Nitrates and Nitrites Detection System in the Drinking Water Using UV Absorption

This paper presents the development of a portable, cheap and easy to use electronic device which can detect the concentration of nitrates and nitrites in drinking water. The device is based on the property of nitrates (NO₃) and nitrites (NO₂) to absorb ultraviolet light. The absorption peak for NO₃ is found at 310nm and 365nm for NO₂. The maximum amount of nitrate in drinking water imposed by the European Union is 50mg/l. Detecting this concentration is the main objective of the implemented system. The application is developed around two UV LEDs with the central wavelength close to the absorption peak of NO₃ and NO₂ and a UV sensor for the detection of the optical power after the UV light is passing through the water probe. Several tests proved that it is necessary to use power LEDs to detect the absorbed light. Thus, after intensive research, it was observed that there are no 310nm power LEDs on the market. For this reason, only the 365nm LED was used for the system's implementation. The final measurements highlighted that even only with the 365nm the device can measure the maximum concentration admitted by law.