二價鎳離子增強lumino-Mn(II)-KIO4化學發光系統性質研究與其應用

Abstract

化學發光是藉由化學反應產生的發光現象。本研究利用流動注入分析法探討Ni2+ 增強 luminol - KIO4 - Mn2+ 系統化學發光的機制。實驗結果顯示在 pH = 13 的鹼性溶液下，添加 400 μM Ni2+於 luminol - Mn2+ - KIO4 系統可使其化學發光強度增加 2 倍左右。在研究的過程中同時對 pH 值、流速、反應物 (luminol、Mn2+、Ni2+、KIO4) 的濃度對化學發光的強度的影響做探討並找出最佳化條件。由放射光譜中，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。 為了瞭解化學發光的反應機制，加入消滅自由基的試劑進行測試，由結果得知，針對 1O2、O2•－、OH• 的自由基消滅劑，如 DMF、ascorbic acid、DMSO 都會抑制訊號的強度。此外，將試劑除氧後化學發光訊號減弱 80 %，表示此化學發光與溶氧有很大的關係。推測 Mn2+、Ni2+ 可以催化 KIO4 與溶氧在強鹼溶液中反應產生活性含氧物質(O2•－、1O2、OH•)來幫助 luminol 的氧化而增強放光效率，所以加入這些專一性的自由基消滅劑都會讓化學發光訊號降低。而Ni2+之所以能增強化學發光度，推測原因可能是當 luminol - Mn2+ - KIO4 系統產生化學發光反應後，在Ni2+的存在下可以幫助luminol 經氧化產生的中間產物 (X*) 將能量傳遞給 3-aminophthalate ion (3-AP)，而產生化學發光現象而讓化學發光強度增強，此現象稱為post-chemiluminescence。 運用luminol - Mn2+ - Ni2+ - KIO4 之化學發光系統可以檢測不同的生化分子如胺基酸、維生素、抗氧化劑等。測試的結果顯示，常見的抗氧化劑，如 bezenediol 與polyphenol類的chlorogenic acid以及兒茶酚胺 (catecholamines) 的多巴胺 (dopamine) 等，對此系統有很好抑制的效果，推測可能是因為這些抗氧化劑能捕捉活性含氧自由基而使化學發光訊號降低。最後我們對抑制效果最好的hydroquinone做一系列的抑制最佳化，改變Mn2+、Ni2+、KIO4的濃度及pH 值，使得hydroquinone有更好的靈敏度，能夠檢測更低的濃度。經抑制最佳化後，hydroquinone的偵測極限可達到0.089 nM。

Chemiluminescence (CL) is produced by the exothermic reaction. We have studied the enhancement in CL for luminol - KIO4 - Mn2+ system caused by nickel (II) ion using flow injection analysis. About 2-fold increase in CL intensity was observed upon addition of 400 μM Ni2+ to the CL system at pH 13.0. The effects of pH, concentrations of reagents (luminol, Mn2+, Ni2+, KIO4) were optimized. In CL emission spectrum, the CL maximum signal occurred at 425 nm, indicating that the CL is caused by luminol in luminol - KIO4 - Mn2+ - Ni2+ system. In order to know the mechanism of the chemiluminescence of luminol - KIO4 - Mn2+ - Ni2+ system, we tested a series of free radical scanvengers for their effect on CL emission. In the presence of 1O2, O2•－and OH˙ scanvengers like DMF, ascorbic acid, DMSO, the CL emission was inhibited. In addition, deoxydenation of sample solutions by purging with nitrogen reduced the CL intensity by 80 %, indicating that oxygen is involved in this CL reaction. The CL-enhancement may result from the reaction of KIO4 and dissolved oxygen in strong alkaline solution to produce reactive oxygen species (ROS) in the prescence of catalytic Mn2+, Ni2+. Radical scavengers inhibited CL emission by their ability to destroy ROS. Experiments also found that when Ni2+ was injected into the mixture of the luminol - Mn2+ - potassium periodate reaction, chemiluminescence signals were produced once again. This phenomenon has been named as post-chemiluminescence (PCL). It was proposed that the intermediate (X) formed during the luminol - Mn2+ - potassium periodate reaction was excited to X* under the action of Ni2+, then the energy of X* was transferred to 3-AP, and 3-AP* emits light at 425 nm. By using the CL system, we tested 45 compounds including amino acids, vitamins, antioxidant for their effect on the CL emission. We found that common antioxidants such as catecholamines and benzenediols showed inhibiting effect on our CL system, The CL-inhibition may result from scanvenging ROS by antioxidants. Finally we did a series of optimization for the best inhibitory effect of hydroquinone, the detection limits for hydroquinone was 8.9×10-11 mol L-1.