Ephedrine–copper–carbon interactions: An electroanalytical investigation

The electrochemical behaviour of ephedrine at carbon fibre electrodes has been investigated as a preliminary step in the development of a decentralised sensor for the alkaloid. The reaction pathway has been examined and key intermediates (principally benzaldehyde) resulting from the electrode processes identified by complementary chromatographic (GC–MS) and spectroscopic methods (NMR). A novel detection strategy has been developed in which the in situ manipulation of pH at the electrode interface induces a shift in the oxidation potential of the ephedrine to a region where it can be readily quantified. The electrochemical basis from which local pH can be controlled is outlined and the detection methodology is examined with respect to the influence of potential interferences (ascorbate and urate).