Calcium Isotopic Fractionation during Ion‐Exchange Column Chemistry and Thermal Ionisation Mass Spectrometry (TIMS) Determination |
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| Authors: | Hong L Zhu Zhao F Zhang Gui Q Wang Yu F Liu Fang Liu Xin Li Wei D Sun |
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| Institution: | 1. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China;2. University of Chinese Academy of Sciences, Beijing, China;3. Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China;4. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing, China |
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| Abstract: | Significant isotopic fractionation can occur during column chemistry and determination by mass spectrometry. Improper correction may produce uncertainties in the isotopic composition of geological samples. We investigated calcium isotopic fractionation during these two processes and set up a model to check data quality. The δ44/40Ca915a value of IAPSO seawater in different Ca cuts (e.g., 0–20, 20–40, 40–60, 60–80 and 80–100%) on column chemistry ranged from ~ 4‰ to 0‰. The more Ca was eluted, the lower the δ44/40Ca915a value of the elution was found. The isotopic fractionation of calcium on the column appeared to follow the exponential law. However, TIMS instrumental fractionation during Ca runs did not always follow the exponential law due to mixing effects from sample reservoirs on the filament. Our results show that errors could be caused if the instrumental fractionation deviates from the exponential law, especially when the fractionation degree is large. To improve the measurement uncertainty, a model is proposed to check the behaviour and degree of instrumental fractionation, which will provide a quick and reasonable verdict on the data quality of TIMS runs. |
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| Keywords: | Ca isotopes isotopic fractionation column chemistry
TIMS
data quality isotopes du Ca fractionnement isotopique chimie sur colonne TIMS qualité des donné es |
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