Document Type

Student Research Paper

Date

Spring 2020

Academic Department

Chemistry and Biochemistry

Faculty Advisor(s)

Lauren E. Toote

Abstract

Ionic mercury (Hg2+) pollution is a common problem in low resource areas where unregulated coal burning and small-scale artisanal gold mining are prevalent. These activities pollute surrounding water sources with Hg2+, which can be converted into the more dangerous methyl mercury by bacteria. Methyl mercury then bioaccumulates in the food chain, and people that obtain water or fish from these sources can be exposed to dangerous amounts of mercury. The EPA and WHO limits for mercury in water are 2 and 6 ppb respectively. Many current detection methods that are sensitive enough to detect mercury at these levels are difficult to utilize in areas where mercury pollution is a problem. This is because the instruments involved are expensive and require complex sample preparation and skilled operators. The goal of this research is to design a lateral flow assay (LFA) that will provide a simpler test for mercury that requires little to no sample preparation and produces a visible signal. In this work, three rhodamine B based probes for Hg2+ detection were synthesized and characterized with NMR, IR, UV-Vis, and fluorescence spectroscopy. The best probe (rhodamine B thiohydrazide) was made using a two-step synthesis with 83% and 19% yields respectively. In the presence of Hg2+ the probe absorbed light at 560 nm and had a limit of detection of 90 ± 10 ppb Hg2+ in acetonitrile solution. This probe was then encapsulated in polystyrene nanoparticles, which were analyzed with dynamic light scattering (DLS) and found to have a hydrodynamic diameter of 90 ± 10 nm. The particles were then incorporated into lateral flow test strips and produced a visible signal in the presence of 200 ppb Hg2+.

Notes

Senior thesis.

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