Abstract
We have studied the enhancement in chemiluminescence (CL) for the oxidation of luminol and gallic acid with potassium periodate caused by acetaldehyde and manganese(II) using a home-made flow injection analysis system. About 2.8-fold increase in CL intensity was observed upon addition of 20 μM Mn(II) to the CL system at pH 13.0. The CL-enhancement may result from the increases in the overall CL efficiency and the fluorescence quantum yield from the production of excited singlet oxygen. The effects of pH, concentrations of reagents (luminol、gallic acid、acetaldehyde、KIO4、Mn(II)), and modes of reagent mixing on CL emission were also investigated and optimized. In CL emission spectrum, the CL maximum signal occurred at 425 nm, indicating that the CL is caused by luminol in luminol / KIO4 / gallic acid / CH3CHO / Mn(II) system. 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 radical scavengers. These results showed that in addition to O2?－, 1O2 and OH․ also participated in the CL reaction. Regarding other metallic ions like Cr(III), Cu(II), Mn(II), Fe(II) and Co(II) in the chemiluminescence, Mn(II) catalyzed illumination signal is strongest, therefore Mn(II) in this system is a better catalyst. The CL system has been applied to the determination of antioxidants such as catecholamines and benzenediols. The detection limits (3σ) for dopamine, L-dopa, epinephrine and norepinephrine were 6.3×10-10, 1.37×10-9, 1.43×10-8 and 5.6×10-10 mol L-1, respectively; for hydroquinone, catechol, resorcinol were 6.8×10-10, 4.5×10-10, 5.83×10-8 mol L-1, respectively. The proposed CL method also exhibited the advantages of wide dynamic range (10-9 - 10-6 mol L-1), good reproducibility (RSD = 0.32 - 1.34 %), and fast detection (20 injections in 5 min). This CL method can be applied to the determination of catecholamines in pharmaceutical and benzenediols in spring water injections with satisfactory results.
Published Version
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