非传统稳定同位素分析技术要点

doi:10.13745/j.esf.sf.2020.4.7

摘要/Abstract

摘要：

高精度高质量的同位素分析技术是开展非传统稳定同位素地球化学工作的前提。同位素分析是不断提取样品真实信息的过程,包括样品制备、化学分离、质谱测定和数据处理4个基本步骤。在同位素分析过程中,每一环节都有可能引入空白或者污染,或造成同位素分馏,引发信息“失真”。为了准确获得样品的真实同位素组成,必须有效避免污染并精准校正在分析过程中可能的干扰。以Ca同位素为例,在总结前人工作的基础上,探讨了各个步骤所涉及的分析要点,为建立其他同位素体系的分析方法提供参考,为后续储库探讨、机理解析及应用研究提供技术支撑。

关键词: 分析技术, 样品制备, 化学分离, 质谱测定, 数据计算, Ca同位素

Abstract:

High-precision and high-quality analytical technique is the foundation of exploring applications of non-traditional stable isotope geochemistry. Actually, isotopic analysis is a process that the real isotopic information concealed in the sample is continuously being extracted, consisting of four basic steps, namely, sample preparation, chemical separation, mass spectrometry and data processing. In the process of isotopic analysis, each step could possibly introduce blank or contamination, and occur isotopic fractionation, which will result into mistaken information. In order to obtain the true isotopic composition of the sample, it is important to avoid contamination effectively and correct interference accurately. In this paper, on the basis of previous works, we take calcium isotope as an example, to discuss the key aspects involved in the four steps. We hope that this paper will help researchers to establish analytical methods in new isotopic systems, and also provide support in reservoir prospecting, mechanism deduction and geological applications.

Key words: analytical technique, sample preparation, chemical separation, mass spectrometry, data processing, Ca isotopes

中图分类号:

P597.2

白江昊, 刘芳, 张兆峰, 安亚军, 李欣, 薛永丽, 徐玉明. 非传统稳定同位素分析技术要点[J]. 地学前缘, 2020, 27(3): 1-13.

BAI Jianghao, LIU Fang, ZHANG Zhaofeng, AN Yajun, LI Xin, XUE Yongli, XU Yuming. Key aspects of non-traditional isotope analysis[J]. Earth Science Frontiers, 2020, 27(3): 1-13.

图/表 7

图1 ln(42Ca/44Ca)-ln(40Ca/44Ca) (据文献[35]修改)

Fig.1 The ln(42Ca/44Ca)-ln(40Ca/44Ca) diagram. Modified from [35].

图2 化学分离前加入双稀释剂和化学分离后加入稀释剂结果对比(原始数据来源于[65])

Fig.2 Comparison of δ44/40Ca values as result of double-spike addition before and after chemical separation. Original data adapted from [65].

图3 在Nu 1700上的Fe同位素与干扰分离情况

Fig.3 Iron isotopic peak shape and isobaric signals measured by Nu 1700

图4 Sr对Ca同位素测试结果的影响(原始数据来源于[65,81])

Fig.4 Sr-doping experiments to test matrix effect on δ44/40Ca analyses. Original data adapted from [65,81].

图5 在TIMS上测定过程中40Ca/42Ca比值的变化

Fig.5 Variation of 40Ca/42Ca ratios during TIMS measurements

图6 Ca同位素双稀释剂校正三维模型图(据文献[77]修改)

Fig.6 Schematic 3D illustration of Ca isotope measurement using double spike correction. Modified from [77].

图7 NIST SRM 915a和IAPSO海水的长期(六年来)测定结果(据文献[82]修改)

Fig.7 Long-term (6 years) δ44/40Ca values of NIST SRM 915a and IAPSO seawaters. Modified from [82].

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