Effect of Aging on Phosphorus Speciation in Surface Deposit of a Vertical Flow Constructed Wetland

International audienceThis study was conducted to determine phosphorus (P) species captured in a vertical-flow constructed wetland (VFCW) system combining a trickling filter followed by FeCl3 injection for phosphate coagulation. Suspended solids (SS) thus formed accumulated over time at the VFCW surface and transformed into a sludge deposit layer, which was shown to concentrate most of the P captured in the system. In order to investigate the effect of aging on P species, representative SS and sludge samples were taken from a wastewater treatment plant that had been in operation for 8 years and analyzed using P fractionation, solution 31P NMR spectroscopy and P and Fe K-edge XANES spectroscopy. A partial mineralization of organic matter was shown by comparing organic carbon contents of SS and sludge materials. Chemical fractionations combined with P and Fe K-edge XANES spectroscopy showed that P was predominantly bound to iron within both samples in the form of ferric phosphate, rather than adsorbed onto ferric oxyhydroxide. Calcium-bound P was more significantly observed in sludge than in SS, suggesting that aging induced the recombination of part of the organic and iron-bound P species into calcium-bound forms, as a possible consequence of the partial mineralization of organic matter

Gold electrodes modified with molecular imprinted acrylate polymer for impedimetric determination of testosterone

International audienceA moleculary imprinted polymer (MIP) sensor was developed for impedimetric detection of testosterone. 4,4'-azobis(4-cyanovaleric acid) initiator was first grafted onto a gold electrode modified by a self-assembled monolayer of thiolamine (11-amino-1-undecanethiol). Methacrylic acid and ethylene glycol dimethacrylate were prepolymerized by photo-polymerization in presence of testosterone as template and then spincoated and polymerized on the functionalized electrode surface. The different steps of MIP sensor fabrication were controlled using electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy and time of flight-secondary ion mass spectrometry. After template removal, the biosensor response, expressed as the variation of charge transfer resistance at the electrode/electrolyte interface measured by EIS, increased linearly with testosterone concentration up to 50 µg.L-1. The sensitivity was 0.28 per log C for testosterone, while it was only 0.0085 and 0.020 for methyltestosterone and 17b-estradiol, respectively. A very good limit of detection (103 ng.L-1) was achieved for testosterone. The sensitivity of the non imprinted polymer sensor, prepared the same way but in absence of template, was 18 times lower than that obtained with the MIP

Gold Electrodes Modified with Molecular Imprinted Acrylate Polymer for Impedimetric Determination of Testosterone

A moleculary imprinted polymer (MIP) sensor was developed for impedimetric detection of testosterone. 4,4’-azobis(4-cyanovaleric acid) initiator was first grafted onto a gold electrode modified by a self-assembled monolayer of thiolamine (11-amino-1-undecanethiol). Methacrylic acid and ethylene glycol dimethacrylate were prepolymerized by photo-polymerization in presence of testosterone as template and then spincoated and polymerized on the functionalized electrode surface. The different steps of MIP sensor fabrication were controlled using electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy and time of flight-secondary ion mass spectrometry. After template removal, the biosensor response, expressed as the variation of charge transfer resistance at the electrode/electrolyte interface measured by EIS, increased linearly with testosterone concentration up to 50 µg.L-1. The sensitivity was 0.28 per log C for testosterone, while it was only 0.0085 and 0.020 for methyltestosterone and 17b-estradiol, respectively. A very good limit of detection (103 ng.L-1) was achieved for testosterone. The sensitivity of the non imprinted polymer sensor, prepared the same way but in absence of template, was 18 times lower than that obtained with the MIP

Unexpected Structure of a Helical N 4 -Schiff-Base Zn(II) Complex and Its Demetallation: Experimental and Theoretical Studies

