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10 May 2012 Sensor array and preconcentrator for the detection of explosives in water
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A sensor system has been constructed that is capable of detecting and discriminating between various explosives presented in ocean water with detection limits at the 10-100 parts per trillion level. The sensor discriminates between different compounds using a biologically-inspired fluorescent polymer sensor array, which responds with a unique fluorescence quenching pattern during exposure to different analytes. The sensor array was made from commercially available fluorescent polymers coated onto glass beads, and was demonstrated to discriminate between different electron-withdrawing analytes delivered in salt water solutions, including the explosives 2,4,6-trinitrotoluene (TNT) and tetryl, the explosive hydrolysis products 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene, as well as other explosive-related compounds and explosive simulants. Sensitivities of 10-100 parts per trillion were achieved by employing a preconcentrator (PC) upstream of the sensor inlet. The PC consists of the porous polymer Tenax, which captures explosives from contaminated water as it passes through the PC. As the concentration of explosives in water decreased, longer loading times were required to concentrate a detectable amount of explosives within the PC. Explosives accumulated within the PC were released to the sensor array by heating the PC to 190 C. This approach yielded preconcentration factors of up to 100-1000x, however this increased sensitivity towards lower concentrations of explosives was achieved at the expense of proportionally longer sampling times. Strategies for decreasing this sampling time are discussed.
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Marc D. Woodka, J. Cory Shpil, Vincent P. Schnee, and J. Michael P. Polcha "Sensor array and preconcentrator for the detection of explosives in water", Proc. SPIE 8357, Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XVII, 83571T (10 May 2012);

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