A robust methodology for high precision isotopic analysis of boron by thermal ionization mass spectrometry using Na2BO2+ ion

A detailed study to develop a robust methodology for determining 11B/10B isotope ratio using sodium metaborate (Na2BO2+) in positive thermal ionisation mass spectrometry (P-TIMS) was performed. Different parameters of sample preparation and sample loading procedure, using single tantalum filament assembly, were optimized and their effects on ion intensity and precision in isotope ratio were evaluated. A comparative evaluation of precision achievable using Na2CO3 and NaCl to adjust the B/Na mole ratio in the sample was also carried out. This was done to confirm the robustness of the approach for analysing different kinds of sample matrices e.g., solids and solutions which require chemical purification and pre-concentration prior to TIMS analysis. NIST isotopic reference material SRM-951 with 11B/10B isotope ratio of 4.044 ± 0.003 was used for various experiments. Loading of boron in the form of boromannitol complex along with sodium carbonate (for solid samples) and with NaCl (for solutions) on the graphite coated single tantalum filament assembly was found to give high precision (better than 1‰) in the isotope ratios using 500 ng to 1 μg of boron. The results were not influenced by variations in the B/Na mole ratio, which is an important aspect of using this methodology for analyzing unknown samples. Robustness of the developed methodology is demonstrated by analyzing solid samples as well as solutions for boron isotopic composition.

A detailed study to develop a robust methodology for determining 11B/10B isotope ratio using sodium metaborate (Na2BO2+) in positive thermal ionisation mass spectrometry (P-TIMS) was performed.Figure optionsDownload as PowerPoint slide