Spectrophotometric reaction-rate method for the determination of nitrite in waters with pyridine-2-aldehyde 2-pyridylhydrazone.

A method for the kinetic determination of submicrogram amounts of nitrite has been developed, based on its acceleration of the rate of bromate oxidation of pyridine-2-aldehyde 2-pyridylhydrazone in acidic medium. The reaction is monitored spectrophotometrically at 372 nm. A comparative study with hydrochloric acid and perchloric acid media shows that the analytical parameters are affected by the type of acid used. Within-day precision, based on ten replicate determinations, was better than 0.011 mu/ml, which corresponds to 2.2-1.5% relative standard deviation at the concentrations examined. Application of this method in the determination of nitrite in water has been discussed. The recovery of nitrite from drinking waters ranges from 90 to 117% and the average relative standard deviation for nitrite determinations in polluted river water is 3.2%. Large amounts of nitrate and ammonium ions do not interfere. However, there is interference by Cu(2+), Pd(2+) and electroactive substances. Major advantages for the method are simplicity, absence of a reagent blank, and the wide determination range.