The main goal of this thesis was the development of capacitive readout technique by using an electronic capacitor instead of a solid-contact material to overcome the main drawbacks of constant potential coulometric readout. The capacitor can be adapted to amplify the current signal with ease, making this technique applicable to various ion sensing. Importantly, the current baseline drift is minimized owing to the ideal capacitive behavior of electronic capacitor. The concept has been extended to all-solid-state membrane electrodes. We reported the use of an electronic circuit to automate the control of the capacitive readout. Discharging the capacitor is executed by short circuiting after each chronoamperometric measurement. Furthermore, the development of a portable device for constant-potential coulometry is presented. A small potentiostat along with dedicated electronic circuits are integrated and fitted in a small box. Finally, a mathematical model is presented to describe the effects of exponential decay currents on the concentration polarization of ion-selective membranes. This approach improved sensitivity and gave higher precision than the traditional potentiometric probes.