Direct separation of boron from Na- and Ca-rich matrices by sublimation for stable isotope measurement by MC-ICP-MS |
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Authors: | Bo-Shian Wang Kuo-Fang Huang Suresh Kumar Aggarwal Pei-Ying Lin |
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Affiliation: | a Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan b Earth Dynamic System Research Center (EDSRC), National Cheng Kung University, Tainan, Taiwan c Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India |
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Abstract: | An improved technique for precise and accurate determination of boron isotopic composition in Na-rich natural waters (groundwater, seawater) and marine biogenic carbonates was developed. This study used a ‘micro-sublimation’ technique to separate B from natural sample matrices in place of the conventional ion-exchange extraction. By adjusting analyte to appropriate pH, quantitative recovery of boron can be achieved (>98%) and the B procedural blank is limited to <8 pg. An additional mass bias effect in MC-ICP-MS was observed which could not be improved via the standard-sample-standard bracketing or the ‘pseudo internal’ normalization by Li. Therefore a standard other than NBS SRM 951 was used to monitor plasma condition in order to maintain analytical accuracy. An isotope cross-calibration with results from TIMS shows that the space-charge mass bias on MC-ICP-MS can be successfully corrected using off-line mathematical manipulation. Several reference materials, including the seawater IAPSO and two groundwater standards IAEA-B-2 and IAEA-B-3, were used to validate this approach. We found that the δ11B of the reference coral JCp-1 was 24.22 ± 0.28‰, corresponding to seawater pH based on the coral δ11B-pH function. |
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Keywords: | Boron isotope Micro-sublimation MC-ICP-MS Mass bias |
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