Liquid scintillator (LS) is commonly utilized in experiments seeking rare events due to its high light yield, transparency, and radiopurity. The concentration of 238U and 232Th in LS consistently remains below 1 ppq (10−15 g/g), and the current screening result is based on a minimum 20-ton detector. Inductively coupled plasma mass (ICP-MS) spectroscopy is well-regarded for its high sensitivity to trace 238U and 232Th. This study outlines a method for detecting 238U and 232Th in LS at the sub-ppq level using ICP-MS, involving the enrichment of 238U/232Th from the LS through acid extraction. With meticulous cleanliness control, 238U/232Th in approximately 2 kg of LS is concentrated by acid extraction with 0.4 (0.3) pg 238U (232Th) contamination. Three standard adding methods are employed to assess recovery efficiency, including radon daughter, 2,5-diphenyloxazole (PPO), and natural non-existent 233U/229Th. The method detection limit at a 99% confidence level of this approach can reach approximately 0.2-0.3 ppq for 238U/232Th with nearly 100% recovery efficiency.
@article{arxiv.2405.06326,
title = {A practical approach of measuring $^{238}$U and $^{232}$Th in liquid scintillator to sub-ppq level using ICP-MS},
author = {Yuanxia Li and Jie Zhao and Yayun Ding and Tao Hu and Jiaxuan Ye and Jian Fang and Liangjian Wen},
journal= {arXiv preprint arXiv:2405.06326},
year = {2026}
}