Construction and evaluation of an ammonium tubular ion-selective electrode with ionophore nonactin.

This paper describes the construction of an ammonium tubular potentiometric detector for flow injection analisys (FIA) in which the high molecular weight polyvinyl chloride (PVC) membrane is applied directly on a conducting support consisting of a mixture of an epoxy resin and graphite. The tubular ammonium ion-selective electrode, without internal reference solution, is based on nonactin as the ionophore and bis-(2-ethylhexyl)-adipate as plasticiser solvent, supported upon a PVC membrane, The electrode exhibited a response of 55.6 mV per concentration decade within the 5.0x10(-5) to 1.0x10(-1) mol/L NH4+ range in TRIS-HCl 0.2 mol/L (pH=6.7) buffer. Potassium ions constituted the greatest analytical interference; the electrode response time was 10 seconds, at 25.0 degrees C.