Procedures for precise measurements of 135Cs/137Cs atom ratios in environmental samples at extreme dynamic ranges and ultra-trace levels by thermal ionization mass spectrometry

TALANTA

卷:174

Article

Dunne, James A.^1,2  Richards, David A.^1,2  Chen, Hsin-Wei^1,3 

[1] Univ Bristol, Bristol Isotope Grp, Bristol, Avon, England

[2] Univ Bristol, Sch Geog Sci, Univ Rd, Bristol BS8 1SS, Avon, England

[3] Univ Bristol, Dept Earth Sci, Queens Rd, Bristol BS8 1RJ, Avon, England

关键词: Radiocaesium;    TIMS;    Interferences;    Scattered Cs-133(+);   

DOI  :  10.1016/j.talanta.2017.06.033

来源: Elsevier

【 摘 要 】

Determination of Cs-135/Cs-137 atom ratios has the potential to be a powerful tool for nuclear forensics and monitoring environmental processes. We present optimized chemical separation techniques and thermal ionization mass spectrometry (TIMS) protocols to obtain precise Cs-135/Cs-137 atom ratios for a range of environmental sample types. We use a combination of double AMP-PAN separation and Sr-spec resin column purification to yield excellent separation from the alkali metals (Rb separation factor > 600), which normally suppress ionization of Cs. A range of emission activators for the ionization of Cs were evaluated and glucose solution yielded the optimal combination of a stable Cs+ beam, minimal low-temperature polyatomic interferences and improved ionization efficiency. Mass-spectrometric determination of low abundance Cs-135 and Cs-137 is compromised by the presence of a very large Cs-133(+) beam, which may be scattered and cause significant spectral interferences. These are explored using multi-static Faraday cup ion counter methods and a range of energy filter settings. The method is evaluated using environmental samples and standards from regions affected by fallout from Chernobyl (IAEA-330) and Fukushima nuclear disasters. Where the intensity of Cs-133(+) is large relative to Cs-135(+) and Cs-137(+) (< 30 cps), minor polyatomic interferences need to be considered. In the absence of a standard with (CS)-C-135, 137/(CS)-C-133 < 1 x 10(-8), we explored the reproducibility of Cs-135/Cs-137 atom ratios at these high dynamic ranges and extremely low abundance (Cs-137 approximate to 12 fg g(-1)) for sediments from an estuarine setting in SW England, UK.

【 授权许可】

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