@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 {2432,
	title = {A new broadly tunable (7.4-10.2 eV) laser based VUV light source and its first application to aerosol mass spectrometry},
	journal = {International Journal of Mass Spectrometry},
	volume = {279},
	number = {2-3},
	year = {2009},
	note = {ISI Document Delivery No.: 399TJTimes Cited: 10Cited Reference Count: 78Hanna, S. J. Campuzano-Jost, P. Simpson, E. A. Robb, D. B. Burak, I. Blades, M. W. Hepburn, J. W. Bertram, A. K.},
	month = {Jan},
	pages = {134-146},
	type = {Article},
	abstract = {A laser based vacuum ultraviolet (VUV) light source using resonance enhanced four wave difference mixing in xenon gas was developed for near threshold ionization of organics in atmospheric aerosol particles. The source delivers high intensity pulses of VUV light (in the range of 10(10) to 10(13) photons/pulse depending on wavelength, 5 ns FWHM) with a continuously tunable wavelength from 122 nm (10.2 eV) to 168 nm (7.4 eV). The setup allows for tight (< 1 mm(2)) and precise focusing (mu rad pointing angle adjustability), attributes required for single particle detection. The generated VUV is separated from the pump wavelengths by a custom monochromator which ensures high spectral purity and minimizes absorptive losses. The performance of the source was characterized using organic molecules in the gas phase and optimal working conditions are reported. In the gas phase measurements, photoionization efficiency (PIE) curves were collected for seven different organic species with ionization energies spanning the full wavelength range of the VUV source. The measured appearance energies are very close to the literature values of the ionization energies for all seven species. The effectiveness of the source for single particle studies was demonstrated by analysis of individual caffeine aerosols vaporized by a pulsed CO2 laser in an ion trap mass spectrometer. Mass spectra from single particles down to 300 nm in diameter were collected. Excellent signal to noise characteristics for these small particles give a caffeine detection limit of 8 x 10(5) molecules which is equivalent to a single 75 nm aerosol, or approximately 1.5\% of a 300 nm particle. The appearance energy of caffeine originating from the aerosol was also measured and found to be 7.91 +/- 0.05 eV, in good agreement with literature values. (C) 2008 Elsevier B.V. All rights reserved.},
	keywords = {Aerosol mass spectrometry, analysis, CROSS-SECTIONS, EFFICIENCY, FUEL-RICH FLAMES, GENERATING PARTICLE BEAMS, ION-TRAP, ONLINE, ORGANIC-COMPOUNDS, PARTICULATE MATTER, PHOTOIONIZATION, SINGLE-PHOTON IONIZATION, SURFACE-ANALYSIS, Vacuum ultraviolet light, VACUUM-ULTRAVIOLET PHOTOIONIZATION},
	isbn = {1387-3806},
	url = {<Go to ISI>://000262821900012},
	author = {Hanna, S. J. and Campuzano-Jost, P. and Simpson, E. A. and Robb, D. B. and Burak, I. and Blades, M. W. and Hepburn, J. W. and Bertram, A. K.}
}
