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