Search results for "Gas Chromatography"
showing 10 items of 750 documents
Simultaneous determination of C1−C8 n-alkyl acetates and corresponding mono-, di- and trichloroacetates on glass capillary columns with programmed te…
1982
Gas chromatography of mixtures of aliphaticn-alkyl acetates (CH3−COOR), chloroacetates (CHCl2−COOR), dichloroacetates (CHCl2−COOR) and trichloroacetates (CCl3−COOR), where the alcohol chain length (R) varied between 1 and 8, has been studied on SE-30, Carbowax 20M and OV-351 glass capillary columns with programmed temperatures from 50°C at 2, 4, 6, 8 and 10°C/min. Compounds in the homologous series are eluted in the direct order from methyl ton-octyl acetate. The isomeric chloro esters are eluted on SE-30 according to their boiling points in the order: mono-, di- and trichloro isomer, whereas on polar columns di- and trichloro esters are eluted in the reverse order. The complete separation …
Analytical study of proteinaceous binding media in works of art by gas chromatography using alkyl chloroformates as derivatising agents.
2001
In this work, we present the results obtained in an analytical study of the different types of proteinaceous binding media most commonly used in paintings, using GC-FID as the technique of analysis and GC-MS as a confirmatory technique. The application of this methodology requires prior hydrolysis of the proteins in the binding media to obtain free amino acids and then volatile derivatives, in this case by reaction with chloroformates due to advantages of speed, safety and the aqueous medium in which the reaction occurs. The method proposed for the proteinaceous binding media study is to calculate the proportions of the different amino acids with respect to alanine. This method provided goo…
Gas-liquid chromatography and lipophilicity of esters of benzoic acids
1987
Abstract The use of gas-liquid chromatographic (GLC) retention indices for the determination of lipophilicity was studied for a series of alkyl and arylalkyl esters of substituted benzoic acids. The regression relationships between the logarithms of the partition coefficients and the retention characteristics measured on two cpillary columns, SE-30 and OV-351, were evaluated. The behaviour of arylalkyl esters and of alkyl esters cannot be expressed in terms of a single regression equation. This is probably a consequence of the effect of the intramolecular hydrophobic interaction upon the retention of arylalkyl esters under GLC conditions. An analysis of the isokinetic relationships revealed…
Characterization of commercial synthetic resins by pyrolysis-gas chromatography/mass spectrometry: application to modern art and conservation.
2009
To characterize a set of synthetic resins, a methodology by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) has been developed. The studied reference materials were commercial versions of a wide range of synthetic resins. For each polymer, the pyrolytic and chromatographic conditions were optimized to adequately resolve the fragment mixture in a short time. The proposed analytical method does not require previous treatment of the sample, and due to its high sensitivity, only a small sample quantity in the microgram range can be used. The pyrolysis temperature was found to have little effect on the obtained pyrograms. The summarized data set for the individual polymer materials, es…
Environmental analysis of chlorinated aromatic thioethers, sulphoxides and sulphones
1993
Abstract Chlorinated aromatic thioethers discussed here are polychlorinated dibenzothiophenes, thianthrenes and diphenylsulphides. Relatively little is known about their occurrence, behaviour and fate in the environment. Polychlorinated dibenzothiophenes and diphenylsulphides have recently been found to be formed in waste combustion and analysed in pulp mill effluents. Chlorinated sulphoxides and sulphones are usually metabolites or oxidation products of different chlorinated aromatic compounds. Different gas chromatographic-mass spectrometric techniques are used in the analysis of the chlorinated thioethers. The sulphoxides and sulphones, because of their higher polarity, can be isolated f…
Detection of poly(methylmethacrylate) wear particles in capsule tissue surrounding endoprotheses by pyrolysis gas chromatography
1982
Pyrolysis gas chromatography (PGC) is used to detect polymer wear particles in capsule tissue surrounding endoprotheses implanted with poly(methylmethacrylate) as bone cement. The method allows the detection of the polymer incorporated in tissue even in the range of 1 weight%.
Alkylation of acidic organic compounds for gas chromatographic analysis
1973
A new alkylation method is proposed. Organic solutions of fatty acids, phenols or barbituric acids are refluxed with an alkylating reagent and solid K2CO3. The reaction mixture is injected directly into the gas chromatograph. The scope of this convenient method for quantitative and qualitative analyses is considerable as different classes of alkylating agents can be used.
Structurally bound lipids in peat humic acids
2001
Humic acids from highly decomposed peat were subjected to oxidation with alkaline cupric oxide (CuO) at 170°C (single oxidation). Oxidation products were isolated as three fractions, oxidized humic acids, fulvic acids and lipophilic compounds. Isolated oxidized humic acids were subsequently re-oxidized (sequential oxidation) under the same conditions, and released lipophilic compounds were isolated. Lipids released during single and sequential oxidations were determined using capillary gas chromatography and mass spectrometry. Identified compounds accounted for 3.3 and 0.12 wt.% of humic acid content, respectively. Lipid profiles of lipophilic fractions released during single and sequential…
Gas chromatography of homologous esters
1985
Abstract The retention behaviour of C 1 C 18 n -alkyl esters of butanoic 2-, 3- and 4-chlorobutanoic acids was examined isothermally at several temperatures on SE-30 and OV-351 capillary columns. Retention increments showing the effects of each position of chlorine substitution are presented. The considerable enhancement of terminal chlorine substitution is discussed together with the corresponding behaviour of the monochloropropanoate esters.
Determination of indoor air quality of a phytosanitary plant.
2011
A new methodology has been developed to determine volatile organic compounds (VOCs) and pesticides in ambient air using membrane based devices as passive samplers. Pesticides were determined by gas chromatography with mass spectrometry detection (GC-MS) after their microwave-assisted extraction (MAE) from the passive sampler and the required clean-up. On the other hand, VOCs were also caught with the same samplers and directly determined by head space (HS) coupled to GC-MS. The use of samplers filled with florisil and activated carbon allows us to catch with a simple device both, VOCs and pesticides, with a high vapor pressure. Results obtained in the deployment of samplers in different sit…