The simultaneous voltammetric determination and detection of oxygen and carbon dioxide: A study of the kinetics of the reaction between superoxide and carbon dioxide in non-aqueous media using membrane-free gold disc microelectrodes

The kinetics of the reaction between superoxide and carbon dioxide are investigated at a 10 μm gold disc microelectrode in three non-aqueous solvent systems (dimethylsulphoxide, N,N-dimethylformamide and acetonitrile), and are observed to be first-order with respect to both superoxide and carbon dioxide in all three cases, with a DISP1-type pathway likely followed. Although the reaction between electrogenerated superoxide and carbon dioxide is fast (as great as 105 M−1 s−1), deconvolution of the two observed signals due to oxygen and carbon dioxide reduction is shown to be possible. Accordingly, an electrochemical sensing strategy is developed for the direct amperometric sensing of both gases in non-aqueous solutions, using a single membrane-free microelectrode immersed in a three-electrode electrochemical cell.