Comparing the capability of collision/reaction cell quadrupole and sector field inductively coupled plasma mass spectrometers for interference removal from 90Sr, 137Cs, and 226Ra

Here we report a quantitative comparison of sector field inductively coupled plasma mass spectrometry (ICP-SFMS) and collision/reaction cell inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) for the detection of Sr-90, Cs-137, and Ra-226 at ultra-trace levels. We observed that the identification and quantification of radioisotopes by ICP-MS were hampered by spectral (both isobaric and polyatomic ions) and non-spectral (matrix effect) interferences. ICP-QMS has been used to eliminate the isobaric Sr-90/Zr-90 interference through the addition of O-2 into the collision cell as a reactant gas. Zr+ ions were subsequently converted into ZrO+, whereas Sr+ ions were not reactive. In addition, the isobaric interference of Ba-137 on Cs-137 was eliminated by the addition of N2O gas in the cell, which led to the formation of BaO+ and BaOH+ products, whereas Cs+ remained unreactive. Furthermore, He and H-2 were used in the collision/reaction cell to eliminate polyatomic ions formed at m/z 226. A comparison of the results obtained by ICP-SFMS after a chemical separation of Sr from Zr and Cs from Ba was performed. Finally, to validate the developed analytical procedures, measurements of the same samples were performed by gamma-ray spectroscopy. (C) 2010 Elsevier B.V. All rights reserved.