Accurate correction for the matrix interference on laser ablation MC-ICPMS boron isotope measurements in CaCO3 and silicate matrices

• Published in: Journal of analytical atomic spectrometry 2021-08, Vol.36 (8), p.1607-1617
• Main Authors: Evans, David, Gerdes, Axel, Coenen, Douglas, Marschall, Horst R, Müller, Wolfgang
• Format: Article
• Language: English
• Subjects: Ablation; Boron; Boron isotopes; Calcium carbonate; Composition; Crystallization; Diameters; Geochemistry; Heterogeneity; High temperature; Interference; Laser ablation; Laser beams; Lasers; Preamplifiers
• ISSN: 0267-9477; 1364-5544
• DOI: 10.1039/d1ja00073j

Knowledge of the boron isotopic composition of natural samples has found wide ranging application in both low and high temperature geochemistry. More recently, the development of boron isotope measurements using highly spatially-resolved analytical techniques is of interest as it is increasingly recognised that many materials are heterogeneous with respect to their boron isotopic composition, and moreover, that this heterogeneity yields valuable information about the environment of formation and/or mechanisms of crystallisation. Here, we build on a recently proposed methodology (Standish et al. [2019] Rapid Commun. Mass Spectrom.33:959) which enables precise and accurate δ11B measurement via LA-MC-ICPMS by accounting for a scattered Ca interference primarily on 10B. We propose minor modifications to this method via the use of 1013 Ω preamplifiers on the Faraday cup of the detector, more precise measurement of the Ca interference, and improved modelling of the shape of this interference correction. This yields single laser spot 2SE precision of ∼0.5‰ with a 70 μm beam (∼7 pg B), ∼1.4‰ with a 40 μm beam (∼2 pg B), and a long-term (1.5 year) intermediate precision in a marble standard with 15 μg g−1 [B] of