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Quadrupole mass filters with added hexapole fields
Zilan Xiao1, XianZhen Zhao, D J Douglas
1Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada.
Rapid Communications in Mass Spectrometry : RCM
|June 17, 2010
Summary
Quadrupole mass filters with added hexapole fields show reduced performance compared to conventional quadrupoles. While some configurations achieve high resolution, overall transmission and stability are negatively impacted by field distortions.
Area of Science:
- Analytical Chemistry
- Mass Spectrometry
- Instrumentation
Background:
- Conventional quadrupole mass filters are widely used for mass analysis.
- Investigating modifications to quadrupole fields can potentially enhance performance.
- Hexapole fields have been experimentally added to quadrupole mass filters.
Purpose of the Study:
- To experimentally evaluate the performance of quadrupole mass filters with added hexapole fields.
- To compare the resolution and transmission of modified quadrupoles against conventional designs.
- To understand the impact of hexapole field magnitude and rod geometry on mass analysis.
Main Methods:
- Six quadrupole mass filters were constructed with added hexapole fields (4%, 8%, 12%).
- Experiments were conducted using both equal and unequal diameter rods to assess field distortions.
- Mass analysis was performed with varying DC polarities and scan line slopes to determine resolution and transmission.
Main Results:
- Quadrupoles with added hexapole fields exhibited significant field distortions.
- Reversed DC polarity (a(x) > 0) enabled higher resolution (> or = 1000) and transmission compared to positive polarity (a(x) < 0).
- Increased hexapole field magnitude decreased resolution, while removing octopole fields improved it. Transmission was 10-300 times lower than conventional quadrupoles.
Conclusions:
- Quadrupole mass filters with added hexapole fields are generally less useful for mass analysis due to lower transmission.
- Despite field distortions, some modified quadrupoles surprisingly achieved resolutions of 1000 or more.
- The results align with theoretical stability diagram calculations, indicating field distortions limit performance.
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