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Ion Mobility Spectrometry (ion + mobility_spectrometry)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Detection of Explosives in Hair Using Ion Mobility Spectrometry

JOURNAL OF FORENSIC SCIENCES, Issue 3 2008
Jimmie C. Oxley Ph.D.
Abstract:, Conventional explosives 2,4,6-trinitrotoluene (TNT), nitroglycerin (NG), and ethylene glycol dinitrate (EGDN) sorbed to hair can be directly detected by an ion mobility spectrometer (IMS) in E-mode (for explosives). Terrorist explosive, triacetone triperoxide (TATP), difficult to detect by IMS in E-mode, was detected in N-mode (for narcotics). Three modes of sample introduction to IMS vapor desorption unit were used: (i) placement of hair directly into the unit, (ii) swabbing of hair and placement of swabs (i.e., paper GE-IMS sample traps) into the unit, and (iii) acetonitrile extracts of hair positioned on sample traps and placed into the unit. TNT, NG, and EGDN were detected in E-mode by all three sample introduction methods. TATP could only be detected by the acetonitrile extraction method after exposure of the hair to vapor for 16 days because of lower sensitivity. With standard solutions, TATP detection in E-mode required about 10 times as much sample as EGDN (3.9 ,g compared with 0.3 ,g). IMS in N-mode detected TATP from hair by all three modes of sample introduction. [source]

Monitoring of Emulsion Polymerisation Processes using Ion Mobility Spectrometry,A Pilot Study

MACROMOLECULAR REACTION ENGINEERING, Issue 2-3 2009
Wolfgang Vautz
Abstract Online monitoring of monomer concentrations in (semi-) batch emulsion polymerisation reactors is important for safe and cost-efficient operation of production plants. In the present pilot study, ion mobility spectrometry was applied for monitoring the concentration during emulsion polymerisation of vinyl acetate (VA) using UV light for ionisation of the headspace of a continuous sample flow. Satisfactory sensitivity for online process monitoring of the monomer concentration in the reactor was observed (LOD 400 ng,·,L,1 air, equivalent to <1%). Furthermore, it is possible to discriminate between VA and other common monomers [butyl acrylate (BA), methyl methacrylate (MMA)]. Using the more efficient , -radiation ionisation, monomer concentration could be measured even in the final latex as a measure of the final product properties. [source]

Particle Characteristics of Trace High Explosives: RDX and PETN,

JOURNAL OF FORENSIC SCIENCES, Issue 2 2007
Jennifer R. Verkouteren M.S.
ABSTRACT: The sizes of explosives particles in fingerprint residues produced from C-4 and Semtex-1A were investigated with respect to a fragmentation model. Particles produced by crushing crystals of RDX and PETN were sized by using scanning electron microscopy, combined with image analysis, and polarized light microscopy was used for imaging and identifying explosive particles in fingerprint residues. Crystals of RDX and PETN fragment in a manner that concentrates mass in the largest particles of the population, which is common for a fragmentation process. Based on the fingerprints studied, the particle size to target for improving mass detection in fingerprint residues by ion mobility spectrometry (IMS) is ,10 ,m in diameter. Although particles smaller than 10 ,m in diameter have a higher frequency, they constitute <20% of the total mass. Efforts to improve collection efficiency of explosives particles for detection by IMS, or other techniques, must take into consideration that the mass may be concentrated in a relatively few particles that may not be homogeneously distributed over the fingerprint area. These results are based on plastic-bonded explosives such as C-4 that contain relatively large crystals of explosive, where fragmentation is the main process leading to the presence of particles in the fingerprint residues. [source]

Monitoring of Emulsion Polymerisation Processes using Ion Mobility Spectrometry,A Pilot Study

Determining the topology of virus assembly intermediates using ion mobility spectrometry,mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2010
Tom W. Knapman
We have combined ion mobility spectrometry,mass spectrometry with tandem mass spectrometry to characterise large, non-covalently bound macromolecular complexes in terms of mass, shape (cross-sectional area) and stability (dissociation) in a single experiment. The results indicate that the quaternary architecture of a complex influences its residual shape following removal of a single subunit by collision-induced dissociation tandem mass spectrometry. Complexes whose subunits are bound to several neighbouring subunits to create a ring-like three-dimensional (3D) architecture undergo significant collapse upon dissociation. In contrast, subunits which have only a single neighbouring subunit within a complex retain much of their original shape upon complex dissociation. Specifically, we have determined the architecture of two transient, on-pathway intermediates observed during in vitro viral capsid assembly. Knowledge of the mass, stoichiometry and cross-sectional area of each viral assembly intermediate allowed us to model a range of potential structures based on the known X-ray structure of the coat protein building blocks. Comparing the cross-sectional areas of these potential architectures before and after dissociation provided tangible evidence for the assignment of the topologies of the complexes, which have been found to encompass both the 3-fold and the 5-fold symmetry axes of the final icosahedral viral shell. Such insights provide unique information about virus assembly pathways that could allow the design of anti-viral therapeutics directed at the assembly step. This methodology can be readily applied to the structural characterisation of many other non-covalently bound macromolecular complexes and their assembly pathways. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Solid-phase microextraction combined with surface-enhanced laser desorption/ionization introduction for ion mobility spectrometry and mass spectrometry using polypyrrole coatings

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2004
Yan Wang
The successful application of polypyrrole (PPY) solid-phase microextraction (SPME) coatings as both an extraction phase and a surface to enhance laser desorption/ionization (SELDI) of analytes is reported. This SPME/SELDI fiber integrates sample preparation and sample introduction on the tip of a coated optical fiber, as well as acting as the transmission medium for the UV laser light. Using ion mobility spectrometry (IMS) detection, the signal intensity was examined as a function of extraction surface area and concentration of analyte. The linear relationship between concentration and signal intensity shows potential applicability of this detection method for quantitative analysis. Extraction time profiles for the fiber, using tetraoctylammonium bromide as test analyte, illustrated that equilibrium can be reached in less than one minute. To investigate the performance of the PPY coating, the laser desorption profile was studied. The fiber was also tested using a quadrupole time-of-flight (Q-TOF) mass spectrometer with leucine enkephalin as test analyte. Since no matrix was used, mass spectra free from matrix background were obtained. This novel SPME/SELDI fiber is easy to manufacture, and is suitable for studying low-mass analytes because of the intrinsic low background. These findings suggest that other types of conductive polymers could also be used as an extraction phase and surface to enhance laser desorption/ionization in mass spectrometry. Copyright © 2003 John Wiley & Sons, Ltd. [source]