Comprehensive GCxGC

The practicability and potential of comprehensive GCxGC coupled to TOFMS (GCxGC-TOFMS) for the analysis of complex mixtures is illustrated in the following application [37]. 

Selected examples of application areas of GCxGC are presented in Table 15.2. For further details about instrumentation and applications of comprehensive GCxGC, the contributions in [32, 38, 39] should be consulted. 

Figures 4 and 5 show the sulfur specific chromatograms (S-GCxGC) of the two above FCC and SCN samples. The sulfiir compounds were also resolved by the GCxGC process into sulfur classes with distinct bands for mercaptans + sulfides, thiophenes, and benzothiophenes. Note that there was a sulfur conm nd in the steam cracked naphtha at approximately X=55 min, Y=110 s. This unknown compound was also found to contain carbon, hydrogen, and oxygen by further GCxGC/AED analysis. Further characterization of the compound may be possible by GC/Mass Spectrometry (GC/MS) using a comprehensive GCxGC/GC/MS set up very similarly to that described in this paper.

The number of theoretical plates N, included in Equation (8), is a measure of column efficiency, which can be individually applied to the two columns of a GCxGC set. But in comprehensive GCxGC, the use of two columns having phases with different characteristics results in the redefinition of peak capacity, a 1 D GC efficiency concept. It also results in the introduction of two new concepts related to the separation behaviour, orthogonality and chromatographic structure, which are specific to GCxGC. These three concepts are discussed in Sections 4.2, 4.3, and 4.4, respectively. 

L. Mondello, P.Q. Tranchida, R EHigo, and L.M. Sidisky, Comprehensive GCxGC for the Analysis of Fats and Oils. Proceedings of the 98th AOCS Annual Meeting Expo, May 13-17, 2007, Qu ec. 

Johnson, K.J. Synovec, R.E. (2002). Pattern recognition of jet fuels comprehensive GCxGC with ANOVA-based feature selection and principal component analysis. Chemometrics and Intelligent Laboratory Systems, Vol.60, No.1-2, (January 2002), pp. 225-237, ISSN 0169-7439... 

Figure 2.133 Two-dimensional GC Principles. (a) Heart cutting with monitor detector and (b) comprehensive GCxGC. 1. Injector 2. primary separation column, first dimension 3. flow switching device 4.

FANES Furnace atomic nonthermal emission GCxGC Comprehensive gas chromatography... 

Janse van Vuuren, M.J., Grobler, T., Bekker, R. 2007. Comprehensive analysis of FT product with GCxGC. Paper presented at the NACS 20th North American Meeting, Houston, TX, June 17-22. 

Fig. 14.13. Chromatograms showing single and comprehensive two-dimensional GC of drugs extracted from urine. (A) GC-FID chromatogram, (B) Pulsed GcxGC chromatogram (C) GCxGC contour plot. Adapted with permission from Ref. [15, Fig. 14.3]. Complete details on separation conditions and analyte identity can be found in the original paper.

The modulator is the heart of the GCxGC system, and is positioned at the confluence of the coupled chromatography columns. The role of the modulator is to trap or isolate compounds present in a given time fraction eluting from the first-dimension column and reinject these components rapidly into the second column. This essentially yields a time-sampled chromatogram, from the first dimension ( D) to the second dimension ( D). It is critical that the modulator is capable of representatively and faithfully sampling peaks eluting from onto D. This can be achieved by either complete or partial transfer of the first-column eluent, however, both techniques are considered comprehensive. 

MDGC, and comprehensive two-dimensional GC, or GCxGC), faster separation techniques (fast GG), fast methods for quality assessment or process control in the flavour area ( electronic noses and fingerprinting MS) and on-line time-resolved methods for analysis of volatile organic compounds (VOGs) such as proton-transfer reaction MS (PTR-MS) and resonance-enhanced multi-photon ionisation coupled with time-of-flight MS (REMPI-TOFMS). The scope of this contribution does not allow for lengthy discussions on all available techniques therefore, only a selection of developments will be described. 

Fig. 15.5 Illustration of how two overlapping peaks S and ip emerging from the first colmnn (a) are resolved in GCxGC after passage to the second column (b) [31]. Reprinted from Marriott, R, Shellie, R., Principles and applications of comprehensive two-dimensional gas chromatography. Trends Anal. Chem. (2002), 21 573-583 with permission from Elsevier...

Eyres, G., Dufour, J.P> Hallifax, G., Sotheeswaran, S., Marriott, P.J. (2005) Identification of character-impact odorants in Coriander and wild coriander leaves using gas chromatography-olfactometry (GCO) and comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GCxGC-TOFMS). J. Sep. Sci. 28 1061-1074. 

Adahchour, M., Beens, J., Vreuls, R.J.J., Brinkman, U.A.T. (2006) Recent developments in comprehensive two-dimensional gas chromatography (GCxGC). Trends Anal. Chem. 25 438-454, 540-553. 

FIGURE 13.7 Instrumental setup of (a) a GCxGC system (Anon., GC x GC Comprehensive Two-Dimensional Gas Chromotography Form No. 209-184 R2.58-REV-1 LECO Corporation, St Joseph, MI 49085 P3, 2008. With permission.) (b) a LC x LC system based on a second-dimension column with two storage loops (T. Hyotylainen, LC x LC switching valves configuration Chromedia Amsterdam P Two Dimensional LC (LC x LC), 2008. With permission.). 

Reichenbach, S., Ni, M., Kottapalli, V., Visvanathan, A., Ledford, E., Oostdijk, J., Trap, H. (2003). Chemical Warfare Agent (CWA) Detection with Comprehensive Two-Dimensional Gas Chromatography (GCxGC). Chemical and Biological Sensing IV, Proc. SPIE 5085 28-36. 

KEYAVORDS Gas chromatography, atomic emission detection, hetero-atom speciation, sulfur, comprehensive two-dimensional gas chromatography, comprehensive two-dimensional gas chromatography/AED, GCxGC/AED, GCxGC, fuels, gasolines, jet fiels... 

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