利用沒食子酸、乙醛與二價錳離子增強過碘酸鉀-luminol學發光系統及其在酚類化合物檢測上的應用

Abstract

本研究主要是使用自行組裝的流動注入分析系統探討乙醛 (CH3CHO)、二價錳離子增強過碘酸鉀 (KIO4) 氧化luminol及沒食子酸 (gallic acid) 的化學發光的機制。在pH 13.0的條件下 於luminol / KIO4 / gallic acid / CH3CHO系統加入 20 μM Mn(II)，可使化學發光的強度增強約2.8倍。推測原因可能是gallic acid被氧化的過程中，產生O2-加速luminol的氧化，進而增強化學發光的強度。CH3CHO可幫助溶解gallic acid氧化時產生之聚合產物，同時它被氧化劑氧化過程中可能會產生活性含氧物質 (reactive oxygen species,ROS)，進而促使系統的發光增強；而金屬離子則能催化luminol氧化反應，使反應快速進行而使發光強度增強。在研究過程中同時對pH值、反應物 (luminol、gallic acid、CH3CHO、Mn(II)、KIO4) 的濃度與混合的方式等因素對化學發光的強度之影響做詳細的探討與最佳化。由放射光譜中，無論luminol單純和gallic acid或CH3CHO反應或在三者都存在之下有無添加Mn(II)都很明顯可以看到只在425 nm 附近有最大的放光強度，可以確認本系統的放光是由luminol 所造成的。 在自由基消滅劑的測試當中，在本系統除了O2?－之外，也會產生部分的1O2 和OH․，因此加入這些有專一性的自由基消滅劑可使化學發光訊號變弱，對於其他金屬離子如 Cr(III)、Cu(II)、Mn(II)、Fe(II) 與 Co(II) 在化學發光的比較上，發現以加入 Mn(II) 的化學發光訊號最強，因此 Mn(II) 對本系統來說是個相當良好的催化劑。運用luminol / KIO4 / gallic acid / CH3CHO / Mn(II) 之化學發光系統可以用來檢測不同的抗氧化劑物質，對於每一種分析物做一系列的抑制最佳化，改變KIO4、luminol、gallic acid、CH3CHO、Mn(II) 的濃度及pH 值，使得各分析物有更好的靈敏度，能夠檢測更低的濃度，如酚類化合物（phenols）中的兒茶酚胺 (catecholamines) 之多巴胺 (dopamine) 偵測極限為0.63 nM、左多巴 (L-dopa) 偵測極限為1.37 nM、腎上腺素 (epinephrine) 偵測極限為14.3 nM、正腎上腺素 (norepinephrine) 偵測極限為0.56 nM；苯二酚化合物 (benzenediols) 中的對苯二酚 (hydroquinone) 偵測極限為0.68 nM、鄰苯二酚 (catechol) 偵測極限為0.45 nM、間苯二酚 (resorcinol) 偵測極限為59.34 nM。此外本系統還具有其他的優點，例如有好的再現性 (RSD = 0.32 - 1.34 %)、廣泛的動力學範圍 (10-9 - 10-6 mol L-1)，及可快速偵測 (五分鐘可以偵測20次)。利用此化學發光的方法應用在臨床上的藥物或者真實樣品的檢測上都有不錯的結果。

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.