Ion-selective electrode for potassium determination

Ion-selective electrodes are devices which detect activity of specific substances and variety of them is really wide . The application of them is one of main analytical techniques in many fields e.g. medical and environmental analysis or process control in industries.

This article describes screen-printed electrode for potassium determination which was manufactured and tested. Potentiometry was chosen as measurement method. Commercial silver chloride electrode was chosen as reference electrode due to the fact that only indicator electrode was a research subject.
During work two types of conductive pastes were prepared. One of them was silver paste based on thermoplastic polyurethane (TPU). The second was graphene paste based on poly(methyl methacrylate) (PMMA).

An essential part of ion selective electrode is membrane. Two membranes which differ in composition were made. For both membranes polyvinyl chloride (PVC) was used as a matrix and valinomycin was used as ionophore which binds potassium ions. Moreover, some of the prepared electrodes had an additional intermediate layer made of a conductive polymer - poly(3,4-ethylene-1,4-dioxythiophene) (PEDOT).

During research only about 10% of the printed electrodes responded to changes in the concentration of K+ ions. The most likely reason of these results is that membrane separated from the substrate.