New sensing techniques using conducting electroactive polymers

The discovery of new electrode materials has greatly expanded the range of detectable compounds using electrochemical methods. Conducting Electroactive Polymers (CEPs) such as polypyrrole, polythiophene and polyaniline represent a new class of organic polymers that are capable of a range of molecular interactions enabling them to interact with the species of interest. In addition the fact that they are conductive and electroactive enables electrical signal generation to be accomplished. Problems however exist due to the dynamic nature of these polymers thereby mitigating against their successful application as sensors. This has also hindered the production of analytically useful, sensitive, and reversible signals using these polymers. This work has sought to examine the problems due to the lack of analytically useful, sensitive, reversible and re-useable signals through the use of CEPs; why the problems exist and ways of overcoming them. The generation of analytically useful signals using the detection of electroinactive anions and cations were considered. The mechanism of signal generation of the CEP-based electroinactive species were investigated using a range of electrochemical techniques. The CEP-based signal generation was carried out through the application of various potential waveforms. Selectivity was achieved by the appropriate choice of current sampling points, applied pulsed potential waveforms and the choice of the counterions employed in the synthesis and eluent. The use of polymer-coated microelectrodes resulted in about 2 to 3-fold improvement in detection limits. Biosensors were also developed using antibody immobilised within CEP matrices and bioactivity was maintained. The polypyrrole antibody electrode system was then used in the detection of a range of proteins. Ab-Ag interaction was achieved through the application of pulsed potential waveforms; at positive applied potential, Ab-Ag interaction was encouraged and the interaction discouraged at negative applied potential. Sensors for specific detection of Human Serum Albumin (HSA), Thaumatin (an artificial sweetener), a large range of anions and halogenated organic acids were developed. The CEP detectors were adapted for use with Flow injection Analysis (FIA) and Ion chromatography. The practical utility of the sensors was determined in real samples; results obtained were comparable with conventional techniques