Date of Award

7-15-2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

David T. Pierce

Abstract

Three projects in chemical analysis are presented. In the first, calibration-free Se(IV) determinations were accomplished using an electrochemical flow cell and stripping potentiometry at an unmodified gold electrode. The method was optimized prior to analysis of water and wheat samples. A detection limit of approximately 0.5 ppb Se(IV) was observed. Method accuracy was good and precision was acceptable (%RSD < 10). In the second project, stripping analysis was also employed, this time to analyze metal ion adsorption on carboxylic acid-modified silica nanoparticles. The metals analyzed were Cu(II), Cd(II), and Pb(II). By using anodic stripping voltammetry, adsorbed metal ions could not be detected, thus the need to separate the sorbent from the free metal ions was eliminated. All three metal ions in this study adsorbed in a nearly one-to-one ratio with the carboxylic acid groups at high pH (∼1000 μmol g-1). The effect of pH on adsorption behavior was also investigated. The third project also employed silica nanoparticles and a flow-through detection system. Co(III)-triethanolamine-doped silica nanoparticles were synthesized and used as catalysts for the luminol-H2O2 chemiluminescence reaction. It was found that the chemiluminescent signal increased linearly with the concentration of nanoparticles in bulk solution. The detection limit for the nanoparticles was 1.5 × 10-12 mol L-1 . Luminol-H2O2 chemiluminescence had superior precision when catalyzed by nanoparticles as compared with the free cobalt(III) complex. It was demonstrated that the nanoparticles met the criteria required for a biosensor label.

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