A FLOW-THROUGH CELL WITH INTEGRATED COULOMETRIC PH ACTUATOR

A flow-through cell with integrated coulometric actuator capable of co ntrolling the pH of a flowing liquid is presented. The cell, consistin g of a rectangular channel with a noble metal actuator electrode depos ited on the bottom, enables the titration of a moving liquid without t he need for pumps and reservoirs of titrant because strong acid or bas e is produced in situ by the electrolysis of water at the electrode su rface. To ensure a homogeneous liquid at the end of the system, convec tional 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 an d pH sensitive ISFETs. The experimental results for the final pH chang e and mixing times were according to theory. The resulting component c an be integrated in miniature chemical analysis systems for providing 'buffer on demand' or for on-line titration purposes. (C) 1998 Elsevie r Science S.A. All rights reserved.