Determination of nitrite in waters by microplate fluorescence spectroscopyand HPLC with fluorescence detection

A selective and versatile fluorescence spectroscopic method for the determi nation of nitrite in waters has been developed. Nitrite reacts in the prese nce of mineral acids with the nonfluorescent N-methyl-4-hydrazino-7-nitrobe nzofurazan forming N-methyl-4-amino-7-nitrobenzofurazan, which can be detec ted by fluorescence spectroscopy with an excitation maximum at lambda = 468 nm and an emission maximum at lambda = 537 nm in acetonitrile. Three new m ethods based on this reaction have been developed: Direct fluorescence spec troscopy, HPLC/fluorescence, or HPLC with UV/vis detector may be selected a s detection techniques. On microplates, high-throughput fluorescence spectr oscopy is achieved, while HPLC/fluorescence provides lower limits of detect ion, and HPLC with UV/vis detection enables evaluation of the reaction with standard instrumentation. Different water samples were investigated using all detection modes, and a photometric standard procedure was successfully employed to validate the new methods with an independent technique.