Comparison of comprehensive two-dimensional gas chromatography in conventional and stop-flow modes

A new mode of operation for comprehensive two-dimensional gas chromatography (GC x GC), stop-flow GC x GC, was introduced recently. In this technique, the flow in the primary column is stopped for a brief period of time during each modulation cycle, allowing for a secondary separation time that is longer than would otherwise be permitted by the modulation period in conventional GC x GC. This allows the modulation period and the secondary separation time to become independent variables, and greatly increases the flexibility of the system. In this paper, separations obtained under similar conditions for both conventional and stop-flow GC x GC are presented, demonstrating the advantages that stop-flow GC x GC provides over conventional GC x GC for certain separations.