Date of Award

5-2003

Level of Access

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor

Mitchell R.M. Bruce

Second Committee Member

Alice E. Bruce

Third Committee Member

François G. Amar

Abstract

Mercury, a highly toxic metal, whose environmental concentration magnifies with ascension of the food chain, is monitored in our waters, food and air. Monitoring mercury is generally done by sample collection, transport to the laboratory; followed by: digestion of the sample, separation of the mercury and detection of the mercury: mostly by cold vapor atomic absorption or, cold vapor atomic fluorescence. These monitoring methods, preclude, routine, in-the-field mercury determination. New analytical techniques have been proposed for in the field determination of mercury. They consist of mercury adsorption onto a sensor or electrode and measuring how much is there either as the adsorbate or, as the analate being removed from the detection device. Many employ gold as an accumulation substrate because of its affinity for mercury. One group of proposed techniques, requires that mercury be reduced electrochemically onto a gold electrode and then removed by anodic current oxidation. The determination of mercury is made from measurements of: the current, or the frequency shift of a surface acoustic wave due to the mass of the accumulated mercury. Our research focused on the electrodepositon and stripping of mercury on gold foil electrodes. We demonstrated by x-ray photoelectron spectroscopy that electrodeposited mercury cannot be completely removed by electrochemical stripping and that with many repetitive deposition and stripping cycles, there is a progressive accumulation of mercury on the gold electrodes which continues to manifest even in mercury free electrolyte solution. The latter was demonstrated by linear sweep voltammetry and temperature programmed desorption of the accumulated mercury. Mercury's toxicity is based on its formation of relatively non-polar complexes and its high affinity for thiol and sulfide functional groups (i.e. the amino acid cysteine). Our electrochemical and conductivity studies of nine metal-thiolate chalcogenides indicated that some form free thiolate ions at high concentrations rather than low ones.

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