Improvements to the analytical performance of ion trap mass spectrometry

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  • March 21, 2019
Creator
  • Kaplan, Desmond Allen
    • Affiliation: College of Arts and Sciences, Department of Chemistry
Abstract
  • Mass spectrometry is a powerful analytical technique that is capable of a wide range of chemical and biological analyses. The quadrupole ion trap mass spectrometer (QITMS) is known for its ruggedness, sensitivity, and high efficiency for tandem mass spectrometry (MS/MS) experiments. Non-idealities in electrode geometry result in small contributions of higher order fields (HOFs) to the primary quadrupolar electric field of the ion trap. These HOFs have been useful in enhancing the resolution, MS/MS efficiency, and sensitivity in the QITMS. A portion of the work presented in this dissertation is intended to serve as a basis for improved ion trap performance through the judicious use of HOFs. Development of rf circuitry and characterization of a compensated cylindrical ion trap (CCIT) mass spectrometer, designed for studying the effects of HOFs, are also described herein. An additional set of grounded electrodes was introduced into the CCIT instrument to remove detrimental effects of capacitive coupling and HOFs were successfully introduced. Mass spectra acquired after the introduction of HOFs showed improvements to the injection efficiency over a broad range of rf voltages. The optimal conditions for resonance ejection in the CCIT occurred at an octapole HOF non-linear resonance, which gave improvements both to mass resolution and sensitivity (i.e., the number of ions detected). Resonance ejection performed at an octapole non-linear resonance was successful in improving the sensitivity of the CCIT for the analysis of volatile organic compounds in the presence of a heavy buffer gas. A novel higher order field ion trap, possessing predominantly octapole fields, was developed. This octapole ion trap exhibited higher trapping capacity than a quadrupole ion trap of similar geometry. However, mass analysis in the octapole ion trap was not achievable because ions were resonantly ejected over a broad frequency range. A second generation octapole ion trap, with improved resonance ejection characteristics, also was developed. Resonance ejection experiments in this geometry were in agreement with ion trajectory simulations, but mass analysis using resonance ejection was again not possible due to broad band ejection. A non-destructive Fourier transform detection method was simulated and found to be viable.
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  • In Copyright
Advisor
  • Glish, Gary
Degree granting institution
  • University of North Carolina at Chapel Hill
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  • Open access
Date uploaded
  • October 20, 2010

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