A Microscale Gas Chromatograph for High-Speed Determinations of Explosive Markers

G. Serrano, L. K. Amos, H. Chang, W. Collin, N. Nunovero, E T. Zellers

This project demonstrates, for the first time, a fully integrated gas chromatographic microanalytical system (µGC) for near-real-time determinations of trace-level vapor concentrations of marker compounds of explosives. This µGC, dubbed INTREPID, will be used for airport screening applications to protect workers and the public from terrorist threats. A top view of the current lab prototype is shown above. It uses an adsorbent-packed, deep-reactive-ion-etched (DRIE) Si/glass microfocuser, a wall-coated DRIE-Si/glass microcolumn, and an integrated array of 4 chemiresistors coated with functionalized thiolate-monolayer-protected gold nanoparticle (MPN) interface layers. A high-volume sampler is connected upstream to reduce analysis time and detection limits. Commercial valves and mini-pumps are used. All functions are set and automatically sequenced by a laptop computer, which runs routines written in-house in LabView. Laboratory testing of the INTREPID lab prototype was performed with the following explosive markers: 2,4- and 2,6-dinitrotoluene (2,4- and 2,6-DNT) and 2,3-dimethyl-2,3-dinitrobutane (DMNB, an explosive taggant). Tridecane (C13) was tested as a potential interference. Calculated limits of detection are 40, 1.5, 2.0 ng, corresponding to 5.4, 0.2, 0.2 ppb, for DMNB, 2,6-DNT and 2,4-DNT, respectively (1-L sample). In the analysis of the mixture of the three markers and C13, all four components are sufficiently resolved and a complete analysis requires just 3.5 min. Several design modifications are currently being implemented that will reduce the size of the prototype, the power dissipation, and the analysis time (to < 2 min). This work is funded by the U. S. Department of Homeland Security, Science and Technology Directorate.