Development and Investigation of the Properties of an Electrochemically Regenerable Chemically Modified Electrode for Chemiluminescence Detection of Analytes in Solution

Claire E. Williams

December 2000

Department of Environmental Sciences, University of Plymouth, Plymouth, U.K.

The aim of this study was to exploit the sensitivity of the chemiluminescent ruthenium tris(2,2'-bipyridine) redox system for analytical purposes by producing electrochemically regenerable electrodes modified with a polymer derivative of this complex. Ruthenium tris(4-methyl-4'-vinyl-2,2'-bipyridine) bis(hexafluorophosphate) was synthesised and subsequently polymerised onto an electrode surface using the technique of cyclic voltammetry.

A potential was applied to the resulting Chemically Modified Electrode (CME) and upon reaction of the ruthenium centres with an analyte in solution, chemiluminescence was observed. Measurement of the emission intensity was used for the determination of the analyte concentration. The ruthenium centres were subsequently regenerated by the reversal of the applied potential. Very little environmentally unfriendly and expensive waste results from this process. This is in direct contrast with current methods which traditionally use the ruthenium tris(2,2'-bipyridine) complex either in solution or immobilised within a membrane for analyses of this type.

Attention was focused upon detection of the oxalate ion and the ruthenium tris(2,2'-bipyridine)/oxalate redox system reported in the literature was used as a model to investigate the capabilities of the CME's produced. A scan rate of 10 V/s between the potential limits of + 0.5 to + 1.5 V at pH 6.5 was established as the optimum conditions. A linear working range for oxalate was observed from 1.9 x 10-2 M to the limit of detection, 1.1 x 10-3 M. The lifetime of a CME was investigated and although the chemiluminescent signal diminished with time, the electrode was still functioning after 24 weeks, a total of over 200 regenerations. A series of amines and valine were also successfully detected using CME's.

In addition, a similar sensor was fabricated from the electropolymerization of a novel ruthenium complex, ruthenium tris(4-methyl-4'-(E-prop-2-enyl)-2,2'-bipyridine) bis(hexafluorophosphate). This was also shown to be capable of chemiluminescence emission and was successfully regenerated.

Two electrochemically regenerable CME's were therefore produced and this research is a valuable advance in the field of chemiluminescent detectors.

© 2000 by Claire E. Williams. All Rights Reserved

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