Characterisation of the molecular ions produced by a dinitroalkane in positive mode ion mobility spectrometry with water, dichloromethane and ammonia reactant ion chemistries

The effects of water at a concentration of less than 3 mg m(-3), ammonia at 0.61 mg m(-3) and dichloromethane at 77.3 mg m(-3) on the composition of reactant ion peaks in the positive mode have been studied using an ion mobility spectrometer coupled to an Extrel quadrupole mass spectrometer at 318 K and atmospheric pressure under nitrogen. Further, the positive mode ion mobility spectra of 2,3-dimethyl-2,3-dinitrobutane at 0.23 and 1.2 mg m(-3) have also been characterised by an ion mobility spectrometry coupled to a mass spectrometry (LMS-MS) operating in the positive ion mode, with water at a concentration of less than 3 mg m(-3), ammonia at 0.61 mg m(-3) and dichloromethane at 77.3 mg m(-3) as dopants. All of the dopants studied yielded 2,3-dimethyl-2,3-dinitrobutane molecular product ions in protonated water and ammonia clusters whose mobilities spanned the range 1.39-1.51 cm(2) V-1 s(-1) at 318 K and atmospheric pressure. The most sensitive and clearly resolved responses were obtained using ammonia. No decomposition of the 2,3-dimethyl-2,3-dinitrobutane molecule was observed. (C) 1998 Elsevier Science B.V. All rights reserved.