Research on On-Line Detection Method and System for Nitrate in Groundwater

Abstract

In order to monitor the concentration of nitrate in groundwater and evaluate water quality, a specialized sensor has been developed to solve the problems of the passivation effect, short life and poor repeatability of electrodes in conventional electrochemical detection, a novel preparation method of copper-sensitive film was proposed, and the method was combined with a microelectrochemical sensing electrode to detect nitrate in water. Microfabrication technology was used to prepare the micro sensor electrode. A total of 0.05 mol/L CuSO4 was added into the supporting electrolyte, and the dissolution and deposition of copper on the surface of the working electrode and the catalytic reduction reaction of nitrate ions were performed. On-line cleaning of microelectrode, in situ deposition of copper-sensitive film and detection of nitrate concentration in water were realized, respectively. An on-line modified electrode was used to detect the nitrate standard sample, achieving a high detection sensitivity (0.031 μA/[μmol L−1]) in the concentration range of 0–3500 μmol/L. The relative standard deviation of the same nitrate standard sample repeated for 15 times was only 2.48%, which improved the long-term repeatability of nitrate detection, and, at the same time, an on-line system was adopted that included an on-line detection system (DS) and a wireless transmission system (WS).