MONITOOL European project : Ifremer analyzes the adsorbed metals on passive samplers

The main driver of MONITOOL project is to respond to European Directive demands for the assessment of chemical status of transitional and coastal waters, allowing the use of passive sampling devices (PSDs) in a regulatory context, enhancing the implementation of the WFD.

Following the MONITOOL wet sampling campaign, most partners sent their DGT to Ifremer in April 2018. More than 150 DGTs were processed a few days after receipt, then eluates were sent for ICP-MS analysis. The analysis of the results is in progress.

DGT are very simple devices to implement, used to extract and concentrate metal cations in situ. Their use has shown that this approach is applicable for many metallic elements (Ag, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn).

When they are immersed they irreversibly accumulate the most "labile" dissolved metal cations (hydrated ions, mineral complexes, small organic complexes), depending on their concentration in the medium and the immersion time.

Contaminants that are dissolved in water (metal cations) first come into contact with the outer shell of the sampler, made of plastic (polycarbonate protective filter). They then migrate through a diffusion hydrogel and deposit irreversibly on a resin for which the metal cations have a very high affinity (Chelex 100 resin).

After recovery, the resin from each DGT is removed and eluted with nitric acid (1M). The eluate is analyzed by ICP-MS to determine the mass (M) of the various metallic elements accumulated in the resin.

It is the diffusion, controlled by the physical properties of the gel, temperature and metal concentration in the medium to be sampled, that determines the accumulation kinetics on the resin.

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