the first column is carried either through the monitor ECD producing the usual ECD
chromatogram, or through the second column and the main ECD. The remarkable
advantage of this technique, in both a qualitative and quantitative sense, is a
consequence of the fact that a valve-less pneumatic system involving a pressurecontrolled live T-piece allows a preselected small fraction to be cut from the eluate of
the first column and to be transferred quantitatively and reproducibly to the second
column. This technique offers complete separation of many compounds coeluting on
a single column, increased selectivity, it supplies very accurate data, but special
two-oven gas chromatographs and skilled personal are necessary for performing
these time-consuming analyses (Schulz et al. 1989). Especially, the combination of
MDGC with mass-selective detection developed into a powerful tool for sensitive
ultra-trace multi-compound analysis in environmental samples (de Geus et al. 2000;
de Boer and Law 2003; Seeley 2012; Tranchida et al. 2012). The MDGC technique
has also been successfully applied to enantiomer separation of chiral environmental
pollutants (Wong and Castellanos 1989; Bordajandi et al. 2005, 2006; Bordajandi
and Gonzalez 2008; Anouti et al. 2010; Cooper et al. 2012; Naude and Rohwer
2012; Perez-Fernandez et al. 2012; Legrum et al. 2015; Wong et al. 2015).
5.3 Comprehensive Capillary Gas Chromatography
(GCxGC)
A technique for the enhanced separation in capillary gas chromatography was
developed in the early 1990s especially aiming at the characterisation of impurities
in the fossil petroleum refinery process (Liu and Philips 1991). This technology was
quickly adopted for environmental pollutant research especially due to the combination of high chromatographic separation power and sensitive mass-selective
detection (Marriott et al. 2003a, b; von Muhlen et al. 2006; Naude and Rohwer
2012; Tranchida et al. 2016) including effect assessment of human exposure (Focant
et al. 2004; Megson et al. 2015). For comprehensive GCxGC, an extraordinarily
high chromatographic resolution is achieved connecting two independently heated
GC columns via a thermal modulator. During the chromatographic processing, a
well-defined portion eluting from the first column (normal length: 20–30 m) is
further trapped, focused in the thermal modulator and reinjected in the second
columns (short column length: 1–3 m). This procedure is continuously repeated
throughout the entire chromatographic separation for the entire eluent from the first
column (see Fig. 5.1). The portions are then transferred into a suitable detection
system for further processing.
Several studies, where GCxGC was employed for the successful characterisation
of complex environmental mixtures, will be presented when environmental levels
and effects of pollutants are discussed. Today, GCxGC techniques in combination
with high-resolution mass-selective detection are an important analytical tool for
80
5 Enantiomer-Selective High-Resolution Gas Chromatography (esHRGC)
chromatogram, or through the second column and the main ECD. The remarkable
advantage of this technique, in both a qualitative and quantitative sense, is a
consequence of the fact that a valve-less pneumatic system involving a pressurecontrolled live T-piece allows a preselected small fraction to be cut from the eluate of
the first column and to be transferred quantitatively and reproducibly to the second
column. This technique offers complete separation of many compounds coeluting on
a single column, increased selectivity, it supplies very accurate data, but special
two-oven gas chromatographs and skilled personal are necessary for performing
these time-consuming analyses (Schulz et al. 1989). Especially, the combination of
MDGC with mass-selective detection developed into a powerful tool for sensitive
ultra-trace multi-compound analysis in environmental samples (de Geus et al. 2000;
de Boer and Law 2003; Seeley 2012; Tranchida et al. 2012). The MDGC technique
has also been successfully applied to enantiomer separation of chiral environmental
pollutants (Wong and Castellanos 1989; Bordajandi et al. 2005, 2006; Bordajandi
and Gonzalez 2008; Anouti et al. 2010; Cooper et al. 2012; Naude and Rohwer
2012; Perez-Fernandez et al. 2012; Legrum et al. 2015; Wong et al. 2015).
5.3 Comprehensive Capillary Gas Chromatography
(GCxGC)
A technique for the enhanced separation in capillary gas chromatography was
developed in the early 1990s especially aiming at the characterisation of impurities
in the fossil petroleum refinery process (Liu and Philips 1991). This technology was
quickly adopted for environmental pollutant research especially due to the combination of high chromatographic separation power and sensitive mass-selective
detection (Marriott et al. 2003a, b; von Muhlen et al. 2006; Naude and Rohwer
2012; Tranchida et al. 2016) including effect assessment of human exposure (Focant
et al. 2004; Megson et al. 2015). For comprehensive GCxGC, an extraordinarily
high chromatographic resolution is achieved connecting two independently heated
GC columns via a thermal modulator. During the chromatographic processing, a
well-defined portion eluting from the first column (normal length: 20–30 m) is
further trapped, focused in the thermal modulator and reinjected in the second
columns (short column length: 1–3 m). This procedure is continuously repeated
throughout the entire chromatographic separation for the entire eluent from the first
column (see Fig. 5.1). The portions are then transferred into a suitable detection
system for further processing.
Several studies, where GCxGC was employed for the successful characterisation
of complex environmental mixtures, will be presented when environmental levels
and effects of pollutants are discussed. Today, GCxGC techniques in combination
with high-resolution mass-selective detection are an important analytical tool for
80
5 Enantiomer-Selective High-Resolution Gas Chromatography (esHRGC)