Stimulated Motion Suppression (STMS): a New Approach to Break the Resolution Barrier for Ion Trap Mass Spectrometry

Abstract

Ion trap is an excellent platform to perform 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 suppression 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. Graphical Abstract ᅟ.

Miniature mass spectrometer signal processing based on ensemble empirical mode decomposition feature enhancement

“…The rigorous analytical experiments necessitate the appropriateness of the performance of the employed miniature mass spectrometer with accepted laboratory techniques. However, minimizing instrument size and power consumption typically accompanies system performance degradation 13,15,16 . Despite the benefits of real‐time, on‐site screening of chemical substances, there is still a gap between the current analytical performances of miniature mass spectrometers and the analytical demands in some practical applications, especially under testing stability and high quantitation accuracy requirements, such as in market surveillance and point‐of‐care analysis 3,15,17 .…”

“…However, minimizing instrument size and power consumption typically accompanies system performance degradation. 13,15,16 Despite the benefits of real-time, on-site screening of chemical substances, there is still a gap between the current analytical performances of miniature mass spectrometers and the analytical demands in some practical applications, especially under testing stability and high quantitation accuracy requirements, such as in market surveillance and point-ofcare analysis. 3,15,17 Due to the inherent instability of direct ionization, miniaturized instrumentation, and field data collection, further adoption of this technology will be contingent on its overall stability and reproducibility.…”

Liquid-Phase Ion Trap for Ion Trapping, Transfer, and Sequential Ejection in Solutions

“…With a minimum ion-neutral damping effect in a vacuum environment, ions with different m/z ratios would possess different motional frequencies in the radio frequency (rf) quadrupole electric field. 12, 30,31 Supplemented with alternating current (AC) and direct current (DC) electric fields, ion trapping, 32,33 isolation, 25,30,34 dissociation, and sequential ejection 35−37 could be achieved in an ion trap. 38 However, the ruling principles of ion motion in solutions are totally different from those in a vacuum environment.…”

“…Indeed, great efforts have been carried out to fabricate and place miniaturized mass analyzers (ion traps or quadrupole rods) in aqueous solutions. − In MS, a quadrupole ion trap is an ion manipulation device operated in vacuum environments, − and it has been widely applied in physics to build an atomic clock and chemistry for molecular structure analysis. With a minimum ion-neutral damping effect in a vacuum environment, ions with different m / z ratios would possess different motional frequencies in the radio frequency (rf) quadrupole electric field. ,, Supplemented with alternating current (AC) and direct current (DC) electric fields, ion trapping, , isolation, ,, dissociation, and sequential ejection − could be achieved in an ion trap . However, the ruling principles of ion motion in solutions are totally different from those in a vacuum environment. , Due to strong viscous damping effects in solutions, ions usually no longer possess characteristic motional frequencies within a rf quadrupole electric field.…”