中国物理学会高能物理分会第十三届全国粒子物理学术会议（2021）

In order to screen the materials for low background detectors for Jiangmen Underground Neutrino Observatory (JUNO) and future double-beta decay experiments, the natural radioactivity of some related materials requires measurement to sub-ppt level. The inductively coupled plasma mass spectroscopy(ICP-MS) is dedicated used to measure the materials with ultra-low radioactivity due to its high sensitivity to trace amounts of 238U and 232Th.   In this talk, we will introduce the precise measurement of U/Th in different materials using ICP-MS. We have successfully measured the U/Th in acrylic to sub-ppt level by vaporizing, and the method detection limit (MDL) at 99% confidence level can reach 0.04/0.09 ppt for 238U/232Th in acrylic. A co-precipitation approach to determine the sub-ppt level of Th and U in copper is developed using ICP-MS with the MDL reaching ～0.1 ppt 238U in copper. The methods for other materials such as PI、SiO2、Teflon and PFA etc will also be introduced in this talk.