Alkali ion sensor based on Prussian blue-covered interdigitated array electrodes

Thin films of ferric ferrocyanide (Prussian Blue) were electrochemically deposited on interdigitated array (IDA) electrodes yielding systems which can be considered as chemi-resistors in sensing alkali ion concentrations in an adjacent electrolyte. From the dependence of the steady-state current on the electrode (bias) potential at variable cation concentrations for different alkali ions and for mixtures of alkali ions, the possibilities of analytical application are elucidated. It is concluded that Prussian Blue-coated IDA electrodes are, in principle, suitable as chemiresistors for the determination of alkali ion concentrations with increasing selectivity in the series Li < Na < K < Rb < Cs.