@article {4644,
	title = {Optimum phase angle for laser desorption ion trap mass spectrometry is dependent on the number of ions produced},
	journal = {International Journal of Mass Spectrometry},
	volume = {191},
	year = {1999},
	note = {ISI Document Delivery No.: 229EETimes Cited: 2Cited Reference Count: 22},
	month = {Aug},
	pages = {69-80},
	type = {Article},
	abstract = {Fur laser desorption sampling within a quadrupole ion trap, the phase and amplitude of the rf potential used to trap the ions, as well as the helium bath gas pressure, are important factors governing sensitivity. This article is concerned with investigating the dependence of trapping efficiency on the phase angle at the time that the laser fires. New data have been acquired demonstrating how the distribution of phase values that yield successful trapping, as well as the optimum phase for trapping, vary with the number of ions produced during the laser desorption event. It will also be shown that the position on the probe where the ions are created is a further factor in determining the optimum phase for trapping. Additional evidence taken from the laser desorption mass spectrometry literature will be used to propose a model for the dependence of the signal intensity versus phase relationship on the number of ions produced. It will be argued that trends in the data observed here are due to the effects of Debye shielding that accompany the desorption of substantial quantities of positive and negative ions. The dependency of the optimum phase angle on the position on the probe where the ions originate is not well understood at this time. Last, it will be shown how the pressure of helium within the trap does not influence the optimum phase value for trapping, but the effects of the bath gas pressure on trapping efficiency and fragmentation are interesting and will be discussed briefly. (Int J Mass Spectrom 190/191 (1999) 59-80) (C) 1999 Elsevier Science B.V.},
	keywords = {DISTRIBUTIONS, ION TRAP, IONIZATION, laser desorption, trapping efficiency},
	isbn = {1387-3806},
	url = {<Go to ISI>://000082179900010},
	author = {Robb, D. B. and Blades, M. W.}
}
@article {4077,
	title = {Analysis of polyaromatic quinones in a complex environmental matrix using gas chromatography ion trap tandem mass spectrometry},
	journal = {Talanta},
	volume = {44},
	number = {6},
	year = {1997},
	note = {ISI Document Delivery No.: XC195Times Cited: 13Cited Reference Count: 21},
	month = {Jun},
	pages = {985-1001},
	type = {Article},
	abstract = {GC/MS and GC/MS/MS in a quadrupole ion trap were used to analyze for anthraquinone, alkyl anthraquinones, benz[a]anthracene-7,12-dione and 9-fluoranone in a sediment obtained from an aluminum smelter settling pond contaminated with polycyclic aromatic hydrocarbons. By standard GC/MS analysis many of these target compounds were either undetectable or their confirmation uncertain because of matrix interferences. Detection and identification were greatly improved by using GC/MS/MS. GC/MS/MS analyses were performed by selecting the molecular ion (M) of a target compound and fragmenting it via collision induced dissociation (CID) to yield product ions corresponding to loss of CO for unsubstituted compounds or CO plus CH3 for alkylated compounds. The CID conditions were optimized using anthraquinone and 2-methylanthraquinone standards by varying the CID excitation energy and RF storage levels to yield optimum amounts of fragment ions. CID experiments were performed using both resonant and non-resonant wave forms. Although both excitation techniques gave comparable results for the removal of matrix interferences, non-resonant excitation provided more characteristic spectra for the alkylated anthraquinones. Monitoring of secondary fragmentation products, such as M-2CO, provided greater discrimination from matrix interferences than the use of primary fragmentation products, such as M-CO. (C) 1997 Elsevier Science B.V.},
	keywords = {CHROMATOGRAPHY, collision induced dissociation, environmental analysis, GAS, ION TRAP, polyaromatic quinones, polycyclic aromatic hydrocarbons, Tandem mass spectrometry},
	isbn = {0039-9140},
	url = {<Go to ISI>://A1997XC19500006},
	author = {Mosi, A. A. and Reimer, K. J. and Eigendorf, G. K.}
}
@article {2811,
	title = {LASER ABLATION ION-TRAP MASS-SPECTROMETRY - ATOMIC AND MOLECULAR MASS-SPECTROMETRY OF METAL, CERAMIC AND POLYMER SAMPLES},
	journal = {Journal of Analytical Atomic Spectrometry},
	volume = {8},
	number = {2},
	year = {1993},
	note = {ISI Document Delivery No.: LB836Times Cited: 20Cited Reference Count: 19},
	month = {Mar},
	pages = {261-267},
	type = {Article},
	abstract = {A quadrupole ion trap was used to characterize metallic, ceramic and polymeric materials by using laser ablation directly inside the storage volume as a sampling and ionization method. A differentially pumped sample probe was utilized to facilitate sample changes and ion trap electrodes with extended hyperbolic surfaces were used to provide more uniform ion storage fields. The effects of sample surface preparation and laser fluence were investigated for stainless-steel samples.},
	keywords = {ATOMIC MASS SPECTROMETRY, CERAMIC AND POLYMERIC SAMPLES, desorption, ION TRAP, laser ablation, METALLIC, MOLECULAR MASS SPECTROMETRY, SPECTROSCOPY},
	isbn = {0267-9477},
	url = {<Go to ISI>://A1993LB83600011},
	author = {Gill, C. G. and Blades, M. W.}
}
