Isotope ratio measurements have been conducted on a series of isotopically distinct pure CO₂ gas samples using the technique of dual-inlet isotope ratio mass spectrometry (DI-IRMS). The influence of instrumental parameters, data normalization schemes on the metrological traceability and uncertainty of the sample isotope composition have been characterized. Traceability to the Vienna PeeDee Belemnite(VPDB)-CO₂ scale was realized using the pure CO₂ isotope reference materials(IRMs) 8562, 8563, and 8564. The uncertainty analyses include contributions associated with the values of iRMs and the repeatability and reproducibility of our measurements. Our DI-IRMS measurement system is demonstrated to have high long-term stability, approaching a precision of 0.001 parts-per-thousand for the 45/44 and 46/44 ion signal ratios. The single- and two-point normalization bias for the iRMs were found to be within their published standard uncertainty values. The values of ¹³C/¹²C and ¹⁸O/¹⁶O isotope ratios are expressed relative to VPDB-CO₂ using the \( {\delta}^{13}{C}_{VPDB-{CO}_2} \) and \( {\delta}^{18}{O}_{VPDB-{CO}_2} \) notation, respectively, in parts-per-thousand (‰ or per mil). For the samples, value assignments between (−25 to +2) ‰ and (−33 to −1) ‰ with nominal combined standard uncertainties of (0.05, 0.3) ‰ for \( {\delta}^{13}{C}_{VPDB-{CO}_2} \) and \( {\delta}^{18}{O}_{VPDB-{CO}_2} \), respectively were obtained. These samples are used as laboratory reference to provide anchor points for value assignment of isotope ratios (with VPDB traceability) to pure CO₂ samples. Additionally, they serve as potential parent isotopic source material required for the development of gravimetric based iRMs of CO₂ in CO₂-free dry air in high pressure gas cylinder packages at desired abundance levels and isotopic composition values.

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已经使用双入口同位素比质谱法（DI-IRMS）对一系列同位素不同的纯CO ₂气体样品进行了同位素比测量。表征了仪器参数，数据归一化方案对样品同位素计量学可追溯性和不确定性的影响。使用纯CO ₂实现了对维也纳PeeDee Belemnite（VPDB）-CO ₂规模的可追溯性同位素参考材料（IRM）8562、8563和8564。不确定度分析包括与iRM值以及测量值的可重复性和可重复性相关的贡献。我们的DI-IRMS测量系统具有很高的长期稳定性，对于45/44和46/44离子信号比，其精度达到0.001千分之几。发现iRM的单点和两点归一化偏差在其已发布的标准不确定性值之内。的值¹³ C / ¹² C和¹⁸ O / ¹⁶氧同位素比率相对表达以VPDB-CO ₂使用\（{\增量} ^ {13} {C} _ {{VPDB- CO} _2} \）和\（{\ delta} ^ {18} {O} _ {VPDB- {CO} _2} \）表示法分别以千分之一（‰或per mil）为单位。对于这些样本，\（{\ delta} ^ {13} {C}的标称组合标准不确定度为（0.05，0.3）‰时，在（−25至+2）‰和（−33至-1）‰之间进行值分配分别获得_ {VPDB- {CO} _2} \和\（{\ delta} ^ {18} {O} _ {VPDB- {CO} _2} \）。这些样品用作实验室参考，为同位素比值（具有VPDB可追溯性）与纯CO ₂样品的值分配提供定位点。此外，它们还可作为潜在的母体同位素来源材料，用于开发基于重量分析的CO ₂在CO _2中的iRM。高压气瓶包装中的无干燥空气处于所需的丰度水平和同位素组成值。

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