Analytical Sciences

A Rapid and Precise Determination of Boron Isotope Ratio in Water and Carbonate Samples by Multiple Collector ICP-MS

Masaharu TANIMIZU,*,** Kazuya NAGAISHI,*** and Tsuyoshi ISHIKAWA**

*Department of Chemistry for Environment, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda 669-1337, Japan
**Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 200 Monobe-Otsu, Nankoku 783-8502, Japan
***Marine Works Japan Ltd., 200 Monobe-Otsu, Nankoku 783-8502, Japan

We developed a method for rapid and precise determination of B isotope ratios by MC-ICP-MS through an optimization of washout method, mass-discrimination correction and chemical separation. Resultant reproducibility of δ¹¹B values was ±0.4‰ (2 × SD) when a simple standard-sample bracketing technique was used, and it was improved to be better than ±0.2‰ by a mass discrimination correction with a ⁷Li/⁶Li isotopic reference. A mixed solution, which consists of HNO₃–HF–mannitol, allowed a rapid washout of B memory in the sample introduction line. The validation of this technique to a wide range of δ¹¹B value and various B signal intensities was confirmed from a series of B reference solutions with δ¹¹B values of –20 to +40‰ and 25 to 125 ng/g B. Analyses of seawater standard (BCR-403) and carbonate standard (JCp-1) with sample sizes of less than 50 ng B gave δ¹¹B values consistent with those determined by TIMS as Cs₂BO₂⁺. The simple and high-precision technique developed here is applicable to various types of commercially supplied multiple collector ICP mass spectrometers without any modification of the sample introduction system from their original instrumental setting.

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