https://doi.org/10.1016/j.snb.2017.07.188

Qin, Y., Alam, A. U., Pan, S., Howlader, M. M., Ghosh, R., Hu, N. X., Jin, H., Dong, S., Chen, C. H., & Deen, M. J. (2018). Integrated water quality monitoring system with pH, free chlorine, and temperature sensors. Sensors and Actuators B: Chemical, 255, 781-790. https://doi.org/10.1016/j.snb.2017.07.188

Accurate, efficient, inexpensive, and multi-parameter monitoring of water quality parameters is critical for continued water safety from developed urban regions to resource-limited or sparsely populated areas. This study describes an integrated sensing system with solution-processed pH, free chlorine, and temperature sensors on a common glass substrate. The pH and temperature sensors are fabricated by low-cost inkjet printing of palladium/palladium oxide and silver. The potentiometric pH sensor has a high sensitivity of 60.6 mV/pH and a fast response of 15 s. The Wheatstone-bridge-based temperature sensor shows an immediate response of 3.35 mV/°C towards temperature change. The free chlorine sensor is based on an electrochemically modified pencil lead, which exhibits a stable and reproducible sensitivity of 342 nA/ppm for hypochlorous acid. Such a free chlorine sensor is potentiostat-free and calibration-free, so it is easy-to-use. The three sensors are connected to a field-programmable gate array board for data collection, analysis and display, with real-time pH and temperature compensation for free chlorine sensing. The developed sensing system is user-friendly, cost-effective, and can monitor water samples in real-time with an accuracy of >82%. This platform enables water quality monitoring by nonprofessionals in a simple manner.

https://doi.org/10.1016/j.snb.2017.07.188