Microfabricated Gas Chromatograph for Rapid, Trace-Level Determinations of Gas-Phase Explosive Marker Compounds

Abstract

A prototype microfabricated gas chromatograph (μGC) adapted specifically for the rapid determination of selected gas-phase marker compounds of the explosive 2,4,6-trinitrotoluene (TNT) at sub-parts-per-billion (<ppb) concentrations in complex mixtures is described. Si-microfabricated focuser, separation column, and sensor array components are integrated with a high-volume sampler of conventional construction to reduce analysis time and the limit of detection (LOD). The primary markers selected as target analytes were 2,4-dinitrotoluene (2,4-DNT, a persistent impurity of TNT) and 2,3-dimethyl-2,3-dinitrobutane (DMNB, a taggant), along with 2,6-dinitrotoluene (2,6-DNT, a less-prominent TNT impurity), which was also included in numerous tests. Selective preconcentration, on-column focusing, temperature-programmed chromatographic separation, and sensor array detection/recognition facilitated determinations of the primary markers in the presence of 20 (or more) interferences within ∼2 min under laptop control. Estimated LODs of 2.2, 0.48, and 0.86 ng were achieved for DMNB, 2,6-DNT, and 2,4-DNT, respectively, which correspond to 0.30, 0.067, and 0.12 ppb in each 1-L air sample collected.

μGC × μGC: Comprehensive Two-Dimensional Gas Chromatographic Separations with Microfabricated Components

“…As shown, the alkanes (compounds 3, 8, 11, and 13) eluted early from the 2 D μcolumn, as expected, and gave sharp peak clusters, with fwhm values ranging from 80 (C 7 ) to 280 ms (C 10 ). The alkene d-limonene and the set of four aromatics (compounds 1, 6,9,12,14) were all retained slightly longer than the alkanes and had fwhm values of 410− 480 ms, with little or no tailing evident. The diether 1,4-dioxane had slightly wider modulated peaks (fwhm = 532 ms).…”

Zebra GC: A fully integrated micro gas chromatography system

“…Table 1-1 Summary and comparison of µGC systemsprovides a detailed comparison of four µGC systems, including Zebra GC, and highlights the features, advantages and disadvantages of different system components. As seen, other reported µGC systems [19][20][21][22][23], while producing promising results, use individually fabricated chips which lead to extra care to avoid compound condensation in cold spots. Also, some of these systems still use conventional components to achieve high performance which can lead to increased energy consumptions or increased analysis time.…”

Chopper-modulated gas chromatography electroantennography enabled using high-temperature MEMS flow control device

“…Less effort has been made toward the fabrication of other necessary μGC components, such as microvalves and micropumps, which are used extensively for fluidic routing and to provide gas flow. Usually, a μGC system is developed using commercially available valves and pumps [16][17][18] , and few research milestones have been accomplished toward microvalve miniaturization 14,19 . In one example, Terry et al 20 reported a magnetically actuated microvalve for sample injection in their seminal work on μGC development.…”