Differential mobility spectrometry (DMS) of nitro-organic explosives and related compounds exhibited the expected product ions of M- or M x NO2- from atmospheric pressure chemical ionization reactions in purified air at 100 degrees C. Peaks in the differential mobility spectra for these ions were confined to a narrow range of compensation voltages between -1 to +3 V which arose through a low dependence of mobility for the ions in electric fields at E/N values between 0 and 120 Td (1 Td = 10(-17) V cm2). The field dependence of ions, described as an alpha parameter, ranged from -0.005 to 0.02 at a separation field of 100 Td. The alpha parameter could be controlled through the addition of organic vapors into the drift gas and was increased to 0.08-0.24 with 1000 ppm of methylene chloride in the drift gas. This modification of the drift gas resulted in compensation voltages of +3 to +21 V for peaks. The improved separation of peaks was consistent with a model of ion characterization by DeltaK or Kl - Kh, where Kl is the mobility coefficient of ions clustered with vapor neutrals during the low-field portion of the separation field waveform and Kh is for the same core ion when heated and declustered during the high-field portion of waveform.

The dependence of the mobilities of gas-phase ions on electric fields from 0 to 90 Td at ambient pressure was determined for protonated monomers [(MH+(H2O)n] and proton bound dimers [M2H+(H2O)n] for a homologous series of normal ketones, from acetone to decanone (M=C3H6O to C10H20O). This dependence was measured as the normalized function of mobility alpha (E/N) using a planar field asymmetric waveform ion mobility spectrometer (PFAIMS) and the ions were mass-identified using a PFAIMS drift tube coupled to a tandem mass spectrometer. Methods are described to obtain alpha (E/N) from the measurements of compensation voltage versus amplitude of an asymmetric waveform of any shape. Slopes of alpha for MH+ versus E/N were monotonic from 0 to 90 Td for acetone, butanone, and pentanone. Plots for ketones from hexanone to octanone exhibited plateaus at high fields. Nonanone and decanone showed plots with an inversion of slope above 70 Td. Proton bound dimers for ketones with carbon numbers greater than five exhibited slopes for alpha versus E/N, which decreased continuously with increasing E/N. These findings are the first alpha values for ions from a homologous series under atmosphere pressure and are preliminary to explanations of alpha (E/N) with ion structure.

Ion mobility spectrometry (IMS) was used to analyze vapors generated directly above pharmaceutical solids warmed in air to 100-200 degrees C. Vapors were characterized by IMS/mass spectrometry to evaluate the air-based atmospheric pressure chemical ionization of components in analgesic medicines. A hand-held IMS was used to determine the suitability of membrane-based instrumentation for routine analyses of large polar molecules. Mobility spectra for seven compounds could be individually represented by single or a few intense product ion peaks. Ion source fragmentations were nonexistent with these pharmaceuticals but complex behavior in the IMS involving ion-molecule clustering was pronounced in certain spectra. Mobility spectra were distinct and recognizable for each compound and binary mixtures of individual ingredients and actual over-the-counter medicines produced mobility spectra suggestive of composite spectra. This work represents a first delineation of complex ion mobility spectra for mixtures using spectra from individual components. These findings support further development of IMS for use in quality control during manufacture of such preparations and in routine screening of powders containing analgesic pharmaceuticals.

Volatile organic compounds (VOCs) emitted into headspace over discrete electronic components including resistors, capacitors, diodes, transistors, and transformers were identified and quantitatively determined in Part 1 of this series using gas chromatography/mass spectrometry. Vapors emissions of VOCs were characteristic of each component and headspace concentrations increased with temperature and persisted with time in most instances. Technology suitable for routine continuous monitoring of air quality based on gas chromatography/differential mobility spectrometry (GC/DMS) was evaluated with the same electronic components here, Part 2 of this series. Distinctive patterns in plots of ion peak intensity, retention time, and compensation voltage were obtained from VOCs from resistors, capacitors, and insulation from wires of a transformer held at 200°C for ten minutes. Intensity of response and analytically rich information produced by GC/DMS suggest further utility also as an air quality monitor or smart smoke alarm with electronics-dense habitats in spacecraft or offices and industrial venues.