- 期刊
胭脂紅與銅離子錯合反應之化學計量研究及其應用於銅離子快速檢測
Chemometric Study of the Complexation of Ponceau 4R with Copper and its Application in Rapid Determination of Copper
摘要
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。雖然過去有幾篇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、濃度與結合常數的關係，全面性地研究在不同pH值下胭脂紅-銅離子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值4至7之間，為一莫耳胭脂紅鍵結一莫耳銅離子；在pH值8至10之間，為四莫耳胭脂紅鍵結三莫耳銅離子；而在pH值11時，則為三莫耳胭脂紅鍵結一莫耳銅離子。另外，結合常數值則是在pH值4到10區間逐漸上升，pH值9的結合常數約為pH值4時候的86倍，而pH值10的結合常數約為pH值4時候的147倍；pH值若提升至11，結合常數值反而大幅下降為pH值4時候的0.08倍。而在銅離子快速檢測的應用方面，當緩衝溶液的pH值設定為9時，胭脂紅-銅離子形成錯合物之專一性不受12種常見的金屬離子之影響(包括鈉離子Na^+、鉀離子K^+、鈣離子Ca^(2+)、鎂離子Mg^(2+)、鎳離子Ni^(2+)、亞鐵離子Fe^(2+)、鋅離子Zn^(2+)、鉛離子Pb^(2+)、錳離子Mn^(2+)、亞鈷離子Co^(2+)、鐵離子Fe^(3+)以及鉻離子Cr^(3+))，此時銅離子檢量範圍於0.1μM 到10μM 之間呈現良好的線性關係 (R^2 ＝ 0.9969)，且重複三次實驗之相對標準差皆小於1%；而最低檢測濃度(Detection limit) 為0.05μM，此時的訊號雜訊比(S/N ratio)仍大於5；在池水樣品中額外添加三種濃度銅離子的回收率在92.8%到101.4%之間亦顯示出優良的定量準確度。本論文所建立的銅離子檢測方法具有快速、低成本、操作簡易而且對環境友善之特點。
並列摘要
Ponceau 4R is a brilliant red dye which is easily faded due to the complexation with copper. Although the interaction between ponceau 4R and copper has been investigated, there is still no consensus about the detailed mechanism and the chemometrics. Therefore, the chemometrics and binding constants of ponceau 4R-copper complex were extensively studied here under a wide pH range by utilizing the relationship among extinction coefficient, concentration, and binding constant. The results showed that the chemometrics of ponceau 4R-copper complex were 1:1, 4:3, 3:1 when the pH were set as 4-7, 8-10 and 11, respectively. Furthermore, the binding constant was gradually increased with pH in the range of 4 to 10. The binding constants at pH 9 and pH 10 were calculated to be 87-fold and 147-fold greater than that at pH 4, respectively. When the pH was elevated to 11, the binding constant was substantially reduced to 0.08-fold of the binding constant at pH 4. For rapid determination of copper, the specificity of ponceau 4R-copper complexation was not interfered by twelve commonly seen co-existence metal ions (including Na^+, K^+, Ca^(2+), Mg^(2+), Ni^(2+), Fe^(2+), Zn^(2+), Pb^(2+), Mn^(2+), Co^(2+), Fe^(3+), and Cr^(3+)) when the pH value was set at 9. The calibration curve showed good linearity in the range between 0.1μM and 10μM (R^2=0.9969) with high reproducibility (RSD＜1%, n=3). The detection limit was 0.05μM when the S/N ratio was higher than 5. The recoveries after spiking three levels of copper ion into pool water samples were between 92.8% and 101.4%, which revealed good accuracy for quantification. The proposed method is fast, low-cost, easy-to-use and eco-friendly for copper determination.