Polymer with pendant diazo-coupling functionality for colorimetric detection of nitrates

Most high-energy compounds contain nitrates. Visual onsite nitrate and nitrite ion detection is, therefore, important for security related issues. Visual also has applications in environmental and biomedical sciences. These ions are colorimetrically detected by diazo coupling reaction between N-(1-naphthyl)ethylenediamine and sulfanilamide (known as the Griess reagent). We report on the synthesis of a polymer with N-(1-naphthyl)ethylenediamine and sulfanilamide side chains (mimicking the Griess reagent). The polymer matrix was further doped with zinc powder that reduces the nitrate ions to nitrite, thus initiating a diazotization reaction. The resultant diazo-coupled product produces a visually distinguishable color change to low nitrate concentration (∼4 ppm).