Monitoring concentration profiles in situ with an ultramicroelectrode probe

Using an ultramicroelectrode placed inside the diffusion layer of a larger working electrode we demonstrated to which extent amperometric and potentio metric detections allow spatially resolved information at the micrometric s cale, so that the composition of a diffusion layer created in the vicinity of a millimetric working electrode can be examined with adequate precision. The validity of both methods was established experimentally in steady stat e conditions through the investigation of a simple redox reaction as well a s for more complex mechanistic situations. The amperometric detection is al so used to probe a time-expanding diffusion layer. thus showing the transit ion from perfect Cottrellian behavior to steady state imposed by spontaneou s convection.