A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in
fulfilment for the requirements for a degree in Masters of Science.
November 2017, Johannesburg. / Metal complexes have a wide range of applications in fields such as medicinal, industrial,
environmental and so on. Determining the formations constants for metal complexes is thus essential
to gather information on complexes. Conventional methods used to study complexation include
spectroscopic methods and the use of voltammetric techniques such as direct current polarography
using a mercury drop electrode. In this work alternative voltammetric methods to study complex
formation are investigated.
Bismuth complexes have important medicinal applications but not much is known about them
because of the difficulties in studying them due to extensive bismuth hydrolysis and precipitation of
hydrolysis products from very low pHs. The aim of this work was to investigate whether using low
concentrations of bismuth (10-6 M) would prevent precipitation in nitrate solutions as predicted in
literature. Differential pulse anodic stripping voltammetry (DPASV) was the technique of choice
because of its low detection limit, even though it has not been widely used in complex formation
studies before. The study revealed that electrochemical response for Bi3+ was not fully reversible using
this technique. Additionally, even at the low concentration precipitation was observed in the acidic
region (investigated via pH titration) and was suspected to be the formation of BiONO3 species.
The second alternative method investigated was the use of mercury film electrodes to replace the use
of the toxic mercury drop electrodes which are being phased out worldwide. This work looked at using
in situ and ex situ plated films, where the in situ measurements proved more reproducible. A number
of challenges were encountered, such as film degradation, peak splitting and ligand adsorption to the
film electrode. Nonetheless, formation constants of lead-glycine complexes were determined under
different experimental conditions and these were found to be reasonably compared to the literature
values. / LG2018
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/24999 |
| Date | January 2017 |
| Creators | Ndlovu, Mapule Prudence |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (xix, 138 leaves), application/pdf |
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