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Evaluation of axial DC offsets during scanning of a quadrupole ion trap for sensitivity improvements
Author(s) -
Vaden Timothy,
Ardhal Ben,
Lynn Bert C.
Publication year - 2001
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.283
Subject(s) - chemistry , ion , ion trap , mass spectrometry , detector , quadrupole , analytical chemistry (journal) , waveform , atomic physics , offset (computer science) , hybrid mass spectrometer , quadrupole ion trap , optics , tandem mass spectrometry , voltage , selected reaction monitoring , physics , chromatography , organic chemistry , quantum mechanics , computer science , programming language
In the normal operation of quadrupole ion trap mass spectrometers, approximately half of the trapped ions are ejected through the source endcap during a mass‐selective instability scan. This reduces the sensitivity of the instrument by ∼50%. In this preliminary study, a circuit was constructed that produced a dipolar DC offset on the axial modulation waveform to recover this lost ion current. A variable (0 to 10 V DC), positive and negative offset was applied to the source and detector endcap, respectively. This DC offset axially displaced the ion cloud toward the detector endcap increasing the probability of detection. Several compounds, including 11 pesticides, were evaluated. Sensitivity enhancements ranged from 13 to 97% (theoretical 100%). No spectral resolution problems were observed; however, a compound‐dependent mass discrimination was observed in several cases. This mass discrimination problem is currently under investigation. Copyright © 2001 John Wiley & Sons, Ltd.