Influence on mass-selective ion ejection of the phase difference between the drive r.f. and the axial modulation potentials

✍ Scribed by G. Dobson; J. Murrell; D. Despeyroux; F. Wind; J.-C. Tabet

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 881 KB
• Volume: 40
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.843

✦ Synopsis

Abstract

The phase difference between the drive r.f. and the axial modulation potential is known to influence significantly the mass shift, and all commercial ion trap mass spectrometers use a fixed value for this difference. However, although this important parameter is partly responsible for the good precision achievable today in most commercial ion traps, little discussion on the variation of the phase difference between the drive r.f. and the axial modulation potential has appeared in the literature. We present here an examination of the influence of a low‐level axial modulation potential superimposed by capacitive coupling between the electrodes. Low‐level axial modulation potentials are used for certain analytical scans such as reverse scan or slow scan speeds. Such low‐level potentials help to prevent deterioration of mass resolution due to, for example, the dissociation of the ions during their resonant ejection from the ion trap. Reverse and forward scans are used to illustrate the mass shift and change in resolution, caused by a change in the phase difference between the drive r.f. potential applied to the ring electrode and the axial modulation potential applied on an end‐cap electrode, in electrospray ionization mass spectra. Copyright © 2005 John Wiley & Sons, Ltd.