Date of Award

2006

Degree Type

Thesis

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Computing, Health and Science

First Advisor

Dr Mary Boyce

Abstract

This study investigated the potential of a number of compounds to act as probes for the indirect detection of inorganic and organic anions separated by capillary zone electrophoresis and using light emitting diodes (LED) as the light source. Desirable characteristics of the probe anion included: high molar absorptivity, moderate to high electrophoretic mobility, and having a wavelength of maximum absorbance near the maximum emission wavelength of a LED. A preliminary study led to the evaluation of eleven possible compounds. Two of these, p-nitrophenol and 4-hydroxy-3,5-dinitrobenzoic acid were selected for further study as they fulfilled the criteria previously mentioned. The optimised BGEs containing p-nitrophenol and 4-hydroxy- 3,5-dinitrobenzoic acid as the visualising agent were used to separate a mixture of 11 anions. Both probes were best suited for the separation and detection of anions of moderate mobility such as phosphate and benzoate. Limits of detection of 0.003 mM were achieved for benzoate using the p-nitrophenol BGE and 0.006 mM for phosphate using the 4-hydroxy-3,5-dinitrobenzoic acid BGE. Multiple co-ionic electrolytes were explored to help increase the ability to efficiently analyse for analytes with a wider range of mobilities. A p-nitrophenol/4-hydroxy-3,5-dinitrobenzoic acid system and a p-nitrophenol/chromate system were investigated. Both systems displayed improvements in peak shape compared to a separation utilising a single probe. The optimised BGEs were then applied to oxalate using samples of interest to the alumina industry. p-nitrophenol displayed potential for the routine analysis of oxalate in high oxalate concentration samples, whereas 4-hydroxy-3,5-dinitrobenzoic acid was the probe of choice for the determination of oxalate in typical Bayer liquor samples.

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