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.