Solid-Contact Ion-Selective Electrodes Based on Graphite Paste for Potentiometric Nitrate and Ammonium Determinations

Robust and easy-to-handle solid-contact ion-selective electrodes (SC-ISEs) based on graphite paste have been developed for the potentiometric detection of NO-3 and NH+4 in environmental samples. Polypyrrole (PPy) has been used as intermediate layer and solid contact between the electron-conducting graphite paste substrate and the ion-conducting polyvinylchloride (PVC)-containing membrane with the immobilized ionophore. For the nitrate- and ammonium-selective electrodes, tridodecylmethylammonium nitrate (TDMA-NO3) and nonactin have been used as ion-complexing compounds, respectively. Both ISEs show nearly Nernstian response in the linear range from 10-5 mol/L to 10-1 mol/L with average slopes of u003e58 mV/decade. The ISEs possess short response times (u003c20 s).