Development of graphite-epoxy screen-printed electrodes selective to nitrate ions

High concentrations of nitrate ions in water can cause eutrophication, while ingestion of these ions can cause methemoglobin and various cancers. Therefore, there is a need for sensitive, selective and inexpensive analytical tools, as an alternative to expensive conventional techniques, to monitor and evaluate the concentration of these ions. The aim of the present investigation is to develop printed graphite-epoxy electrodes modified with PVC membranes for the potentiometric determination of nitrate ions. The electrodes were manually printed in the laboratory with inks prepared from epoxy resin and graphite at different percentages and particle sizes. The printed electrodes were characterized by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy, prior to their modification with PVC membrane. The chrono-potentiometric response of the electrodes was evaluated with NO3- ion solutions. The best printing and electrochemical behavior of electrodes was obtained with inks containing 76 % of modified conductive phase-modified graphite nanoparticles. The developed ion-selective electrodes showed response to nitrate ions with a super-Nernstian slope, detection limits in the order of 10 mmol L-1, response times of 10 to 12 seconds and selectivity in the presence of NO2-, SO42-, Cl-, Br-, I- and CrO42- ions. The developed electrodes were used for the indirect determination of chloride ions in water samples by potentiometric titration.