Clarisse Mariet

Ripening of catanionic aggregates upon dialysis.

We have studied the dialysis of surfactant mixtures of two oppositely charged surfactants (catanionic mixture) by combining HPLC, neutron activation, confocal microscopy, and NMR. In mixtures of n-alkyl trimethylammonium halides and n-fatty acids, we have demonstrated the existence of a specific ratio between both surfactant contents (anionic/cationic almost equal to 2:1) that determines the morphology, the elimination of ions, and the elimination of the soluble cationic surfactant upon dialysis. In mixtures prepared with lower anionic surfactant contents, ill-defined aggregates are formed, and dialysis quickly eliminates the ion pairs (H+X-) formed upon surfactant association and also the cationic surfactant until a limiting 2:1 ratio is reached. By contrast, mixtures prepared above the anionic/cationic 2:1 ratio form micrometer-sized vesicles resistant to dialysis. These closed aggregates retain a significant number of ions (30%) over 1000 hours, and dialysis is unable to eliminate the soluble surfactant. The interactions between surfactants have been estimated by measuring the partitioning of the CTA molecules between the catanionic bilayer, the bulk solution, and mixed micelles when they exist. The mean extraction free energy per CTA in the membrane has been found to increase by 1 kBT to 2 kBT as the soluble surfactant is depleted from the bilayer, which is enough to stop the dialysis. The vesicles produced above the anionic/cationic 2:1 ratio are formed by frozen bilayers and are resistant to extensive dialysis and therefore show an interesting potential for encapsulation as far as durability is concerned.

Relevance of NH4F in acid digestion before ICP-MS analysis.

In order to implement a simpler, less expensive and more safe sample dissolution procedure, we have substituted the HF-HClO(4) mixture by NH(4)F. By testing three certified reference materials, lichen 336, basalt BE-N, soil 7, it was found that the three-reagents digestion without HF and HClO(4) (HNO(3)+H(2)O(2)+NH(4)F was used) was very effective for the pretreatment of ICP-MS measurement. The comparison was based on the measurement results and their uncertainties. All are reference material for amount contents of different trace elements. The accuracy and precision of the developed method were tested by replicate analyses of reference samples of established element contents. The accuracy of the data as well as detection limits (LODs) vary among elements but are usually very good (accuracy better than 8%, LODs usually below 1 microg/g in solids). ICP-MS capabilities enable us to determine routinely 13 and 16 minor and trace elements in basalt and soil.

Heavy metal bioaccumulation by the bryophyte Scleropodium purum at three French sites under various influences: rural conditions, traffic, and industry

An active biomonitoring of the heavy metals pollution experiment was undertaken by means of the bryophyte species Scleropodium purum transplanted at three different sites exposed to rural, traffic, or industrial influences. Concentrations of about 40 elements in S. purum were determined by instrumental neutron activation analysis and inductively coupled plasma mass spectrometry. Accumulation rates of heavy metals were determined in the three sites. These accumulation rates in polluted sites were matched together and also to those recorded at the rural site. The changes of the accumulation rate of heavy metals in S. purum versus their concentrations in PM10 particles simultaneously collected above show some different accumulation properties of S. purum according to elements and sites. S. purum has a weak efficiency in the three sites to accumulate elements like V, Cr, Cu, Zn, As, Se, Sb, and Pb originating from atmospheric hot sources generally enriched in particulates matter (PM10), whereas it is particularly high for Br, Th, and Rb. For other elements, Co, La, Ce, and Hf, and rare earth elements, Fe, Sr, Nb, Ti, Al, and Sc, the collection efficiency by S. purum is intermediate. In the industrial site Dunkerque, a magnification of the collection efficiency by S. purum for elements originating from steel and aluminum productions and petroleum refinement suggests that these metals could be enriched in coarse particles with a better accumulation by the bryophyte with respect to PM10.

