A Rapid and Sensitive Colorimetric Reagent for Nitrogen Dioxide in Air

High speed instrumentation requires a colorimetric reagent capable of detecting traces of nitrogen dioxide with little delay for color development. Rate of color development and sensitivity of Griess-type reagent have been improved by adding a promoter (R-salt) and optimizing the concentrations of diazotizing and coupling reagents. Field tests show that the new instrument-reagent combination can resolve short-duration peaks in NO₂ concentrations of 5 to 10 pphm.