Novel Focusing Technology Developed to Improve the Ion Transmission Efficiency of Mass Spectrometers

May 16, 2022 | By ZHANG Qiangling

According to a cover story on Analytical Chemistry, a novel electrostatic field ion funnel focusing technology, which was also called DC-ion funnel, was proposed by researchers from Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences (CAS).

It successfully realized ion focusing with only a DC electric field, so as to improve the sensitivity of mass spectrometers.

Proton transfer reaction mass spectrometry (PTR-MS) is a valuable tool in many fields. However, how to ensure the high sensitivity under the condition of reducing volume and power remains a difficult problem for the miniaturized mobile PTR-MS (M-PTR-MS). To improve the sensitivity of PTR-MS instruments, researchers generally use a radio frequency (rf)-focusing electric field in the drift tube to focus ions, which will increase the power consumption and volume, so it is not suitable for the M-PTR-MS.

In this research, scientists replaced the conventional ring electrode with five curved electrodes and metal meshes welded to the curved electrode. The diminishing inner diameter of the five curved electrodes they designed helps the efficient ion focusing. That’s how they realized the DC-ion funnel focusing in DC electrical field.

The new structure has many advantages. Compared to the conventional drift tube, the sensitivity for the DC-ion funnel drift tube was improved from 3.8 to 7.3 times with this new technology. Aside from that, the soft ionization in PTR-MS was able to be retained for the novel DC-ion funnel drift tube.

Scientists applied this DC-ion funnel technology to the M-PTR-MS for mobile monitoring atmospheric VOCs. The result was impressive.

Another advantage is that the DC-ion funnel can easily be coupled to other types of mass spectrometers to increase their detection sensitivity, which can provide a key technical support for the development of leading-edge mass spectrometers.

This work was supported by the National Natural Science Foundation of China, the Youth Innovation Promotion Association, CAS, China, the Anhui Provincial Key R&D Program, and the HFIPS Director's Fund etc.

Focusing effect of the DC-ion funnel (Image by ZHANG Qiangling)

Cover art of this paper (Image by ZHANG Qiangling)

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