Semester

Fall

Date of Graduation

2013

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Chemistry

Committee Chair

Fred L. King

Committee Co-Chair

Patrick S. Callery

Committee Member

Lisa A. Holland

Committee Member

Glen P. Jackson

Committee Member

Ronald B. Smart

Abstract

This dissertation sought to find conditions that enabled the characterization of weapons of mass destruction, be that chemical, explosives, or biological, and find unique ion signals for those materials. Chapter 2 examines how to improve the analytical capability of the pulsed glow discharge through an increased understanding of the ionization processes inherent to the technique. Results of a parametric evaluation of ionization processes in the plasma demonstrated that within the glow discharge ion source there are conditions that can be determined which will enhance the signal of the analytical ion. A key innovation was the determination, that in constant power operations, optimal analyte signals could be found 6-8 mm in distance from the cathode and at shorter pulse widths and duty cycles. For the first time, the behavior of argon doubly charged species was characterized in these pulsed plasmas. Whereas the goal of Chapter 2 was to understand the fundamental characteristics of the pulsed glow discharge, Chapters 3 and 4 strive to expand its future possibilities through the coupling of gas chromatography and the pulsed glow discharge ion source to achieve chemical speciation. Chemical speciation can be achieved through structural information from the plateau region and molecular ion information from the afterpeak region and both can be acquired simultaneously. The ability of the pulsed glow discharge to acquire both pieces of information gives the analyst a greater degree of confidence in the identification of the compound; no other technique is capable of providing both pieces of information simultaneously. The purpose of these studies was to determine if the time-gated pulsed glow discharge coupled with gas chromatography mass spectrometry could provide adequate information to detect a chemical warfare agent metabolite or an explosive related compound. We were able to demonstrate that the pulsed glow discharge provides structural information during the plateau for the analytes and we learned that it was important to control the analyte concentration introduced to the plasma so that it does not quench the afterpeak signal. Future directions would focus on lowering the analyte concentration sufficiently. In Chapter 5, we hypothesized that the separation of particles by size would enhance the ability to discriminate between different sources of a Bacillus anthracis surrogate. Size selection was combined with analytical techniques to enhance the capability of identifying biological signatures of bacterial spores. It was found that size separation permitted a more rapid determination by SEM to confirm the presence of spores, but did not enhance the ability of Raman to identify the spores. Ultimately, results from these analyses can be used to build a library to determine an organism's unique biological signature that can be correlated with known growth and processing methods to identify how, when, and where the sample was produced.

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