茜素红S催化动力学光度法测定痕量铜(Ⅱ)及机理探究

Determination of trace copper(Ⅱ) by catalytic kinetic spectrophotometry and research of its reaction mechanism

研究了在pH 5.0的柠檬酸-NaOH缓冲介质中, 以邻菲口罗啉（phen）作活化剂, 痕量Cu（Ⅱ）对H2O2氧化茜素红S（ARS）的褪色反应存在明显的催化作用, 由此建立了测定痕量Cu（Ⅱ）的催化动力学光度法. 应用了正交试验法确定最佳条件, 测定了有关动力学参数. 该方法的检出限为6.3×10^-9 g/mL, 线性范围为0～0.8 μg/mL, 应用于茶叶、自来水等水样中痕量铜的测定. 同时, 对反应机理进行了探究.

A new kinetic method is described for the determination of copper（ Ⅱ ） based on its catalytic effect on the oxidation of alizarin S by hydrogen peroxide in citric acid-sodium hydroxide buffer solution （pH 5.0）. The reaction is followed spectrophotometrically by measuring the rate of change for the absorbance of coloured product at 423 nm. Experimental conditions are optimized by orthogonal test and the kinetic parameters of both the catalyzed and uncatalyzed reactions are reported. Nanogram amounts of Cu（ Ⅱ ） （0.0 - 800 ng/mL） can be determined with good accuracy and reproducibility. The influences of some other ions were investigated and the method was found to have good selectivity. It has been applied to the determination of copper（ Ⅱ ） in tea and tap water samples, and satisfactory results have been obtained. The mechanism of the catalytic reaction is also reported.