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Updated: Sep 17, 2025

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Published on: July 27, 2018
Dual-Channel Off-Axis Ion Funnel With a Deflection Electrode
Mengfei Shan1, La Chen1,2, Jun Wang1
1The Research Institute of Advanced Technologies, Ningbo University, Ningbo, China.
Rationale:
In electrospray ionization mass spectrometry (ESI-MS) systems, two critical challenges persist: (1) under-expanded supersonic jets at the atmospheric pressure interface (API) cause ion losses and reduced transmission efficiency; (2) residual solvents and charged droplets entering vacuum stages lead to contamination and elevated chemical noise, degrading analysis accuracy.
Methods:
A dual-channel off-axis ion funnel with a deflection electrode (DC-OFIDE) was developed to address these challenges. This device integrates three core components: an ion drift channel (IDC), an ion funnel channel (IFC), and a deflection electrode. The IDC and IFC are separated by conjoined gaps. Ions within the gas stream emanating from the API are extracted from the IDC via a deflection field, while a retarding axial field prolongs ions' residence time, ensuring efficient transfer to the IFC. This DC-OFIDE features an enlarged entrance aperture (Φ18 mm) to accommodate a multi-capillary interface, enhancing compatibility with high-conductance sample introduction systems.
Results:
Compared with the original conventional ion funnel (CIF), the DC-OFIDE achieved a threefold enhancement in caffeine ion intensity and a broader m/z transmission window. It demonstrated robust neutral and droplet suppression, maintaining 80% ion intensity even under tripled serum volume infused. In drug screening of hair samples, baseline noises in drug ion peaks were reduced by 36%-82%, with a quadrupled signal-to-noise ratio improvement observed for 6-monoacetylmorphine.
Conclusions:
This DC-OFIDE significantly enhances ion transmission efficiency and chemical noise suppression in ESI-MS, establishing its potential for high-fidelity analysis of complex samples.
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