@article {2609,
	title = {A laser desorption-electron impact ionization ion trap mass spectrometer for real-time analysis of single atmospheric particles},
	journal = {International Journal of Mass Spectrometry},
	volume = {281},
	number = {3},
	year = {2009},
	note = {ISI Document Delivery No.: 426SSTimes Cited: 3Cited Reference Count: 73Simpson, E. A. Campuzano-Jost, P. Hanna, S. J. Robb, D. B. Hepburn, J. H. Blades, M. W. Bertram, A. K.},
	month = {Apr},
	pages = {140-149},
	type = {Article},
	abstract = {A novel aerosol ion trap mass spectrometer combining pulsed IR laser desorption with electron impact (EI) ionization for single particle studies is described. The strengths of this instrument include a two-step desorption and ionization process to minimize matrix effects; electron impact ionization, a universal and well-characterized ionization technique; vaporization and ionization inside the ion trap to improve sensitivity; and an ion trap mass spectrometer for MSn experiments. The instrument has been used for mass spectral identification of laboratory generated pure aerosols in the 600 nm-1.1 mu m geometric diameter range of a variety of aromatic and aliphatic compounds, as well as for tandem mass spectrometry studies (up to MS3) of single caffeine particles. We investigate the effect of various operational parameters on the mass spectrum and fragmentation patterns. The single particle detection limit of the instrument was found to be a 325 nm geometric diameter particle (8.7 x 10(7) molecules or 22 fg) for 2,4-dihydroxybenzoic acid. Lower single particle detection limits are predicted to be attainable by modifying the El pulse. The use of laser desorption-electron impact (LD-EI) in an ion trap is a promising technique for determining the size and chemical composition of single aerosol particles in real time. (C) 2009 Elsevier B.V. All rights reserved.},
	keywords = {AERODYNAMIC LENSES, Aerosol mass spectrometry, AEROSOL-PARTICLES, CHEMICAL-ANALYSIS, CONTROLLED DIMENSIONS, Electron impact ionization, ENVIRONMENTAL PARTICLES, INVERSE FOURIER-TRANSFORM, LENS-NOZZLE SYSTEM, NUMERICAL CHARACTERIZATION, ORGANIC AEROSOLS, Particle laser, Single particle analysis, THERMAL VAPORIZATION, vaporization},
	isbn = {1387-3806},
	url = {<Go to ISI>://000264728600006},
	author = {Simpson, E. A. and Campuzano-Jost, P. and Hanna, S. J. and Robb, D. B. and Hepburn, J. H. and Blades, M. W. and Bertram, A. K.}
}
@article {2431,
	title = {A study of oleic acid and 2,4-DHB acid aerosols using an IR-VUV-ITMS: insights into the strengths and weaknesses of the technique},
	journal = {Physical Chemistry Chemical Physics},
	volume = {11},
	number = {36},
	year = {2009},
	note = {ISI Document Delivery No.: 491ADTimes Cited: 3Cited Reference Count: 66Hanna, Sarah J. Campuzano-Jost, Pedro Simpson, Emily A. Burak, Itamar Blades, Michael W. Hepburn, John W. Bertram, Allan K.},
	pages = {7963-7975},
	type = {Article},
	abstract = {An investigation of oleic acid and 2,4-dihydroxybenzoic (DHB) acid aerosols was carried out using an aerosol mass spectrometer with pulsed lasers for vaporization and ionization and an ion trap for mass analysis. The extent of ion fragmentation was studied as a function of both vaporization energy and ionization wavelength. Low CO2 laser energies in the vaporization stage and near-threshold single photon ionization resulted in the least fragmented mass spectra. For DHB, only the molecular ion was observed, but for oleic acid fragmentation could not be eliminated. Tandem MS of the main fragment peak from oleic acid was carried out and provided a tool for compound identification. Photoionization efficiency curves were also collected for both DHB and oleic acid and the appearance energies of both parent and fragment ions were measured. Evidence for fragmentation occurring post-ionization is given by the similar appearance energies for both the parent and fragment ions. The results from this study were compared with those from similar experiments undertaken with time-of-flight (TOF) mass analyzers. The degree of fragmentation in the ion trap was considerably higher than that seen with TOF systems, particularly for oleic acid. This was attributed to the long storage interval in the ion trap which allows time for metastable ions to decay. Differences in the degree of fragmentation between the ion trap and TOF studies also provided further evidence for fragmentation occurring post-ionization. For 2,4-dihydroxybenzoic acid, the long delay prior to mass analysis also allowed time for reactions with background gases, in this case water, to occur.},
	keywords = {ATMOSPHERIC PARTICLES, CHEMICAL-ANALYSIS, ENVIRONMENTAL PARTICLES, GENERATING PARTICLE BEAMS, INVERSE FOURIER-TRANSFORM, LASER-DESORPTION/IONIZATION, ORGANIC-COMPOUNDS, QUADRUPOLE ION-TRAP, TRAP MASS-SPECTROMETER, VACUUM-ULTRAVIOLET PHOTOIONIZATION},
	isbn = {1463-9076},
	url = {<Go to ISI>://000269548300022},
	author = {Hanna, S. J. and Campuzano-Jost, P. and Simpson, E. A. and Burak, I. and Blades, M. W. and Hepburn, J. W. and Bertram, A. K.}
}
