The understanding of mechanisms involved in the controlled release of active molecules from the polymer matrix requires the study of hydration phenomenon. Fluorescence and attenuated total reflection Fourier transform infrared (ATR−FTIR) spectroscopies were used to analyze the earlier steps of hydration in acrylic copolymers. The effect of hydration on the anisotropy of the PRODAN fluorescent probe showed a change in the dynamics of the macromolecular chains. By using ATR−FTIR spectroscopy, the structure of dissolved water in polymers was studied. The evolution of this structure was performed as hydration proceeds by band decomposition of the νOH vibration on the basis of the four-state model which allows discriminating bound from free molecules: in the “early” stages of hydration, the water network appears drastically perturbed as compared to that of bulk pure water, this perturbation vanishing in the “later” stages of hydration. Besides, this study reveals that the polymer carbonyl groups constitutes the major water binding sites as it was deduced from their progressive engagement in H bonds in the time course of hydration. The rate and extent of this process was observed to be correlated with the hydrophobicity of polymers. The present findings, obtained on similar time scales from noninvasive techniques, indicate that both dynamic and structural consequences of hydration are correlated in most of the polymers here studied.
of H20-substantially more negative than AH for the solvation of water monomer. Concluding RemarksAn important point to be made from this study is that to describe hydrogen bonding between water and the propylene carbonate solvent, wre have had to use a continuum model, wffiereas for the hydrogen bonding between water molecules in dilute solution, we have had to use a specific chemical association model. The combined infrared and nmr data conclusively eliminate cyclic trimer and suggest that an open dimer is the only
A substantial number of pesticides are still very difficult to analyse in water at the 0.10 µg/L level, the maximum allowable concentration for the quality of water intended for human consumption set by the European Union. Among them are the widely used polar non-selective glyphosate herbicide and its major degradation product AMPA.Several chromatographic methods have been developed for the analysis of glyphosate and AMPA. Methods involving liquid chromatography seem to give better results since glyphosate and AMPA are very polar compounds. The nature of chromatographic phase depends on the detection mode selected. For instance, ionic phases are combined with conductimetric detection [1], mass spectrometry detection [2,3], UV or fluorescence after post-column derivatization with OPA [4], ninhydrin [5,6,7] or Al 3+ -morin reagent [8]. With a precolumn derivatization with 9-fluorenylmethylchloroformate (FMOC-Cl) for instance, reversed phase column may be used before fluorescence or UV detection.A pre-concentration of sample is necessary to reach the limit of quantification of 0.10 µg/L. Without any pre-concentration, the best performances were obtained by LC-MS analysis with a limit of detection (L. The aim of this study was to reach a limit of quantification lower than 0.10 µg/L without any pre-concentration or purification of samples before analysis. The work was oriented along two ways:1. Improvement of a published method involving LCFluorescence analysis after pre-column FMOC derivatization for direct determination of glyphosate and AMPA in water samples at the 0.10 µg/L level that is suitable for monitoring purposes (part I). This choice is explained below.2. Development of a new method based on derivatization of glyphosate and AMPA with fluorogenic reagents. The first results of this work are presented in part II with 4-chloro-7-nitrobenzofurazan reagent.Among the methods described in literature for the analysis of glyphosate and AMPA in water by liquid chromatography, the way of pre-column derivatization along with fluorescence detection was selected because its easy use. Few coupling reagents have been tested: dansyl chloride [10], ptoluenesulfonyl chloride [11,12] Abstract. An analytical method has been developed for the determination of glyphosate herbicide and its metabolite aminomethylphosphonic acid (AMPA) in natural waters to a level of 0.10 µg/L with a good linearity in the range 0.10-2.00 µg/L and coefficients of variation under 20 % for each spiked level. The procedure involves a precolumn derivatization step with 9-fluorenylmethylchloroformate (FMOC-Cl) yielding highly fluorescent derivatives of the analytes which then can be determined by HPLC with fluorescence detection. The method is used for analysis of natural (surface and ground) and treated waters. Matrice effects have been pointed out, particularly the effects of hard ionic content and the effects of chlorine residues into treated waters.
Articles you may be interested inRelaxation and anharmonic couplings of the O-H stretching vibration of asymmetric strongly hydrogen-bonded complexes J. Chem. Phys. 127, 044501 (2007); 10.1063/1.2753840Hydrogen-bonded OH stretching modes of methanol clusters: A combined IR and Raman isotopomer study Refinements on solvation continuum models: Hydrogen-bond effects on the OH stretch in liquid water and methanol EXPERIMENTAL The V OH fundamentals were measured on a Perkin-Elmer model 621 instrument. They were practically the same as their values given in previous publications. The first overtones were measured on a Cary-17 in-
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.