用Landolt催化反应诱导期测定痕量铜

USING LANDOLT CATALYTIC REACTION INDUCTION PERIOD DETERMINES TRACE COPPER

本文基于铜离子(Ⅱ)对 S_2O_8^(2-)氧化 I^-的催化作用具有较高的选择性,并利用体系中引入抗坏血酸产生的 Landolt 效应,计算了总包反应的表现活化能,建立了以死停终点法指示 Landelt 诱导期测定痕量铜的新方法.本研究中催化主反应所产生 I_2被引入的抗坏血酸立即还原,故抗坏血酸一旦全部耗竭即诱导期结束,体系中出现游离 I_2与 I^-组成的氧化还原电对,在光亮铂指示电极上产生指示电流,该电流被监测线路中灵敏检流计立即显示,以计时法测此诱导期.结果表明,诱导期的倒数1/t 与铜(Ⅱ)浓度在3.0×10^(-7)～3.0×10^(-11)g/ml 范围内有良好的线性关系.检测下限达1.0×10^(11)g/ml,人发、人尿样品测定结果满意。

A trace amount of copper(Ⅱ)is determined by using its catalytic effect on the oxidation of iodide by S_2O_8^(2-) in acidic medium.The landolt effect is produced by adding ascorbic acid.The induction period is measured by monitoring the dead-stop end-point.1/t is linear relationship with Cu(Ⅱ)concentration in range of 3.0×10^(-7)～3.0×10^(-11)g/ml.The method is used to determine trace Cu(Ⅱ)in hair and urine samples with satisfactory results,and the apparent activation energy of the catalytic reaction is measured as E=64.95 kJmol^(-1)