Methodology: Boron Isotope Analysis
Boron has two naturally occurring isotopes 10B (19.9%) and 11B (80.1%). Due to a relatively large mass difference (10%) between the two isotopes and high volatility, the boron isotope ratio ranges from −70 to +60‰ in natural materials and has been used as a tracer for studying continental weathering, plate subduction processes, pH variability in the oceans and anthropogenic pollution. Boron isotopic ratios are conventionally expressed in delta notation (δ11B), which denotes the deviation of measured 11B/10B ratios from the standard in parts per thousand using the equation below:
Purification: Quantitative recovery of boron from the matrix is required for boron isotope measurements in carbonates and water. Low-blank separation of boron from the matrix is conducted by means of extraction chromatography using boron-specific chelating resin (Amberlite IRA-743) following the method of Giri et al., 2019.
B isotope measurement: Boron isotope measurements are performed with a Neptune Plus multi-collection inductively coupled plasma mass spectrometer (MC-ICP-MS) following the method in Giri et al., 2019.
Giri, S.J.; Swart, P.K.; Pourmand, A., 2019: The influence of seawater calcium ions on coral calcification mechanisms: Constraints from boron and carbon isotopes and B/Ca ratios in Pocillopora damicornis. Earth and Planetary Sciences Letters, vol. 519, pp.130-140.