| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 96 === In this study, a chemiluminescence (CL) method based on the Co(II)-luminol-NH2OH system has been developed. The flow-injection analysis (FIA) system was used to measure the CL produced from the oxidation of luminol. The reducing agent, hydroxylamine, interacted with dissolved oxygen in water to produce superoxide ion (O2˙-), which caused the CL with luminol in the presence of cobalt(II) as a catalyst in an alkaline solution. For the Co(II)-luminol-NH2OH CL, a 93-fold increase in CL intensity was observed upon addition of 10-5 M Co(II) at pH 13. The effects of pH, flow rate, concentration of reagents (cobalt(II), luminol, hydroxylamine), and modes of reagent mixing on CL emission were also investigated and optimized. We found flow rate: 5 mL/min, pH 13, 2*10-4 M NH2OH, 10-4 M Co(II) with 3 μM luminol for optimum CL.
In emission spectrum, the CL maximum signal occurred at 425 nm. So the CL is caused by luminol in Co(II)-luminol-NH2OH system. When the dissolved oxygen was removed from the solution by purging with nitrogen, the CL intensity decreased by 66.65%, this might indicate that superoxide ion played a major role in this CL reaction. The scavengers of reactive oxygen species, such as superoxide dismutase, ascorbic acid, DMSO, and 1,4-diazabicyclo[2,2,2]octane were added into the reaction system. The CL intensity decreased greatly in the presence of these scavengers of radical. These results showed that in addition to O2˙-, 1O2 and OH˙ also participated in the CL reaction.
The CL system has been applied to the determination of antioxidants such as dopamine (dynamic range: 1~5 μM, LOD: 0.18 μM), hydroquinone (dynamic range: 0.05~0.25 μM, LOD: 0.013 μM), catechol (dynamic range: 1~5 μM, LOD: 0.11 μM), resorcinol (dynamic range: 1~6 μM, LOD: 0.20 μM), ascorbic acid (dynamic range: 0.5~4 μM, LOD: 0.14 μM), tannic acid (dynamic range: 0.2~1.0 μM, LOD: 0.042 μM), and some amino acids such as methionine (dynamic range: 5~40 μM, LOD: 1.64 μM), and tyrosine (dynamic range: 5~25 μM, LOD: 1.82 μM). The antioxidants destroyed the radicals involved in the CL reaction, causing a decrease in CL emission. The dynamic ranges varied for different antioxidants with different antioxidative power. Some interferences such as 10-5 M Cr(III), 10-4 M Ni(II), and 10-4 M Mn(II) should be avoided.
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