Mapping Of Concentrations In The Vicinity Of Microelectrodes: Study Of The Mass Transport In Steady State And Transient Regimes. Elaboration Of Enzyme-modified Electrodes.

Based on a model previously developed in the laboratory accounting for the influences of diffusion and spontaneous convection on the mass transport of electroactive species, further studies were performed to better understand the contributions of each mode: linear diffusion, hemispherical diffusion, migration, spontaneous convection and convection induced by density gradients. The mapping of concentration profiles in the vicinity of electrodes was realized during electrochemical experiments in steady state and dynamic regimes. Detections with highly spatial resolution were perfomed by amperometry using ultramicroelectrodes as probes of concentration. Experimental results were found in good agreement with the theoretical predictions of the model in particulary when spontaneous convection takes place. The limits of this model were also establihed in case of convection induced locally by density gradients. This work gives the possibility to map concentration profiles above enzyme-modified electrodes. We present here our preliminary contribution about the elaboration of microelectrodes modified by glucose oxidase.