A flow-through cell with integrated coulometric pH actuator

A flow-through cell with integrated coulometric actuator capable of controlling the pH of a flowing liquid is presented. The cell, consisting of a rectangular channel with a noble metal actuator electrode deposited on the bottom, enables the titration of a moving liquid without the need for pumps and reservoirs of titrant because strong acid or base is produced in situ by the electrolysis of water at the electrode surface. To ensure a homogeneous liquid at the end of the system, convectional and diffusional mass transport processes are described. Also an expression for the final pH is derived. Measurements were carried out with a flow through system having an integrated actuator electrode and pH sensitive ISFETs. The experimental results for the final pH change and mixing times were according to theory. The resulting component can be integrated in miniature chemical analysis systems for providing ‘buffer on demand’ or for on-line titration purposes.