Petersen Sierra V, Schrag Daniel P
Harvard University, Department of Earth and Planetary Sciences, 20 Oxford Street, Cambridge, MA, 02138, USA.
Rapid Commun Mass Spectrom. 2014 Nov 15;28(21):2371-81. doi: 10.1002/rcm.7022.
The measurement of multiply substituted isotopologues of CO2 derived from carbonate has allowed the reconstruction of paleotemperatures from a single phase (CaCO3 ), circumventing uncertainty inherent in other isotopic paleothermometers. Traditional analytical techniques require relatively large amounts of carbonate (3-8 mg per replicate), which limits the applicability of the clumped isotope proxy to certain geological materials such as marine microfossils, commonly used for paleoclimate reconstructions.
Clumped isotope ratio measurements of small samples were made on a new, high-efficiency, dual-reservoir sample-preparation inlet system attached to a Thermo-Finnigan MAT 253 mass spectrometer. Sample gas produced on the inlet is introduced from a 10 mL reservoir directly into the source via a capillary. Reference gas fills an identical 10 mL reservoir installed between the reference bellows and the capillary. The gas pressures in the two reservoirs are initially balanced, and are allowed to decrease together over the run.
Carbonate samples from 1 mg to 2.6 mg produced Δ47 values equivalent to those from the traditional two-bellows method with identical single-sample precision (1 SE = 0.005-0.015‰) and external standard error (SE = 0.006-0.015‰, n = 4-6). The size of sample needed to achieve good precision is controlled by the sensitivity of the mass spectrometer and the size of the fixed reservoirs and adjacent U-trap installed on our inlet.
The high-precision clumped isotope measurements of small aliquots of carbonate obtained in this method allows for the application of this proxy to a wider range of geological sample materials, such as marine microfossils, that until now have been nearly impossible to analyze given sample size limitation.
对源自碳酸盐的二氧化碳多重取代同位素异构体的测量，使得从单一相（碳酸钙）重建古温度成为可能，规避了其他同位素古温度计中固有的不确定性。传统分析技术需要相对大量的碳酸盐（每次重复分析3 - 8毫克），这限制了团簇同位素指标在某些地质材料（如常用于古气候重建的海洋微化石）中的适用性。
在连接到赛默飞世尔科技MAT 253质谱仪的新型高效双储液器样品制备进样系统上，对小样品进行团簇同位素比率测量。进样口产生的样品气从一个10毫升的储液器通过毛细管直接引入离子源。参比气填充安装在参比波纹管和毛细管之间的一个相同的10毫升储液器。两个储液器中的气压最初保持平衡，并在运行过程中一起下降。
1毫克至2.6毫克的碳酸盐样品产生的Δ47值与传统双波纹管法相当，具有相同的单样品精度（1标准误差 = 0.005 - 0.015‰）和外部标准误差（标准误差 = 0.006 - 0.015‰，n = 4 - 6）。实现良好精度所需的样品大小由质谱仪的灵敏度以及我们进样口上安装的固定储液器和相邻U型捕集器的大小控制。
通过该方法获得的小份碳酸盐的高精度团簇同位素测量，使得该指标能够应用于更广泛的地质样品材料，如海洋微化石，而这些材料由于样品大小限制，迄今为止几乎无法进行分析。
