A micro gas chromatograph for high-speed determinations of explosive markers

A complete gas chromatographic (μGC) microanalytical system for near-real-time determinations of marker compounds of explosives at low concentrations is demonstrated. This μGC, dubbed INTREPID, uses an adsorbent-packed micromachined DRIE-Si/glass microfocuser, a wall-coated 1 × 1 cm DRIE-Si/glass microcolumn (1-m channel length), and an integrated array of 4 chemiresistors coated with functionalized thiolate-monolayer-protected gold nanoparticle (MPN) interface layers. A high-volume sampler of conventional design is interfaced to the font-end of the microsystem to reduce limits of detection (LOD) and the analytical duty cycle. Instrument control and data acquisition are executed automatically via Labview code run from a laptop computer. The marker compounds consisted of the TNT byproducts, 2,4- and 2,6-dinitrotoluene, and the taggant, 2,3-dimethyl- 2,3-dinitrobutane. n-Tridecane was used as a representative interference. The combination of retention time and response pattern facilitated the identification of each marker. A full analysis was achieved in < 3.5 min with LODs in the low- or sub- parts-per-billion range for a preconcentrated air-sample volume of 1 L.