Date of Award
Level of Access Assigned by Author
Doctor of Philosophy (PhD)
Second Committee Member
Jayendran C. Rasaiah
Third Committee Member
Howard H. Patterson
The major goal of this dissertation was to combine modern mass spectral techniques and advanced ab-initio molecular orbital calculations for analytical characterization of complex sample mixtures. Multidimensional mass spectral techniques and theoretical molecular modeling approaches were developed to identify disinfection by-products (DBPs) that were present in drinking water samples from local sources. Analogous methodologies that utilized thermochemical analysis, including both experimental and theoretical calculations, were employed to improve analytical resolution and identify components of a complex petroleum mixture. In the process of developing these multidimensional methods, we were able to address challenges such as solvent contamination that are associated with identification of DBPs using conventional methods. Moreover, we were able to develop a complementary theoretical method that utilizes proton transfer (PT) energy profiles for proton affinity (PA) determinations. The use of highly accurate and precise thermochemical data such as PAs can be advantageous for unknown identification when mass spectral data and/or fragmentation patterns are not available in commercial databases. In chapter 1 of this thesis, a brief review of the experimental approaches is presented. The application of the GC/FT-ICR MS for identification of DBPs in drinking water is discussed in chapter 2; in part one of this chapter, a comprehensive literature review of the research field is presented. Part 2 of chapter 2, focuses on addressing the issues related with the solvent artifact complications and the use of solid-phase microextraction method for DBP analysis. In chapter 3, we show the importance of the determination of the experimental gas phase basicity as an additional analytical dimension for mass spectral analysis of unresolved GC peaks. In chapter 4, an overview of quantum mechanical methods for the determination of structures and energetics is provided. For example, the decomposition reaction of dichloromethanol catalyzed by a water molecule is discussed. Various important details on high accuracy ab-initio G2 and G3 calculations and the utility of the PT energy profile for PA determination of reagent and halogenated compounds are discussed in chapter 5. In chapter 6, we show the utility of combined experimental and theoretical study on potential C7H8 isomers in gasoline samples.
Silwal, Indira K.C., "Characterization of Unknown Chemicals Using Gas Chromatography/Fourier Transform Ion Cyclotron Resonance Mass Spectrometry and AB-Initio Calculations" (2008). Electronic Theses and Dissertations. 901.
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