Thorsten; Pöhler

Bergische Universität Wuppertal, Wuppertal, North Rhine-Westphalia, Germany

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Publications (3)7.18 Total impact

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    ABSTRACT: Three-dimensionally (3D) resolved ion trajectory calculations within the complex viscous flow field of an atmospheric pressure ion source are presented. The model calculations are validated with spatially resolved measurements of the relative sensitivity distribution within the source enclosure, referred to as the distribution of ion acceptance (DIA) of the mass analyzer. In previous work, we have shown that the DIA shapes as well as the maximum signal strengths strongly depend on ion source operational parameters such as gas flows and temperatures, as well as electrical field gradients established by various source electrode potentials (e.g., capillary inlet port potential and spray shield potential). In all cases studied, distinct, reproducible, and, to some extent, surprising DIA patterns were observed. We have thus attempted to model selected experimental operational source modes (called operational points) using a validated computational flow dynamics derived 3D-velocity field as an input parameter set for SIMION/SDS, along with a suite of custom software for data analysis and parameter set processing. Despite the complexity of the system, the modeling results reproduce the experimentally derived DIA unexpectedly well. It is concluded that SIMION/SDS in combination with accurate computational fluid dynamics (CFD) input data and adequate analysis software is capable of successfully modeling operational points of an atmospheric pressure ion (API) source. This approach should be very useful in the computer-aided design of future API sources.
    Journal of the American Society for Mass Spectrometry 06/2013; · 3.59 Impact Factor
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    ABSTRACT: In this study, the validation and analysis of steady state numerical simulations of the gas flows within a multi-purpose ion source (MPIS) are presented. The experimental results were obtained with particle image velocimetry (PIV) measurements in a non-scaled MPIS. Two-dimensional time-averaged velocity and turbulent kinetic energy distributions are presented for two dry gas volume flow rates. The numerical results of the validation simulations are in very good agreement with the experimental data. All significant flow features have been correctly predicted within the accuracy of the experiments. For technical reasons, the experiments were conducted at room temperature. Thus, numerical simulations of ionization conditions at two operating points of the MPIS are also presented. It is clearly shown that the dry gas volume flow rate has the most significant impact on the overall flow pattern within the APLI source; far less critical is the (larger) nebulization gas flow. In addition to the approximate solution of Reynolds-Averaged Navier-Stokes equations, a transport equation for the relative analyte concentration has been solved. The results yield information on the three-dimensional analyte distribution within the source. It becomes evident that for ion transport into the MS ion transfer capillary, electromagnetic forces are at least as important as fluid dynamic forces. However, only the fluid dynamics determines the three-dimensional distribution of analyte gas. Thus, local flow phenomena in close proximity to the spray shield are strongly impacting on the ionization efficiency.
    Journal of the American Society for Mass Spectrometry 08/2011; 22(11):2061-9. · 3.59 Impact Factor
  • Source
    Proceedings of the 58th ASMS Conference on Mass Spectrometry and Allied Topics, Salt Lake City, UT, USA; 01/2010

Publication Stats

11 Citations
7.18 Total Impact Points

Institutions

  • 2013
    • Bergische Universität Wuppertal
      • Physical and Theoretical Chemistry
      Wuppertal, North Rhine-Westphalia, Germany
  • 2011–2013
    • RWTH Aachen University
      • Chair and Institute of Jet Propulsion and Turbomachinery
      Aachen, North Rhine-Westphalia, Germany
  • 2010
    • Salt Lake City Community College
      Salt Lake City, Utah, United States