Nanogram-scale boron isotope analysis through micro-distillation and Nu Plasma 3 MC-ICP-MS

Area of Science:

• Geochemistry
• Paleoceanography
• Analytical Chemistry

Background:

• Boron isotope (δ11B) analysis of marine carbonates is vital for reconstructing past ocean pH and atmospheric pCO2.
• Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS) offers high throughput and ionization efficiency for such analyses.

Purpose of the Study:

• To evaluate the performance of a Nu Instruments Plasma 3 MC-ICP-MS for δ11B measurements.
• To develop and validate a straightforward methodology for nanogram-scale boron isotope analysis.

Main Methods:

• Boron purification from carbonate matrices using micro-distillation (95°C, ≥15h) for high recovery.
• Testing of different sample introduction systems (30, 50, 170 μL min⁻¹) and detector configurations (FC11/FC12, FC12/IC).
• Validation using certified reference materials (JCt-1, JCp-1, RM 8301, ERM-AE121) and in-house standards.

Main Results:

• Achieved low average blank values (14 ± 6 pg) comparable to literature minima.
• The 30 μL min⁻¹ nebuliser system showed superior signal intensity per mass of boron.
• The FC12/IC detector configuration provided accurate results for low boron signals (<0.35 V).
• Validated methodology demonstrated excellent long-term reproducibility for in-house standards.

Conclusions:

• The developed methodology offers a robust and easily adoptable approach for nanogram-scale δ11B analysis.
• This technique enhances the capability to reconstruct past oceanographic conditions using marine archives.
• The study highlights the effectiveness of MC-ICP-MS with optimized introduction and detection systems for precise boron isotope measurements.