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Development of Microfluidics-based Platform for Detection of Nitrite in Water using Optical Readout Method

The consumption of contaminated water in our daily life can cause adverse effects. Organic or inorganic pollutants may be toxic, and their ignorant use might lead to numerous health hazards. The significant presence of nitrites in water has proven to have a deadly effect on human life. There is an emergent need to develop a platform for the detection of nitrite in water. In this paper, we have adopted the optical detection readout method for this purpose. By testing and analyzing three different experimental arrangements, we have proposed and identified the most preferable one for the effective implementation of water quality monitoring. Colorimetric analysis using the Griess reagent has been opted for in this work. With the use of a Light-Emitting Diode (LED) as a light source and three types of photodetectors, nitrite is detected in water samples thereby computing its absorbance with correspondence to the color change observed. The comparative study concludes that the LED-phototransistor pair has the best linearity and sensitivity among the three. With context to the results, a platform has been developed to measure the concentration of nitrite in water using phototransistors. This platform encourages the use of a microfluidics-based approach as it grants us benefits of minimal reagent consumption, size reduction, and precise control of the flow of liquids. The microfluidic chip is fabricated by incorporating soft lithography using Polydimethylsiloxane (PDMS) polymer. A Raspberry Pi board along with an Arduino board is interfaced with the microchannel to aid automation. By changing the parameter set for detection along with the necessary changes, fluid analysis of any parameter can be carried out with this platform.