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Study on the Complexation of Ponceau 4R with
Copper and Its Application on Xenobiotics Detection
Ponceau 4R,Copper ion,Chelation,Stoichiometry,Competitive reaction,Xenobiotics,
|Publication Year :||2016|
|Abstract:||胭脂紅是一種亮紅色的染色劑，其鮮豔的顏色容易在與銅離子作用後消退。雖然過去有幾次關於胭脂紅和銅離子交互作用的研究，但是學者們對其作用機制與化學計量關係，卻沒有給出一致性的答案。本研究利用吸光係數與結合常數的關係，全面性地研究在不同pH值下銅離子-胭脂紅錯合物的化學計量關係與結合常數。結果顯示染劑和金屬離子的化學計量關係受pH值影響，在pH 4.0—7.0間，為一分子銅離子鍵結一分子胭脂紅；在pH 8.0—10.0間，為三分子銅離子鍵結四分子胭脂紅；而在pH 11.0時，則為一分子銅離子鍵結三分子胭脂紅。此外，全世界最暢銷的除草劑-嘉磷塞，其本身也與銅離子有著極易螯合的特性。由於嘉磷塞和胭脂紅在酸性環境下，兩者分別與銅離子形成錯合物後，其穩定性有著極大差異 (在pH 5.0下，銅離子-胭脂紅錯合物的穩定結合常數為1.37 × 104，而嘉磷塞-銅離子錯合物的穩定結合常數則為1.26 × 1018)，故利用嘉磷塞和胭脂紅會競爭銅離子的行為，可以設計出一款銅離子-胭脂紅試劑 (20µM銅離子-40µM胭脂紅)，在嘉磷塞加入試劑後，解離的銅離子-胭脂紅錯合物會造成明顯的變色行為，在吸收光譜法下 (λ = 506 nm) 觀察此變色現象就可以準確定量嘉磷塞含量，線性檢測濃度範圍為5—20 µM (CV < 5%, n = 3)，檢測極限為1 µM。|
Ponceau 4R is a brilliant red dye which is easily bleached due to the chelation with copper ion. Although the interaction between ponceau 4R and copper ion has been investigated extensively, there is no consensus about the detailed mechanism and the stoichiometry. The stoichiometries and binding constants of copper-ponceau 4R complex were studied under different pH values by calculating the relationship between extinction coefficient and binding constant. The results showed that the formation ratio of metal:dye was dependent on the pH value in the system. Three different pH range were tested, which were pH 4.0—7.0, pH 8.0—10.0 and pH 11.0, the metal:dye ratio formed were 1:1, 3:4 and 1:3 respectively. Furthermore, the world's best-selling herbicide, glyphosate, is also found to be very easy to chelate copper ion. Due to the great difference in the stabilities of copper-ponceau 4R complex and copper-glyphosate complex under acidic condition (binding constant of copper-ponceau 4R complex is 1.37×104 at pH 5.0 and copper-glyphosate complex’s is 1.26×1018 at pH 5.0), hence, a copper-ponceau 4R reagent (20µM copper ion-40µM ponceau 4R) was designed based on the competitive reaction between ponceau 4R and glyphosate in this study. After adding glyphosate to the solution, an obvious color change was occurred due to the dissociation of copper-ponceau 4R complex and the change in absorbance can be detected with the presence of glyphosate precisely (λ = 506 nm). The linear dynamic range for glyphosate was 5—20 µM (CV < 5%, n = 3) and the limit of detection (LOD) was 1 µM.
|Appears in Collections:||生物機電工程學系|
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