Spectrophotometric Determination of Nitrite Based on Its Catalytic Effect on the Oxidation of 2, 2′-Azinobis(3-ethylbenzothiazoline-6-sulfonic acid)

Abstract

A kinetic method for the spectrophotometric determination of a micro amount of nitrite in natural water was developed with 2, 2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) by batchwise and flow-injection techniques. ABTS is oxidized by nitrite in an acidic medium beyond the amounts of stoichiometric completion. The nitrite in each sample was determined by relationship between the absorbance or the peak height and the concentration of standard nitrite solution. By both methods, 10ppb levels of nitrite can be determined. The main drawback of the proposed method involves severe interference due to oxidizing cations. These cations could be effectively removed by the introduction of an ammonium form cation-exchange resin. By using the batchwise method, the relative standard deviation for 10 measurements of 100ppb nitrite was 1.2%. The procedures have been applied successfully to the determination of nitrite in natural water samples, such as rain water.