岩矿测试

文章摘要

李立武,王广,李中平,杜丽,曹春辉.稳定同位素质谱与同位素光谱结合的方法分析氧同位素¹⁷O/¹⁶O[J].岩矿测试,2013,32(3):392-397

LI Li-wu,WANG Guang,LI Zhong-ping,DU Li,CAO Chun-hui.A Method for Combining a Stable Isotope Mass Spectrometer with an Isotopic Spectroscope to Analyze the ¹⁷O/¹⁶O[J].Rock and Mineral Analysis,2013,32(3):392-397.DOI:

稳定同位素质谱与同位素光谱结合的方法分析氧同位素¹⁷O/¹⁶O

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A Method for Combining a Stable Isotope Mass Spectrometer with an Isotopic Spectroscope to Analyze the ¹⁷O/¹⁶O

投稿时间：2012-12-03 修订日期：2013-02-20

DOI：

中文关键词: 氧17 三氧同位素光腔衰荡光谱非质量分馏效应

英文关键词: oxygen 17 triple oxygen isotopes cavity ring down spectroscope mass-independent isotope fractionation

基金项目:中国地质大调查项目(1212011120276, 12120113015100)

作者	单位
李立武	中国科学院油气资源研究重点实验室, 甘肃兰州 730000
王广	国家地质实验测试中心, 北京 100037
李中平	中国科学院油气资源研究重点实验室, 甘肃兰州 730000
杜丽	中国科学院油气资源研究重点实验室, 甘肃兰州 730000
曹春辉	中国科学院油气资源研究重点实验室, 甘肃兰州 730000

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中文摘要:

传统的氧同位素分析方法一般将各种形式的氧转化为CO₂,再通过稳定同位素质谱测定其氧同位素组成,由于二氧化碳中的¹⁷O和¹³C在质谱中有相同的质荷比m/z,这种方法不能测得¹⁷O同位素的丰度,三氧同位素(¹⁶O、¹⁷O、¹⁸O)丰度分析的关键是¹⁷O同位素丰度的分析。为了测量¹⁷O同位素丰度,一般需要先将各种形式的氧转化为O₂,然后利用稳定同位素质谱进行分析,转化过程复杂或者有危险。本文提出了一种新思路,应用稳定同位素质谱与碳同位素光谱相结合的方法分析¹⁷O/¹⁶O。先采用传统方法将各种形式的氧转化为CO₂,再由多接收器稳定同位素质谱计测得CO₂的质谱峰高比45/44(记为R₄₅),同位素光谱如光腔衰荡光谱测得¹³C/¹²C(定义为R₁₃),计算其同位素比值¹⁷O/¹⁶O=(R₄₅-R₁₃)/2,方法的分析精度好于±0.08‰(1σ)。该方法是在传统方法的基础上,增加一个CO₂碳同位素光谱分析步骤,通过简单的数据处理就可以获得¹⁷O同位素组成,而无需将各种形式的氧转化为O₂,¹⁸O同位素样品制备方法成熟,无危险性,且分析精度优于或相当于其他测试方法。

英文摘要:

Since the discovery of mass-independent isotope effects, the study of triple oxygen isotope abundance has become a focus and frontier. In traditional oxygen isotopic ratio analysis methods, multiform oxygen is converted to CO₂ and the oxygen isotopic ratios of CO₂ are measured by Stable Isotope Mass Spectrometer. However, this method cannot be used to measure ¹⁷O isotopic abundance because ¹⁷O and ¹³C in carbon dioxide have the same m/z. The key for the triple oxygen isotope abundance analysis is to analyze the ¹⁷O isotopic abundance. To measure the ¹⁷O isotopic abundance multiform oxygen to O₂ is usually converted and then analyzed by Stable Isotope Mass Spectrometer, although the conversion process is complicated and/or dangerous. In this paper a new way to measure ¹⁷O/¹⁶O by Stable Isotope Mass Spectrometer and Isotopic Spectroscope is presented. The traditional method to convert multiform oxygen to CO₂ is adopted. The CO₂ was then analyzed by Stable Isotope Mass Spectrometer to obtain m/z 45/44 (defined as R₄₅), and by isotopic spectroscope such as cavity ring down spectroscope (CRDS) to obtain ¹³C/¹²C (defined as R₁₃). The ¹⁷O/¹⁶O was calculated by ¹⁷O/¹⁶O=(R₄₅-R₁₃)/2. This method has an analytical precision which is better than ±0.08‰ (1σ). The new method is based on the traditional method with the addition of an analysis step of the carbon isotopic spectroscope for CO₂. With simple data processing, the ¹⁷O isotope composition was obtained without conversion of the multiform oxygen to O₂. Moreover, there is no risk in sample preparation for ¹⁸O isotopic analysis, and the precision is better than, or equal to, other methods.

主管单位：	中国科学技术协会
主办单位：	中国地质学会岩矿测试技术专业委员会国家地质实验测试中心