Photometric Determination of Trace Amounts of Nitrites Based on Its Catalytic Effect on the Oxidation of Cresol Red by Potassium Bromate

In a dil H2SO4 solution,the oxidation of cresol red by KBrO3 was catalyzed by the presence of trace amounts of nitrite,leading to colorfading of cresol red.Linear relationship between the magnitude of decrease in color intensity at 564 nm (ΔA=A0-A) and the concentration of nitrite ion was kept in the range of 8.0-140.0 μg·L-1,with detection limit of 0.98 μg·L-1.In its application to the determination of nitrite in 4 water samples from different sources,values of RSD′s (n=6) and recovery found were 1.9%-3.1%.