Abstract
A simple, selective and sensitive kinetic method for the determination of nitrite in water was developed. The method is based on the catalytic effect of nitrite on the oxidation of methylene blue (MB) with bromate in a sulfuric acid medium. During the oxidation process, absorbance of the reaction mixture decreases with the increasing time, inversely proportional to the nitrite concentration. The reaction rate was monitored spectrophotometrically at ฮป = 666 nm within 30 s of mixing. Linear calibration graph was obtained in the range of 0.005โ0.5 ฮผg mLโ1 with a relative standard deviation of 2.09 % for six measurements at 0.5 ฮผg mLโ1. The detection limit was found to be 0.0015 ฮผg mLโ1. The effect of different factors such as acidity, time, bromate concentration, MB concentration, ionic strength, and order of reactants additions is reported. Interference of the most common foreign ions was also investigated. The optimum experimental conditions were: 0.38 mol Lโ1 H2SO4, 5 ร 10.4 mol Lโ1 KBrO3, 1.25 ร 10.5 mol Lโ1 MB, 0.3 mol Lโ1 sodium nitrate, and 25ยฐC. The proposed method was conveniently applied for the determination of nitrite in spiked drinking water samples.