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Analytical Chemistry
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TECHNICAL NOTE
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Sensitivity and Robustness Enhancements by using V-Shape
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Ion Funnel in FTICR-MS
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Liulin Deng†§, Xiangfeng Chen*†‡, Wan Li†, Ze Wang†, Yiling Elaine Wong†, and T-W.
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Dominic Chan*†
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†
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P. R. China
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‡
Department of Chemistry, The Chinese University of Hong Kong, Hong Kong SAR,
Shandong Academy of Sciences, Jinan, Shandong, P. R. China
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§
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Pacific Northwest National Laboratory, Washington, USA
Biological Sciences Division and Environmental Molecular Sciences Laboratory,
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# Address correspondence to: Professor T.-W. D. Chan, Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China. E-mail:
[email protected], Dr. X. Chen, Shandong Academy of Sciences, Jinan, China. E-mail:
[email protected].
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Analytical Chemistry
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ABSTRACT
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In this paper, a new configuration of the ion funnel interface (i.e., V-shape ion funnel
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(V-IF) for high ion transmission efficiency and robustness enhancement was
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developed and implemented on FTICR-MS. The performance of the V-IF was
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compared with that of a home-built orthogonal ion funnel. An order of magnitude of
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improvement in sensitivity was achieved for various peptides and proteins. The
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performance of the instrument was maintained for a long period by neutral molecule
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removal. Other ion transmission patterns, such as gentle ion transmission, adduct ion
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removal, and radio frequency (RF)-driven CID, was also realized in V-IF by varying
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the RF potentials. V-IF is believed to be a novel ion guide that has promising
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applications in mass spectrometry.
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Analytical Chemistry
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INTRODUCTION
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Electrospray ionization (ESI)1 is one of the most important ion generation methods in
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mass spectrometry for large biomolecules such as peptides (or proteins)2 and DNA3–4
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analysis. Although ESI is believed to have fairly high ionization efficiency, only a
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small fraction (approximately 0.01%–0.1%) of analyte ions is successfully transported
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to the mass analyzer.5–7 A large fraction of the ions is believed to be lost when passing
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through the conductance limiting orifices. In low vacuum regions, conventional
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electrostatic ion optical devices, such as the Einzel lens,8–10 are ineffective in focusing
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the ion beam presumably because of the ion–molecule collisions and space charge
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effect. The situation is alleviated by using multipole ion guides (e.g., quadrupole,
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hexapole, and octupole).11–12 By using radiofrequency (RF) potentials, ions can be
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manipulated, focused, and transmitted in medium vacuum conditions (
