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Quadrupole mass spectrometry under the influence of magnetic field

Syed, Sarfaraz Uddin (2012) Quadrupole mass spectrometry under the influence of magnetic field. Doctoral thesis, University of Liverpool.

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Abstract

A Quadrupole Mass Spectrometer (QMS) is an instrument for measuring concentrations of atoms and molecules by separating atomic and molecular ions according to their mass-to-charge ratios (m/z). It consists primarily of an ion source, quadrupole mass filter (QMF) and detector. Generally, QMF resolution can be improved by increasing the number of rf cycles of the alternating electric field the ion experiences when passing through the mass filter. In order to improve the resolution, the dimensions of the QMF or the operating parameters are to be changed. However geometric modifications to improve performance increase the manufacturing cost and usually the size of the instrument. A low cost method to increase the resolution of a given QMS is the application of magnetic field to the mass filter. The work is mainly concerned with the performance of a QMS under the influence of magnetic field. Significant improvement in QMS performance was obtained under certain magnetic field conditions, and these have been explained in terms of our theoretical model developed in the University of Liverpool. The theoretical approach assumed in the model is that the QMF contains hyperbolic rods as electrodes and that the magnetic field acts over the full length of the mass filter assembly. This model is capable of accurate simulation of spectra allowing the user to specify different values of mass spectrometer dimensions and applied input signals. The model has been upgraded for better sensitivity, and to simulate the QMF at very high number of rf cycles. Simulation and experimental results were presented for different conditions. This work also demonstrates the modeling of mass spectra of gases using the theoretical model for stability zones 1 and 3. The performance of QMF operating in stability zones 1 and 3 has been derived and a relationship between maximum obtainable resolution and scan line is obtained.

Item Type:Thesis (Doctoral)
Uncontrolled Keywords:The item describes the performance of a quadrupole mass spectrometer under the influence of a magnetic field in addition to the conventional electric fields required for its operation.
Subjects:T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments, Research Centres and Related Units:Academic Faculties, Institutes and Research Centres > Faculty of Engineering > Department of Electrical Engineering and Electronics
Status:Unpublished
ID Code:5533
Deposited On:08 Aug 2012 12:28
Last Modified:08 Aug 2012 12:28

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