Graduation Year

2020

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Chemistry

Major Professor

Theresa Evans-Nguyen, Ph.D.

Committee Member

Andreas Muller, Ph.D.

Committee Member

Abdul Malik, Ph.D.

Committee Member

Xiaopeng Li, Ph.D.

Keywords

Ambient Desorption and Ionization, Differential Mobility Spectrometry, Field Asymmetric Ion Mobility spectrometry, Forensics, Nuclear forensic analysis, Isotope Ratio Measurement

Abstract

In forensics and nuclear-forensics, the current lab-based analytical technique employed can be laborious, time consuming, and less suitable for in-situ and real time screening. However, it is important to develop fast and fieldable instrumental technique, without a tradeoff for its high throughput, for drug screening and radionuclear analysis. The underlying factors to be considered in the instrument development ranges from: high potency of samples, even at very low concentration; complex nature of samples in the surrounding environment; real-time chemical composition variation; and instrument size, weight and power (SWAP) consideration. Differential mobility spectrometry (DMS), also known as field asymmetric waveform ion mobility spectrometry (FAIMS), had been a promising rapid gas-phase separation technique, deployable for field applications. Ionized samples are separated and characterized based on their nonlinear motion of their gases under the influence of a differential high and low electric field at or near atmospheric pressure.

The implementation of DMS in this study is divided into three parts: (1) Direct analysis in real time (DART) ionization was employed as a robust solvent-less ionization technique, coupled to DMS to demonstrate their combined utility and compatibility. Herein, amphetamine and derivatives were analyzed suggesting a promising alternative for rapid separation and characterization of new psychoactive substances. (2) Flowing atmospheric-pressure afterglow (FAPA) desorption/ionization source was coupled with DMS for the first time for metal-ion speciation. The FAPA-DMS hybrid was used for separation and detection of individual ionic species from cobalt and nickel complexes with acetylacetonate in standard mixtures. (3) Using nano-electrospray source, DMS was coupled to a linear ion trap MS for pre-filtration of uranyl ion from fission products analogue. Subsequently, isotopic measurement was conducted on the uranyl ion. The 235U/238U ratio measured correlate with the result obtained from certified reference material (CRM) of natural uranium, employed in this study.

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