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 diazonium salt is formed, which causes a fluorescent reddish-orange dye color of the solution to change into a non fluorescent blue color. The reaction was monitored fluorimetrically by measuring the decrease in fluorescence intensity of safranin O at (λ_ex/λ_em = 536 nm/579 nm) by a fixed-time method. The experimental conditions were optimized. Under the optimum conditions in the concentration range of 7.5–400 ng/ml, a linear calibration curve (r² = 0.9978) was obtained with a detection limit of 7.5 ng/ml. The method was applied successful ly to the determination of nitrite in spiked water and NO₂ in the atmosphere, as sampled by a liquid droplet method. Received August 23, 1999. Revision February 29, 2000.