A sensitive reagentless pH probe with a ca. 120 mV/pH unit response

The use of a basal plane pyrolitic graphite electrode immobilised with two redox active species each capable of undergoing a two-electron, two-proton redox process has allowed the development of a sensitive pH probe over a wide pH and temperature range. When the values of the peak potentials of the two processes are combined they shift by ca. 120 mV/pH unit at 25 °C, as measured against two independent, defined reference electrodes.