Spectrophotometric determination of trace amounts of nitrite ion based on its catalytic effect in the reaction between thymol blue and bromate

A simple, sensitive, and selective method for rapid determination of nitrite is described which is based on its catalytic effect in the reaction between thymol blue and bromate in acidic media. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance at 543 nm by a fixed time method of 2.0 min. The method allows the determination of nitrite in the range 0.4-1500 ng/ml. The relative standard deviation for seven determinations of 40 ng ml(-1) nitrite is 1.54% and the detection limit of the method is 0.32 ng ml(-1). The method is applied to the determination of nitrite in water. (C) 1997 Academic Press.