International audienceA new Zn‐N4‐Schiff base L=((±)‐trans‐N,N’‐Bis(2‐aminobenzylidene)‐1,2‐diaminocyclohexane) complex was synthesized and fully characterized, showing an unexpected self‐assembled double‐stranded helicate structure. The X‐ray crystal analysis of the Zn2L2 complex ((C40H44N8Zn2,CH2Cl2, a=14.2375(3) Å, b=16.7976(4) Å, c=16.1613(4) Å, monoclinic, P21/n, Z=4) shows a centrosymmetrical structure in which zinc atoms are in distorted tetrahedral environments, revealing an M‐ (R, R) left‐handed helicity in its asymmetric unit. However, it was observed that this dinuclear complex is thermodynamically unstable in the presence of small water amounts and undergoes demetallation into free N4‐Schiff base ligand and ZnO nanoparticles. This hydrolysis process was thoroughly identified and monitored through detailed 1H NMR, DOSY NMR analysis. The reaction mechanism of this demetallation event was elucidated by using the DFT method, involving an activation energy smaller than 13 kcal/mol. Besides, a theoretical mechanism of the demetallation process is given for the first time

Thermal stability and degradation of thermally stable prepolymers under controlled atmosphere IV. Thermal stability and degradation of cross-linked systems prepared from cyanate monomers

International audienceWe report the results of a study on the thermal degradation of cyanate prepolymers and corresponding materials prepared in the molten state by the homopolymerization of monomers in a controlled atmosphere (nitrogen) and in the temperature range of 100 to 500degreesC. We propose degradation mechanisms for these materials based on the analysis of physicochemical data obtained by the differential scanning calorimetry, thermogravimetric analysis, gas chromatography-mass spectrometry and Fourier transform infrared spectroscopy of volatile organic compounds and residues after the thermal cycle. These mechanisms depend on the structure of the carbon skeleton

Polymère à empreinte moléculaire: synthèse, caractérisation et étude de la capacité d'extraction de la testostérone dans des matrices aqueuses

International audienc

Study of Prepolymerization Complex Formation in the Synthesis of Steroid-Based Molecularly Imprinted Polymers

International audienceThe preparation of steroid-based molecularly imprinted polymers (MIPs) based upon noncovalent interaction is particularly suited for selective capture of steroid hormones in biological and environmental samples. The success of this method lies in the optimization of the interaction between steroids (template) and methacrylic acid (functional monomer) in the prepolymerization mixture. NMR techniques coupled with DFT calculations were used to evaluate the capacity of the methacrylic acid to bind a steroid for future applications. The androstane derivative steroids considered in the present study have two functional groups at C3 and C17, which may interact with the methacrylic acid. These can be hydroxyl or ketone groups. Experimental results show that the steroids can be divided in three groups corresponding to the ketone type at C3, the H-bond strength increasing with the number of double bonds. DFT calculations are in very good agreement with experimental results, showing increasing binding energy from no bonds, a single bond, and two double bond steroids. For steroids holding a hydroxyl group the binding energy obtained in the solvent model is comparable to the binding energy of single bond ketone steroids

Phenolic resins (II) - Influence of the chemical structure of high molecular weight molecules and on the mechanisms of cross-linking and on the final structure of the resins

International audienceThe physicochemical characterization of the structures of the oligomers (n < 4) in resols has been carried out by fragmenting monomers in LC/UV/MS andLC/LJV/MS/MS. Fragmentation mechanisms are related to the numbers and positions of substituents on the aromatic ring and to the types of oligomer junctions. It was more difficult to determine the structures of phenol hemiacetals and dimer berniacetals because of the large number of position isomers. The resols were prepared with differing molar ratios R = Formaldehyde/Phenol and catalysts. They were cross-linked using two industrially recommended heat cycles. The progression of resin cross-linking was determined by solid state C-13 NMR (CP/MAS). The residual percentage of monomers and oligomers at n < 4 was determined in leachates (water and methanol) and characterized by LC/UV/MS. The results for cross-linking advancement were correlated with the various synthesis parameters (ratio R, type of catalyst and heat cycle)