[MTT48-P05] Development of seawater stable Ba isotope analysis by DS-TIMS technique
Keywords:Ba stable isotopes, double spike technique, seawater
The variation of stable Ba isotope ratios in the ocean is on the order of sub-permil. Therefore, detection of the seawater Ba isotope ratio changes requires high-precision analytical technique. In this study, we developed a method to analyze seawater Ba stable isotope composition with high- precision and high-accuracy using double-spike thermal ionization mass spectrometry (DS-TIMS). The spike used in this study was 134Ba-136Ba double spike with 134Ba/136Ba ratio of 2.5. Ba isotope ratios were measured with Thermo Triton TIMS in Kochi Core Center. Mass spectrometric conditions as well as conditions of double-spike data analysis were thoroughly optimized by repeated analysis of Ba reagents (NIST SRM3104a and an in-house reference reagent) to obtain the highest precision from a single dataset. With the optimized analytical conditions, the external precision of the δ138/134Ba value of multiple reagent analyses was +/- 0.01 ‰ (2SD, n = 6). We will also discuss about the remaining issues for seawater analyses.