Optimisation of poly(vinyl chloride) matrix membrane ion-selective electrodes for ammonium ions

Abstract

Poly(vinyl chloride)(PVC) matrix membrane electrodes for the determination of ammonium ions have been studied with respect to sensor and solvent mediator parameters. Nonactin, narasin, monensin and salinomycin were used as sensors and dioctyl adipate, diethyl adipate, 2-nitrophenyl phenyl ether, dioctyl phenylphosphonate, dioctyl sebacate, dibutyl phthalate and tripentyl phosphate as solvent mediators. The best ion-selective electrodes (ISEs) for ammonium ions were based on nonactin with dioctyl adipate as the plasticising solvent mediator, and the electrode based on salinomycin with dioctyl adipate as solvent mediator was its closest rival. The use of the copolymer VAGH (with 6% hydroxyl as vinyl alcohol) admixed with PVC produces matrix membranes of similar ammonium ISE properties to the PVC system and the free hydroxyl groups offer prospects for enzyme immobilisation when setting up enzyme electrodes for the determination of ammonium ions.