The investigation of the factors influencing the limit of detection of microelectrode chemical sensors using AC impedance spectroscopy and cyclic voltammetry

Electrochemical sensors are widely used to determine the concentration of a substance in solution. Provided the mass transport of the substance to the electrode controls the rate of oxidation/reduction then the current associated with the process will be proportional to the concentration of the substance in solution. The convergent geometry of the microelectrode enhances mass transport of the substance to the microelectrode and circumvents the need for stirring and also presents the possibility of lower detection limits in comparison to conventional sized electrodes. However, as a result of the very high impedances and very small currents associated with the microelectrode, the expected lower detection limits have not yet been achieved. The aim of the work presented here was to investigate the factors limiting the resolution of the measurand current of the microelectrode using AC impedance spectroscopy and cyclic voltammetry