An assessment of various types of reference electrode for use in continuous potentiometric analysis with particular application to highly pure waters

The suitability of a number of reference electrodes for use in the continuous potentiometric analysis of highly pure water has been assessed. The electrodes were chosen to be as representative as possible of their class, but several electrodes of novel design were also included. The electrodes were tested for the constancy of their potentials over 100 d of continuous operation in 10–5 mol l–1 sodium hydroxide solution (a simple model boiler water) and for the extent to which they were affected by ultraviolet light, particulate matter and changes in flow-rate and ionic strength. The times taken by the electrodes to recover from changes in temperature, from an interruption in the flow of sample and from being immersed in buffer solutions were measured and proved to be important characteristics in discriminating between the over-all performance of electrodes.It was concluded that conventional types of electrode, whether calomel or silver-silver chloride, with ceramic frit junctions and unsaturated potassium chloride electrolytes, were superior in almost every respect to the other types tested.