Improved radiocesium purification in low-level radioactive soil and sediment samples prior to 135Cs/137Cs ratio measurement by ICP-MS/MS

The Cs-135/Cs-137 isotopic ratio allows to characterize the potential sources of radioactive contamination in the environment. This ratio is usually determined in highly contaminated environmental samples by combining selective radiochemistry with mass spectrometry measurement. In contrast, few data are available at the environmental level of Cs-137 (< 1 kBq.kg(-1)) due to the occurrence of interferents (Ba, Mo, Sb and Sn) in the mass range of interest and due to the very few radiocesium atoms. To obtain enough radiocesium from an environmental material with low levels of radioactivity, a large sample must be analyzed. In the present work, a new method of Cs extraction and purification has been developed allowing for the first time to analyze 100 g of ash of soil or sediment in only one week. The achieved chemical performances are excellent with a Cs-137 recovery yield from soil and sediment samples, deduced from gamma spectrometry, above 80% and decontamination factors of 1.4 x 10(7), 5.7 x 10(4), 2.3 x 10(5) and 1.5 x 10(4) for Ba, Mo, Sb and Sn respectively.

Automated summary

The Cs-135/Cs-137 isotopic ratio is used to characterize the sources of radioactive contamination in the environment. Existing data for Cs-137 at environmental levels are limited due to interferents and low concentrations. This study developed a new method for extracting and purifying Cs, allowing for analysis of large samples of soil or sediment ash. The method showed excellent chemical performance, with high decontamination factors for interferents.