Modulation of Collective Ion Motion in Paul Trap and its Applications in Charge Detection Mass Spectrometry

Yi-Teng Hsiao^1*, Szu-Wei Chou¹, Shih-Chieh Yang¹, Yao-Hsin Tseng¹, Yi-Kun Lee¹, Pin-Dou Lee¹, Chun-Yen Cheng¹

¹AcroMass Technologies, Inc., Taiwan

* Presenter:Yi-Teng Hsiao, email:tonyhsian@gmail.com

Paul trap is a device widely used for chemical analysis, which confines charged particles through alternating electric fields. The motion of each in-trap ion can be ideally described by Mathieu equation. And, in principle, it can be spectrally adjusted or modulated by de-tuning the amplitude or frequency of the driving radio frequency (RF) wave or exerting extra excitations. However, the collective ion motion is always affected via ion-ion interactions. In this work, we measure the ejection signal of the in-trap protein ion packet (Cytochrome C, 12,327 Da) to the charge-sensing particle detector (CSPD) through the stable-unstable ion motion tuning, as the mass spectrum. It is found that, with some extra modulation --- such as the defects in RF waveform, frequency up-lift, and external electric pulses, the ion motion becomes more collective (synchronized). The detection signal will be thus much narrower and less dispersive, which this method turns out to be a mass measurement approach within high resolution.

Keywords: Paul trap, ion motion, charge detector, mass spectrometry