UBC Theses and Dissertations
New methods and instrumentation for electrospray ionization -- mass spectrometry Schneider, Bradley B.
A current challenge in the field of ESI-MS is the development of high-throughput methods and devices to use a mass spectrometer more efficiently. This research provides means to improve the interface between the ion source and the mass spectrometer, and insights into the mechanism involved as ions traverse the interface region. In addition, new methods and instrumentation to improve the sensitivity, stability, and throughput of an ESI-MS are developed. This thesis deals with improving the motion of ions within the atmospheric pressure source region and the interface region of an ESI-MS. The first section describes the development of a model for the determination of the rates of collision - induced dissociation (CID) of biomolecules within the interface region of an ESI-MS. The model describes the variation of the gas number density within the first stage of the vacuum system. Various factors, such as the mass of the collision gas, the mass of the ion, the collision energy, and the properties of the collision gas are investigated. This model is used to predict the degree of fragmentation for biomolecules with various instrumental parameters. The mechanisms leading to ion fragmentation in the interface region are investigated in order to increase the degree of structural information that can be obtained from ESI-MS. The second part of this thesis introduces a new method of focusing ions generated within the atmospheric pressure ion source region. This section describes the development of improved ESI sources based upon the incorporation of an atmospheric pressure ion lens near the tip of the electrospray capillary. The new ion sources are more stable and more sensitive than previous ones. Various parameters, such as lens potential, lens position, sprayer orientation, and solution flow rate are examined. The new ion sources are particularly beneficial for the analysis of protein digests because the lens increases the ratio of multiply charged ions relative to singly charged ions. In addition, the background noise is decreased and the positional requirements for the sprayer are reduced. The third part describes the extension of the ion lens technology to address issues in high-throughput ESI-MS. This section describes the use of potentials applied to atmospheric pressure ion lenses to enable and disable multiple sprayer ion sources. New two and four-sprayer ion sources are developed and tested. These multiple sprayer ion sources greatly increase the sample throughput when compared to commercial single sprayer ion sources. The mechanical blocking devices that are currently used for indexing of commercial multiple sprayer ion sources are no longer needed. This simple setup is much less expensive, and can very rapidly enable and disable the individual sprayers. In addition, these new high throughput ion sources are capable of simultaneously sampling ions from more than one electrospray capillary.
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