Improvements on high-precision measurement of bromine isotope ratios by multicollector inductively coupled plasma mass spectrometry

• The isobaric interferences in bromine isotope measurements were effectively solved.
• An overall external reproducibility of ±0.1‰ for δ81Br has been achieved.
• Counter cations effect was due to bromine loss and diffusive isotope fractionation.

A new, feasible procedure for high-precision bromine isotope analysis using multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) is described. With a combination of HR mass resolution mode and accurate optimization of the Zoom Optics parameters (Focus Quad: −1.30; Zoom Quad: 0.00), the challenging problem of the isobaric interferences (40Ar38ArH+ and 40Ar40ArH+) in the measurement of bromine isotopes (79Br+, 81Br+) has been effectively solved. The external reproducibility of the measured 81Br/79Br ratios in the selected standard reference materials ranged from ±0.03‰ to ±0.14‰, which is superior to or equivalent to the best results from previous contributions. The effect of counter cations on the Br+ signal intensity and the instrumental-induced mass bias was evaluated as the loss of HBr aerosol in nebulizer and potential diffusive isotope fractionations.

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