紫外荧光法测铀过程中影响因素的分析

Analysis of Influencing Factors on Ultraviolet Fluorescence Determination of Uranium

目的研究溶液pH值及Fe^(3+)、Mn^(2+)对铀酰离子荧光特性的影响。方法采用紫外荧光法测量液体样品中的微量铀。结果溶液pH值在3~10时对标准加入法测微量铀无明显影响;pH值为6左右时,单位铀浓度增长所对应的荧光增长计数最多,测量结果最接近标准值,pH值为13左右时已无法进行测量。Fe^(3+)、Mn^(2+)会熄灭铀的荧光,对测量产生负干扰,1 ng/m L铀溶液中Fe^(3+)的最大允许量为10μg/mL,Mn^(2+)的最大允许量为0.1μg/mL;可通过预处理或适当稀释样品溶液的方法来降低Fe^(3+)、Mn^(2+)的干扰。结论采用标准加入法测量时应尽量控制p H值在3~10之间;Fe^(3+)、Mn^(2+)与荧光增强剂形成的络合物会吸收紫外光,对铀的测量产生负干扰。当待测样品铀浓度超出测铀量程是测量结果偏高,无法得出准确结果。

Objective Purpose of the research.To study the effect of p H value and;Fe^3＋,Mn^2＋on the properties of uranyl ion fluorescence.Methods Using ultraviolet fluorescence method of measuring trace uranium in samples of liquid.Results The standard addition method has no obvious influence to measure the concentration of uranium when the p H value at about 3～ 10.The optimal conditions for uranium determination is the p H value about 6.It cannot be measured when p H value is about13.;Fe^3＋,Mn^2＋play negative interference on uranium determination,they can absorb exciting light and quenched the fluorescence of uranyl cations.The fluorescence intensity is decreased on the condition that the concentration of;Fe^3＋is 10μg / m L or Mn^2＋is 0.1μg / m L.The negative interference can be reduced by pretreated method or dilution of sample solution.Conclusion Standard addition measurement method should try to control the p H value between 3 ～ 10;;Fe^3＋,Mn^2＋complexes formed with fluorescent enhancers will absorb UV-light,negatively affecting the measurement of uranium.When the sample of uranium measured concentrations exceeding the high range measurement result,it is not an accurate result.