Mechanistic aspects of nitrate-selective electrodes with immobilsed ion exchangers in a rubbery membrane

Abstract

The response mechanism of nitrate ion selective electrodes (ISEs) containing covalently bound quaternary ammonium salt sensor molecules has been investigated using ¹⁵N tracer studies, ion exchange measurements and surface analysis by electron microscopy using energy dispersive X-ray analysis. The ISEs were shown to operate by surface ion exchange mechanism with no involvement of ion diffusion though the membrane. Ion selectivity was shown to be dependent on a solvent mediator increasing membrane surface permeability towards nitrate allowing ion exchange to occur. A new sub-category of classification for electrodes of this type is proposed.