First-principle modeling and characterization of thermal modulation in comprehensive two-dimensional gas chromatography using a microfabricated device

Thermal modulation of analyte effluents at a junction between serially connected complementary columns is a critical process in comprehensive two-dimensional gas chromatography (GC × GC). However, little effort has been made to theoretically study this process with a full understanding of key phenomena. We developed a theoretical model of single-stage thermal modulation processes based on fundamental physics of gas chromatography (GC) with the aim to elucidate factors leading to improvements in GC × GC analyses. Model predictions were compared with experimental data obtained using our microfabricated thermal modulator (μTM) operating as a single-stage thermal modulator. Built upon one-dimensional (1D) GC theory, our model predicted the temporal and spatial distribution of analyte concentration within a thermal modulator (TM) channel during periodically repeating modulation cycles, each consisting of a cooling and heating period and yielding sharp peaks from a broad first dimension peak. Our model incorporated the effect of the location of the incoming 1D Gaussian peak to the μTM, with respect to the onset of the cooling period and the influence of cold interconnects on the thermal modulation process. Excellent match between experiment and simulation was obtained. Finally we proposed a few design modifications which could drastically improve performance of our μTM.