• 中文核心期刊
  • 中国科技核心期刊
  • CSCD来源期刊
  • DOAJ 收录
  • Scopus 收录

常用锂同位素地质标准物质的多接收器电感耦合等离子体质谱分析研究

Study on Measurements of Lithium Isotopic Compositions for Common Standard Reference Materials Using Multi-Collector Inductively Coupled Plasma-Mass Spectrometry

  • 摘要: 锂同位素研究是非传统稳定同位素地球化学研究的前沿, 已广泛应用于从地表到地幔的岩石圈及流体等固体地球科学的研究领域.准确测定锂同位素比值是应用该同位素体系的前提.本文报道了国际上7种常用地质标准物质(BHVO-2、JB-2、BCR-2、AGV-2、NKT-1、L-SVEC、IRMM-016) 的锂同位素组成数据.分析中采用硝酸-氢氟酸混合酸消解岩石标准样品, 通过3根阳离子交换树脂(AG50W-X8, 200~400目)填充的聚丙烯交换柱和石英交换柱对锂进行分离富集, 利用Neptune型多接收器电感耦合等离子体质谱(MC-ICP-MS)测定锂同位素比值, 使用标准-样品交叉法(SSB)校正仪器的质量分馏.实验得到这7种常用地质标准物质的锂同位素组成与测试精度(2SD)分别为:δ7LiBHVO-2—L-SVEC=4.7‰±1.0‰(n=53), δ7LiJB-2—L-SVEC=4.9‰±1.0‰(n=20), δ7LiBCR-2—L-SVEC=4.4‰±0.8‰(n=8), δ7LiAGV-2—L-SVEC=6.1‰±0.4‰(n=14), δ7LiNKT-1—L-SVEC=9.8‰±0.2‰(n=3), δ7LiL-SVEC—L-SVEC=-0.3‰±0.3‰(n=10), δ7LiIRMM-016—L-SVEC=0.0‰±0.5‰(n=10), 这些数据在误差范围内与国际上已发表的数据一致.Li同位素分析精度可以达到大约0.5‰, 长期的分析精度即外部重现性≤±1.0‰, 达到了国际同类实验室水平.7种常用地质标准物质的锂同位素组成数据的发表为锂同位素研究提供了统一的标准, 使地质样品的锂同位素数据的质量监控成为可能.在基质效应的研究中, 使用不同量的IRMM-016配制的标准溶液过柱, 深入探讨了样品量对锂同位素测定值的影响, 结果表明, 在现有测试精度下, 只要分析样品的锂含量达到100 μg/L, 且不超过树脂的承载量, 样品的锂同位素组成在误差范围内与真值吻合, 样品量的大小不影响锂同位素测定结果的准确性.

     

    Abstract: Non-traditional lithium isotope is a frontier in isotope geochemistry and has been applied to the studies of Solid Earth Sciences, such as the lithosphere and fluids from the Earth's surface to the mantle. Lithium isotopic compositions of 7 standard reference materials BHVO-2, JB-2, BCR-2, AGV-2, NKT-1, L-SVEC and IRMM-016 are reported in this paper. The rock standards were digested with HNO3-HF mixed acids. Cation exchange resin AG50W-X8 was used for the separation of Li from other elements. Li isotope ratios were determined by Multi-Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS), and isotopic mass fractionation was calibrated by standard-sample bracketing. The Li isotopic compositions and the analytical uncertainties (reported in 2SD) of analyzed standard reference materials were: 7LiBHVO-2-L-SVEC=4.7‰±1.0‰ (n=53), 7LiJB-2-L-SVEC=4.9‰±1.0‰ (n=20), 7LiBCR-2-L-SVEC=4.4‰±0.8‰ (n=8), 7LiAGV-2-L-SVEC=6.1‰±0.4‰ (n=14), 7LiNKT-1-L-SVEC=9.8‰±0.2‰ (n=3), 7LiL-SVEC-L-SVEC=-0.3‰±0.3‰ (n=10), 7LiIRMM-016-L-SVEC=0.0‰±0.5‰ (n=10). The results were in good agreement with published data within analytical uncertainties. The accuracy of this method is about ±0.5‰ and the long-term external precision (2SD) of replicate analyses including the entire pretreatment procedure is less than ±1.0‰, and is similar to the state of the art method. The reported data of 7 standard reference materials provided a new standard framework for Li isotope research, and enabled the evaluation of the quality of data retrieved from geological samples. The influence of sample size was also assessed by loading different amounts of separated IRMM-016 solutions. The results show that when the lithium concentration has reached 100 μg/L, the measured lithium isotopic compositions are in coincidence with the accepted value within uncertainty, and the sample size does not affect the accuracy of measurements.

     

/

返回文章
返回