Skierszkan E K, Amini M, Weis D
Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, 2020-2207 Main Mall, Vancouver, V6T 1Z4, Canada,
Anal Bioanal Chem. 2015 Mar;407(7):1925-35. doi: 10.1007/s00216-014-8448-6. Epub 2015 Feb 5.
The isotopic double-spike method allows for the determination of stable isotope ratios by multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) with accuracy and precision in the range of ∼0.02 ‰ amu(-1), but its adoption has been hindered by the perceived difficulties in double-spike calibration and implementation. To facilitate the implementation of the double-spike approach, an explanation of the calibration and validation of a (97)Mo-(100)Mo double-spike protocol is given in more detail than has been presented elsewhere. The long-term external standard reproducibility is 0.05 ‰ on δ(98/95)Mo measurements of standards. δ(98/95)Mo values for seawater and U.S. Geological Survey (USGS) reference materials SDO-1 and BCR-2 measured in this study are 2.13 ± 0.04 ‰ (2 SD, n = 3), 0.79 ± 0.05 ‰ (2 SD, n = 11), and -0.04 ± 0.10 ‰ (2 SD, n = 3) relative to the NIST-SRM-3134. The double-spike method corrects for laboratory and instrumental fractionation which are not accounted for using other mass bias correction methods. Spike/sample molar ratios between 0.4 and 0.8 provide accurate isotope measurements; outside of this range, isotope measurements are inaccurate but corrections are possible when standards and samples are spiked at a similar ratio.
同位素双稀释剂法可通过多接收电感耦合等离子体质谱仪（MC-ICP-MS）测定稳定同位素比率，其准确度和精密度范围约为0.02‰ amu⁻¹，但由于人们认为双稀释剂校准和实施存在困难，该方法的采用受到了阻碍。为便于实施双稀释剂方法，本文对⁹⁷Mo-¹⁰⁰Mo双稀释剂方案的校准和验证进行了比其他地方更详细的解释。标准物质δ⁹⁸/⁹⁵Mo测量的长期外部标准重现性为0.05‰。本研究中测量的海水以及美国地质调查局（USGS）参考物质SDO-1和BCR-2的δ⁹⁸/⁹⁵Mo值相对于NIST-SRM-3134分别为2.13±0.04‰（2SD，n = 3）、0.79±0.05‰（2SD，n = 11）和-0.04±0.10‰（2SD，n = 3）。双稀释剂法可校正实验室和仪器分馏，而其他质量偏倚校正方法无法考虑这些因素。稀释剂/样品摩尔比在0.4至0.8之间可提供准确的同位素测量结果；超出此范围，同位素测量不准确，但当标准物质和样品以相似比例加标时可进行校正。
