Nitrate-Selective Electrode Developed by Electrochemically Mediated Imprinting/Doping of Polypyrrole

Nitrate-selective electrodes have been developed by electropolymerizing pyrrole onto glassy-carbon electrodes in the presence of NaNO 3 . Electrochemical variables were used to optimize the potentiometric response of the electrodes and to maximize the selectivity for nitrate over potentially interferent anions. Calibration plots with near-Nernstian slopes for nitrate were observed, -56±1 mV/decade (n=18), over a linear range of four decades of concentration (5.0×10 -5 -0.50 M nitrate). The electrodes had detection limits of (2±1)×10 -5 M nitrate (n=18). The commercially available nitrate-selective electrodes suffer from interference by lipophilic anions, such as perchlorate and iodide. Compared to these electrodes, the polypyrrole-based nitrate electrodes demonstrated improved selectivity coefficients for perchlorate and iodide by as much as 4 orders of magnitude (K pot NO3-,ClO4- =5.7×10 -2 , K pot NO3-,I- =5.1×10 -2 ). An electrochemically mediated templating mechanism is proposed to explain the observed high selectivity for nitrate