Self-plasticized Ca²⁺-selective electrode with polyaniline and copolymer of aniline and 2,5-dimethoxyaniline as solid contact layers

To address solubility, plasticizer leakage, and ionic carrier issues in PVC-based solid ion-selective electrodes, a novel plasticizer-free photocurable solid Ca²⁺-selective electrode (GC/PANI/CPANI/Ca²⁺(PBA)-ISE) was developed using a novel electrode structure. A new Ca²⁺-sensitive membrane based on poly(butyl acrylate) (PBA) was synthesized by ultraviolet polymerization, with conductive polyaniline (PANI) as the solid contact layer and a copolymer of aniline and 2,5-dimethoxyaniline (CPANI) as the coating. All potential electrochemical tests were carried out on the prepared Ca²⁺-selective electrode. The response slope of the electrode was 28.33 mV decade⁻¹, the detection limit was 6.9 × 10⁻⁶ M, the stable linear range was 1 × 10⁻⁶ to 1 × 10⁻² M, and it had a good Nernst response. The chronopotentiometric analysis and water layer tests showed that the potential drift of GC/PANI/CPANI/Ca²⁺(PBA)-ISE was as low as 0.0125 mV s⁻¹ and 1.247 mV h⁻¹. In addition, the interference tests of environmental factors were carried out. When the electrode was in different interference light and gas environments, the potential changes of 1.6 × 10⁻⁴ mV s⁻¹ and 1.2 × 10⁻³ mV s⁻¹ were observed. Compared with previous reports and commercial electrodes, the prepared GC/PANI/CPANI/Ca²⁺(PBA)-ISE showed good electrochemical performance, and the recovery rate in Ca²⁺ test solutions was higher (97.2–99.9%). This study provided theoretical insights to address solubility, plasticizer leakage, and ion carrier leakage issues in solid-state contact ion-selective electrodes. At the same time, this study provided a new structure and preparation method for the preparation of all-solid-state Ca²⁺-selective electrode.