Exploring High-Charge-Density Polyelectrolytes as Membrane Component for Solid Contact Ion-Selective Electrodes

Abstract

Polyanions have been introduced as replacements for poly(vinyl chloride) (PVC) and potassium tetrakis(4-chlorophenyl)borate (KTpClPB) in the preparation of solid contact potassium-ion selective electrodes (K+-ISEs). Partly carboxylated PVC (PVC-COOH) and a fully charged polyanion, sodium poly(4-styrenesulfonate) (NaPSS), were used, culminating in the fabrication of three-component ion-selective membranes (ISMs). The comparison with a PVC-based ISM showed significantly reduced potential drifts during conditioning (from ∼1.3 to ∼0.2 mV/h) and a constant drift rate. Reduced drift is attributed to the presence of counter-charges in the polymer and the large molecular weight of the polyanions, therefore decreasing the leaching of the components resulting in degradation of the membrane. The ISEs utilizing the hydrophilic and highly charged NaPSS as the polymer matrix exhibit similar water layer formation compared to the PVC-based ISEs, and maintained a sensitivity of 54 ± 1 mV/dec and a selectivity over sodium of −3.1 (log mathematical equation) after 1 week in solution, suggesting an alternative approach to the standard membrane preparation protocol.