Portable comprehensive two-dimensional micro-gas chromatography using an integrated flow-restricted pneumatic modulator

Two-dimensional (2D) gas chromatography (GC) provides enhanced vapor separation capabilities in contrast to conventional one-dimensional GC and is useful for the analysis of highly complex chemical samples. We developed a microfabricated flow-restricted pneumatic modulator (FRPM) for portable comprehensive 2D micro-GC (μGC), which enables rapid ²D injection and separation without compromising the ¹D separation speed and eluent peak profiles. ²D injection characteristics such as injection peak width and peak height were fully characterized by using flow-through micro-photoionization detectors (μPIDs) at the FRPM inlet and outlet. A ²D injection peak width of ~25 ms could be achieved with a ²D/¹D flow rate ratio over 10. The FRPM was further integrated with a 0.5-m long ²D μcolumn on the same chip, and its performance was characterized. Finally, we developed an automated portable comprehensive 2D μGC consisting of a 10 m OV-1 ¹D μcolumn, an integrated FRPM with a built-in 0.5 m polyethylene glycol ²D μcolumn, and two μPIDs. Rapid separation of 40 volatile organic compounds in ~5 min was demonstrated. A hybrid 2D contour plot was constructed by using both ¹D and ²D chromatograms obtained with the two μPIDs at the end of the ¹D and ²D μcolumns, which was enabled by the presence of the flow resistor in the FRPM.