Redox Potential Measurements in Microbiological Media and Some Applications

Summary

An apparatus has been designed and used to investigate the behavior of different type of “inert electrodes” of noble metals (platinum, gold) in model and microbiological media, in weak buffer solutions. These noble metal electrodes cannot be recommended for the determination of oxidation potentials in these systems. Glass electrodes are recommended for such experiments. The suitability of these electrodes for work in weak buffer systems has been evaluated and the influence of oxygen and of hydrogen ions determined. It has been established that within physiological limits the electrode redox-function does not depend on changes in the oxygen content of the medium or on the hydrogen ion activity. The potential of a redox-electrode in a weak buffer culture is considered (from an instrumental point of view) as a stationary potential. The absolute value of the stationary potential has been determined by Potentiometric titration, and examples of this determination are given. The interdependence of the potential with other parameters such as pH, content of dissolved oxygen, amount of micro-organism, and limiting concentration of substrate etc. is illustrated,

In agreement with the 2nd International Convention on E.M.F. and electrode potentials, adopted by I.U.P.A.C. in 1953, the term “oxidation potential” is more correct as it directly characterizes the oxidation capacity of the medium and conforms with the system of designations recommended by the Convention. In this paper the term “oxidation potential” is preferred.