Electrochemical time-of-flight responses at double-band generator-collector devices under pulsed conditions

For a double-microelectrode device, the time required to a species generated at the first electrode to diffuse towards the second one and be collected is the time-of-flight t(f). This time is related to the specific distance d separating the two electrodes by equation d = K root Dt(f), where D is the diffusion coefficient of the species and K a constant which depends on: (i) the geometry of the device, (ii) the type of experiment and (iii) the criterion used to evaluate the flight time. Electrochemical time-of-flight (ETOF) methods are often based on pulsed potential techniques and allow the diffusion coefficient of a generated species to be precisely evaluated. However, to be accurate, these methods require the knowledge of K. We report hereafter numerical simulations of ETOF responses as a function of geometrical parameters of the device and type of experiment performed. To be used under any given specific case values of K can be determined considering zone diagrams based on kinetic limiting behaviors of the simulated responses. The validity of these calculations were tested successfully by performing experiments in aqueous solutions of Fe(CN)(6)(3-) with ETOF measurements of Fe(CN)(6)(4-). This was achieved either in open solution or in a microchannel without convection. (c) 2006 Elsevier B.V. All rights reserved.