A wireless, portable integrated micro-fluidic platform is proposed and applied for the determination of nitrite anions in water. The colourimetric analysis of nitrite is based on the Griess reagent, and the colour intensity of nitrite Griess reagent complex is detected using a low cost Paired Emitter Detector Diode technique. The micro-fluidic device employed a photoswitchable micro-valve, controlled by white light and generated using a light emitting diode. This low-cost and low-power detector exhibited very low limits of detection (34 ± 0.1 μg L-1). Freshwater samples were analysed and the results were compared to those generated with a conventional UV-Vis spectrophotometer showing good agreement. The suitability of the analyser for the precise and continuous measurement of samples was established. In addition, its small size and low weight offered the advantage of portability, while its data logging capabilities allowed for independent nitrite monitoring. Moreover, integration of a wireless communication device allowed for the instrument to be controlled and results to be downloaded remotely.