Potassium Ion Selective Electrode Using Polyaniline and Matrix-Supported Ion-Selective PVC Membrane

Solid-state potassium ion selective electrode (K
⁺
ISE) has been the most studied chemical sensors due to its practical importance in biomedical applications. One of the major obstacles that prevented widespread use of solid-state K
⁺
ISE has been output potential drift problem. In this paper, we developed an electrochemical sensing unit in which working, counter, and reference electrodes are integrated in a single plane as all-solid-state form. In order to mitigate the output potential drift, a polyaniline intermediate layer and salt-saturated polyvinylebutyral top coating are introduced in the working and reference electrodes, respectively. Using cyclic voltammetry (CV), uniform layers of polyaniline are deposited on carbon electrode, as confirmed by scanning electron microscope observation. Potentiometry and electrochemical impedance spectroscopy measurement on our K
⁺
ISE show high sensitivity (60.5 mV/decade), low concentration for the limit of detection (10
^-5.8
M), and large range of linear detection (10
^-5
-1 M), and superior selectivity of K
⁺
ISE against NH4
⁺
, Na
⁺
, Mg
²⁺
, Ca
²⁺
, and Fe
³⁺
. With its high potential to be miniaturized, we foresee that our solid-state K
⁺
ISE will motivate the future applications in microdevices for clinical analysis, agricultural, and environmental applications.