Losses of ions during forward and reverse scans in a quadrupole ion trap mass spectrometer and how to reduce them

Vladimir M. Doroshenko, Robert J. Cotter

Research output: Contribution to journalArticle

Abstract

The higher order fields present in the quadrupole ion trap may have beneficial effects such as increases in mass resolution in the mass-selective instability or resonance ejection modes of operation, but may also result in losses of ions due to nonlinear resonances. In this work, the reduction in ion intensities observed in the mass spectra of polyethylene glycol (PEG 1000) has been utilized to monitor the ion losses resulting from these higher order fields during the rf voltage scans in both the forward and reverse directions. Extensive ion losses were observed in reverse rf voltage scans at q(z) = 0.64 (a(z) = 0), which corresponds to octopole resonance at β(z) = 1/2. The losses depended upon rf voltage scan rate and ion mass being greater for lower scan rates and lower masses. For ions of m/z 877, losses of up to 60% of the stored ions were observed at low scan rates (4 Da/s), but were minimal at higher scan rates. Thus, it is possible to avoid such losses during reverse scans by scanning the region q(z) = 0.64 at rates in excess of 4 x 104 Da/s. In forward rf voltage scans, ion storage was considerably more reliable; with significant losses observed only at very high scan rates near the region q(z) = 0.78 (hexapole resonance at β(z) = 2/3).

Original languageEnglish (US)
Pages (from-to)1141-1146
Number of pages6
JournalJournal of the American Society for Mass Spectrometry
Volume8
Issue number11
DOIs
StatePublished - Nov 1997

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Mass spectrometers
Ions
Electric potential
Scanning

ASJC Scopus subject areas

  • Structural Biology
  • Spectroscopy

Cite this

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title = "Losses of ions during forward and reverse scans in a quadrupole ion trap mass spectrometer and how to reduce them",
abstract = "The higher order fields present in the quadrupole ion trap may have beneficial effects such as increases in mass resolution in the mass-selective instability or resonance ejection modes of operation, but may also result in losses of ions due to nonlinear resonances. In this work, the reduction in ion intensities observed in the mass spectra of polyethylene glycol (PEG 1000) has been utilized to monitor the ion losses resulting from these higher order fields during the rf voltage scans in both the forward and reverse directions. Extensive ion losses were observed in reverse rf voltage scans at q(z) = 0.64 (a(z) = 0), which corresponds to octopole resonance at β(z) = 1/2. The losses depended upon rf voltage scan rate and ion mass being greater for lower scan rates and lower masses. For ions of m/z 877, losses of up to 60{\%} of the stored ions were observed at low scan rates (4 Da/s), but were minimal at higher scan rates. Thus, it is possible to avoid such losses during reverse scans by scanning the region q(z) = 0.64 at rates in excess of 4 x 104 Da/s. In forward rf voltage scans, ion storage was considerably more reliable; with significant losses observed only at very high scan rates near the region q(z) = 0.78 (hexapole resonance at β(z) = 2/3).",
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