False positive signals in the detection of explosives using ion mobility spectrometry: organic acids

Twenty varieties of fruits (fruits, berries, vegetables) were studied, the presence of trace amounts of which in samples causes false positive signals in explosives detectors based on the ion mobility spectrometry method. These signals are due to the presence of organic acids in the fruits, which effectively form negative ions. The mobilities of some types of these acid ions are close to or coincide with the mobilities of explosive substance ions. Specifically, ions of ascorbic or citric acid, malic acid, tartaric acid, adduct anions of oxalic and malic acids, adduct anions of citric and malic acids are identified by the detector as ions of 2,4-dinitrotoluene, 1,2,3-trinitroxypropane, octogen, and 2,4,6-trinitrotoluene, adduct anions of hexogen and lactic acid, respectively.