This study has two aspects. One concerns the development of a sensitive differential pulse polarographic (DPP) method and its use to conduct a preliminary study of natural waters to detect the presence of nitrosoamines, and the second, where the study was carried out in greater detail, is the investigation of the kinetics of reduction of N-nitrosodimethylamine (NDMA) in aqueous solution. An optimization study was first conducted to identify the conditions that give the greatest sensitivity. Conditions investigated were different supporting electrolytes and solvent mixtures. Supporting electrolytes used were 0.10 M solutions of acids, bases and salts, and the solvent mixtures studied were ethanol/water mixtures. The effect of various supporting electrolytes and various ethanol/water mixtures on peak current was studied in order to select the conditions that give the greatest sensitivity for the determination of nitrosoamine concentrations. The lowest nitrosoamine concentration that can be detected in a solution (limit of detection) was determined. The optimum supporting electrolytes for N-nitrosoamines and the C-nitrosoamine were respectively found to be 0.10 M H2S04 and 0.10 M NaOH. Aqueous solutions were also found to give greater sensitivity than ethanol/water mixtures. The presence of nitrosoamines in some natural water samples was then checked using differential pulse polarography (DPP).Concentrations of nitrosoamines in these water samples were determined using the optimum conditions. The analyte analytes studied were 4-nitroso-N,N-dimethylaniline (4NDMA); Nnitrosodibutylamine (NDBA),N-nitrosodi-n-propylamine (NDPA) and N-nitrosodiphenylamine (NDPhA). All four nitrosoamines were detected in some of the
selected natural water samples .
The kinetics of the electrochemical reduction of NDMA was studied using controlled
potential coulometry, linear scan voltammetry (LSV) and cyclic voltammetry (CV).
Controlled potential coulometry was first used to determine the number of electrons
transferred (n) in the reduction reaction. Two moles of electrons were found to be required
for the reduction of one mole of NDMA solution, at a stationary mercury drop electrode
(SMDE). The major product obtained, identified by UVNIS spectroscopy, was
dimethylamine (DMA). / Ph.D. (Chemistry) North-West University, Mafikeng Campus, 2005
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/11319 |
| Date | January 2005 |
| Creators | Hlophe, Mbhuti |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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