气体同位素比值质谱仪

仪器介绍：Thermo Scientific 253 Plus 10 kV 同位素比质谱仪是 MAT 253 系列的全面升级版，专为团簇同位素、极低丰度及超微量样品的高精度测量而设计。其核心是 10 kV IRMS 技术平台，通过重新设计的磁体、离子光学和镀金全金属密封结构，将峰形、稳定性与信噪比推向新高度；新型10¹³ Ω放大器能显著降低放大器噪声，使m/z 47、48等极弱离子束也能被更准确测量，为 Δ₄₇、Δ₄₈等团簇同位素研究提供可靠数据。支持O₂、CO₂等气体连续流或双路模式进样分析。仪器集成Isodat软件，可自动完成数据采集，满足从常规稳定同位素到前沿团簇同位素的全面需求，是当今灵敏度、线性度和精度最高的气体同位素比质谱仪之一。

碳酸盐团簇同位素实验室目前配置有全自动微量碳酸盐装置（Kiel Ⅳ）、自主研发的离线手动CO₂气体纯化线、半自动离线CO₂气体纯化线和全自动在线碳酸盐酸解和气体纯化系统。具有CO₂平衡气体和碳酸盐固体标准制备和分析能力。目前储备有常规碳酸盐碳氧同位素标准如NBS-19和NBS-18，团簇同位素标准如IAEA-C1、IAEA-C2、GU-1和一系列自主合成的碳酸钡实验室内部标准。目前主要实现的测试项目有：1）微量（50~150 μg）方解石、文石碳氧同位素分析；2）常量（5~10 mg）方解石、文石、白云石团簇同位素分析。

收费标准：4000元/样；测试事宜请联系仪器管理员。

测试要求：单次酸解测量样品量为8~10 mg（以CaCO₃为准），粉末需充分研磨，手捏无颗粒感；生物样明确含有机质时，建议采用优级纯5%次氯酸钠粉末浸泡后离心清洗，样品上样前需45摄氏度烘干48小时以上，具体方法参考Fiebig et al. 2024; 粉末样品需明确矿物相，如提供XRD扫线数据，尤其是混合相样品，以方便氧同位素酸解校正；样品数据主要使用经ETH国际标准校准后的C1，C2，和实验室内部监控碳酸盐参考物质进行处理，并以I-CDES90标尺输出数据。校正过程利用47.5半杯信号结合实验室内部背景处理Python代码进行仪器线性校正，并采用D47Crunch程序处理，全流程误差传递控制。本实验室目前碳酸盐Δ₄₇和Δ₄₈的长期重现性（2 SE; n > 10）分别优于0.010‰和0.040‰。

建议阅读文献：

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Dennis, K.J., Affek, H.P., Passey, B.H., Schrag, D.P.Eiler, J.M., 2011. Defining an absolute reference frame for ‘clumped’ isotope studies of CO2. Geochim. Cosmochim. Acta 75, 7117-7131.

Fernandez, A., Muller, I.A., Rodriguez-Sanz, L., van Dijk, J., Looser, N.Bernasconi, S.M., 2017. A Reassessment of the Precision of Carbonate Clumped Isotope Measurements: Implications for Calibrations and Paleoclimate Reconstructions. Geochemistry Geophysics Geosystems 18, 4375-4386.

Bernasconi, S.M., Muller, I.A., Bergmann, K.D., Breitenbach, S.F.M., Fernandez, A., Hodell, D.A., Jaggi, M., Meckler, A.N., Millan, I.Ziegler, M., 2018. Reducing Uncertainties in Carbonate Clumped Isotope Analysis Through Consistent Carbonate-Based Standardization. Geochem. Geophys. Geosyst. 19, 2895-2914.

Fiebig, J., Bajnai, D., Löffler, N., Methner, K., Krsnik, E., Mulch, A.Hofmann, S., 2019. Combined high-precision ∆48 and ∆47 analysis of carbonates. Chem. Geol. 522, 186-191.

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