Inlet backflushing device for the improvement of comprehensive two dimensional gas chromatographic separations

Comprehensive two-dimensional gas chromatography (GC × GC) is recognised as a powerful tool for the separation of complex mixtures of volatile and semi-volatile compounds. In the analysis of challenging samples containing highly concentrated, active analytes or those with complicated matrices, it is often the case that less than ideal chromatography is produced. GC × GC chromatograms of such samples typically contain broad, tailing analyte bands. This results in difficulties with quantitation and poor utilisation of the separation space. In this study we investigated the inlet and the modulator as the potential sources of these tailing bands. A simple inlet backflushing device was developed to isolate the inlet from the primary column after the injection, and a similar setup was used to isolate the modulator from the primary column. The device allowed us to divert carrier gas flow back through the inlet at a specified time after the injection, while allowing analytes to pass through the column for separation. Analytes retained within the inlet were prevented from entering the column, and were subsequently removed via the carrier gas split line. The study revealed that the inlet plays a significant role in the development of tailing chromatographic bands, while the modulator simply modulates the already elongated band. Inlet backflushing is a cheap, simple and effective tool that can be used to improve the chromatography of problematic GC × GC analyses of samples consisting of concentrated and active analytes, those derived from natural products and containing complicated matrices.