ASG 2253 GC×GC-TOFMS
ASG 2502 GC×GC-FID
ASG 2901 GC×GC-FID

Comprehensive two-dimensional gas chromatography (GC×GC) provides an enormously enhanced selectivity compared to conventional gas chromatography. Due to the coupling of capillary columns of different polarity it is possible to separate complex mixtures into single components.
The core part of the two-dimensional separation, the so-called modulator, is located between the first and the second dimension. The function of the modulator is the accumulation of components, which elute from the first column simultaneously, refocussing and injecting them into the second column for further separation.
This process can be performed by regular cycles of cold- and hot-jets (thermal modulation), or by adjusting the carrier gas flow in the second dimension (flow modulation). The schematic structure of a GC×GC instrument is given in the following figure.

In the following figure you can see a representative, two-dimensional chromatogram of conventional diesel fuel according to EN 590, as well as the results of the data evaluation and quantification.
The separation was achieved using a reversed column combination consisting of a 50% phenyl-substituted column as 1st dimension and 100% polydimethylsiloxane as 2nd dimension.

Compared to conventional middle distillates, HVO and XtL fuels are characterised in particular by the low proportion of aromatic hydrocarbons. For the analysis of these low contents, the application of GCxGC-FID with a detection limit of 0.05% (m/m) is particularly suitable.

For samples that differ greatly in composition from conventional middle distillates, for example through a higher boiling range, further analytical methods are available with high-temperature GCxGC-FID or -MS (ASG 2501 or ASG 2221).