A route to unbuffered pH monitoring: A novel electrochemical approach

Carbon paste electrodes modified by various dihydroxyquinone derivatives are investigated using both cyclic voltammetry and square wave voltammetry in order to ascertain suitability as voltammetric pH sensors. These electrodes show a Nernstian response to the change of pH, with a potential shift close to the theoretical value, 59.2 mV per pH unit at 298 K. Moreover, their capability of measuring the pH of the unbuffered solution with less than 5% error can be attributed to the occurrence of both inter- and intra- molecular hydrogen bonding present within the system. The efficacy of the compounds to be used as materials for solid state pH sensors is discussed