Simulation Study of a Novel Cylindrical Direct Current-Ion Funnel to Improve Ion Transmission

Area of Science:

• Analytical Chemistry
• Mass Spectrometry

Background:

• Proton transfer reaction mass spectrometry (PTR-MS) is crucial for on-line volatile organic compound (VOC) detection.
• Enhancing PTR-MS sensitivity is a key research objective.
• Traditional radio frequency (RF) enhancement methods present challenges like complex fields and ion fragmentation.

Purpose of the Study:

• To develop a novel cylindrical direct current (DC)-ion funnel drift tube for PTR-MS.
• To improve ion transmission efficiency and reduce complexity compared to existing methods.

Main Methods:

• A novel cylindrical DC-ion funnel drift tube was designed, incorporating DC-focusing electrodes (DC-FEs).
• Ion trajectory simulations were used to optimize DC-FE dimensions, voltage, and pressure.
• Simulations analyzed ion transmission efficiency and kinetic energy distribution.

Main Results:

• The novel DC-ion funnel achieved an optimal ion transmission efficiency of 81.4% (m/z 100), a fivefold increase over spherical DC-ion funnels.
• The technique demonstrated effective ion compression in an atmospheric ion guide, reaching 90.3% transmission efficiency.
• Simulations confirmed ions were guided to the central axis within a 1 mm diameter.

Conclusions:

• The developed cylindrical DC-ion funnel enhances PTR-MS sensitivity using only a DC electric field, avoiding RF complexities.
• This novel structure offers a simpler design and superior ion transmission efficiency compared to spherical DC-ion funnels.
• The DC-ion funnel is suitable for PTR-MS drift tubes and adaptable for other mass spectrometry techniques requiring sensitivity enhancement.