Nitrogen dioxide monitoring using alternative sorbent-based cotton fabric with smartphone-integrated colorimetric detection

Abstract

A cost-effective and sustainable approach for monitoring the concentration of nitrogen dioxide (NO₂) in air was developed using smartphone-based colorimetric detection and passive air sampling. The cotton-based adsorbent moistened with triethanolamine was assembled into a passive sampler to sample NO₂ in air. NO₂ was then converted to nitrite which reacted with the Griess reagent on the cotton pads to produce a pink product. The product was photographed in a light-controlled box and subsequently analyzed using a custom-built app to convert it to NO₂ concentration. The detection and quantification limits were 0.07 and 0.21 µg, respectively. Field deployment of the developed approach for 48 and 96 h in high-traffic areas demonstrated NO₂ measurements statistically comparable with that of spectrophotometric analysis at a 95 % confidence level. In addition, the on-site monitoring of NO₂ by the developed approach was also agreed with active sampling in connection with a chemiluminescence-based NO₂ analyzer. The developed approach demonstrated effective ambient NO₂ monitoring in high-traffic areas along Suthep Road, Muang, Chiang Mai, Thailand, with continuous measurements over three days. This approach enabled a cost-effective acquisition of more spatially and temporally representative air pollution data. It aligns with the UN Sustainable Development Goal 3 by helping to reduce health risks from hazardous chemicals and environmental pollution.