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Ultra-trace determination of 135Cs/137Cs isotopic ratio by thermal ionization mass spectrometry with application to Fukushima marine sediment samples

Abstract

The isotopic ratio of 135Cs/137Cs has been highlighted as a useful long-term tracer for radioactive contamination source identification after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. Determination of this ratio in environmental samples is still challenging due to the extremely low levels (< 1 pg g-1) of 135Cs and 137Cs. When applying TIMS for the analysis of 135Cs/137Cs, the main problems come from the ion ionization depression effect caused by the sample matrix elements and the ionization inhibitor (Rb). Moreover, isobaric and polyatomic species generate interfering signals at the interested masses. Therefore, chemical separation procedure with high separation factors for the matrix and interfering elements needs to be established. In this work, we reported a novel method for the determination of 135Cs/137Cs isotopic ratio in environmental samples. A combination of single AMP-PAN column separation and an ion exchange chromatography purification were used for sample preparation. High separation factors (104-108) for major matrix and interfering elements (Ca, Fe, Mg, Na, Ba etc.) were achieved. The separation of Cs and Rb (separation factor > 500) made the ion ionization depression effect of Cs negligible. This method was capable for the measurement of isotopic ratios of radiocesium at femtogram levels. The measurement precision for 135Cs/137Cs ratios were mostly better than 10% for samples contained as low as 10 fg 137Cs. Reference materials were measured and the results were compared with literature values. This method was successfully applied for the measurement of 135Cs/137Cs isotopic ratios in the marine sediments collected in the western North Pacific after the FDNPP accident for radioactive assessment in the marine environment.

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Publication details

The article was received on 05 Nov 2018, accepted on 07 Dec 2018 and first published on 07 Dec 2018


Article type: Paper
DOI: 10.1039/C8JA00380G
Citation: J. Anal. At. Spectrom., 2018, Accepted Manuscript
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    Ultra-trace determination of 135Cs/137Cs isotopic ratio by thermal ionization mass spectrometry with application to Fukushima marine sediment samples

    W. Bu, L. Tang, X. Liu, Z. Wang, M. Fukuda, J. Zheng, T. Aono, S. Hu and X. Wang, J. Anal. At. Spectrom., 2018, Accepted Manuscript , DOI: 10.1039/C8JA00380G

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