Electrochemical detection of metals can be done at polycrystalline gold ultramicroelectrodes using repetitive cyclic voltammetry (RCV), a detection method sharing some similarities with anodic stripping voltammetry (ASV). Each cycle of the potential waveform for RCV involves application of a negative preconcentration potential (for 50 to 300 ms) followed by a cyclic voltammetry (CV) scan at 20 to 1000 V/s. The response due to the metals is evident at potentials negative of the region for oxide formation in the resulting CVs. Metals are deposited at the Au surface by underpotential deposition (UPD) processes. Any metal that can be analyzed by RCV could potentially be quantified using UPD-ASV at Au (rather than by ASV at Hg).
The UPD kinetics of Pb and Cu at polycrystalline Au were examined by setting kinetic parameters (rate constant, symmetry factor, and electrosorption valency) within a simulation program used to generate simulated CVs. Reasonably good agreement between experimental and simulated CVs was possible using the simulation, with the same kinetic parameters used to generate simulated CVs to match experimental CVs over a range of sweep rates for each system. Using this method, the following rate constants (k) were estimated: for UPD of Cu in H2SO4 and HClO4, ks ~ 36000 s−1 and 11000 s−1, respectively, and for UPD of Pb in H2SO4, ks ~ 400000 s−1. <p> Repetitive cyclic voltammetry was applied to the detection of metals separated by capillary electrophoresis. Separation of Tl+, Cd2+, Cu2+, Pb2+, Zn2+, Ni2+, Co2+ and Mn2+ was demonstrated in 0.01 mol/L acetic acid and 0.01 mol/L ammonium acetate(pH ~ 4.6) using RCV. While stacking is commonly exploited for sensitivity enhancement during injection, it was shown that detection-end stacking is also useful.
A novel technique named electrophoretic extraction (EE) was developed for analysis of particle-containing solutions (e.g. soil extracts or other colloidal suspensions). EE involves application of backpressure during CE to prevent particles from entering the separation capillary: the applied pressure is regulated so analyte ions enter the capillary and migrate to the detector, whereas other particles are prevented from entering the capillary. The feasibility of this approach was demonstrated.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-08022007-125411 |
| Date | 15 August 2007 |
| Creators | Nelson, Lana Johanne |
| Contributors | Baranski, Andrzej S. |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-08022007-125411/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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