Axial thermal gradients in microchip gas chromatography

• Axial thermal gradients were generated along microfabricated gas chromatography columns.
• A thermal gradient reduced separation time by focusing the injection band during separation.
• Signal-to-noise ratio, peak symmetry and resolution were improved by the focusing effect of the gradient.

Fabrication technologies for microelectromechanical systems (MEMS) allow miniaturization of conventional benchtop gas chromatography (GC) to portable, palm-sized microfabricated GC (μGC) devices, which are suitable for on-site chemical analysis and remote sensing. The separation performance of μGC systems, however, has not been on par with conventional GC. Column efficiency, peak symmetry and resolution are often compromised by column defects and non-ideal injections. The relatively low performance of μGC devices has impeded their further commercialization and broader application. In this work, the separation performance of μGC columns was improved by incorporating thermal gradient gas chromatography (TGGC). The analysis time was ∼20% shorter for TGGC separations compared to conventional temperature-programmed GC (TPGC) when a wide sample band was introduced into the column. Up to 50% reduction in peak tailing was observed for polar analytes, which improved their resolution. The signal-to-noise ratios (S/N) of late-eluting peaks were increased by 3–4 fold. The unique focusing effect of TGGC overcomes many of the previous shortcomings inherent in μGC analyses.