NIST RM 8301 Boron Isotopes in Marine Carbonate (Simulated Coral and Foraminifera Solutions): Inter‐laboratory δ¹¹B and Trace Element Ratio Value Assignment

Abstract

The boron isotopic ratio of 11B/10B (δ11BSRM951) and trace element composition of marine carbonates are key proxies for understanding carbon cycling (pH) and palaeoceanographic change. However, method validation and comparability of results between laboratories requires carbonate reference materials. Here, we report results of an inter‐laboratory comparison study to both assign δ11BSRM951 and trace element compositions to new synthetic marine carbonate reference materials (RMs), NIST RM 8301 (Coral) and NIST RM 8301 (Foram) and to assess the variance of data among laboratories. Non‐certified reference values and expanded 95% uncertainties for δ11BSRM951 in NIST RM 8301 (Coral) (+24.17‰ ± 0.18‰) and NIST RM 8301 (Foram) (+14.51‰ ± 0.17‰) solutions were assigned by consensus approach using inter‐laboratory data. Differences reported among laboratories were considerably smaller than some previous inter‐laboratory comparisons, yet discrepancies could still lead to large differences in calculated seawater pH. Similarly, variability in reported trace element information among laboratories (e.g., Mg/Ca ± 5% RSD) was often greater than within a single laboratory (e.g., Mg/Ca < 2%). Such differences potentially alter proxy‐reconstructed seawater temperature by more than 2 °C. These now well‐characterised solutions are useful reference materials to help the palaeoceanographic community build a comprehensive view of past ocean changes.

Surface pH Record (1990–2013) of the Arabian Sea From Boron Isotopes of Lakshadweep Corals—Trend, Variability, and Control

“…Additionally, we measured the boric acid standard, European Reference Materials (ERM) AE121 during each analytical session. The long‐term average of δ 11 B of AE‐121 is 19.69‰ ± 0.28‰ (2σ, n = 20) (Figure ), which agrees well with the recently reported value within their uncertainty based on the compilation of five reputed laboratories (19.64‰ ± 0.17‰; Stewart et al., 2021); thereby, validating the robustness of our analytical method.…”

“…The coral reference standard JCp‐1 is not commercially available in India due to the Convention on International Trade in Endangered Species of Wild Fauna and Flora import restriction, thus, we were unable to process matrix match carbonate standard through micro‐distillation technique. An alternate matrix match inorganic reference material, NIST RM 8301 is now commercially available (Stewart et al., 2021), however, these data sets were generated much before the standard became commercially available. We have micro‐distilled seawater standard, NASS6 in each batch and measured δ 11 B during each analytical session.…”

Sub‐Permil Interlaboratory Consistency for Solution‐Based Boron Isotope Analyses on Marine Carbonates

“…Due to changes in CITES regulations (i.e., Convention on International Trade in Endangered Species of Wild Fauna and Flora ; http://www.cites.org), neither of these biogenic carbonate materials are currently available for international distribution by the Geological Survey of Japan, but they remain common reference materials in many laboratories (e.g., Farmer and Hönisch 2016, Lazareth et al 2016, Raddatz et al 2016, Stewart and Anagnostou 2016, Jurikova et al 2019). Efforts are ongoing to find suitable replacements, and two isotope standard solutions artificially produced with carbonate matrices (NIST RM 8301 (coral) and NIST RM 8301 (foram)) will soon become available as consistency reference materials for boron isotopic and trace metal isotope studies (Stewart et al 2020).…”

Dichotomy between Regulation of Coral Bacterial Communities and Calcification Physiology under Ocean Acidification Conditions

“…The accuracy and precision of δ 11 B results were assessed using carbonate standards NIST RM 8301 Coral and JCp-1. Measured values for these reference materials during sample analysis were, respectively, 24.35‰ ± 0.26‰ (2 standard deviations; n = 34) and 24.06‰ ( n = 2), which were within uncertainty of interlaboratory consensus values ( 83 , 86 ). Seven total procedural blank measurements were made alongside samples in this study (average of 104 pg of boron).…”

“…The limit of detection for each element for each run was determined as three standard deviations above the mean of the blanks. The percent relative standard deviation was calculated for each elemental ratio from replicate measurements ( n = 37) of a matrix-matched control material (NIST RM 8301 Coral) to assess analytical precision ( 83 ). The majority of the measured trace elements had an uncertainty of ≤±2% (Li/Ca, Al/Ca, Na/Ca, Mg/Ca, Co/Ca, Cu/Ca, Rb/Ca, Sr/Ca, Cd/Ca, Sb/Ca, Ba/Ca, Nd/Ca, Pb/Ca, and U/Ca), with B/Ca, Fe/Ca, Ni/Ca, and Zn/Ca ≤ ±5% and V/Ca, Mn/Ca, and Mo/Ca ≤ ±10%.…”