SELECTIVE DETECTION OF VAPORS

摘要

A detection system and method are disclosed for detecting vapors of specific compounds in air. Vapors such as explosives are stripped from surfaces using heat and suction from a hand-held sample gun (120), are collected on surfaces coated with gas chromatograph material which trap explosives vapors but repel nitric oxide, then are desorbed and concentrated in one or more cold spot concentrators (212, 214). The vapors in hydrogen carrier gas are separated by a high speed gas chromatograph (250), after which specific vapors are decomposed in two pyrolyzers (276, 278) arranged in parallel and the resulting nitric oxide is detected. A low temperature pyrolyzer (278) with silver produces NO from nitramines or nitrite esters; a high temperature pyrolyzer (276) decomposes all explosives vapors to permit detection of the remaining explosives. Also disclosed is a series arrangement of pyrolyzers (352, 354) and gas chromatographs (360, 368) and an NO detector (370) to time-shift detection of certain vapors and facilitate very fast, selective analyses.