镉(Ⅱ)-靛蓝胭脂红-溴酸钾体系催化动力学光度法测定土壤中痕量镉

Catalytic kinetic spectrophotometric determination of trace cadmium in soil by means of cadmium(Ⅱ)-indigo carmine-KBrO_3 system

基于在盐酸介质中,以α,α′-联吡啶为活化剂,镉（Ⅱ）对溴酸钾氧化靛蓝胭脂红褪色反应有灵敏的催化作用,建立了测定镉（Ⅱ）的动力学新方法。研究了该催化褪色反应的最佳动力学条件和参数。以610 nm为测定波长,镉（Ⅱ）在0.02～0.4μg/mL的范围内工作曲线呈线性关系,检出限为2.72 ng/mL。催化反应为动力学一级反应,表现活化能为183.17 kJ/mol,反应速率常数为1.8×10^-3s^-1。考察了20多种共存离子的影响,表明本方法具有较好选择性。方法用于土壤中痕量镉的测定,相对标准偏差小于3.6%,试样加标回收率为95.7%～102.8%。

A new kinetic spectrophotometric method for determination of trace Cd（Ⅱ） has been proposed. Cd（Ⅱ） can sensitively catalyze the discoloration reaction of indigo carmine and potassium bromate in HCl medium and in the presence of α,α′-bipy as activator. The optimum kinetic conditions of the catalytic reaction has been investigated. The wavelength for the determination is 610 nm. The linear range for determination of Cd（Ⅱ） is 0.02-0.4 μg/mL with the detection limit of 2. 72 ng/mL. The results from the studies suggested that the catalytic reaction was first-order and the apparent activation energy of this reaction was 183.17 kJ/mol,and the apparent rate constant was 1.8×10^-3s^-1. The interferences of foreign ions were also studied. The procedure has been used to determine Cd in soil sampies,with the relative standard deviation of below 3. 6% and the average recovery of 95. 7%- 102. 8%.