Enhancement of luminol chemiluminescence by carbon dioxide in the absence of any added oxidant: Instrumentation and applications

cope and method of study. The purposes of this study are (1) to develop a versatile instrumentation for continuous-flow chemiluminescence determinations and (2) to study the effect of carbon dioxide on the metal ion or complex-stimulated luminol chemiluminescence in the absence of any added oxidant. The performance of the instrument was examined with respect to all aspects of flow injection analysis by using a slow and a fast chemiluminescent reaction. The carbon dioxide enhanced chemiluminescence of luminol/rate modifier systems in the absence of added oxidant was characterized, and a novel optical sensor for carbon dioxide based on its enhancement on the luminol chemiluminescence was developed.;Findings and conclusions. The chemiluminescence detection system consists of three basic parts: a peristaltic pump, a flow cell, and a photon detector. By incorporating a rotating disc into the flow cell, the reaction efficiency, therefore the chemiluminescence intensity, is greatly increased because the rotation of the disc helps to mix the reactants thoroughly. The disc is also an ideal bed for immobilization of reagents; in such cases, the increase in chemiluminescence intensity caused by the rotation of the disc is even more pronounced. This instrument is versatile. All operations in a flow injection analysis can be achieved by simply changing the pattern of tubing connection to the flow cell. The chemiluminescence of luminol can be greatly enhanced by carbon dioxide either in the presence or in the absence of an added oxidant. The enhancement is dependent on the rate modifier used; the largest enhancement was found when cobalt(II) phthalocyanine (CoPc) was used as the rate modifier. In the absence of an added oxidant, dissolved oxygen and the trace amount of peroxide formed from the oxidation of luminol are important to the chemiluminescent reaction. The enhancement results from the formation of free radicals in the reaction between carbon dioxide and peroxide. The...