New ICP-MS/MS Method Developed to Detect Low Levels of Radioactive Contamination in the Environment

A team of researchers in Orsay, France, have developed a new method for detecting low levels of radioactive contamination in the environment (1). The team created a new inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS) method that can measure the ¹³⁵Cs/¹³⁷Cs isotopic ratio, which is a powerful tool for tracing the origin of radioactive contamination.

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The ¹³⁵Cs/¹³⁷Cs ratio is unique to the source of radiocesium; therefore, it can provide information about contamination origin. For example, the ratio can distinguish between radiocesium released from nuclear power plants and that released from nuclear weapons testing. The ¹³⁵Cs/¹³⁷Cs ratio is used to determine the source of radiocesium in the environment. Measuring this ratio is particularly important in the aftermath of nuclear accidents or incidents. Additionally, knowing the ¹³⁵Cs/¹³⁷Cs ratio can help researchers better understand the transport and behavior of radiocesium in the environment, which can aid in developing remediation strategies. The accurate measurement of this ratio can also help assess the impact of radioactive contamination on human and environmental health.

The ¹³⁵Cs/¹³⁷Cs ratio has previously been measured in highly contaminated environmental matrices, such as those collected near nuclear accident exclusion zones and former nuclear test areas. However, there have been few measurements of the ratio at environmental levels (<1 kBq/kg) because of the challenges associated with measuring such low levels of radiocesium content while dealing with large mass interferences.

To overcome these challenges, the researchers developed a highly selective procedure for Cs extraction/separation combined with the efficient mass spectrometry measurement of ca. 100 g of soil. Their ICP-MS/MS method uses N₂O, He, and NH₃ in the collision-reaction cell to achieve a powerful suppression of ¹³⁵Cs and ¹³⁷Cs interferences. By adjusting the flow rates of these gases, the team achieved a high Cs sensitivity of more than 1.105 cps/(ng/g) and low background levels at m/z 135 and 137 lower than 0.6 cps.

To verify the accuracy of their method, the team analyzed two certified reference materials (IAEA-330 and IAEA-375) commonly used in the literature as validation samples and three sediment samples collected in the Niida River catchment (Japan) impacted by the Fukushima fallout. The results showed that their method was highly accurate and effective in detecting low levels of radioactive contamination in environmental samples.

The development of this new ICP-MS/MS method is an important step in detecting low levels of radioactive contamination in the environment. The ability to accurately measure the ¹³⁵Cs/¹³⁷Cs isotopic ratio will help researchers trace the origin of radioactive contamination and better understand its impact on the environment and human health.

Reference

(1) Magre, A.; Boulet, B.; Isnard, H.; Mialle, S.; Evrard, O.; Pourcelot, L.Innovative ICP-MS/MS Method To Determine the ¹³⁵Cs/¹³⁷Cs Ratio in Low Activity Environmental Samples. Anal. Chem. 2023, ASAP. DOI: 10.1021/acs.analchem.3c00207