多接收电感耦合等离子体质谱Cu同位素测定中的干扰评估

多接收电感耦合等离子体质谱（MC—ICP—MS）是高精度测定铜同位素的新方法，然而在测定中也可能存在干扰。为此对MC—ICPMS Cu同位素测定中的可能干扰进行了评估。主要包括以下方面的内容：（1）对所用标准物质和试剂进行了纯化，所用标准物质和试剂对Cu同位素的同质异位素干扰可以忽略；（2）运用K和／参数进行了讨论，其中K为样品中的Cu浓度与标准溶液中Cu浓度的比值,f为在一定Cu浓度的标准溶液中干扰信号相对于^63Cu真实信号的比值。理论模拟表明，当K值小于1时，即使在质量为63处的干扰很小，对ε^65 Cu的影响也可能很大；（3）通过对理论模拟结果与实际测定结果的对比，发现对所用的试剂而言质量数为65的干扰可以忽略不计；（4）实际测定结果表明，当样品中Cu的浓度是标样中Cu的浓度的0．5～4倍时，测试获得的样品的ε^65值与其真值在误差范围内一致；（5）对潜在的基质效应重点研究了Fe和Co对Cu同位素测定的影响。实验结果表明，当Fe／Cu〈100，Co／Cu〈7时，Fe，Co不影响Cu同位素比值的测定；（6）10个月的重现性研究结果为ε^65=3．5±1．0（2SD）。该测定值在误差范围内与文献报道的值一致

Assessment of Interferences in Cu Isotope Ratio Measurements Using Multiple-Collector Inductively Coupled Plasma Source Mass Spectrometry

Multiple-collector inductively coupled plasma source mass spectrometry （MC-ICP-MS） is a relatively new technique for high precision copper isotopic ratio measurements. However, potential interferences may exist in the measurements of ^65Cu/^63Cu ratios. Assessment of the interferences and effects of Cu concentration on the analyses of Cu isotope compositions using MC-ICPMS is presented here. The problem is first investigated by measuring the abundances of Na in the samples to be able to conclude that the isobaric interference of these polyatomic ions is negligible in this study. Secondly, by assuming that there is no interfering signal at mass 63, the anticipated effect of interference at mass 63 on 665 Cu measurement is modeled. The modeling result shows that even the interfering signal is very small, its effect on the ε^65 Cu value can still be between sample and standard is large. Thirdly, by comparison significant when the difference in Cu concentrations of the modeling results and actual measurements, it has been shown that the isobaric interference on mass 63 is negligible. Fourthly, the results of actual measurements show that the true 65 Cu value can be obtained if the Cu concentration of a sample solution is within the range of 0.5 - 4.0 times of that of the standard. Fifthly, the possibility of matrix effects on measured ^65Cu/^63Cu ratios has been investigated. Of primary concern in this study are the effects of Fe and Co contents on the measured ^65 CU/^63 Cu ratio. This has been examined using synthetic mixtures with Fe：Cu and Co：Cu molar ratios ranging from 0.1 to 100, and 0.5 to 10, respectively. Results of these experiments show that there is no clear dependence of ^65Cu/^63Cu on Fe/Cu 〈 100, Co/Cu 〈 7 respectively under the working conditions. Finally, the results of repeated measurements over a period of ten months show that the ε^65 Cu value of the Romil Cu solution obtained from these analyses is 3.5 ±1 （2sd） relative to NBS standard