镧(Ⅲ)催化过氧化氢氧化丽春红褪色光度法测定痕量镧

Fading spectrophotometric determination of trace lanthanum based on its catalytic effect on oxidation of ponceau by peroxide

基于在盐酸介质中,La(Ⅲ)催化过氧化氢氧化丽春红(3-羟基-4-(2-磺基-4-〔4-苯磺基偶氮〕偶氮苯)-2,7-萘二磺酸钠)的褪色反应,建立了一个灵敏度高的测定痕量La(Ⅲ)的催化动力学光度分析法。讨论了酸度、试剂用量、温度、干扰离子等因素的影响;研究了反应的最佳条件;测定了一些动力学参数。催化反应的表观活化能为66.63kJ/mol。该方法测定La(Ⅲ)的线性范围为0.08～1.6μg/mL,检出限为0.045μg/mL。不需要预先分离,可将本方法用于沙子样品中痕量镧的测定,回收率为96.0%～111.5%。

A sensitive method for determination of lanthanum（Ⅲ） by kinetic spectrophotometry was established based on the catalytic effect of trace lanthanum（Ⅲ） on the fading reaction of ponceau with hydrogen peroxide. The influence of acidity, dosage of reagents, temperature and other factors on the reaction was discussed. The optimum conditions of the reaction and some kinetic parameters were optimized. The apparent action energy of the reaction was 66.63 kJ/mol. The linear range was 0.08-1.6 μg/mL for lanthanum, and the detection limit was 0. 045 μg/mL. The proposed method has been successfully applied to the determination of trace lanthanum in sand samples without previous separation with the recovery of 96. 0%--111.5%.