Annex Troubleshooting

Abstract

The chapter provides some typical examples of chromatograms and contour plots where some of the most common problems of GCxGC can visually be identified. These problems are explained and the most plausible practical solutions are described. The high speed and the special requirements of the 2D separation, the GCxGC transfer process becomes particularly delicate or prone to problems during method development. Peak shape and eventually GCxGC resolution are affected by both categories of parameters. The types of troubleshooting observed in GCxGC are chromatographic peak distortion and analyte degradation, programmed temperature separations, wraparound, and modulation process. Low programming temperature rates of the 1 D column can result in widening of the chromatographic peak, which in addition can show a typical asymmetry (tailing peak) derived from extra column effects and from active points in the column. In GCxGC, slow temperatures ramps should be preferred when working with oven programmed temperature because the application of fast oven temperature ramps can adversely affect the possible 2 D structure and peak shape visualization in the contour plot as well as the separation itself. Wraparound occurs when the retention time of a compound in the 2 D column exceeds the modulation period. It can be identified in the 2 D profile by the elution of the affected compound during the subsequent modulation cycle(s). The enhanced separation power provided by GCxGC can partially be lost if the resolution achieved in the first dimension is not preserved during modulation and separation in the second dimension.