Electrochemical manipulation of localised pH: application to electroanalysis

The electrochemical manipulation of the local pH at a polymer functionalised electrode has been achieved in order to enhance the electrochemical response to cationic analytes. The changes in pH have been shown to provide a method for significantly enhancing the analytical signal towards the model compounds, dopamine and p-aminophenol. The procedure was found to operate irrespective of the electrical properties of the film. The main requirement for this electroanalytical system is that the film contains acidic groups within the polymer backbone. In the carboxylic acid functionalised polypyrrole film studied here, the performance was found to be greatest when the bulk solution pH was less than the pKa of the acid groups. The mechanism attributed to the enhanced response is elucidated and the limitations of the technique are assessed.