在H_3PO_4介质中,苄基三乙基氯化铵(BTEAC)增敏剂存在下,痕量镧(Ⅲ)对高碘酸钾氧化硫酸耐尔蓝(NBS)的反应具有阻抑作用,据此建立了阻抑动力学光度法测定痕量镧(Ⅲ)的新方法.研究了吸收光谱、试剂用量、干扰离子等因素的影响,测定了反应动力学参数.在最佳实验条件下,方法线性范围为0.4～120 μg/L,检出限为3.36×10~(-7)g/L.催化反应为动力学一级反应,表观活化能为101.04 kJ/mol,反应速率常数为2.3×10~(-3)/s.反应在表面活性剂存在下,其灵敏度提高3倍.此法用于稀土氧化物中镧的测定,结果同原子吸收光谱法的结果相一致,相对标准偏差小于2.0%,试样加标回收率为100%～101%.
Trace lanthanum(Ⅲ) has an inhibitory effect on the reaction between nile blue sulfate and KIO_4 in the medium of H_3PO_4 using benzyltriethylammonium chloride as sensitizer. Therefore,a new inhibitory kinetic spectrophotometric method was established for the determination of trace lanthanum (Ⅲ). The factors shch as absorption spectra, acidity, concentrations of reagent, influence of coexisting ions were discussed and the kinetic conditions were studied. Under the optimum conditions, the linear range was 0.4-120 μg/L. The detection limit was 3.36 × 10~(-7) g/L. The catalytic reaction was the first order reaction with the apparent activation energy of 101.04 kJ/mol and the reaction rate constant of 2.3×10~(-3)/s. The sensitivity was increased by 3 times in the presence of surfactant. The method was used in the determination of lanthanum(Ⅲ) in rare earth oxides, with the relative standard deviation of below 2.0% and the average recovery of 100%-101%.
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