Aspects of the present disclosure are directed to a pH control device. The device comprises a substrate, on which is defined a flow path adapted to receive a liquid. The device further comprises a set of electrodes, which includes a pH sensing electrode and pH generation electrodes. The electrodes are arranged along the flow path. The pH sensing electrode is arranged so as to be subjected to a change in pH of a portion of the liquid on the flow path, as caused by the pH generation electrodes. In addition, the device includes a controller, which is configured to apply a voltage across the pH generation electrodes, based on a signal obtained via the pH sensing electrode and a reference electrode. This enables local control a pH of the liquid portion. The device may further be embodied as a sensor, additionally comprising a detection electrode.