Automation of boron chromatographic purification for δ¹¹B analysis of coral aragonite

Abstract

Rationale:To detect the small changes in past pH , the boron isotope ratio of coral carbonates, expressed as the δ 11 B value, needs to be both precise and accurate (2sd <<1‰). Boron measurements by Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) require the boron to be carefully purified before analysis, which is time consuming, and requires specialist training. Here, we use the prepFAST-MC method that enables the automatic extraction of B (up to 25 ng load) from a CaCO 3 matrix.Methods: Samples were purified using the prepFAST-MC automated system with ã 25-μL column of Amberlite IRA743 resin. Boron isotope measurements were performed by MC-ICPMS. The effects of matrix load, speed of sample loading onto the column, and blank contamination were tested to evaluate the effects on the purification process. The optimised protocol was tested on various standards and samples of aragonite corals. Results:The blank contribution for the approach is~60 pg and is negligible given our sample size (<0.2% sample size). Efficiency of matrix removal is demonstrated with the addition of up to 1.6 mg of dissolved low-B calcium carbonate to NIST SRM 951 with no impact on the accuracy of δ 11 B values. The Japanese Geological Survey Porites reference material JCp-1, boric acid standard NIST SRM 951, and seawater, all processed on the prepFAST-MC system, give δ 11 B values within error of literature values (δ 11 B JCp-1 = 24.31 ± 0.20‰ (2sd, n = 20); δ 11 B NIST 951 = −0.02 ± 0.15‰ (2sd, n = 13) and δ 11 B Seawater = 39.50 ± 0.06‰ (2sd, n = 2)). Results obtained from the coral Siderastrea siderea purified with the prepFAST-MC system show an average offset from the manual ion-exchange protocols of Δδ 11 B = 0.01 ± 0.28‰ (2sd, n = 12). Conclusions:Our study demonstrates the capacity of the prepFAST-MC method to generate accurate and reproducible δ 11 B values for a range of materials, without fractionation, with efficient matrix removal and with negligible blank contribution.

A Rapid, Simple, and Low‐Blank Pumped Ion‐Exchange Column Chromatography Technique for Boron Purification From Carbonate and Seawater Matrices

“…In contrast, the peri-column yields TPBs of 11 ± 16 pg of boron (n = 33), which are less variable and smaller in size. These results are similar to those reported by de la Vega et al ( 2020) using prepFAST-MC (de la Vega et al, 2020) and substantially smaller than the previously designed peri-column method where solutions are in contact with the peristaltic pump tubing (Wei et al, 2014).…”

“…[Ca] in the purified samples were all below 0.1% of the amount loaded onto columns (Figures 2a and 2b). This indicates that both methods demonstrated similar and effective matrix element removal, consistent with the literature (Chen et al, 2016;de la Vega et al, 2020;Foster, 2008;Guerrot et al, 2011).…”

“…Currently, most commonly used methods for boron purification are based on ion exchange, gravity column chromatography (Foster, 2008; Foster et al., 2013; Gutjahr et al., 2021; Stewart et al., 2021), and to a lesser extent microsublimation (Buisson et al., 2021; Misra et al., 2014; Rodríguez‐Díaz et al., 2024), batch method (Douville et al., 2010; Lécuyer et al., 2002), and pumped chromatography systems (de la Vega et al., 2020; Wei et al., 2014). The benefit of traditional ion exchange gravity column chromatography techniques lies in the generation of accurate and precise boron isotope data (Gutjahr et al., 2021; Stewart et al., 2021).…”

Comparison of Implicit and Explicit Solvent Approaches in Ab Initio Evaluation of Thermochemistry in Solution: Application in Studying Boron Isotope Fractionation in Water

“…Additionally, the equilibrium of boron species in seawater also plays a key role in studying and reconstruction of ancient seawater pH and atmospheric pCO 2 via analysis of boron isotopic ratios in marine shell fossils. − To that end, an accurately determined equilibrium constant of the following isotope exchange reaction between aqueous boric acid and borate ( k 3–4 ): normalB false( OH false) 3 + normalB false( OH false) 4 − ⇆ 11 10 normalB false( OH false) 3 + normalB false( OH false) 4 − 10 11 is of central importance and has been the subject of numerous studies discussed in the following. As the other more recent applications of studying the equilibrium between boron isotopes in water, we can refer to the identification of nitrate pollution sources and elucidation of shale weathering in the critical zone …”

Accurate and precise determination of the boron isotope ratio by QQQ-ICP-MS: application to natural waters and carbonates

“…Additionally, the composition and uniformity of the distillate matrix play a critical role in a possible ICP-MS matrix mismatch between the sample and bracketing standard. Traditionally boron is separated from matrix elements through ion exchange chromatography with a boron specic Amberlite resin 14,15,25,34,35,54,55,63 or by micro-distillation processes. 32,56 In the present study we have utilized the microdistillation method and have improved upon the existing protocol.…”