GCxGC

MDGC and GCxGC have recently been reviewed [917-921a],... 

GCxGC is most often applied for target analysis. Main application areas for GCxGC are to be found where unresolved peaks are the norm, i.e. for atmospheric organics (e.g. urban air), food and flavour (organoleptics), (petro)chemical and forensic analyses,... 

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

With recent instrumental development, such as fast LC, fast GC and two-dimensional gas chromatography (GCxGC) and advanced tandem hybrid MS detection systems (i.e., QqTOF, QqLIT, Orbitrap) the analysis of complex mixtures... 

In order to manipulate the selectivity of the FT synthesis, there needs to be an understanding of the parameters that control the selectivity. Within Sasol there are many activities to ensure more accurate measurements, e.g., developments in the two-dimensional gas chromatography (GCxGC) technique. This discussion will give a flavor of what Sasol is doing regarding the understanding of Fe-LTFT selectivity. 

AN INCREASE IN THE ACCURACY OF THE FT PRODUCT ANALYSIS WITH GCxGC... 

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. 

Another approach in GC is that of using more power in the separation by doing GCxGC. In this approach, a second column is used with a different type of stationary phase than the primary stationary phase, and fast chromatography using TOF-MS as the detector is carried out [39]. This technique uses only TOF-MS as the detector since it has the most sensitivity for fast-eluting peaks. The method has been applied to complicated matrix analysis. 

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.

Thus, comparing GC-MS with GCxGC, in the former instance, we have... 

FIGURE 10.1 Contrast between GCxGC and GC-MS. In the former, solutes are continuously analyzed in the second dimension, to ideally provide separation on D. In the latter, the MS will simply record all ions that arise from ionization processes in the source, regardless of... 

However, signal also depends on detector data acquisition rate noise increases with increased detection acquisition rate. Since GCxGC peaks are narrow, necessitating higher detection frequencies, S/N ratio improvements are not as great as might be initially anticipated. 

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. 

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