We have conducted feasibility studies based on chronocoulometry of nitrate for the purpose of fabricating a miniaturized sensor. Detection and monitoring of nitrate ion in surface water are important because of environmental and ecological influence of nitrate. For this application, sensors should be small, stand-alone, and have a low detection limit. Conventional nitrate sensing methods (spectroscopy, chromatography, electrophoresis, etc.) Do not meet aforementioned requirements because of the cumbersome sample preparation and complex implementation. Electrochemical detection is simple and a sensor can be easily miniaturized when using this method. The proposed electrochemical cell (silver working electrode, platinum counter electrode, ag/agcl reference electrode, and sodium hydroxide supporting electrolyte) shows high sensitivity for the nitrate ion detection. Oxygen dissolved in aqueous electrolyte interferes with the nitrate detection, but was successfully removed by a simple differential approach.