Methods and limitations of 'clumped' CO2 isotope (Δ47) analysis by gas-source isotope ratio mass spectrometry
Methods and limitations of 'clumped' CO2 isotope (Δ47) analysis by gas-source isotope ratio mass spectrometry
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DOI：
10.1002/jms.1614
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发表时间：
2009-09-01
影响因子：
2.3
通讯作者：
Came, R.
中科院分区：
文献类型：
--
作者：
Huntington, K. W.;Eiler, J. M.;Came, R.
多取代同位素体的地球化学（“聚集同位素”地球化学）检查天然物质中含有一种以上稀有同位素的分子、分子式单元或部分的丰度（例如（COO）-C-13-O-18-O-16，（OO）-O-18-O-18，N-15（2），（COO 22-）-C-13-O-18-O-16）。这些物种构成了碳酸盐聚集同位素测温法的基础，并在各种自然过程中经历了独特的分馏，但最初的报告几乎没有提供其分析的细节。在这项研究中，我们提出了详细的数据和参数的理论和实际的限制，精密度，标准化方法，仪器线性和相关问题的双入口气体源同位素比质谱（IRMS）的聚集同位素分析。我们证明了长期的稳定性和亚十分之一每密耳的精度在47/44的比率，计数系统组成的法拉第杯通过一个10（12）Ω电阻器登记在三个Thermo-Finnigan 253 IRMS系统。基于对加热的CO2气体的分析，其在可能的同位素体之间具有同位素的随机分布，我们记录并校正了（1）分析物CO2分子之间的同位素交换和（2）实际和测量的47/44比率之间的关系中的微妙非线性。对于质量-47异常（主要是C-13-O-18键丰度异常的测量）的测量，通常可以达到千分之0.01的外部精度，并遵循计数统计。我们的方法和仪器固有的精度的当前技术限制类似于百万分之5（ppm），而非均质天然材料的测量精度更典型地类似于10 ppm（均为1 s.e.）。这些分别对应于+/- 1.2摄氏度和+/- 2.4摄氏度的碳酸盐聚集同位素测温误差。版权所有（C）2009约翰威利父子有限公司
The geochemistry of multiply substituted isotopologues ('clumped-isotope' geochemistry) examines the abundances in natural materials of molecules, formula units or moieties that contain more than one rare isotope (e.g. (COO)-C-13-O-18-O-16, (OO)-O-18-O-18, N-15(2), (COO22-)-C-13-O-18-O-16). Such species form the basis of carbonate clumped-isotope thermometry and undergo distinctive fractionations during a variety of natural processes, but initial reports have provided few details of their analysis. In this study, we present detailed data and arguments regarding the theoretical and practical limits of precision, methods of standardization, instrument linearity and related issues for clumped-isotope analysis by dual-inlet gas-source isotope ratio mass spectrometry (IRMS). We demonstrate long-term stability and subtenth per mil precision in 47/44 ratios for counting systems consisting of a Faraday cup registered through a 10(12) Omega resistor on three Thermo-Finnigan 253 IRMS systems. Based on the analyses of heated CO2 gases, which have a stochastic distribution of isotopes among possible isotopologues, we document and correct for (1) isotopic exchange among analyte CO2 molecules and (2) subtle nonlinearity in the relationship between actual and measured 47/44 ratios. External precisions of similar to 0.01 parts per thousand are routinely achieved for measurements of the mass-47 anomaly (a measure mostly of the abundance anomaly of C-13-O-18 bonds) and follow counting statistics. The present technical limit to precision intrinsic to our methods and instrumentation is similar to 5 parts per million (ppm), whereas precisions of measurements of heterogeneous natural materials are more typically similar to 10 ppm (both 1 s.e.). These correspond to errors in carbonate clumped-isotope thermometry of +/- 1.2 degrees C and +/- 2.4 degrees C, respectively. Copyright (C) 2009 John Wiley & Sons, Ltd.