Doctor of Philosophy (PhD)
The association mechanism between hydrophobic organic compounds (HOC) and dissolved humic materials (DHM) has continued to be one of the interesting areas in environmental applications. The goal of the research reported in this dissertation is to investigate the association behavior of HOC with DHM. The first part of this research involves steady-state fluorescence measurements of these multi-component systems to study the effect of DHM content on the association mechanism of HOC, in particular using pyrene as a model. Results showed that steady-state fluorescence alone may not provide enough information about the quenching mechanism of pyrene with DHM. Lifetime based fluorescence measurements allow for a deeper mechanistic understanding as compared to the traditional steady-state technique. However, photobleaching, dissolved oxygen, and HOC adsorption to cell walls are problems encountered in lifetime measurements. These effects can directly complicate the interpretation of fluorescence lifetime results. Therefore, a new approach to frequency-domain lifetime measurements, based on frequency segmentation and recombination, was developed during the second part of this dissertation research to address these experimental considerations. The frequency segmentation and recombination method was evaluated using a simple two component system consisting of fluorescein and rhodamine B mixture. Comparison of experimental data collected in traditional and segmented fashion with simulated data demonstrated the validity of the technique. The newly developed method was applied to mixtures of pyrene and DHM to further investigate the pyrene quenching mechanism with DHM. Finally, the chemical effect of chiral pesticides (coumachlor, difenacoum, warfarin, and napropamide) in the presence of Leonardite humic acid standard (LHAS) was investigated by use of steady-state fluorescence spectroscopy. In addition, the chiral recognition ability and enantiomeric selectivity of LHAS with pure enantiomers of 1,1'-bi-2-naphthol bis (trifluoro - methanesulfonate) and 1-(9-anthryl)-2,2,2-trifluoroethanol, used as probes of the interaction, were investigated using liquid-state 19F NMR spectroscopy. To further study DHM enantioselectivity with chiral compounds, the interaction of R or S-1-(9-anthryl)-2,2,2-trifluoroethanol with LHAS was evaluated for samples monitored in the dark and exposed to light for different time periods by use of high performance liquid chromatography.
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Marwani, Hadi M., "Probing the Association Behavior of Hydrophobic Organic Compounds with Dissolved Humic Materials" (2007). LSU Doctoral Dissertations. 1538.
Isiah M. Warner