Synthesis and studies on the analytical functions of a highly selective spectrophotometric reagent 2-(8-quinolylazo)-5-N,N′-dimethylaminobenzoic acid

A new highly-selective chromogenic reagent, 2-(8-quinolylazo)-5-N,N′-dimethylaminobenzoic acid (QAMB) has been synthesized. In pH 4.0–8.0 medium, the reagent reacts only with cobalt or copper ions to form blue–green complexes. In alkaline medium, the reagent also reacts with nickel, mercury and palladium ions to form blue complexes. Therefore, QAMB may be the most selective among heterocyclic azo-chromogenic reagents. The physical and chemical properties of QAMB and its colour-formation reaction with cobalt ions have been studied in detail. A new spectrophotometric method for the determination of cobalt in iron and steel samples has been developed.