Electrolyte-Flow-Controlled Reference Electrode using Hydrogen Pressure for an Ultra-Long-Life Rumen pH Sensor

We invented a novel Ag/AgCl reference electrode (RE) system that could control electrolyte outflow using hydrogen pressure and simultaneously deposit AgCl, so that rumen pH could be monitored for two years or more. To overcome a fatal problem of air bubbles insulating a valve liquid junction RE, a platinum electrode system was introduced to apply hydrogen pressure to the junction to remove air bubbles. We prototyped the RE system and demonstrated that potential could be measured from the insulated state. In this system, AgCl deposition simultaneously occurred with hydrogen evolution, and this solved the AgCl dissolution problem of a miniature Ag/AgCl electrode. We experimentally confirmed that AgCl deposition prolonged lifetime of the electrode. By applying the proposed system to a miniature pH sensor, its lifetime was estimated to be 2.1 years.