Potassium ion-selective polyaniline solid-contact electrodes based on 4′,4″(5″)-di-tert-butyldibenzo-18-crown-6-ether ionophore

Abstract

New ion-selective electrodes for potassium were developed and tested employing 18-crown-6-ether, dibenzo-18-crown-6-ether, and 4′,4″(5″)-di-tert-butyldibenzo-18-crown-6-ether ionophores in PVC membranes with a polyaniline solid contact between the membranes and the Pt substrate. We compared the response characteristics of the solid-contact electrodes (SCEs) based on these ionophores and various plasticizers. Among the three ionophores, 4′,4″(5″)-di-tert-butyldibenzo-18-crown-6-ether-based SCE produced the best results exhibiting a high reproducibility with negligible drifts in the standard potential with a response slope (RS) of 58.2 mV/decade: the detection limit (DL) of the potassium ion was 10−5.80 M with linearity over five decades. This is a significant improvement for the response slope and detection limit compared to SCEs with valinomycin, 2,3-naphtho-15-crown-ether, and dibenzo-15-crown-5-ether ionophore, which showed 53–56 mV/decade of RS and 10−5.3 M of DL. The response slope, detection limit, and selectivity were compared with other K+ ISEs reported until present. Finally, the new SCE was applied to determine potassium ions in artificial human serum with satisfactory results. However, the detection limit for the artificial serum was slightly diminished yielding a value of 10−5.19 M (6.5 × 10−3 mM) which is still good. Electrodes with polypyrrole in place of polyaniline exhibited comparable results.