ABSTRACT
This chapter details the use of conventional electrochemical sensors for the measurement of pH, dissolved oxygen, redox potential, and dissolved carbon dioxide. It mainly covers in situ sensors, which are mounted directly in the bioreactor. First, the principal requirements for in situ sensors is discussed. The chapter summarizes the performance of present pH sensors in comparison to the requirements and shows that still no ideal pH sensor exists, but it lists new sensors which eliminate some current limitations. Besides optical pH measurements many publications promote the ion-selective field-effect transistor pH electrodes. All of the dissolved-oxygen (DO) sensors operate on the principle of reduction of oxygen at the surface of a noble-metal electrode, the cathode. Volatile substances are potentially interfering substances. Interferences come from gases which are reduced at the cathode.
