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 90Sr, 137Cs, and 226Ra 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 90Sr/90Zr interference through the addition of O2 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 137Ba on 137Cs 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 H2 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 γ-ray spectroscopy.

Figure optionsDownload high-quality image (75 K)Download as PowerPoint slideResearch highlights▶ This study showed that an ICP-QMS with a collision/reaction cell offered an efficient way to directly eliminate the isobaric interference between 90Sr and 90Zr with oxygen addition. ▶ In addition, N2O addition caused Ba+ to react, leading to the formation of BaO+ and BaOH+, whereas Cs+ remained unreactive due to its inability to form bonds. ▶ These analytical methods provided a means to directly measure the concentration of 90Sr or 137Cs in a sample with high precision and accuracy and without chemical separation from the matrix. ▶ Extraction chromatography followed by measurements with ICP-SFMS at cooled plasma conditions was shown to eliminate possible isobaric and/or polyatomic interferences with 90Sr, 137Cs, and 226Ra.