Interdigitated array microelectrodes as electrochemical sensors

Abstract

We investigated electrochemical measurements with interdigitated array ( IDA) electrodes in both stationary solutions and flow systems. In a stationary solution, we achieved a very low detection limit of 10 pM of reversible redox species by using substitutional stripping voltammetry, which is a new type of stripping voltammetry using an IDA microelectrode. In flow systems, current enhancement by redox cycling is less effective than that in a stationary solution. The flow rate dependence of redox cycling is constant in the amperometric region, varies with coulometric yield in the quasi-amperometric region, and is inversely proportional to the 2/3 power of the volume flow rate in the coulometric region. A low detection limit of 5 fg (32 amol) is obtained for dopamine due to the high current density and low background noise level (0.1 pA) at the carbon-based IDA microelectrode used as a detector for liquid chromatography. A new separation approach is demonstrated which combines electrochemical detection and a molecular template. The electrode is first partly covered with print molecules and then modified with silane coupling reagent. The catechol-imprinted electrode shows the usual diffusion-limited cyclic voltammogram of catechol and has a diminished response against all catecholamines. The selectivity between catechol and epinephrine is about 100 when the electrode is used as an electrochemical detector in liquid chromatography.