Dual Chemiluminescence of Mn2+-Luminol System and Its Applications
Date Issued
2009
Date
2009
Author(s)
Huang, Tsung-Yuan
Abstract
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 flow-injection analysis, we found that addition of aldehydes (CH3CHO, CH3CH2CHO), metal ions (Mn2+, Fe3+, Co2+) and phenolic compounds (pyrogallol、gallic acid) to the luminol-KIO4 solution enhanced the CL emission by two orders of magnitude. Radical-scavenging studies revealed that reactive oxygen species (ROS) such as •O2-, •OH, and 1O2 play crucial roles in CL enhancement. This CL system provides a sensitive way to determine phenolic compounds such as hydroquinone, catechol, and dopamine.he results from flow-injection analysis suggest that more than one CL pathways are possible. Therefore stopped-flow spectrometer was used to measure the time courses of the CL profiles, trying to detect the existence of multiple CL emission. First, we have tested all possible combinations of luminol, Mn2+, KIO4, acetaldehyde and gallic acid that exhibit intense CL emission. We found that several of the combinations produced multiple CL. We then performed a systematic study on the dual CL of the luminol-Mn2+-KIO4 system. By suitable adjustment of the reagent (luminol, KIO4, Mn2+) concentrations at pH above 13.0, dual CL was observed within 2 sec. ROS-scavenging studies using selective scavengers for O2- (glutathione), •OH (uric acid, DMSO, methanol), and 1O2 (NaN3, 1,4-diazabicyclo[2,2,2]octane) suggest that the 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. he 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. For example, hydroquinone, catechol, trolox, and sesamol inhibited both peaks, though to different extent. Uric acid, pyrogallol, gallic acid, and catecholamines inhibited the first peak, but further enhanced the second peak. 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 Ni2+、Zn2+ also enhanced the CL emission. In the future, we will try to develop more efficient systems for detecting biomolecules, antioxidants, drugs and metal ions.
Subjects
luminol
chemiluminescnec
potassium periodate
free radical
flow-injection analysis
stopped-flow spectrometry
Type
thesis
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