et al. introduced a precoating with 0.1 % PEG 400. The PEG molecules are thought to be adsorbed tightly to the residual active sites of the support. This precoating procedure was also used by Brochmann-Hanssen and Baerheim Svendsen in their gas chromatographic studies on... 

As already observed by Brochmann-Hanssen and Baerheim Svendsen, dehydration of atropine and scopolamine may take place under certain experimental conditions. In their gas chromatographic studies on atropine and scopolamine, Solomon et al.1 made the same observations. 

In a gas chromatographic study on biologically important amines, Fales and Pisano1 investigated some indole bases, such as tryptamine and serotonine. When the indole bases were gas chromatographed on a 0.75 % SE-30 column on Gas Chrom P, extensive tailing was observed, probably due to adsorptive interactions between the compound and the support. However, when a thicker layer of SE-30 was used (4 %) the compounds showed well-formed peaks without tailing. 

In a gas chromatographic study of the effect of methoxy substitution and configuration of heteroyohimbine alkaloids on the retention times on a 1 % SE-30 packed column, Beckett... 

Molecular statistic and gas chromatographic study of hydrocarbons adsorption on the modified layer silicates and silica in the Henry region... 

GAS CHROMATOGRAPHIC STUDIES OF THE ADSORPTION OF HYDROCARBONS ON ORGANODERIVATIVES OF LAYER SILICATES AND SILICA... 

For gas chromatographic studies, a Chrom-5 chromatograph with a flame-ionization detector was used employing a sampling column of dimensions 100 cm x 0.3 cm and 250 cm X 0.3 cm. After filling with the respective adsorbents of 0.20-0.25 mm radius fraction, the columns were conditioned for 6 h at 70-170°C in a flow of the carrier gas (nitrogen). The liquid adsorbate samples (volume not exceeded 0.2 pi) were introduced... 

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