“…In particular, it has been established that a fixed charge distribution varying linearly with position inside the membrane lead to higher permselectivity than an homogeneous membrane with the same value of the average charge concentration when the coions enter the membrane through the highly charged side [11,15]. It is the main purpose of this paper to contribute to this area and to extend our previous work in this field [15] by investigating the electrochemical impedance and the effect of non-linearity on the validity of impedance measurements of an inhomogeneous ion-exchange membrane system. The system under study is constituted by an inhomogeneous membrane with negative fixed charge varying linearly with position and two diffusion boundary layers on both sides of the membrane, ionic transport being described by the Nernst-Planck and Poisson equations.…”