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Theses in progress

Development of highly selective solid phase extraction media for studying migration processes of radioactive contaminants into the environment

Host laboratory: Research Laboratory on the Future of the Radioactive Sites Pollution (LELI)​

Beginning of the thesis: October 2018

Student name: Marine BOUDIAS

Subject description

In recent decades, human activities (atmospheric nuclear testing, nuclear accidents, uranium mining) have released many artificial and natural radionuclides onto the Earth's surface. Although their abundance is extremely low, their presence in the different compartments of the biosphere can lead to chronic exposures of humans and the environment, the consequences of which need to be assessed. Among these radionuclides, Ra-226 and Cs-137 occupy a special place from a radiological point of view. Due to their chemical properties, their metabolic pathways are similar to those of calcium and potassium, respectively, and can thus increase the internal dose. Therefore, there is a need to better understand the biogeochemical dynamics and transfer processes of these radionuclides between the different compartments of the biosphere.

Samples taken from transfer areas are often small volumes with very complex matrices and concentrations of Ra-226 and Cs-137 close to instrumental detection limits. Direct analysis of these samples by mass spectrometry may encounter obstacles such as small sample quantities, insufficient detection limits, the impact of spectral interference, or large matrix effects. For this, separation and preconcentration of the sample prior to analysis is necessary. These protocols are often tedious, time-consuming, lead to poor recovery rates and are not suitable for small volume samples. For this reason, the development of new analytical techniques is necessary, allowing the selective extraction of target elements from their matrix in order to purify and pre-concentrate them. These new techniques must be capable of handling small sample volumes, of the order of pL.

One of the objectives of the thesis is to test for the first time the feasibility of manufacturing highly selective supports based on ion-printed polymer technology for the separation and preconcentration of radium and caesium in natural samples. In parallel, a second approach will consist in grafting the surface of a solid support with a macrocycle-type extractant molecule, highly specific for the targeted ions. The best of the two approaches (ion fingerprints or macrocycle-type molecules) will then be miniaturized in order to be able to analyze small volumes of samples, of the order of pL. After optimization of the extraction protocol, applications to real samples will be carried out.


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