Hydrocarbons capillary column chromatography

The most widely used method of analysis for methyl chloride is gas chromatography. A capillary column medium that does a very good job in separating most chlorinated hydrocarbons is methyl siUcone or methyl (5% phenyl) siUcone. The detector of choice is a flame ionisation detector. Typical molar response factors for the chlorinated methanes are methyl chloride, 2.05 methylene chloride, 2.2 chloroform, 2.8 carbon tetrachloride, 3.1, where methane is defined as having a molar response factor of 2.00. Most two-carbon chlorinated hydrocarbons have a molar response factor of about 1.0 on the same basis. 

The conventional approach to solvent extraction is the batch method. Early work with this method was hampered by the low concentration of the compounds present and the relative insensitivity of the methods of characterization. Thus lipids and hydrocarbons have been separated from seawater by extraction with petroleum ether and ethyl acetate. The fractionation techniques include column and thin-layer chromatography with final characterisation by thin-layer chromatography, infrared, and ultra-violet spectroscopy and gas chromatography. Of these techniques, only gas chromatography is really useful at levels of organic matter present in seawater. With techniques available today such as glass capillary gas chromatography and mass spectrometry, much more information could be extracted from such samples [20]. 

EPA. 1990a. Chlorinated hydrocarbons by gas chromatography capillary column technique. Method 8121. Washington, DC U.S. Environmental Protection Agency, 1-21. 

Gas-Liquid Chromatography. In gas-liquid chromatography (GLC) the stationary phase is a liquid. GLC capillary columns are coated internally with a liquid (WCOT columns) stationary phase. As discussed above, in GC the interaction of the sample molecules with the mobile phase is very weak. Therefore, the primary means of creating differential adsorption is through the choice of the particular liquid stationary phase to be used. The basic principle is that analytes selectively interact with stationary phases of similar chemical nature. For example, a mixture of nonpolar components of the same chemical type, such as hydrocarbons in most petroleum fractions, often separates well on a column with a nonpolar stationary phase, while samples with polar or polarizable compounds often resolve well on the more polar and/or polarizable stationary phases. Reference 7 is a metabolomics example of capillary GC-MS. 

Methods have been described for determining chlorinated aliphatic hydrocarbons in soil and chemical waste disposal site samples. The latter method involves a simple hexane extraction and temperature programmed gas chromatographic analysis using electron capture detection and high resolution glass capillary columns. Combined gas chromatography-mass spectrometry was used to confirm the presence of the chlorocarbons in the samples [4],... 

Lee, M. L., Vassilaros, D. L., White, C. M., Novotny, M. Anal. Chem. 51, 1979, 768-773. Retention indices for programmed-temperature capillary-column gas chromatography of polycyclic aromatic hydrocarbons. 

More than 100 compounds are released in the atmosphere of urban areas by automobiles, and there is a close relation between the atmospheric hydrocarbon composition and the composition of gasolines and automobile exhausts. The full range of compositions of gasolines has been reported by Sanders and Maynard.They identified 180 of the 240 compounds separated by capillary-column gas chromatography. Detailed fiiel compositions were reported by other investigators, and exhaust hydrocarbon compositions were reported by Neligan et a/.,McEwen, and, more recently. Papa et Jacobs, ... 

Samples are analysed using gas chromatography coupled with mass spectrometry (GC-MS). This instmment separates the organic hydrocarbons in the extract with a very high resolution fused silica capillary column prior to mass spectrometric detection. Acquisition parameters have been customized to detect the target list of 162 hydrocarbons with the sensitivity required to obtain 1 part-per-trillion reporting limits which represents an innovation in these analytics. 

Paputa-Peck, M. C., R. S. Marano, D. Schuetzle, T. L. Riley, C. V. Hampton, T. J. Prater, L. M. Skewes, T. E. Jensen, P. H. Ruehle, L. C. Bosch, and W. P. Duncan, Determination of Nitrated Polynuclear Aromatic Hydrocarbons in Particulate Extracts by Capillary Column Gas Chromatography with Nitrogen Selective Detection, Anal. Chem., 55, 1946-1954(1983). 

F. P. DiSanzo and V. J. Giarrocco, Analysis of pressurized gasoline-range liquid hydrocarbon samples by capillary column and PIONA analyzer gas chromatography , J. Chromatogr. Sci. 26 258-266 (1988). 

Figures 4a—c. Capillary column gas chromatograms of the aromatic hydrocarbon fraction of selected samples from the Nordlinger Ries. M+ = molecular ion, BP = base peak in the corresponding mass spectra. The sample from 151.5 m of well NR-10 contains steroid olefins due to incomplete liquid chromatography separation.

Strup, P. E., Wilkinson, J. E., and Jones, P. W. Trace Analysis of Polycyclic Aromatic Hydrocarbons in Aqueous Systems Using XAD-2 Resin and Capillary Column Gas Chromatography-Mass Spectrometry Analysis in Carcinogenesis. Vol. Ill, ed. by P. W. Jones and R. I. Freudenthal, Raven Press, New York 1978. 

Novotny, M. Retention Indices for Programmed-Temperature Capillary-Column Gas Chromatography of Polycyclic Aromatic Hydrocarbons. Anal. Chem., 51, 768 (1979). 

The hydrocarbon oil index within PLC-4 was determined in accordance with the draft standard ISO/DIS 9377-4, which has recently been adopted as ISO/FDIS 9377-2 [2], Briefly, water samples are extracted with n-hexane or petroleum ether. After clean-up of the extracts on a Florisil column, hydrocarbons are detected and quantified by capillary gas chromatography with flame ionisation detection (GC-FID, Fig. 1). 

The 1-alkene/n-alkane ratios in the oil, measured by capillary-column gas chromatography/mass spectroscopy, also increase with the addition of inert diluent (Figure 6). This effect and the previously demonstrated dependence on heating rate are consistent with a free-radical mechanism. In addition, we noted that alkene/alkane ratios for even-numbered hydrocarbons are significantly higher the ratios for odd-numbered ones. We do not understand this effect at this time but suspect that it is related to the structure of kerogen and the mechanism of its pyrolysis. 

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