Uniform-temperature, microscale thermal modulator with area-adjusted air-gap isolation for comprehensive two-dimensional gas chromatography

In comprehensive two-dimensional gas chromatography (GC × GC), thermal modulation is an important process to enhance the detectability of a volatile organic compound analyte and compound separation capacity. For increased detectability, we explore a method to enhance the temperature uniformity of a microfabricated thermal modulator with an area-adjusted air-gap spacer. The area-adjusted spacer controls the spatial distribution of heat transfer to increase the temperature uniformity of the analyte passing through the device's channel. This enables higher analyte peak-amplitude enhancement (PAE) during thermal modulation, thereby increasing detectability of the analyte. The influence of varying spacer area on temperature uniformity was characterized by simulation, and its effect on PAE was experimentally estimated. With an optimized spacer design, we achieved a 25% increase in PAE (34–42) for 10 ppm n-octane vapor.