Optimization of collision/reaction gases for determination of 90Sr in atmospheric particulate matter by inductively coupled plasma tandem mass spectrometry after direct introduction of air via a gas-exchange device

Nuclear power plant accidents release radioactive strontium 90 (Sr-90) into the environment. Monitoring of 90Sr, although important, is difficult and time consuming because it emits only beta radiation. We have developed a new analytical system that enables real-time analysis of Sr-90 in atmospheric particulate matter with an analytical run time of only 10 min. Briefly, after passage of an air sample through an impactor, a small fraction of the sample is introduced into a gas-exchange device, where the air is replaced by Ar. Then the sample is directly introduced into an inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) system equipped with a collision/reaction cell to eliminate isobaric interferences on Sr-90 from Zr-90(+), (YH+)-Y-89-H-1, and Y-90(+). Experiments with various reaction gas conditions revealed that these interferences could be minimized under the following optimized conditions: 1.0 mL min(-1) O-2,10.0 mL min(-1) H-2, and 1.0 mL min(-1) NH3. The estimated background equivalent concentration and estimated detection limit of the system were 9.7 x 10(-4) and 3.6 x 10(-4) ng m(-3), respectively, which are equivalent to 4.9 x 10(-6) and 1.8 x 10(-6) Bq cm(-3). Recoveries of Sr in PM2.5 measured by real-time analysis compared to those obtained by simultaneously collection on filter was 53 +/- 23%, and using this recovery, the detection limit as PM2.5 was estimated to be 3.4 +/- 1.5 x 10(-6) Bq cm(-3). That is, this system enabled detection of Sr-90 at concentrations < 5 x 10(-6) Bq cm(-3) even considering the insufficient fusion/vaporization/ionization efficiency of Sr in PM2.5. (C) 2017 Elsevier B.V. All rights reserved.