High precision determination of 228Ra and 228Ra/226Ra isotope ratio in natural waters by MC-ICPMS

A new methodology has been developed for precise and accurate determination of 228Ra and the radium isotope ratio (228Ra/226Ra) by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) in natural water. The method was tested on waters from Lake Kinneret (The Sea of Galilee) and saline springs that flow into it.The radium is pre-concentrated from 60 L of Lake Kinneret water (or 2 L of the saline springs water) by co-precipitation with MnO2. The separation of radium from the matrix elements was conducted by BioRad® AG50W-X8 and Sr Spec® resins. The instrumental limit of detection for 226Ra and 228Ra was 5 fg mL−1 (0.05 ppq) or 0.1 and 30 dpm L−1, respectively, and the absolute limit of detection 0.005 fg. Internal precision of the radium isotope ratio (228Ra/226Ra) in Lake Kinneret for 228Ra concentration as low as 0.10 fg L−1 (0.06 dpm L−1) was 2.8% (2σ) and external precision was 10% (2σ, n = 9).

Ion signal of 228Ra and 226Ra in Lake Kinneret (The Sea of Galilee), northern Israel measured by MCICPMS. Upper left corner: Areal photo of the lake.Figure optionsDownload high-quality image (110 K)Download as PowerPoint slide