An Electrochemical Sensor System With Renewable Copper Nano-Clusters Modified Electrode for Continuous Nitrate Determination

An automatic electrochemical sensor system based on a sequential injection analysis technique for continuous nitrate determination is demonstrated. A three-electrode-system (Pt-Pt-Ag/AgCl), in which the Pt working-electrode was modified with renewable copper nano-clusters, was designed and fabricated to implement sensitive and reproducible nitrate detection under a programmed operation protocol. Based on an optimal potential protocol, the continuous renewal of copper sensing material was achieved on the working-electrode surface to ensure each measurement could be performed on a fresh and highly active copper surface, which guaranteed that automotive and continuous nitrate determination could be performed in a long period of time. The experiment results revealed that the response of the sensor system toward standard nitrate samples was linear and reproducible with an average sensitivity of 1.093 μA/mg · L
^-1
over the concentration range from 0 to 12.1 mg/L in a continuous long-term operation. The standard deviation for the fluctuation of the sensitivity was only 0.036 during the continuous repeated measurements. The developed system was used to detect nitrate in real freshwater samples. The results were in good agreement with the data obtained by the standard ultraviolet spectrophotometric method for nitrate detection with the maximal difference of 16.64%.