共存离子对时间分辨荧光法测定痕量铀的影响

时间分辨荧光法分析痕量铀具有灵敏度高、操作简便等优点,但是受共存离子的影响很大,准确度评价较低,分析结果误差过大。本工作研究了时间分辨荧光法测定焦磷酸体系中UO2+2时几种干扰离子如H+、Fe3+、NO-3等的影响,为痕量铀样品预处理方法的确定提供重要依据。结果表明:H+对UO2+2的荧光猝灭主要表现为荧光物质的破坏;NO-3对铀络合物荧光体系的影响表现为对激发光的吸收;Fe3+的影响表现为对激发光和荧光的吸收。对于质量浓度为2μg/L的铀溶液,当c(H+)=0.037 5mol/L时,UO2+2的荧光强度下降了44.4%;当ρ(Fe3+)=20mg/L时,UO2+2的荧光强度基本猝灭完全。

Influence of Interfering Ions on Analyses of Trace Uranium by Time Resolved Fluorescence Method

Interfering ions are the main influencing factors to time resolved fluorescence(TRF) analyses of trace uranium. The influence of H⁺, Fe³⁺ and NO^-₃ are studied in this paper. The fluorescence intensity of uranyl fluorescent complex is greatly affected by nitric acid. The fluorescence are completely quenched when the concentration of nitric acid is 0.075 mol/L. The concentration and lifetime of fluorescent complex are reduced by the addition of H⁺. The fluorescence intensity is also affected by Fe³⁺ and NO^-₃ because of the absorption of exciting light.