摘要:
本文利用多接收电感耦合等离子体质谱仪（MC-ICP-MS）建立了高精度Cd同位素组成测试方法。测试过程中，采用样品-标样间插法（Standard- Sample Bracketing，SSB）与Ag作外标相结合的方式进行仪器的质量分馏校正。建立方法的过程中，对锥组合、Ag添加量、干扰元素（Pd、Sn、In和Zn）的影响、浓度效应、全流程空白进行了评估，结果表明：1）使用X锥+Jet锥组合，其灵敏度更适合低含量样品的测试；2）Ag的添加量总体不影响Cd同位素测试结果，但需控制在合理的范围，本实验室最终确定Ag的浓度为30~40ng/mL；3）干扰元素In和Zn对Cd同位素测试无影响，但微量的Sn和Pd会影响Cd同位素的测试结果，需实时监控；4）浓度效应结果显示，当样品与标准溶液Cd浓度比值为0.25~1.5之间时，可获得满意的结果；5）全流程空白小于42pg，能满足地质样品高精度测试需要。利用本文建立的方法对NIST SRM 3108进行了长期监控（2020年7月~2021年6月），测试结果为0.00±0.05（2σ，下同），与统计的文献报道值一致。运用该方法，对两个水系沉积物元素含量标样GSD-11 (GBW07311)、GSD-12 (GBW07312)和两个锰结核标样Nod-A-1、Nod-P-1进行了Cd同位素组成测试，测试结果分别是：-0.29±0.16、-0.06±0.16、0.09±0.08和0.07±0.10，与文献报道的测试结果和精度一致，表明本文建立的方法是准确、可靠的。
Abstract:
In this paper, a high-precision Cd isotope analysis method on MC-ICP-MS has been established using a multi-collector inductively coupled plasma mass spectrometer (Neptune plus). In the process of analyzing, Standard- Sample Bracketing (SSB) and Ag as an external standard have been combined to correct the mass fractionation of the instrument. Key factors such as the cone combination, the addition of Ag amount, the influence of interfering elements (Pd, Sn, In, and Zn), the concentration effect, and the full-process blanks have been evaluated during the establishment of the method, and the results showed that: 1) The use of the combination of the X cone + the Jet cone is more suitable for the samples with low Cd contents in terms of its sensitivity; 2) The addition of Ag does not affect the results of Cd isotope testing in general, but the amount should be within a reasonable range, and in this study it is determined that the optimal concentration of Ag added should be 30~40ng/mL; 3) The interfering elements In and Zn show hardly any effect on Cd isotope testing, but trace amounts of Sn and Pd might have affected the Cd isotope results, which must be monitored in real time; 4) Concentration effect results show that when the sample/standard ratio of Cd concentration is between 0.25~1.5, satisfactory results could be obtained; 5) The full process blank is less than 42pg, which could meet the needs of high-precision testing of geological samples. The method established in this paper has been utilized for long-term monitoring of NIST SRM 3108 (July 2020~June 2021), yielding the result of 0.00±0.05 (2σ, the same below), which is consistent with the statistically reported values in the literature. Using this method, the Cd isotopic composition of two pelagic sediment elemental content samples GSD-11 (GBW07311) and GSD-12 (GBW07312) and two manganese-nodule samples Nod-A-1 and Nod-P-1 have been analyzed, and the results, -0.29±0.16, -0.06±0.16, 0.09±0.08 and 0.07±0.10 respectively, are consistent with the data and accuracy reported previously, indicating that the method established in this study is accurate and reliable.
百度学术
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