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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
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A Method for Combining a Stable Isotope Mass Spectrometer with an Isotopic Spectroscope to Analyze the 17O/16O
Received:December 03, 2012  Revised:February 20, 2013
DOI:
Key words: oxygen 17  triple oxygen isotopes  cavity ring down spectroscope  mass-independent isotope fractionation
Author NameAffiliation
LI Li-wu Key Laboratory of Petroleum Resources Research, Chinese Academy of Sciences, Lanzhou 730000, China 
WANG Guang National Research Center for Geoanalysis, Beijing 100037, China 
LI Zhong-ping Key Laboratory of Petroleum Resources Research, Chinese Academy of Sciences, Lanzhou 730000, China 
DU Li Key Laboratory of Petroleum Resources Research, Chinese Academy of Sciences, Lanzhou 730000, China 
CAO Chun-hui Key Laboratory of Petroleum Resources Research, Chinese Academy of Sciences, Lanzhou 730000, China 
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Abstract:
      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 17 O isotope composition was obtained without conversion of the multiform oxygen to O2. Moreover, there is no risk in sample preparation for 18 O isotopic analysis, and the precision is better than, or equal to, other methods.