Thick-film voltammetric pH-sensors with internal indicator and reference species

The following paper describes the development of a screen-printed voltammetric pH-sensor based on graphite electrodes incorporating both internal indicator (i.e., phenanthraquinone) and reference species (i.e., dimethylferrocene). The key advantages of this type of system stem from its simplicity, low cost and ease of fabrication. More importantly, as opposed to conventional voltammetric systems where the height of the voltammetric peaks is taken into account to quantify the amount of a species of interest, here, the difference between the peak potential of the indicator species and the peak potential of the reference species is used. Thus, this measurement principle makes the electrochemical system presented here less dependent on the potential of the reference electrode (RE), as is often the case in other electrochemical systems. The developed system displays very promising performances, with a reproducible Super Nernstian response to pH changes and a lifetime of at least nine days.