Method for 90Sr Analysis in Environmental Samples Using Thermal Ionization Mass Spectrometry with Daly Ion-Counting System

In this work, a new 90Sr analysis method was developed using the Isotopx Ltd., Phoenix X62 thermal ionization mass spectrometer (TIMS). Excellent ion beam sensitivity was demonstrated with the detection of 1 mBq (0.2 fg) 90Sr on a Daly ion-counting system. The abundance sensitivity for the 90Sr/88Sr ratio was 2.1 × 10–10, and this could ensure measurement of 100 Bq·kg–1 (19 fg·g–1) 90Sr in an environmental sample with 100 μg·g–1 stable strontium concentration. For analytical method validation, 90Sr was determined in two certified reference materials, for example, wild berry (IRMM-426) and freshwater lake sediment (NIST-4354), for the first time in the history of TIMS. This mass spectrometry method is faster than conventional radiometric techniques; however, interference from 90Zr and peak tailing on the higher mass side from 88Sr must be considered for a reliable 90Sr determination.