An investigation of dynamic amperometric currents at recessed, membrane covered planar and hanging mercury drop electrodes has been conducted. Two expressions for current transients were found to have different convergent properties depending oil the value of dimensionless time T = Dt/L-2, where D is diffusion coefficient, t is time and L is the recess depth for a recessed electrode, the membrane thickness for a membrane covered electrode and the radius of the mercury drop for a hanging mercury drop electrode. A simple but accurate solution function was derived which consisted of the rapid convergent elements of these two expressions; this proved to be valid for the entire response time range allowing a dynamic simulation and a route to computing the diffusion coefficient of an electroactive solute through the diffusion barriers at the working electrode. (c) 2007 Elsevier B.V. All rights reserved.