Page 109 - Multidimensional Chromatography

Orthogonal GC–GC 101

Figure 4.14 The same sample as that shown in Figure 4.13, but obtained in this case by
using a BPX5–BP20 (1.0 m in length) column combination. The lower GC trace looks essen-
tially the same as the equivalent one shown in Figure 4.13. The short second column appar-
ently does not alter the total chromatogram greatly–most of the separation here is determined
by the long first column. However, when the data are transformed to the 2D space, we can now
obtain the full resolution produced by the polar BP20 column. This result shows that the selec-
tion of the second dimension column is critical to the success of the separation. We have
‘tuned’ the separation based on the need to separate oxygenated from non-oxygenated prod-
ucts, and different compound classes within oxygenated products, e.g. alcohols and ketones.

4.5 QUANTITATIVE ASPECTS

Applications of GC GC can be grouped into the broad categories of qualitative
and quantitative studies. By far the more numerous are qualitative studies, and in
this group will be included those studies that also pay attention to the retention
aspects of GC GC. By quantitative studies, we take to mean those that involve
measurement of peak responses in terms of area or height, and therefore offer the
analysis of the relative proportions of the various components. Frysinger and co-
workers (37, 38) have primarily studied the use of GC GC to investigate petro-
chemical pollution at or around military (naval) bases. These authors have studied