Date of Award

2015

Degree Type

Thesis

Degree Name

Master of Science (Chemistry)

School

School of Natural Sciences

Faculty

Faculty of Health, Engineering and Science

First Advisor

Professor Glenn Hyndes

Second Advisor

Dr Magda Wajrak

Third Advisor

Professor Yoko Fujikawa

Abstract

Contamination of drinking water is a serious health issue in many developing countries and there is a recognised need for low cost portable systems that are capable of analysing drinking water down to low ppb levels. Anodic Stripping Voltammetry (ASV) instruments meet these requirements but suffer interferences from other species which may also be present in the sample, particularly organics, other metals and sulfides. The last of these has received surprisingly little attention in the literature, despite being a proven interferent.

This study investigates the impact of each of these interference types, as well as a number of traditional and novel techniques in resolving them in a three phase process. First, each interferent was evaluated individually to determine the concentration at which it would significantly and reliably cause significant errors in the determination of arsenic by ASV. Secondly, each individual interferent was subjected to a number of pretreatments to determine the most suitable pretreatment method to remove that interference. Thirdly, a combined pretreatment method, capable of pretreating a single sample contaminated with significant levels of all three interferent types was developed and tested.

Modifications to the basic analysis methodology provided by the instrument manufacturer had to be made, particularly in the elimination of residual interferents affecting clean test solutions analysed after a contaminated test solution. A number of pretreatment methods were successful for sulfide contamination, however only the ion exchange resin was reliably successful for copper interference and only UV digestion was totally successful for organic contamination at the levels investigated. Although other pretreatment methods did partially improve the response of test solutions contaminated with the organic interferent,their performance was not sufficient to consider them for the final combined pretreatment method. The final combined pretreatment method for all three interferences was successfully tested on artificial sample solutions.

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