Gas chromatography in environmental analysis

This chapter presents the applications of gas chromatography in environmental analysis. Most of the applications that are present are established and widely practiced by environmental laboratories. The discussion is by no means a review of the current scientific literature, although some more recent developments will be sited. Other sources are available if a current review of the literature is required (7-10). Because of the large volume of information that surrounds the use of gas chromatography in environmental analysis, only selected topics... 

Natangelo, M.,Tavazzi, S., and Benfenati, E. (2002). Evaluation of solid phase microextraction-gas chromatography in the analysis of some pesticides with different mass spectrometric techniques application to environmental waters and food samples, Anal Lett., 35(2), 327-338. 

El-Bayoumy, K., M. O Donnell, and D. Hoffmann Determination of aromatic amines in sidestream smoke by gas chromatography in Environmental carcinogens. Method of analysis and exposure measurement. Passive smoking, edited by l.K. O Neill, K.D. Brunnemann, B. Dodet, and D. Hoffmann, lARC, Lyon, France, lARC Sci. Publ. No. 81 (1987) 269-277. 

Santos, E.J. and Galceran, M.T. (2002)The application of gas chromatography to environmental analysis. Trends in Analytical Chemistry 21,672-685. 

In general, capillary gas chromatography provides enough resolution for most determinations in environmental analysis. Multidimensional gas chromatography has been applied to environmental analysis mainly to solve separation problems for complex groups of compounds. Important applications of GC-GC can therefore be found in the analysis of organic micropollutants, where compounds such as polychlorinated dibenzodioxins (PCDDs) (10), polychlorinated dibenzofurans (PCDFs) (10) and polychlorinated biphenyls (PCBs) (11-15), on account of their similar properties, present serious separation problems. MDGC has also been used to analyse other pollutants in environmental samples (10, 16, 17). 

Most applications in environmental analysis involve heart-cut GC-GC, while comprehensive multidimensional gas chromatography is the most widely used technique for analysing extremely complex mixtures such as those found in the petroleum industry (21). 

These small columns,(usually 10 mm X 1-4.6 mm i.d.) are normally packed with 10-40 p.m sorbents such as Cig-bonded silica, Cg-bonded silica or styrene-divinylbenzene copolymer. These sorbents are not very selective and more selective sorbents, such as the immunosorbent (94), have also been used with good results. Coupling of SPE-gas chromatography is in fact the one most often used in environmental analysis because it reaches a high level of trace enrichment, eliminates water and elutes retained compounds easily with an organic solvent that can be injected into the gas chromatograph. 

Within Severn Trent a modified version of this procedure is utilised for the analysis of malodorous emissions. The most significant difference in this approach compared to those already discussed is the use of high resolution gas chromatography in combination with olfactory detection. This method also combines physico-chemical and olfactometric or sensory techniques but in an alternative manner. Utilisation of gas chromatography combined with odour detection is not a new concept and has been employed fairly commonly for the analysis of food aromas, essential oils and other fragrances. The technique is equally applicable to environmental problems and is used frequently in this laboratory for the analysis of atmospheric emissions and taste and odours in water. Three important benefits accrue from this approach in the context of odour emission analysis. 

Gas chromatography (GC) is the most common analytical technique for the quantitative determination of organic pollutants in aqueous and nonaqueous samples. In environmental analysis, a very low detection limit is required to determine the pollutants at trace levels. Such low detection can be achieved by sample concentration followed by cleanup of the extract to remove interfering substances. Sample extractions and cleanup procedures are described in detail in Chapter 5 of Part 1 of this text. 

Gas chromatography/mass spectroscopy (GC/MS) is probably the best technique to identity a wide array of unknown organic substances in sample matrices. It is also the most positive confirmatory test to determine the presence of pollutants in the sample. Its application in environmental analysis has grown up enormously in the last decade. 

Panic, O. and T. Gdrecki. 2006. Comprehensive two-dimensional gas chromatography (GC x GC) in environmental analysis and monitoring. Anal. Bioanal. Chem. 386 1013-1023. 

The burner heads used in such cool flame emission studies are often simply quartz tubes. Figure 12 shows the burner system used by Arowolo and Cresser27 for automated gas-phase sulfide determination, for example. Other species determined by cool flame emission techniques include chloride, bromide, and iodide, which give intense emission in the presence of indium.29 The main application of cool flame emission techniques in environmental analysis is in speciation studies, for example for the separate determination of sulfite and sulfide, or as element-selective detectors in gas chromatography. 

Brown RH. 1988a. Determination of benzene, toluene and xylene in industrial air by charcoal tube, solvent desorption and gas chromatography. In Fishbein L, O Neill JK, eds. Environmental carcinogens method of analysis and exposure measurement Vol. 10-benzene and alkylated benzene. New York, NY Oxford University Press, 225-233. 

Lucas SV. 1984. GC/MS (gas chromatography/mass spectrophotometry) Analysis of organics in drinking water concentrates and advanced waste treatment concentrates, Vol. 2 Computer-printed tabulations of compound identification results for large-volume concentrations. Battelle Laboratories, Columbus, OH for U.S. Environmental Protection Agency, Office of Research and Development, Health Effects Research Laboratories, RTP, NC. Report No. EPA -600/1-84-020A. 397. 

The first of the separation techniques to be used in process measurement was gas chromatography (GC) in 1954. The GC has always been a robust instrument and this aided its transfer to the process environment. The differences between laboratory GC and process GC instruments are important. With process GC, the sample is transferred directly from the process stream to the instrument. Instead of an inlet septum, process GC has a valve, which is critical for repetitively and reproducibly transferring a precise volume of sample into the volatiliser and thence into the carrier gas. This valve is also used to intermittently introduce a reference sample for calibration purposes. Instead of one column and a temperature ramp, the set up involves many columns under isothermal conditions. The more usual column types are open tubular, as these are efficient and analysis is more rapid than with packed columns. A pre-column is often used to trap unwanted contaminants, e.g. water, and it is backflushed while the rest of the sample is sent on to the analysis column. The universal detector - thermal conductivity detector (TCD)-is most often used in process GC but also popular are the FID, PID, ECD, FPD and of course MS. Process GC is used extensively in the petroleum industry, in environmental analysis of air and water samples" and in the chemical industry with the incorporation of sample extraction or preparation on-line. It is also applied for on-line monitoring of volatile products during fermentation processes" ... 

Kataoka, H., Derivatization reactions for the determination of amines hy gas chromatography and their apphcations in environmental analysis, J. Chromatogr., 133, 19-34, 1996. 

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