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

ABSTRACT

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.