Chip-scale gas chromatography: From injection through detection

Miniaturized gas chromatography (mu GC) systems hold potential for the rapid analysis of volatile organic compounds (VOCs) in an extremely compact and low-power enabled platform. Here, we utilize microfabrication technology to demonstrate the single chip integration of the key components of a mu GC system in a two-step planar fabrication process. The 1.5 x 3 cm microfluidic platform includes a sample injection unit, a micromachined semi-packed separation column (mu SC) and a micro-helium discharge photoionization detector (mu DPID). The sample injection unit consists of a T-shaped channel operated with an equally simple setup involving a single three-way fluidic valve, a micropump for sample loading and a carrier gas supply for subsequent analysis of the VOCs. The innovative sample injection technique described herein requires a loading time of only a few seconds and produces sharp and repeatable sample pulses (full width at half maximum of approximately 200 ms) at a carrier gas flow rate that is compatible with efficient chromatographic separation. Furthermore, our comprehensive characterization of the chip reveals that a wide variety of VOCs with boiling points in the range of 110-216 degrees C can be analyzed in less than 1 min by optimizing the flow and temperature programming conditions. Moreover, the analysis of four VOCs at the concentration level of one part per million in an aqueous sample (which corresponds to a headspace concentration in the lower parts-per-billion regime) was performed with a sampling time of only 6 s. The mu DPID has demonstrated a linear dynamic range over three orders of magnitude. The system presented here could potentially be used to monitor hazardous VOCs in real time in industrial workplaces and residential settings.