SPECTROPHOTOMETRIC REACTION RATE METHOD FOR THE DETERMINATION OF NITRITE BY CATALYTIC ACTION ON NILE BLUE A BROMATE REACTION

A kinetic method developed for the determination of ultra-trace amounts of nitrite based on its catalytic effect on the reaction between potassium bromate and Nile blue A in strongly acidic media is reported. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of Nile blue A at 645 nm by the fixed-time method. The decrease in absorbance during the first 0.5-3.0 min of the reaction is related to the concentration of nitrite in the range of 0.002-0.500 µg.ml . The detection limit of 0.001 µg.ml was achieved for the nitrite ion. The relative standard deviation for 0.0100 µg.ml nitrite is 1.0%. Most common anions and cations did not interfere in the measurement. The procedure was successfully applied for the determination of nitrite in natural water and salt