1985 Volume 34 Issue 1 Pages 43-47
A new and rapid spectrophotometric method for the determination of a micro amount of nitrite ion was established. Bromide was found to be oxidized by micro amounts of nitrite in the presence of sulfuric acid, and the resulting species had an absorption maximum at 268nm and the absorption increased with an increase in reaction period. Nitrite ion ranging from 0.5 to 5ppm could be determined using this kinetic reaction. Addition of Bindschedler's Green Leuco base(BGL) as oxidation-reduction indicator to the system gave a remarkable increase in sensitivity (λmax=715nm). By the aid of BGL, a more sensitive method has been developed for the determination of micro amounts of nitrite ion based on the above reaction system. The analytical procedure was as follows. One cubic centimeter of 6.0 mol dm-3 sulfuric acid and 3 cm3 of 6.0 mol dm-3 sodium bromide solution were placed in a test tube fitted with a stopper. Then 5 cm3 of sample solution containing less than 0.4 ppm of nitrite was added to the above solution. After 1 cm3 of 0.1 (w/v) % BGL was added, the test tube placed in a water bath at 25 °C. The absorbance was measured at 715 nm with 10mm cell against water at 10min after the addition of the sample solution. By this method, nitrite ion ranging from 0.05 to 0.40ppm can be determined. The relative standard deviation was 1.7% (n=5) at the nitrite ion level of 0.3ppm. Copper (II), iron(III), iodide, and sulfite showed interferences in this method. The proposed method was applied to the determination of nitrite ion in samples of river-water.
