Catalytic homogeneous electrochemical reactions have been studied with reciprocal derivative chronopotentiometry (RDCP) using an exponential time current both under transient and stationary conditions. The general expressions for the chronopotentiometric potential-time and derivative curves obtained are applicable for spherical electrodes of any radius, including planar electrodes and ultramicroelectrodes as limiting cases. The use of this programmed current has the particularity that it enables to achieve a stationary state very quickly, even when the chemical rate constants are not very high and, under these conditions a simple and quantitative characterisation of catalytic processes can be carried out. Moreover, the RDCP response is always peak-shaped, even for very high homogeneous rate constants for which the stationary response in cyclic voltammetry has a sigmoid feature. The experimental verification of the theoretical predictions has been carried out by analysing the electrocatalytic reduction of the heteropolyanion PW12O403- in an aqueous sulphuric media with an excess of nitrite. (c) 2008 Elsevier Ltd. All rights reserved.