Photometric determination of nitrite.

A new sensitive colour reaction for nitrite determination is presented. The method is based on the reaction of nitrite with p-aminobenzoic acid to form a diazonium ion, which is coupled with 8-hydroxyquinoline, in alkaline medium, to form a reddish-orange water-soluble azo dye. Diazotization and coupling are very fast and control of temperature is unnecessary. Moreover, the colour is stable and its intensity is in direct proportion to nitrite concentration over a wide range.