Waveboard artifacts generate ghost resonances consistent with equations for predicting ion motion in commercial quadrupole ion traps

Eur. J. Mass Spectrom. 11, 15–21 (2005)
DOI: 10.1255/ejms.711

Waveboard artifacts generate ghost resonances consistent with equations for predicting ion motion in commercial quadrupole ion traps

Kwenga F. Sichilongo^a,* and Bert C. Lynn Jr^b
^aUniversity of Zambia, Department of Chemistry, PO Box 32379, Lusaka 10101, Zambia. E-mail: ksichilo@natsci.unza.zm
^bDepartment of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA

ABSTRACT:

Real-time experiments, involving fragmentation of the precursor molecular ion of n-butylbenzene (m/z 134) to produce product ions C⁷H⁺₇(m/z 91) and C⁷H⁺₇ (m/z 92), were used to observe the motion of ions in a commercial quadrupole ion trap. Initially, ghost resonance peaks were observed for excitation of the precursor ion at q_z values of 0.4 and 0.5 on the q_z axis of the stability diagram. Further experiments involving generation of two-dimensional contour plots confirmed that these ghost peaks, which were in agreement with mathematical equations describing the motion of ions in a quadrupole field, arose due to waveboard artifacts. Two-dimensional contour surface plots showed non-linear secular frequency canyons from a q_z value of 0.5 to higher values corresponding with higher drive radio frequency (rf) voltages on the stability diagram. This observation confirmed that ions are subjected to non-linear effects in this mass scan range. The octapole and hexapole field lines were observed at q_z values of 0.65 and 0.78, respectively.

Keywords: precursor ions, product ions, secular frequency, multipole fields, resonance, stability diagram, non-linear, ion trap, quadrupole

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