Applications of Multidimensional Chromatography

Multidimensional chromatography techniques (GCxGC and GC-GC) are used when the mixtures to be separated are very complex because of a high number of analytes (hydrocarbons, essential oils, pesticides, etc.) or because of the number of interfering compounds from the matrix susceptible to coelution with the molecules of interest 

For a more exhaustive view on multidimensional chromatography and its usage, one can refer to the synthesis articles by Marriott and Shellie (2002), Dalliige, Beens, and Brinkman (2003), and Mondello et al. (2008). -  

Theory of gas chromatography. In Modern Practice of Gas Chromatography, 4th ed., Grob, R. L. and E. F. Barry, Eds. Hoboken, NJ John Wiley Sons. 

Bjdrklund, J., R Tollback, C. Hiame et al. 2004. Influence of the injection technique and the column system on gas chromatographic determination of polybrominated diphenyl ethers./. Chromatogr. A 1041 201-220. 

Electrospray Ionization Mass Spectrometry Fundamentals, Instrumentation, and Applications. New York Wiley-Interscience. 

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In this present chapter, the applications of multidimensional chromatography using various types of coupled techniques for the analysis of industrial and polymer samples, and polymer additives, are described in detail. The specific applications are organized by technique and a limited amount of detail is given for the various instrumental setups, since these are described elsewhere in other chapters of this volume. 

The coupling of supercritical fluid extraction (SEE) with gas chromatography (SEE-GC) provides an excellent example of the application of multidimensional chromatography principles to a sample preparation method. In SEE, the analytical matrix is packed into an extraction vessel and a supercritical fluid, usually carbon dioxide, is passed through it. The analyte matrix may be viewed as the stationary phase, while the supercritical fluid can be viewed as the mobile phase. In order to obtain an effective extraction, the solubility of the analyte in the supercritical fluid mobile phase must be considered, along with its affinity to the matrix stationary phase. The effluent from the extraction is then collected and transferred to a gas chromatograph. In his comprehensive text, Taylor provides an excellent description of the principles and applications of SEE (44), while Pawliszyn presents a description of the supercritical fluid as the mobile phase in his development of a kinetic model for the extraction process (45). 

The use of multidimensional chromatography in environmental analysis has been reviewed in the literature (1-6). Of the multidimensional systems described in previous chapters, GC-GC liquid chromatography LC-LC and LC-GC, whose applications to environmental analysis will be detailed in this chapter, are the ones most often used in environmental analysis. 

Table 15.1 Selected applications of multidimensional gas chromatography in flavour research...

Wright, D.W. 1997. Application of multidimensional gas chromatography techniques to aroma analysis. In Techniques for Analyzing Food Aroma (R. Marsili, ed.) pp. 113-141. Marcel Dekker, New York. 

D. W. Wright, Application of Multidimensional Gas Chromatography Techniques to Aroma Analysis. In Techniques for Analyzing Food Aroma R. Marsili, Ed. Marcel Dekker New York, 1997 pp 113-141. 

The application of multidimensional gas chromatography (MDGC) to essential oil analysis is a great development in the determination of such complex samples. This is an appropriate approach when there are zones on the chromatogram where the peaks are not well resolved, which is a common situation in natural samples. The fractions corresponding to the zones with unresolved peaks are transferred to a second column containing a different stationary phase, where they are separated and completely resolved. Therefore MDGC permits the separation of poorly resolved peaks and increases resolution, with the final result of an improvement in both identification and quantification of components of essential oils. 

Moreover, applications of multidimensional ion chromatography utilizing mixedmode phases are very interesting. In those separations, ion-exchange and reversed-phase interactions equally contribute to the retention mechanism of ionic and polar species [32,33]. These alternative techniques are also described in Chapter 6. 

De Alencastro, L.R, Grandjean, D., and Tarradellas, J. (2003) Application of multidimensional (heart-cut) gas chromatography to the analysis of complex mixtures of organic pollutants in environmental samples. Chimia, 57, 499 - 504. 

Lorenzo D, Paz D, Davies P, ViUamil J, Vila R, Canigueral S, Dellacassa E. Application of multidimensional gas chromatography to the enantioselective characterisation of the essential oil of Eupatorium buniifolium Hooker et Arnott. Phytochem. Anal. 2005 16 39-44. 

J. C. Giddings, Use of multiple dimensions in analytical separations in Multidimensional Chromatography Techniques and Applications, H. J. Cortes (Ed.), Marcell Dekker, New York, Ch. 1-27 (1990). 

Multidimensional chromatography has important applications in environmental analysis. Environmental samples may be very complex, and the fact that the range of polarity of the components is very wide, and that there are a good many isomers or congeners with similar or identical retention characteristics, does not allow their separation by using just one chromatographic method. 

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). 

Drug discovery applications also provide insights for the eventual determination of the compounds in a forensic or toxicological setting this is another area in which multidimensional chromatography allows the direct injection of bodily fluids. For... 

HPLC as a purification technique and as a tool for process monitoring has become increasingly attractive and will find many new applications in the future. Low pressure LC, probe LC, and micro-LC are techniques important to the future of process chromatography. Specialized detectors and multidimensional chromatographic approaches are also of increasing use. Additional literature is available.22 33-36... 

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