@article {2785,
	title = {Ion trap mass analysis at high pressure: an experimental characterization.},
	journal = {Journal of Mass Spectrometry},
	volume = {45},
	year = {2010},
	month = {2010 Jan},
	pages = {26-34},
	abstract = {<p>In recent years, it has become increasingly interesting to understand the performance of mass spectrometers at pressures much higher than those employed with conventional operating conditions. This interest has been driven by several influences, including demand for the development of reduced-power miniature mass spectrometers, desire for improved ion transfer into and through mass spectrometers, enhanced-yield preparative mass separations, and mass filtering at the atmospheric pressure interface. In this study, an instrument was configured to allow for the performance characterization of a rectilinear ion trap (RIT) at pressures up to 50 mtorr with air used as the buffer gas. The mass analysis efficiency, mass resolution, isolation efficiency, and collision-induced dissociation (CID) efficiency were evaluated at pressures ranging from 1 to 50 mtorr. The extent of degradation of mass resolution, isolation efficiency and ion stability as functions of pressure were characterized. Also, the optimal resonance ejection conditions were obtained at various pressures. Operations at 50 mtorr demonstrated improved CID efficiency in addition to peak widths of 2 and 5 m/z units (full width at half-maximum, FWHM) for protonated caffeine (m/z 195) and Ultramark (m/z 1521) respectively.</p>
},
	keywords = {Equipment Design, Ions, Mass Spectrometry, Pressure, Proteins},
	issn = {1096-9888},
	doi = {10.1364/AO.50.001792},
	author = {Song, Qingyu and Xu, Wei and Smith, Scott A and Gao, Liang and Chappell, William J and Cooks, R Graham and Ouyang, Zheng}
}
@article {2798,
	title = {Mass selection of ions from beams using waveform isolation in radiofrequency quadrupoles.},
	journal = {Analytical Chemistry},
	volume = {81},
	year = {2009},
	month = {2009 Mar 1},
	pages = {1833-40},
	abstract = {<p>A waveform isolation method is described for the mass-selective transmission of ions through quadrupole mass filters, and it is implemented on a new tandem mass analyzer instrument. The method features the application of broad-band waveforms comprising appropriate frequencies to cause mass-selective instability in ions of particular mass-to-charge (m/z) and to transmit all others. The experiment is implemented in a tandem quadrupole system in which the first mass filter is a rectilinear ion trap (RIT) operated in a continuous mass-selective mode to transmit ions of ions of one or more arbitrarily selected m/z value(s). The second analyzer was used to verify the quality of the mass selection achieved using the first analyzer via conventional quadrupole ion trap mass-selective instability scanning. A new subtype of product ion tandem mass spectrometry (MS/MS) scan, termed the summed product ion scan, is demonstrated with a mixture of biological compounds. It is used to characterize product ions arising after simultaneous isolation and collisional activation of multiple precursor species, in this case ions of the same analyte generated in different charge states. The summed product ion scan can be useful for enhancing sensitivity for the analyte of interest or for providing more comprehensive information about an analyte than is available by monitoring a single ionized form of the analyte. The analytical performance of the waveform isolation method is tested using simple drug mixtures, and its potential for increasing overall yields in preparative mass spectrometry is explored briefly. It is shown that efficiencies of ca. 70\% of ion transfer to a surface for ion soft landing surface can be achieved. The upper mass range is limited by axial acceleration arising from the stretched geometry, and one solution to this problem is provided.</p>
},
	keywords = {Carmustine, Cytarabine, Electrospray Ionization, Ions, Mass, Mass Spectrometry, Mathematics, Melphalan, Radio Waves, Spectrometry, Tandem Mass Spectrometry},
	issn = {1520-6882},
	doi = {10.1364/AO.50.001792},
	author = {Song, Qingyu and Smith, Scott A and Gao, Liang and Xu, Wei and Voln{\'y}, Michael and Ouyang, Zheng and Cooks, R Graham}
}
