Electrochemical Determination of Chemical Oxygen Demand (COD) in Surface Water Using a Microfabricated Boron-Doped Diamond (BDD) Electrode by Chronoamperometry

Chemical oxygen demand (COD) is an important indicator of the degree of organic pollution in water. However, the development of integrated and batch COD electrochemical sensors has always been challenging. In this study, a three-electrode integrated electrochemical sensor for the measurement of COD in surface water was evaluated. Using microfabrication with a microelectromechanical system (MEMS), the sensor was mass-produced and integrated with boron-doped diamond (BDD), Pt, and Ag/AgCl electrodes on the chip. The determination of glucose in optimal conditions provided a linear range from 5 to 200 mg L-1, a detection limit of 3.899 mg L-1, and satisfactory linearity (R-2) of 0.998. As the sensor was fabricated by MEMS technology, good reproducibility was experimentally verified with relative standard deviations less than 4%, which suggests mass production of the sensor. The sensor was calibrated to be relatively stable in the presence of Cl- and NO2-. A low-cost, miniature (6 mm(2)), and stable COD sensor was designed using microfabrication technology that may be mass-produced to build a water quality detection network in the Internet of Things era.