Luminol-Co(II)-NH2OH系統之雙重化學發光探討與其在分析上的應用

Abstract

Chemiluminescence (CL) is produced by the exothermic reaction. This study focused on the dual chemiluminescence of luminol-Co(II)-NH2OH. We found that concentrations of Co(II), EDTA, NH2OH and pH could lead to dual chemiluminescence. To know more about it, we’ve tried many conditions to construct the luminol-Co(II)-NH2OH system. The results from stopped flow experiments showed that low concentrations of Co(II)(less than 3 uM) produced only one peak. At higher concentrations of Co(II) dual chemiluminescence appeared. Addtion of EDTA caused suppression and delayed of dual CL, suggesting the importance of free Co(II). Moreover, concentration of NH2OH and pH values between 12.5 and 13.5 were also required for the observation of dual CL. In order to know the mechanism of the dual chemiluminescence of luminol-Co(II)-NH2OH system, we tested a series of free radical scanvengers for their effect on CL emission. In the present of 1O2 scanvengers like NaN3, 1,4-diazabicyclo[2.2.2]octane and DMF, dual CL emission was enhanced. Addition of ˙OH scanvengers such as CH3OH , DMSO and uric acid, inhibited peak 2 of dual CL. Captopril, a ˙O2- scanvenger, could inhibit and delay CL peaks. We concluded that ˙O2- is involved in the CL emission of peak 1, while ˙O2- and ˙OH play key role for the second CL peak. By using the dual chemiluminescence of luminol-Co(II)-NH2OH system, we tested 58 compounds including amino acids, vitamins, antioxidants, reducing compounds and drugs for their effect on the CL emission. We found that phenolic compounds showed inhibiting effect on our CL system, especially benzenediol compounds, flavonoids and polyphenolic compounds. It was found that compounds bearing a dihydroxybenzene group, exhibited best inhibition on peak 1. Previous studies have suggested that dihydroxybenzenes were good superoxide anion radical scanvenger, causing CL inhibition. We proposed that superoxide anion radical plays a critical role in both CL peaks. The results suggest that this system could be used to screen the scanvenge activities and antioxidant activities of the compounds. Using the selectivity from inhibitng either peak 1 or peak 2, we could make use of the dual chemiluminescence of luminol-Co(II)-NH2OH for the analytic detection.