Comprehensive GCxGC technique

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. 

Furthermore, in some cases, these detectors may be used in conjunction with a higher chromatographic resolution/selectivity to minimize matrix interference. Comprehensive two-dimensional gas chromatography (GCxGC) has been under development for more than ten years [10(and references contained therein)] as an enhanced resolution technique. The technique involves continuously transferring or modulating short time periods from a primary column, the first dimension, to a second column of different polarity or selectivity, which serves as the second dimension. The modulation period is typically less than the peak widths observed on the... 

If each separation mechanism applied to the resolution of a mixture is defined as a separation "dimension," the subsequent application of different separation mechanisms can be called a multidimensional approach. This chapter briefly introduces the concept of multidimensionality in the context of GC separations and discusses how switching from traditional multidimensional GC (MEXjC or GC-GC) to comprehensive two-dimensional GC (GCxGC) dramatically enhances the potential of the technique. 

The total number of cells is the theoretical peak capacity, For a comprehensive two-dimensional technique such as GCxGC, is the product of the peak capacities of the D and D columns Cn and n, respectively) ... 

As illustrated above, GCxGCxGC is currently not yet practical. LCxGCxGC appears to be more feasible. In the development of a system for the latter technique, the question of how to interface the various dimensions holds a key position. To answer this question, it is wise to first look in more detail at how subsequent dimensions in a comprehensive system can be interfaced. In GCxGC, just as in LC xLC , the D analyses are usually performed on-the-fly. That is, the separation on the first column continues while the previous time fraction is analysed on the second column. Two other operational approaches... 

Cavagnino, D., Bedini, R, Zilioli, G. and Trestianu, S. (2003) Improving sensitivity and separation power by using LVSL-GCxGC-FID technique for pollutants detection at low ppb level. Poster at the Gulf Coast Conference, Comprehensive Two-Dimensional GC Symposium, 2003. 

Comprehensive two-dimensional gas chromatography (GCXGC) is a recent technique, proposed in the 90s by Philips (Liu and Phillips, 1991). Analytes eluting from a first and... 

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