CHARACTERIZATION OF THE ION MOBILITY SPECTROMETRIC BEHAVIOR OF A DINITROBUTANE UNDER VARYING CONDITIONS OF TEMPERATURE AND CONCENTRATION

The decomposition of 2,3-dimethyl-2,3-dinitrobutane in an ion mobility spectrometer operating in the positive and negative modes is describe d. The results of: varying the concentration of 2,3-dimethyl-2,3-dinit robutane between 0 and 0.12 mg m(-3) in nitrogen; varying the temperat ure between 317 and 455 K; and the effects of water, dichloromethane a nd ammonia reactant ion chemistries on the response of an ion mobility spectrometer are reported. The observed behaviour is consistent with the decomposition of 2,3-dimethyl-2,3-dinitrobutane to 3-methyl-3-nitr obut-1-ene and then to 2,3-dimethylbut-1,3-diene in a two stage proces s. Molecular ions with reduced mobilities attributable to species base d on NO2- are also observed simultaneously in the negative mode, suppo rting the proposed decomposition mechanism. The activation energies fo r the decomposition process, estimated from temperature programmed ion mobility spectrometry, are found to be lower than that previously rep orted. This may be attributed to the electron withdrawing nature of th e hydrated proton in the molecular cluster ion. (C) 1998 Elsevier Scie nce B.V. All rights reserved.