Improving the Performances of a “Brick Mass Spectrometer” by Quadrupole Enhanced Dipolar Resonance Ejection from the Linear Ion Trap

Abstract

Previously, a miniature mass spectrometer driven by a sinusoidal frequency scanning technique, named as Brick mass spectrometer, was developed in our lab ( Jiang et al. Anal. Chem. 2017 , 89 , 5578 ). The frequency scanning technique enabled miniaturized electronics and broader mass range, but it was also limited in reduced mass resolution and sensitivity due to a relatively low operating radio frequency (rf) voltage in comparison with the conventional voltage scanning technique. To improve performances of the Brick mass spectrometer, a quadrupole enhanced dipolar resonance ejection (QE-dipolar resonance ejection) method was proposed in this work. After optimization, mass resolution and sensitivity of the Brick mass spectrometer could be improved by no less than 2 times, and space charge effects within the ion trap could also be reduced. Furthermore, this QE-dipolar resonance ejection method is effective at elevated pressures, which would potentially allow us to further miniaturize the Brick mass spectrometer by operating it at higher pressures. This method is also applicable to any ion trap operated in either frequency scanning mode or voltage scanning mode and operated in either miniaturized instruments or benchtop instruments.

Boosting the Sensitivity and Selectivity of a Miniature Mass Spectrometer Using a Hybrid Ion Funnel

“…A sinusoidal frequency scanning technique was developed to extend mass range of a CAPI based “brick” mass spectrometer . More recently, mass resolution of the “brick” mass spectrometer was further improved by applying a new ion ejection method: the quadrupole enhanced dipolar resonance ejection …”

“…48 More recently, mass resolution of the "brick" mass spectrometer was further improved by applying a new ion ejection method: the quadrupole enhanced dipolar resonance ejection. 49 As a continuous effort in improving analytical performances of the CAPI based MS system, a hybrid ion funnel was developed in this study and integrated into the first vacuum stage of a CAPI based miniature mass spectrometer. This ion funnel has two regions: a rectangular ion funnel region at the ion entrance and a planar quadrupole field region at the ion exit.…”

Towards Higher Sensitivity of Mass Spectrometry: A Perspective From the Mass Analyzers

“…By applying a DC voltage on the ejection electrodes in a LIT MS, the ions are moved from the central axis of the four electrodes to near the eject slit and were more easily ejected (Li et al, 2018). Xu's group proposed a quadrupole enhanced (QE) dipolar resonance ejection method which was implemented in their home-built "brick" mass spectrometer (Jiang et al, 2017;Jiang, et al, 2018). A quadrupolar excitation signal was coupled with a RF signal to form a combined signal (Figure 1B).…”

Quantification and evaluation of ion transmission efficiency in two‐stage vacuum chamber miniature mass spectrometer

“…10 However, a miniature mass spectrometer is less sensitive than a commercial instrument, limiting its direct use in specific scenarios. Many factors restrict the sensitivity of miniature mass spectrometer, such as low ionization efficiency of an ion source, 11,12 low ion transmission efficiency of the instrument, 13,14 poor performance of mass analyzer, 15 low impact energy, 16 and space charge effect. 17 Among them, the ion transmission efficiency of each component in the instrument is the key factor affecting the sensitivity because most of the ion loss occurs in the transmission process.…”