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