Raman spectroscopic measurement guidelines for carbon isotopic composition of CO2

Unlocking ultimate precision of intensity and area ratio measurements in Raman spectroscopy: Insights from simulation, experimentation, and theory and implications for isotope ratio analysis

“…From Table S3 and Figure 7, the average σ 0 α I =σ α I when changing w CCD from 15 to 5 μm in the simulation is 0.57, which is consistent with the value of 0.58 obtained from Equation (27). Similarly, when changing f from 80 to 160 cm, the mean value of σ 0 α I =σ α I in the simulation is 0.74, which is consistent with the value of 0.71 obtained from Equation (28). Consequently, with reasonable accuracy, Equations ( 25) and ( 26) can predict the relative change in σ α I , which indicates the improvement in σ α I resulting from enhanced instrumental performance.…”

“…Since work reported by Li et al, 24 several σ δ 13 C measurements of CO 2 by Raman spectroscopy with precision below 1‰ have been reported. 22,24,27,28 Achieving precision less than 1‰, even in this study, where Γ w /Δx w is large, requires 13 I þ F:D: more than 10 6 (e À ) (Figure 5). Earlier studies 24,27,28 with smaller Γ w /Δx w require even more 13 I þ F:D: (Equations 22 and 23).…”

“…Isotope ratio analysis is a challenging analysis that demands the highest degree of precision. In recent years, nondestructive local isotope analysis methods have been developed for various substances, such as H 2 O, 20,21 CO 2 , [22][23][24][25][26][27][28][29][30][31][32] H 2 , 33,34 N 2 , 35 humic acids, 36 and calcite. 37 Local nondestructive δ 13 C measurement of CO 2 by Raman spectroscopy has long been the subject of research; it has recently been investigated actively for application to various PVTX conditions.…”

“…37 Local nondestructive δ 13 C measurement of CO 2 by Raman spectroscopy has long been the subject of research; it has recently been investigated actively for application to various PVTX conditions. 22,23,[26][27][28]32 However, because of the large variation of more than two orders of magnitude in the reported precision (σ δ 13 C ) of δ 13 C measurements (Table 1), some researchers 24 assert that this method is applicable to natural samples, whereas other researchers 23,26 consider that it is limited to samples with highly variable or greater δ 13 C. Although the magnitude of the weakest peak intensity is commonly regarded as a factor indicating the precisions of α I and α A (σ α I and σ α A ), 25,27 this factor alone does not account for the reported variation in σ δ 13 C (Table 1). Identifying parameters that strongly affect σ α I and σ α A would help improve σ δ 13 C , but no comprehensive or quantitative studies particularly addressing the precision of α I and α A have been conducted to date.…”

Raman spectroscopic evaluation of precision of oxygen isotope ratio of carbon dioxide

“…As for the isotope analysis using micro-Raman spectroscopy, five reports of the relevant literature have described carbon isotope analysis of CO2 (Arakawa et al, 2007;Li et al, 2018;Yokokura et al, 2020;Cui et al, 2021;Wang et al, 2022). One report describes nitrogen isotope analysis of N2 (Yamamoto and Hagiwara, 2022).…”