Doctoral Dissertations

Date of Award

5-2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Zi-Ling Xue

Committee Members

Frank Vogt, Michael D. Best, Thomas A. Zawodzinski

Abstract

The work in this dissertation focuses on the detection and analysis of trace chemicals in biological and environmental samples. Methods for the electrochemical detection of heavy metals Cd(II) [cadmium] and Pb(II) [lead], and the catalytic metal Pd(II) [palladium] in pharmaceutical ingredients have been optimized without the necessity of sample pretreatment. The metals can be analyzed simultaneously as well as individually, and the study includes the first known instance of the use of anodic stripping voltammetry (ASV) to detect metals in dimethyl sulfoxide (DMSO) solutions. Another method, based on ASV, has been optimized and evaluated for the purpose of mercury(II) analysis in a representative active pharmaceutical ingredient (API) and excipient. A pyridine-functionalized thin film has been fabricated to selectively preconcentrate hexavalent chromium [Cr(VI)] anions for electrochemical detection. Glassy carbon electrodes were modified through physical deposition of single-walled carbon nanotubes (SWNTs) on the electrode surface, followed by electrochemical deposition of a sol-gel containing a 2-pyridine functional group. The use of SWNTs has increased sensitivity for Cr(VI) detection in aqueous solutions, providing a detection limit of 0.3 µg L-1 (micrograms per liter). Two new processes to pretreat blood samples have been developed. The treatments are based on a Fenton-like advanced oxidation process (AOP). The first method is performed with a simple convection oven over a period of five hours, while the second uses microwave irradiation for six minutes. These novel methods allow for either cost-effective pretreatment through the use of the common lab oven, or time savings through the use of the synthesis microwave. The pretreated biological samples were further analyzed via anodic stripping for quantification of copper in the whole blood. A novel, disposable, Bi (bismuth)-based colorimetric sensor was developed for the detection of toxic hydrogen sulfide (H2S) gas. Using a simple laboratory setup to generate the H2S in a total volume of 1.35 L (liters), the sensor was able to qualitatively detect the analyte down to 30 ppb (parts per billion), indicating its ability to be used in industrial settings and manufactured into an inexpensive product for the determination of bad breath.

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