Development of micro-fluidic nitrate-selective sensor based on doped-polypyrrole nanowires

This paper presents a flow-through, nitrate-selective, electrochemical sensor developed by electropolymerization (doping) of polypyrrole nanowire (PPy-NW) electrodes. The flow-through micro-fluidic platform enabled a realistic and controlled testing environment. Cyclic voltammetry, amperometry and flow-through analysis were performed to evaluate the sensor performance for determination of nitrate ions in two sets of calibration solutions (DI water and IAPSO standard seawater). The sensor response was linear over the range from 10 μM (0.14 ppm Nitrate-N) to 1 mM (14 ppm Nitrate-N), with a sensitivity of 1.17–1.65 nA/μM and detection limit of 4.5 ± 1 μM or 0.063 ± 0.014 ppm Nitrate-N. The electrochemically doped PPy-NW electrodes show improved selectivity for chloride, sulfate, phosphate and perchlorate ions, without the loss from interfering ions.