A limitation to the widespread application of chemiluminescence (CL) technique often lies in the poor selectivity of the CL reaction. A novel concept was proposed to address this selectivity problem. Two CL reactions, not just one reaction as generally used before, were used for the recognition of sodium azide from other similar radical scavengers. These two reactions have the same oxidant and catalyst but different enhancer. By coupling two CL reactions, i.e. H₂O₂-acetonitrile-tetracycline (working reaction) and H₂O₂-acetonitrile-melatonin (reference reaction), sodium azide could be clearly identified and quantitatively determined in the presence of other similar compounds. It is because that sodium azide only quenches the CL signal of the working reaction, whereas other similar compounds quench the CL signal of both working reaction and reference reaction. As a preliminary application, this novel technique has been employed to determine sodium azide in the reagents of the commercial insulin kit.

Key words: chemiluminescence, sodium azide, recognition, coupling, working reaction, reference reaction