Year

1991

Degree Name

Doctor of Philosophy

Department

Department of Chemistry

Abstract

The development of novel electrochemical sensors and solid phase on-line derivatisation devices using conducting polymeric materials has been investigated in this work. Polypyrrole was the material of choice due to its merits over other conducting polymers, particularly the ease of synthesis and the ability to incorporate a wide range of counterions.

Polypyrroles containing a range of chemically active substances have been electrochemically synthesised and their properties characterised using various techniques. Incorporation of the desired substances was verified using elemental analysis, amino acid analysis, fast atom bombardment mass spectrometry (FABMS) and energy dispersive X-ray (EDX) analysis. The electroactivity and conductivity of these polymers were evaluated using chronopotentiometry, cyclic voltammetry and cyclic resistometry.

The electrochemical release of counterions, such as anthraquinone-2,6-sulphonic acid (AQSA), dichromate, human serum albumin (HSA) and pyridine-2,6-dicarboxylic acid (PDCA), from polypyrrole polymers has been investigated. It was found that the rate of release of the counterion is a function of the counterion size, charge and hydrophobicity. The applied potential and the solution conditions (ionic strength, pH, supporting electrolyte and solvent) also affected the rate of release.

Polypyrrole was coated onto platinum and thin mercury film electrodes, and the capability of preconcentrating metal ions by complexation and/or precipitation using these electrodes have been investigated. Experimental results demonstrated that polypyrrole modified electrodes were able to chemically preconcentrate silver ions and subsequently generate voltammetric signals. Polypyrrole modified electrodes were also found to enhance selectivity for the detection of dichloramine over other chloramine species.

Polypyrroles containing diethyldithiocarbamate (DTC) and aryl sulfatase (AS) have been investigated for use as polymeric reagents in a reactor for on-line derivatisation. The DTC ligands were electrochemically released from the polymer into the eluent to form copper-DTC and nickel-DTC complexes for subsequent detection. Polymer immobilised AS catalysed the derivatisation of p-nitrocatecholsulfate (PNCS) to p-nitrocatechol which enhanced the sensitivity of PNCS detection.

This study has indicated that it is possible for polypyrroles containing chemically active substances to be used as electrochemical sensors and solid phase on-line derivatisation devices.

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