Improvement of Amperometric Sensor Used for Determination of Nitrate with Polypyrrole Nanowires Modified Electrode

Polypyrrole(PPy) nanowire modified electrodes were developed by template-free electrochemical method based on graphite electrode. The modified electrode was characterized by their amperometric response towards nitrate ions. Before reduction of nitrate ions, electrochemical solid-phase extraction (EC-SPE) of nitrate in/on modified electrodes was conducted. It is found that the unusual nanowired structure of polypyrrole layer (instead of well known cauliflower structure) allows us to increase the effective surface area of the electrode and subsequently the sensitivity. And the effects of electrochemical preparation parameters of PPy nanowire modified electrodes on their corresponding characters were evaluated. The experimental results show that the electrochemical preparation parameters of the modified electrodes such as scan rate, polymerization potential, temperature of polymerization solution and polymerization time have significantly effects on the morphology of PPy nanowires and subsequently effective surface area of the electrode and electroreduction current density of nitrate. The determination sensitivity may be varied according to the modification parameters. Under a certain polymerization conditions, the corresponding sensitivity reaches 336.28 mA/M cm(2) and the detection limit is 1.52×10(-6) M. The proposed method was successfully applied in the detection of nitrate in the real samples.