Enhancement in Chemiluminescence by Carbonate for Cobalt(II)-catalyzed Oxidation of Luminol with Hydrogen Peroxide

Chemiluminescence (CL) from the cobalt(II)‐catalyzed oxidation of luminol with hydrogen peroxide was dramatically enhanced by the presence of carbonate. The CL signal increases by several orders of magnitude over a wide range of concentrations of Co(II), luminol, or hydrogen peroxide. A limit of detection of 10−12 M for Co(II) and luminol and 10−8 M for hydrogen peroxide can be achieved. The CL emission spectrum exhibits a maximum at 425 nm, indicating that the excited 3‐aminophthalate is the emitting species. ESR spin‐trapping experiments revealed a large increase in the production of hydroxyl and carbonate radicals by the presence of carbonate, which is responsible for the enormous CL enhancement. Uric acid, ascorbic acid, acetaminophen, and p‐hydroxyphenyl acetic acid are capable of scavenging the radicals, thereby inhibiting the CL emission. The inhibition of CL intensity can be used to determine these substances at the sub‐micromolar level.