Chip-scale gas chromatography: From injection through detection

Abstract

Miniaturized gas chromatography (µGC) 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 µGC system in a two-step planar fabrication process. The 1.5 Â 3 cm microfluidic platform includes a sample injection unit, a micromachined semi-packed separation column (µSC) and a micro-helium discharge photoionization detector (µDPID). 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°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 µDPID 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.

Compact prototype microfabricated gas chromatographic analyzer for autonomous determinations of VOC mixtures at typical workplace concentrations

“…Reconciling the trade offs among VOC mixture pre-selection, pre-concentration, separation, and recognition/detection functions was central to realizing effective system-level performance. Collectively, the operational features and performance characteristics of the PEMM-1 prototype demonstrated in this study exceed those demonstrated with other prototype μGCs reported to date 28,29,[31][32][33][34][35][36][50][51][52][53] . Future work on optimizing sensor coating strategies should yield improvements in peak shapes and reductions in LODs.…”

“…Notwithstanding the OPH sensor, the excessive tailing of which renders it of less value as a detector, the speed and resolution obtained were quite good. Taken together with the peak capacities, which ranged from 80 to 103 among the sensors for a 4 min separation based on MBK, and the peak production rates, which ranged from 20-25 per min (also based on MBK), the chromatographic performance of the PEMM-1 exceeds that of other reported GC prototypes employing microfabricated separation components 28,29,[31][32][33][34][35][36][50][51][52][53] .…”

“…Such multi-VOC measurements are currently only possible with portable GCs [1][2][3][4] and transportable FTIR 5 and GC-MS 6,7 instruments, which are too large and expensive for routine evaluations of personal exposures. Although significant advances have been reported recently in the design and development of individual μGC components for preconcentration [8][9][10][11] , separation [12][13][14][15][16][17][18][19][20] ,detection [21][22][23][24][25] , and systems that combine one or more such microdevices with conventional GC components [26][27][28][29] , surprisingly few reports have appeared on integrated and/or packaged μGC systems in which the core analytical components were microfabricated [30][31][32][33][34][35][36] .…”

Highly Sensitive and Selective VOC Sensor Systems Based on Semiconductor Gas Sensors: How to?

“…This approach has been miniaturized with the goal to achieve sensor systems for nearly continuous monitoring operating in adsorption/desorption cycles. However, these systems today are typically based on closed pre-concentrators combined with micro-pumps leading to systems that are not low-cost [51,52]. We have developed a new approach based on open …”

Microscale Gas Chromatography with Microsensor Array Detection: Challenges and Prospects

“…Research and development on microscale gas chromatographic (μGC) systems for analyzing mixtures of volatile organic compounds (VOCs) conducted over the past few decades has produced some significant advances in component device designs, system integration strategies, and performance [1][2][3]. Yet, early projections of inexpensive, pocket-sized instrumentation capable of autonomous, quantitative analysis of airborne VOC mixtures remain unrealized.…”