New Optical and Electrochemical Probes for Trace Chemicals with Health and Environmental Impacts

The work in this dissertation focuses on the development of probes for the analysis of trace chemicals in samples with health and environmental impacts. A paper, Cu(copper)-based colorimetric probe was developed for the detection of toxic hydrogen sulfide (H₂S) gas. A modified Kipp’s apparatus was used to generate desired concentrations of H₂S in a total volume of 1.35 L (liters). The probe shows a qualitative response down to 60 ppb (parts per billion), indicating its ability to be used in industrial settings as a replacement for the commonly used lead acetate strips. When used in conjunction with a handheld colorimeter and smartphone, the probe can quantitatively detect the gas to a concentration of 16 ppb, which is below concentrations responsible for bad human breath. A method for the electrochemical detection and speciation of inorganic arsenic in pharmaceutical components has also been optimized. A gold electrode modified with a pyridine-functionalized layer has been developed to preconcentrate hexavalent chromium [Cr(VI)] anions for analysis by cathodic stripping voltammetry (CSV). The gold electrodes were modified through chemical deposition of a thiol sol-gel layer on the electrode surface, followed by the incorporation of gold nanoparticles (AuNPs) and a 2-pyridine functional group. The utilization of AuNPs has increased the sensitivity for detection of Cr(VI) anions in aqueous media, with a limit of detection of 93 ng L^-1[L^-1].