Measurement of Hydrodynamics and Dissolved Oxygen with a Polarographic Microelectrode

Besides for electrochemical analysis, polarographic electrodes can be used for the determination of hydrodynamic parameters in aqueous media. For this latter application, a three-segment microelectrode has been developed with which vectorial hydrodynamic parameters (liquid velocity and turbulence intensity) can be determined via electrodiffusion. With oxygen instead of the normally used ferri-/ferrocyanide system, the microelectrode can be employed for hydrodynamic measurements in aerated aqueous solutions independent on coalescence behavior. Experiments show that in contrast to Laser-Doppler Anemometry and Hotfilm Anemometry the electrodiffusion electrode can also be used in aerated solid suspensions. Moreover, using the probe with oxygen as the depolarizer, it is possible to measure hydrodynamic parameters and dissolved oxygen concentration at the same time. As an example, the simultaneous determination of hydrodynamics and oxygen in aerobic batch fermentation (Erwinia herbicola) is presented.