B American Society for Mass Spectrometry, 2018 J. Am. Soc. Mass Spectrom. (2018) 29:1738Y1744
Stimulated Motion Suppression (STMS): a New Approach
to Break the Resolution Barrier for Ion Trap Mass
State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua
University, Beijing, 100084, China
Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA
Abstract. Ion trap is an excellent platform to per-
form tandem mass spectrometry (MS/MS), but
has an intrinsic drawback in resolving power.
Using ion resonant ejection as an example, the
resolution degradation can be largely attributed to
the broadening of the resonant frequency band
(RFB) between ion motion and driving alternative-
current (AC). To solve this problem, stimulated
motion suppression (STMS) was developed.
The key idea of STMS is the use of two suppres-
sion alternative-current (SAC) signals, which both have reversed initial phases to the main AC. The SACs can
block the unexpected sideband ion resonances (or ejections), therefore playing a key role in sharpening the RFB.
The proof-of-concept has been demonstrated through ion trajectory simulations and validated experimentally.
STMS provides a new and versatile means for the improvement of the ion trap resolution, which for a long time
has reached the bottleneck through conventional methods, e.g., increasing the radio-frequency (RF) voltage and
decreasing the mass scan rate. At the end, it is worth noting that the idea of STMS is very general and principally
can be applied in any RF device for the purposes of high-resolution mass analysis and ion isolation.
Keywords: Ion trap, Resonant ejection, High-resolution, Stimulated motion suppression
Received: 11 January 2018/Revised: 7 May 2018/Accepted: 7 May 2018/Published Online: 29 May 2018
uadrupole ion traps, developed by Paul and Steinwedel in
the 1950s , made a revolutionary impact on mass
spectrometry (MS)  by opening a brand-new field of ion
manipulation and mass analysis. Due to the rapid development
in this field, a variety of ion traps have been developed, includ-
ing cylindrical , linear [4, 5], rectilinear , toroidal , and
halo . These ion traps are currently employed in lab-scale
instruments such as LTQ (Thermo Scientific, San Jose, CA,
USA)  and Qtrap (AB Sciex, Concord, Canada) , as well
as miniaturized ones such as Mini 12 (Purdue, West Lafayette,
IN, USA)  and Tridion-9 (Torion Technologies, American
Fork, UT, USA) . It is commonly recognized that the ion
trap has superior features such as single-device MS/MS 
and ion storage for gas phase ion processing. However, mass
resolution of ion traps is typically characterized as unit resolu-
tion, which is especially challenging to maintain for miniature
instruments [13, 14]. Although higher resolutions can be
achieved, scan speed is typically compromised .
During mass analysis, analyte ions are first trapped and
stored and then ejected according to their mass to charge ratio
(m/z) to produce a mass spectrum. The resolving power R of the
obtained mass spectrum depends on the mass broadening Δm
relative to the nominal mass at ejection m,i.e.,R = m/Δm .
In other words, for a specific ion species, the lowest available
Δm determines the optimal resolving power of the trap. Many
Electronic supplementary material The online version of this article (https://
doi.org/10.1007/s13361-018-1995-x) contains supplementary material, which
is available to authorized users.
Correspondence to: Xiaoyu Zhou; e-mail: firstname.lastname@example.org,
Zheng Ouyang; e-mail: email@example.com