IC-MC-ICP-MS测量环境水样品中钚同位素比值的方法研究

为了实现快速分离钚与其他基体，准确测定钚同位素比值，建立了离子色谱(IC)与多接收电感耦合等离子体质谱(MC-ICP-MS)联用测定环境水样品中钚同位素比值的方法。实验选取7.5 mol/L硝酸作为色谱柱的上柱液，以0.35 mol/L HNO₃和0.01 mol/L HF的混合溶液为淋洗液，用Pu计数最高点法（peak apex ratio）作为最终同位素比值的测定方法。实验对模拟环境水样进行测定，测量相对标准偏差为0.50%，与Pu标准同位素比值的相对偏差为5.7%。采用该方法对实际环境水样品进行测定，测量相对标准偏差为0.97%，与传统的TBP-7402色谱柱离线分离法测量的钚同位素比值进行对比，相对偏差为1.3%。结果表明，该方法的样品预处理简单、分离速度快、结果可靠，具有广阔的应用前景。

Determination of Pu Isotope Ratio in Environmental Water Samples by IC-MC-ICP-MS

The environmental sampling (ES) analysis is one of important nuclear safeguards’ technologies of International Atomic Energy Agency (IAEA), which has been used for detecting the undeclared nuclear activities. Plutonium is regarded as the significant element in nuclear safeguards. In the aspect of ES, bulk analysis is adept at the analysis of plutonium ratio in environmental samples. In this paper, the method of on-line analysis of plutonium ratio in water samples was established by combination of ion chromatography (IC) and multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS). The separation conditions of liquid chromatographic column, the column acidity, eluent composition were optimized. The AS4A-SC anion chromatographic column was made sure as separation medium. The separation conditions in which the acidity of column was 7.5 mol/L and the eluent composition was 0.35 mol/L HNO₃ mixed with 0.01 mol/L HF were determined by optimization experiments. The concentrations of uranium in various types of environmental water samples were measured. The interface was determined in order to combine IC and MC-ICP-MS. The effect was confirmed better when using PEEK two way valve to connect IC and MC-ICP-MS. The technique of peek apex ratio was adapted as the method for the measurement of dynamic plutonium ratio by MC-ICP-MS. The simulated water samples were measured. The RSD is 0.50%, and the relative bias compared with the plutonium certified reference material is 5.7%. The actual water samples were also measured. The RSD is 0.97%, and the relative bias is 1.3% compared with the typical separation methods by TBP and 7402 chromatography column. This method has high efficiency and fast analytical speed, which can be used for the measurement of plutonium ratio in other environmental samples with more complicated matrices.