Degree

Doctor of Philosophy (PhD)

Department

Department of Chemistry

Document Type

Dissertation

Abstract

Electrification ionization is a method to produce ions from solid samples by charge separation. This separation of charge can be enhanced by organic molecules known as matrix compounds to produce highly charged molecules. In this research, new methods were developed for the application of electrification ionization for surface analysis and the ionization mechanism was investigated. First, an electrification ionization matrix was used for tissue imaging using laser ablation. A two-component matrix of 2-nitrophloroglucinol and silica nanoparticles was found to increase the number of multiply charged ions from the tissue. Images of mouse brain with multiply charged ions were obtained. In a second study, a method for electrification ionization was developed using a pulsed valve for material removal. The pulsed valve was directed at a thin metal foil with sample and matrix deposited on the opposite side. The resulting ions were sampled into a mass spectrometer. The method had an ion production time of 4 seconds but had limited spatial resolution. To improve spatial resolution, a piezoelectric cantilever striker with a needle tip attached to the arm was used. A lateral resolution of around 1 mm was obtained with the piezoelectric cantilever and the temporal resolution was comparable to the pulsed valve. Highly charged ions of peptides and proteins deposited on foil were obtained. With an improved nanoparticle co-matrix, lipid and gangliosides were detected from tissue. The addition of nanoparticles improved the ionization of molecules from tissue under both atmospheric and high vacuum conditions. To understand the ionization mechanism, sublimation electrification of matrix was studied. Electrification produces a current when the matrices are sublimed. The sign of the current depended on the compound sublimed. The polarity of the current could be altered by the application of an electric field or by changing the pH. The results are interpreted as separation of charge in particles ejected from stress cracking crystals.

Date

11-12-2019

Committee Chair

Murray, Kermit K.

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