Kinetic spectrofluorimetric determination of nitrite in water samples and nitrogen dioxide in the atmosphere sampled by the liquid droplet method

A simple, sensitive and selective kinetic spectrofluorimetric determination of NO2 sampled by the droplet method in the atmosphere was proposed on the basis of the reaction of safranin O with nitrite. By this reaction, a diaz onium salt is formed, which causes a fluorescent reddish-orange dye color o f the solution to change into a non fluorescent blue color. The reaction wa s monitored fluorimetrically by measuring the decrease in fluorescence inte nsity of safranin O at (lambda(ex)/lambda(em) = 536 nm/579 nm) by a fixed-t ime method. The experimental conditions were optimized. Under the optimum c onditions in the concentration range of 7.5-400 ng/ml, a linear calibration curve (r(2) = 0.9978) was obtained with a detection limit of 7.5 ng/ml. Th e method was applied successfully to the determination of nitrite in spiked water and NO2 in the atmosphere, as sampled by a liquid droplet method.