Measuring the stable isotope compositions of atmospheric CO₂ is common in earth and atmospheric sciences, and various analytical methods have been developed utilizing continuous‐flow (CF) or dual‐inlet (DI) isotope ratio mass spectrometry (IRMS). Air is typically collected via passive, manual, or automated collection methods and the volume of the air sample ranges from 10 to 300 mL for CF‐IRMS to >1 L for DI‐IRMS to yield a measurable amount of atmospheric CO₂ gas. It has been determined that the integrity of vials and flasks for air sample storage can be compromised after 3 days of air collection for δ¹³C values and within 10 hours for δ¹⁸O values. Air samples must be purified after collection to remove constituents of air, such as Ar, O₂, N_2, N₂O and water vapor, to avoid isobaric interferences during mass spectrometric measurement. Purification is generally undertaken by utilizing commercial or custom made preconcentration devices, the Blanking method for CF‐IRMS, or an offline/online cryogenic separation using a vacuum line for DI‐IRMS. Ambient N₂O is a component of air that may affect analytical results and thus must either be corrected for or be removed using a gas chromatographic column. In some cases, water is removed during air collection by using a common chemical desiccant, magnesium perchlorate (Mg (ClO₄)₂) or by a dry ice‐alcohol mixtures (‐78 °C). Lastly, a linearity issue for IRMS due to the low amount of purified CO₂ from a typical ambient air sample must be considered. In general, analytical precisions of 0.02 – 0.21 ‰ and 0.04 – 0.34 ‰ for CF‐IRMS and 0.01 – 0.02 ‰ and 0.01 – 0.02 ‰ for DI‐IRMS are expected for δ¹³C and δ¹⁸O measurements, respectively.

中文翻译：

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同位素比质谱法（IRMS）测量大气中CO2的碳氧同位素组成的技术

测量大气中CO ₂的稳定同位素组成在地球和大气科学中很常见，并且已经开发了多种利用连续流（CF）或双入口（DI）同位素比率质谱（IRMS）的分析方法。通常通过被动，手动或自动收集方法收集空气，空气样品的体积范围从CF-IRMS的10到300 mL到DI-IRMS的> 1 L，以产生可测量量的大气CO ₂气体。它已经确定，小瓶和瓶用于空气样品存储的完整性可以后空气收集3天被破坏为δ ¹³ C值，并在10小时的时间δ ¹⁸O值。采集后必须净化空气样品，以去除空气成分，例如Ar，O ₂，N _2， N ₂ O和水蒸气，以避免质谱测量期间的等压干扰。纯化通常通过使用商业或定制的预浓缩设备，CF‐IRMS的消隐方法或使用DI‐IRMS真空线的离线/在线低温分离来进行。N ₂ O是空气中的一种成分，可能会影响分析结果，因此必须通过气相色谱柱进行校正或除去。在某些情况下，使用普通的化学干燥剂高氯酸镁（Mg（ClO ₄）₂）或干冰酒精混合物（‐78°C）。最后，必须考虑由于典型环境空气样本中净化的CO ₂量少而导致的IRMS线性问题。在0.02一般而言，分析精度- 0.21‰，0.04 - 0.34‰为CF-IRMS和0.01 - 0.02‰，0.01 - 0.02‰，DI-IRMS预计为δ ¹³ C和δ ^18次ö测量，分别。