Nonlinear resonance effects during ion storage in a quadrupole ion trap

Abstract

Contributions of higher-order fields to the quadrupolar storage field produce nonlinear resonances in the quadrupole ion trap. Storing ions with secular frequencies corresponding to these nonlinear resonances allows absorption of power from the higher-order fields. This results in increased axial and radial amplitudes which can cause ion ejection and collision-induced dissociation (CID). Experiments employing long storage times and/or high ion populations, such as chemical ionization, ion-molecule reaction studies, and resonance excitation CID, can be particularly susceptible to nonlinear resonance effects. The effects of higher-order fields on stored ions are presented and the influence of instrumental parameters such as radiofrequency and direct current voltage (qZ and az values), ion population, and storage time are discussed.

A Theoretical Method for Characterizing Nonlinear Effects in Paul Traps with Added Octopole Field

“…Moreover, the nonlinear fields are regarded as the main factor in the degradation of the ion trap performance. For instance, the resultant nonlinear effects, such as ion delay ejection [31,32], nonlinear resonance [33,34], and frequency shift [35,36], are considered to be harmful to the mass resolution, sensitivity, and mass accuracy, respectively. With the in-depth study, the nonlinear fields have been found to be beneficial and have the potential to break the performance barrier and develop new operation modes of the ion trap.…”

Nonlinear Ion Harmonics in the Paul Trap with Added Octopole Field: Theoretical Characterization and New Insight into Nonlinear Resonance Effect

“…The nonlinear resonance potentially gives rise to the ion loss and the sensitivity degradation of the ion trap instruments [12][13][14][15][16]. It is meaningful to predict the rf working voltage (represented by the q value), at which the nonlinear resonance occurs.…”

“…The weight can increase to 10% or higher in some Paul trap geometrical variations [5], such as cylindrical [6] and rectilinear ion traps [7]. The nonlinear fields inevitably introduce a series of nonlinear effects into the ion motion, such as frequency shift [8][9][10], amplitude variation [11], nonlinear resonance [12][13][14][15][16], and thus have great impacts on the trap performance, in terms of mass resolution [8], mass accuracy [9], sensitivity [12], and tandem MS (MS/MS) efficiency [10,15], etc.…”

“…From these characteristic harmonics, the detailed composition of the nonlinear fields in the trap can be readily determined. Second, the nonlinear harmonics of ion motion are the unique reason for the nonlinear resonance effect [12][13][14][15][16]. Depending on the corresponding types of the nonlinear harmonics, the nonlinear resonance can be classified into single-direction (i.e., z or r direction) and r-z coupled resonances [16].…”

Study of ghost peaks resulting from space charge and non-linear fields in an ion trap mass spectrometer

“…a decrease in the parameter range for q z trapping ions). 21 The main resulting e †ects are the following : (i) erroneous m/z measurements which correspond to mass shifts,22 (ii) distortion of peak shapes23 and (iii) a loss of the higher m/z ions when the lower m/z ions are abundant. 20 IonÈion interactions also lead to large ion excursions away from the center of the ion trap and ions approach the end-caps in addition to the ring electrode.…”