Fosu Benjamin R, Ghosh Prosenjit, Mishra Divya, Banerjee Yogaraj, K Prasanna, Sarkar Amrita
Centre for Earth Sciences, Indian Institute of Science, Bangalore, 560012, India.
Divecha Centre for Climate Change, Indian Institute of Science, Bangalore, 560012, India.
Rapid Commun Mass Spectrom. 2019 Jan 30;33(2):203-214. doi: 10.1002/rcm.8304.
Acid digestion of carbonates to release CO is a crucial and sensitive step in sample preparation for clumped isotope analysis. In addition to data reduction and instrumental artefacts, many other uncertainties in the clumped isotope analysis of carbonates arise from the method used for the preparation of CO . We describe here an in-house-designed reaction vessel that circumvents degassing and contamination problems commonly associated with the McCrea-type digestion protocols.
We designed a leak-free break seal reaction vessel (made of Pyrex™) suitable for prolonged acid digestion at 25°C. Using this new vessel, several carbonate reference materials widely used in the clumped isotope community and other in-house laboratory standards were acid-digested and analysed for their δ C, δ O and Δ values with a dual inlet MAT 253 isotope ratio mass spectrometer following standard gas chromatography purification and data evaluation protocols.
Long-term reproducibility in Δ determination was established using international references and in-house working standards as follows (mean and SE): Carrara-1 (0.395 ± 0.002‰, n = 43), Carrara-2 (0.441 ± 0.003‰, n = 22), OMC (0.587 ± 0.004‰, n = 16), NBS 19 (0.393 ± 0.005‰, n = 10), NBS 18 (0.473 ± 0.003‰, n = 5), ETH 1 (0.271 ± 0.005‰, n = 7), ETH 3 (0.698 ± 0.005‰, n = 3), MZ (0.715 ± 0.002‰, n = 3) and several others.
A new method using a break seal tube was found to be efficient for the clumped isotope analysis of carbonates that require longer reaction time at 25°C. This method yields good precision in Δ analysis and was found to be suitable for acid digestions at any desired temperature.
碳酸盐的酸消解以释放CO是团簇同位素分析样品制备中的关键且敏感步骤。除了数据处理和仪器假象外，碳酸盐团簇同位素分析中的许多其他不确定性源于用于制备CO的方法。我们在此描述一种自行设计的反应容器，该容器可以避免通常与麦克雷型消解方案相关的脱气和污染问题。
我们设计了一种无泄漏的破裂密封反应容器（由派热克斯玻璃制成），适用于在25°C下进行长时间的酸消解。使用这个新容器，对团簇同位素领域广泛使用的几种碳酸盐参考物质以及其他内部实验室标准进行酸消解，并按照标准气相色谱纯化和数据评估方案，用双入口MAT 253同位素比率质谱仪分析它们的δC、δO和Δ值。
使用国际参考物质和内部工作标准，在Δ测定中建立了长期重现性，如下所示（平均值和标准误差）：卡拉拉-1（0.395±0.002‰，n = 43），卡拉拉-2（0.441±0.003‰，n = 22），OMC（0.587±0.004‰，n = 16），NBS 19（0.393±0.005‰，n = 10），NBS 18（0.473±0.003‰，n = 5），ETH 1（0.271±0.005‰，n = 7），ETH 3（0.698±0.005‰，n = 3），MZ（0.715±0.002‰，n = 3）以及其他几种。
发现一种使用破裂密封管的新方法对于需要在25°C下更长反应时间的碳酸盐团簇同位素分析是有效的。该方法在Δ分析中具有良好的精密度，并且发现适用于在任何所需温度下的酸消解。
