Determination of δ11B by HR-ICP-MS from mass limited samples: Application to natural carbonates and water samples

• Published in: Geochimica et Cosmochimica Acta
• Main Authors: Misra, Sambuddha, Owen, Robert, Kerr, Joanna, Greaves, Mervyn, Elderfield, Henry
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2014
• Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems; Planktonic foraminifera
• Online Access: http://eprints.esc.cam.ac.uk/3103/; http://eprints.esc.cam.ac.uk/3103/1/SM.pdf; http://eprints.esc.cam.ac.uk/3103/2/SM.jpg; http://eprints.esc.cam.ac.uk/3103/3/mmcSM.doc; http://www.sciencedirect.com/science/article/pii/S0016703714003949; https://doi.org/10.1016/j.gca.2014.05.047

We present an improved method for accurate and precise determination of the boron isotopic composition (11B/10B) of carbonate and water samples using a mineral acid matrix and HR-ICP-MS. Our method for δ11B determination utilizes a micro-distillation based boron purification technique for both carbonate and seawater matrices. The micro-distillation method is characterized by low blank (?0.01 ng-B) and 99.8 ± 5.7% boron recovery. We also report a new ICP-MS method, performed in a hydrofluoric acid matrix, using a jet interface fitted Thermo® Element XR that consumes <3.0 ng-B per quintuplicate analyses (±0.5‰, 2σ, n = 5). A comparatively high matrix tolerance limit of ?50 ppb Na/K/Mg/Ca characterizes our ICP-MS method. With an extremely low procedural blank (?0.05 ± 0.01 ng-B) the present isotope method is optimized for rapid (\~25 samples per session) analysis of small masses of carbonates (foraminifera, corals) with low boron abundance and small volume water samples (seawater, porewater, river water). Our δ11B estimates of seawater (39.8 ± 0.5‰, 2σ, n = 30); SRM AE-120 (-20.2 ± 0.5‰, 2s, n = 33); SRM AE-121 (19.8 ± 0.4‰, 2s, n = 16); SRM AE-122 (39.6 ± 0.5‰, 2s, n = 16) are within analytical uncertainty of published values. We apply this new method to assess the impacts of laboratory handling induced sample contamination and seawater physio-chemical parameters (temperature, pH, and salinity) on marine carbonate bound δ11B by analyzing core-top planktonic foraminifera samples