The Nernst-Planck-Poisson (NPP) model is a general approach to the description of the electro-diffusion processes which lead to the formation of the membrane potential. It takes into consideration several parameters of ion-selective electrodes (ISEs) which are ignored in simpler models. This paper presents a critical comparison between the NPP model and simpler models. The influence of different parameters on the detection limit of ISEs is discussed. This is achieved by comparing direct predictions of the models and, in contrast to any earlier treatment, by inverse modelling. This makes it possible to simultaneously find out which set of physical parameters of the system will produce the desired detection limit. (c) 2010 Elsevier Ltd. All rights reserved.