The Kinetic characteristics of Luminol-Mn2+-KIO4 multiple Chemiluminescence and Applications in Hydroxyl Antioxidant Detection

Luminol is a common chemiluminescence (CL) reagent. Luminol-based CL reaction, which emits light at 425 nm, is usually carried out in alkaline solution and in the presence of an oxidant and a catalyst. Using Stopped-flow- spectrometry, we found that addition of Mn2+ metal ion to the luminol-KIO4 solution not just enhanced the CL emission by two orders of magnitude but also produced multiple CL emission. A systematic study on the multiple CL of the luminol-Mn2+-KIO4 system was performed. First, we have tested all possible combinations of luminol, Mn2+, KIO4, and pH. By suitable adjustment of the reagent concentrations at pH above 13.0, multiple CL was observed within 5 sec. Radical-scavenging studies revealed that reactive oxygen species (ROS) such as ‧O2-, ‧OH, and 1O2 play crucial roles in CL enhancement. ROS -scavenging studies using selective scavengers for O2- (glutathione), ‧OH (uric acid), and 1O2 (1,4-diazabicyclo[2,2,2]octane) suggest that the initial and first peak might be due to the generation of O2- and ‧OH through the catalytic effect of Mn2+, while the second peak might be attributed to the production of 1O2 through the Mn2+-complex involving ligands such as IO4-, OH-, O2, and luminol anion.
This CL system provides a sensitive way to determine phenolic compounds such as catechol, dopamine, and (+)-enpinephrine. The important features of the dual CL for the luminol-Mn2+-KIO4 system are that the relative intensity of the two peaks can easily be controlled by adjusting the reagent concentrations and that the CL signal with different intensity ratio of the two peaks may respond quite differently to the analytes in terms of selectivity and sensitivity. Thus this CL system can provide a large variety of probes by changing the relative intensity of the two CL peaks, thereby improving the selectivity and sensitivity of the analysis. Adding ascorbic acid, 6,7-dihydroxy-falvone, and 7,8–dihydroxy-flavone not only inhibited the CL emission, but also made the time of signal 2 produced delay. In the future, we will try to develop more efficient systems for detecting biomolecules, antioxidants, drugs and metal ions.