A liquid-membrane type nitrate-selective electrode was improved to lower the influence of contaminants by modifying its inner electrode system from Ag | AgCl | Cl- to Ag | Ag+. The NO3--selective electrode displayed a linear response to the concentration of NO3- with a Nernstian slope of -53 ± 1 mV decade-1, in the concentration region between 10-5 and 2 mol dm-3 (M). The NO3- detection limit was about 10-5 M. The electrochemical response of this electrode was stable for more than 30 days. The deterioration in responding characteristics due to the coexistence of Cl- was suppressed by use of the Ag | Ag+ redox couple in the absence of Cl- inside the NO3--selective electrode.
Keywords: Nitrate; ion-selective electrode; monitoring; soil; tetraheptylammonium ion.