Ionogel-based hybrid polymer-paper handheld platform for nitrite and nitrate determination in water samples

[EN] Nowadays, miniaturization and portability are crucial characteristics that need to be considered for the development of water monitoring systems. In particular, the use of handheld technology, including microfluidics, is exponentially expanding due to its versatility, reduction of reagents and minimization of waste, fast analysis times and portability. Here, a hybrid handheld miniaturized polymer platform with a paper-based microfluidic device was developed for the simultaneous detection of nitrite and nitrate in real samples from both, fresh and seawaters. The platform contains an ionogel-based colorimetric sensor for nitrite detection and a paper-based microfluidic device for the in situ conversion of nitrate to nitrite. The platform was fully characterized in terms of its viability as a portable, cheap and quick pollutant detector at the point of need. The calibration was carried out by multivariate analysis of the color of the sensing areas obtained from a taken picture of the device. The limits of detection and quantification, for nitrite were 0.47 and 0.68mgL-1, while for nitrate were 2.3 and 3.4mgL-1, found to be within the limits allowed by the environmental authorities, for these two pollutants. Finally, the platform was validated with real water samples, demonstrating its potential to monitor nitrite and nitrate concentrations on-site as a first surveillance step before performing extensive analysis. This project has received funding from the European Union Seventh Framework Programme (FP7) for Research, Technological Development and Demonstration under grant agreement no. 604241. The funding support from Gobierno de España, Ministerio de Ciencia y Educación de España” under grant PID2020-120313 GB-I00/AIE/10.13039/501100011033, and Gobierno Vasco Dpto. Educación for the consolidation of the research groups (IT1271-19) are also acknowledged. RC-C acknowledges funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 778001. Special thanks to (SGIker) of the University of the Basque Country (UPV/EHU). FB-L and LB-D acknowledge the “Red de Microfluídica Española” RED2018-102829-T.