Preparation of a New Inexpensive Paper-Based Sensor for the Detection of Nitrite and Nitrate Species in Water

A low-cost, disposable, paper-based microfluidic analytical device (µPAD) has been developed for the measurement of nitrite and nitrate in water, with a color intensity-based response. The µPAD was fabricated using Whatman filter paper No. 1 and a glossy, self-adhesive backing. Nitrite was measured by the Griess reaction, and for nitrate determination, nitrate was reduced to nitrite in situ on the paper with zinc nanoparticles (ZnNPs). We chose ZnNPs because they outperformed zinc microparticles (ZnMPs). The system showed linear calibration ranges of 0.01−1.25 mM for nitrite and 0.04−1.25 mM for nitrate. The detection limits were 0.003 and 0.008 mM,respectively. The method showed no interference from common ions present in water. The results of real samples were consistent with the spectrophotometric reference method, so the proposed µPAD is suitable for rapid measurement of nitrite/nitrate concentrations at sampling sites of environmental and drinking waters.