Versatile Three-Dimensional-Printed Platform for Nitrite Ion Analyses Using a Smartphone with Real-Time Location

Nitrogen-based chemicals represent one of the most important family of compounds in freshwater and marine ecosystems. The nitrogen cycle is responsible for spreading nitrogen compounds all over the environment in an equilibrium manner. Mankind's industrial activities have harshly contributed to the disruption of the nitrogen cycle and its consequences have severely affected Earth's ecosystems. Tracking the chemicals involved in the nitrogen cycle have become a crucial point in fighting against eutrophication and global water acidification. A smartphone readout-based system has been developed to determine the concentration of nitrite ion (the nitrogen compound that possess higher toxicity) in environmental samples. The device was fabricated by means of three-dimensional printing to allow easy design modification to fit any smartphone. Moreover, the system took advantage of the less explored potential of ambient light sensor contained within the smartphones. Finally, "ALSens" application was developed to be used by nontrained personnel to not only determine nitrite ion concentration but also to automatically send relevant parameters (analyte, day, hour, location, and concentration) of the assay for tracking purposes to an open online database, allowing a worldwide mapping of nitrite ion concentration. Considering the devastating implications of nitrogen cycle disruption, these systems for nitrite ion screening will suddenly become a standard global monitoring approach.