2-Amino-5,7-dimethyl-1,8-naphthyridine as a fluorescent reagent for the determination of nitrite

A new fluorescent reagent 2-amino-5,7-dimethyl-1,8-naphthyridine (ADMND) was proposed for the determination of trace nitrite. The reaction is based on the diazotization of naphthyridine amine with nitrite to form a diazonium salt that hydrolyzed when boiling to give hydroxyl group substituted naphthyridine. Fluorescence quenching degree of ADMND by nitrite ion is linear in the nitrite concentration range of 1 × 10−7 to 2.5 × 10−6 mol l−1 with a detection limit of 4.06 × 10−8 mol l−1. Reaction and determination acidity for nitrite is the same which made the method much simpler compared with the widely accepted fluorescence method with DAN as a fluorescence reagent.