Epov V.N.,CNRS Institute of Analytical Sciences
Physical Chemistry Chemical Physics | Year: 2011
A novel approach is suggested to investigate the mechanisms of chemical complexation reactions based on the results of Fujii with co-workers; they have experimentally observed that several metals and metalloids demonstrate mass-independent isotope fractionation during the reactions with the DC18C6 crown ether using solvent-solvent extraction. In this manuscript, the isotope fractionation caused by the magnetic isotope effect is used to understand the mechanisms of chemical exchange reactions. Due to the rule that reactions are allowed for certain electron spin states, and forbidden for others, magnetic isotopes show chemical anomalies during these reactions. Mass-independent fractionation is suggested to take place due to the hyperfine interaction of the nuclear spin with the electron spin of the intermediate product. Moreover, the sign of the mass-independent fractionation is found to be dependent on the element and its species, which is also explained by the magnetic isotope effect. For example, highly negative mass-independent isotope fractionation of magnetic isotopes was observed for reactions of DC18C6 with SnCl2 species and with several Ru(iii) chloro-species, and highly positive for reactions of this ether with TeCl6 2-, and with several Cd(ii) and Pd(ii) species. The atomic radius of an element is also a critical parameter for the reaction with crown ether, particularly the element ions with [Kr]4d n5sm electron shell fits the best with the DC18C6 crown ring. It is demonstrated that the magnetic isotope effect in combination with the theory of orbital hybridization can help to understand the mechanism of complexation reactions. The suggested approach is also applied to explain previously published mass-independent fractionation of Hg isotopes in other types of chemical exchange reactions. © the Owner Societies 2011.
Krimm I.,CNRS Institute of Analytical Sciences
MedChemComm | Year: 2012
In the fragment-based drug design approach, methods for rapid identification of the ligand-binding site are essential. The INPHARMA experiment, a ligand-observed NMR experiment based on the nuclear Overhauser effect, is tested here with fragment-like molecules and the glycogen phosphorylase enzyme that contain multiple binding sites. The results illustrate the potential of the method for the FBDD process and demonstrate that the INPHARMA experiment is particularly useful to study the binding specificity of the fragments and to assess the ligand binding mode in the presence of a reference ligand. © 2012 The Royal Society of Chemistry.
Karamanis P.,CNRS Institute of Analytical Sciences |
Pouchan C.,CNRS Institute of Analytical Sciences
Journal of Physical Chemistry C | Year: 2013
A study about the size-dependence of the hyperpolarizability-enhancement observed in metal-functionalized finite graphene species is presented. The reported ab initio and density functional results suggest that edge-passivation of graphene fragments with metallic agents (in this case Li) triggers an impressive enhancement of the second hyperpolarizability at the static limit. However, such a trend holds only in small graphene-type fragments. Strong evidence is provided showing that the specific effect drastically weakens with increasing the size of the graphene fragments regardless of their shape. The observed hyperpolarizability-enhancement in small systems and its severe decrease with increasing the size of the graphene species is qualitatively explained in terms of their charge transfer polarization mechanism. © 2013 American Chemical Society.
Polotsky A.A.,RAS Institute of Macromolecular Compounds |
Plamper F.A.,RWTH Aachen |
Borisov O.V.,CNRS Institute of Analytical Sciences
Macromolecules | Year: 2013
We present a theory of a conformational collapse-to-swelling transition that occurs in aqueous dispersions of multiresponsive (pH- and thermoresponsive) microgels upon variation of ionic strength, temperature, or pH. Our theory is based on osmotic balance arguments and explicitly accounts for ionization equilibrium inside microgel partices. The theory predicts complex patterns in the dependence of the microgel particle dimensions on the control parameters: An increase in temperature leads to worsening of the solvent quality for the gel forming LCST-polymers and to concomitant decrease in the dimensions of the gel particles. This collapse of the gel particles provoked by an increase in temperature occurs either smoothly (at high or low ionic strength), or may exhibit a jump-wise character at intermediate ionic strength. The theory further predicts that the degree of swelling of microgel particles varies nonmonotonously and exhibits a maximum as a function of salt concentration at a pH close to the pK. This nonmonotonous variation of the particle dimensions occurs continuously at temperatures below or slightly above LCST (good or marginal poor solvent strength conditions, respectively), whereas at higher temperatures the jump-wise swelling of the gel particles is followed by either continuous or jump-wise collapse induced by progressive increase in the salt concentration. A decrease/increase in pH leads to deswelling of the weak polyacid/polybase gel particles, which occurs smoothly at temperatures below LCST, but may exhibit a discontinuity above LCST. These theoretical predictions can be used for design of smart stimuli-responsive microgels. © 2013 American Chemical Society.
Determination of 136 pharmaceuticals and hormones in sewage sludge using quick, easy, cheap, effective, rugged and safe extraction followed by analysis with liquid chromatography-time-of-flight-mass spectrometry
Peysson W.,CNRS Institute of Analytical Sciences |
Vulliet E.,CNRS Institute of Analytical Sciences
Journal of Chromatography A | Year: 2013
The aim of this study was to develop an analytical method for the analysis of a wide range of hormonal steroids and pharmaceutical compounds in sewage sludge. Thus, 136 substances were selected, including 119 pharmaceuticals and 17 hormonal steroids. An innovative sample preparation procedure based on the quick, easy, cheap, effective, rugged and safe (QuEChERS) method was developed. The analysis was then performed using liquid chromatography coupled with time-of-flight mass spectrometry. This analytical procedure was validated by evaluating the specificity, quadratic curve fitting, recovery, reproducibility and limits of detection and quantification. The method allows the analysis of the majority of the target compounds with limits of detection ranging from 1. ng/g to 2500. ng/g, depending on the nature of the substance. The protocol was then successfully applied to various types of sludge (limed, digested, dried, liquid and composted) collected in several sewage works in France. Among the target compounds, 34 were quantified at levels up to 6000. ng/g. Among the most commonly detected pharmaceuticals were the antiemetic domperidone (mean concentration 769. ng/g) and the antiepileptic lamotrigine (mean concentration 31. ng/g) whose presence had, to our knowledge, never been shown in sludge. © 2013 Elsevier B.V.