Raman spectroscopic measurement guidelines for carbon isotopic composition of CO2

Abstract

In principle, Raman spectroscopy can be applied to quantitatively measure the carbon isotopic composition (13CO2/12CO2) of CO2 in single fluid inclusion. Based on our recent work, it could be expressed as, 13CO2/12CO2 = (I13CO2/I12CO2)·(σ12CO2/σ13CO2), in which the ratio of cross section (σ12CO2/σ13CO2) is determined from Raman spectra of standard CO2 sample. In fact, before Raman spectroscopy can widely be utilized to quantitatively determine the carbon isotopic composition of CO2, it is necessary to improve the measurement accuracy and precision of 13CO2/12CO2. In this study, it is devoted to understand the factors which may affect the accuracy and precision of measured 13CO2/12CO2. Based on the discussion on error analysis, the Raman spectroscopic measurement guidelines are provided to ensure the accuracy and precision of measured 13CO2/12CO2. Additionally, this method is utilized to measure the 13CO2/12CO2 of analytical synthetic and natural CO2 samples in order to evaluate its reliability.