Potential of ion imprinted polymers synthesized by trapping approach for selective solid phase extraction of lanthanides

Ion imprinted polymers (IIPs) specific to lanthanides were synthesized using neodymium ions (Nd3+) as template ions. Nd3+ ions form binary complex ions with 5,7-dichloroquinoline-8-ol (DCQ) or vinylpyridine (VP), or ternary complex ions with both DCQ and VP in 2-methoxyethanol, before copolymerization in the presence of styrene and divinylbenzene as monomer and cross-linker, respectively. DCQ was expected to be trapped in the synthesized polymers pores. The template ion removal was then optimized. For the first time, the DCQ leakage was determined by HPLC-UV during the template removal and the sedimentation steps before solid-phase extraction (SPE) packing. It was observed that the trapped DCQ was unfortunately lost in significant amounts, up to 51%, and that this amount varied from one synthesis to another. The grinded and sieved polymers were next packed in SPE cartridges. The study of the SPE profiles obtained with the IIPs synthesized either with the binary or the ternary complex confirmed the prominent role of DCQ on the selectivity of an IIP by comparison with a non-imprinted polymer (NIP), i.e. a polymer synthesized under the same conditions as those of the IIP but without template ions. The influence of the porogenic solvent on the selectivity was also investigated by replacing 2-methoxyethanol by acetonitrile or dimethylsulfoxyde (DMSO). The polymers synthesized in DMSO led to the most repeatable results when elution solutions with a gradual decrease in pH were percolated through the cartridge. This is why DMSO was used to optimize the SPE protocol in order to maximize the difference of extraction yield between the IIP and the NIP, i.e. promoting a selective retention on the IIP. A value of about 30% was obtained for La3+, Ce3+, Nd3+, and Sm3+. Nevertheless, with the optimized SPE protocol, IIPs from different syntheses did not have the same SPE behavior, which may result from different random leakages of DCQ. This demonstrates for the first time the main limitation of the IIPs synthesized in bulk with the trapping approach for their use in SPE.

A PIXE and ICP-MS Analysis of Metallic Atmospheric Contaminants in Tree Bark Tissues, A Basis for Biomonitoring Uses∗

The qualitative and quantitative metallic content of tree barks of Argania spinosa (L.) Skeels were studied. Argania spinosa is an endemic species in Morocco. This tree is adapted to semi-arid climates and exposed to specific conditions of relative humidity, temperature, wind, and particle transport. Three sites were sampled in Morocco: the large town of Rabat, the harbor of Agadir, and Aït Baha, a countryside location exposed to continuous desert wind. The methodologies included (1) in situ microanalysis with proton-induced X-ray emission (PIXE) and (2) trace element determinations by mass spectrometry with inductively coupled plasma (ICP-MS) associated with extraction procedures. Both methods allowed detection of elements coming from different bark compartments. The profile of airborne contaminants in the barks was typical of the sampling sites. The level of lead in barks sampled in Rabat reached 100 ng cm−2, or higher, while it varied between 3 and 35 ng cm−2 in Aït Baha. The in situ study of the microscopic structure of the bark provided the location of major and minor elements at various depths inside the bark. A differential between free deposit on the bark surface and penetrated content was found for the major and trace elements. The free deposit on the bark surface was suspected to be mostly the result of recent contamination. Part of the contaminants spread out on the surface penetrated the superficial suber. This long-term accumulation affected mostly Pb. In deeper levels, airborne elements at low concentrations and elements resulting from root uptake were concurrently present and resulted in a complex situation, as noted for zinc.

Photochemical Synthesis and Versatile Functionalization Method of a Robust Porous Poly(ethylene glycol methacrylate-co-allyl methacrylate) Monolith Dedicated to Radiochemical Separation in a Centrifugal Microfluidic Platform

The use of a centrifugal microfluidic platform is an alternative to classical chromatographic procedures for radiochemistry. An ion-exchange support with respect to the in situ light-addressable process of elaboration is specifically designed to be incorporated as a radiochemical sample preparation module in centrifugal microsystem devices. This paper presents a systematic study of the synthesis of the polymeric porous monolith poly(ethylene glycol methacrylate-co-allyl methacrylate) used as a solid-phase support and the versatile and robust photografting process of the monolith based on thiol-ene click chemistry. The polymerization reaction is investigated, varying the formulation of the polymerisable mixture. The robustness of the stationary phase was tested in concentrated nitric acid. Thanks to their unique “easy-to-use” features, centrifugal microfluidic platforms are potential successful candidates for the downscaling of chromatographic separation of radioactive samples (automation, multiplexing, easy integration in glove-boxes environment, and low cost of maintenance).