Flow modulation comprehensive two-dimensional gas chromatography–mass spectrometry using ≈4 mL min−1 gas flows

• Fine optimization of the configuration of a flow modulator has been performed.
• Satisfactory flow modulation at gas flows of ≈4 mL min−1 was achieved.
• Flow-modulated GC × GC is extended to practically all commercial MS devices

The main objective of the herein described research was focused on performing satisfactory flow modulation (FM), in comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC–MS), using an MS-compatible second-dimension gas flow of approx. 4 mL min−1. The FM model used was based on that initially proposed by Seeley et al. [3]. The use of limited gas flows was enabled through fine tuning of the FM parameters, in particular the duration of the re-injection (or flushing) process. Specifically, the application of a long re-injection period (i.e., 700 ms) enabled efficient accumulation-loop flushing with gas flows of about 4 mL min−1. It was possible to apply such extended re-injection periods by using different restrictor lengths in the connections linking the modulator to the auxiliary pressure source. FM GC × GC–MS applications were performed on a mixture containing C9–10 alkanes, and on a sample of essential oil. GC × GC–MS sensitivity was compared with that attained by using conventional GC–MS analysis, in essential oil applications. It was observed that signal intensities were, in general, considerably higher in the FM GC × GC–MS experiments.