An Evaluation of High Performance Liquid Chromatography-UV for the Multi-Residue Analysis of Organophosphorous Pesticides in Environmental Water

Abstract

In this study isocratic high performance liquid chromatography in the reversed-phase mode (RP-8 or RP-18 column) with UV-detection (254 nm), was evaluated for the analysis, directly or after extraction, of organophosphorous pesticides in environmental water.

Fifteen pesticides were studied and good resolution was obtained for eight by direct analysis of a multi-residue water sample. Reproducibility in terms of retention times was found to be very good. Linear calibration curves were obtained down to 0.5ng/μL (3 ng injected) with a coefficient of variation near 10%. The limit of quantitation for direct analysis was found to be 0.5mg/L (3ng) in water. However, by extraction with methylene chloride or ethyl acetate and concentration of the extract some of the pesticides could be determined at 0.5 μg/L (ppb) in water.     

Core–shell and gradient morphology polymer particles analyzed by X‐ray photoelectron spectroscopy: Effect of monomer feed order

The synthesis of composite latex particles possessing core–shell and gradient morphologies, respectively, using seeded starve‐fed semibatch emulsion polymerization of styrene (St) and methyl methacrylate (MMA) is presented. The focus is on the effect of the monomer feed order on the particle morphology development. The particle morphology is assessed using a novel approach which entails comparing the experimental surface composition as a function of polymerization time (particle growth) obtained by X‐ray photoelectron spectroscopy with the predicted surface composition using a mass balance mathematical model. Both types of composite latexes (core–shell and gradient) feature changes with polymerization time in the oxygen/carbon surface composition which enables one to track the morphology development. Differential scanning calorimetry is also implemented to analyze the extent of phase separation. The monomer feed order is shown to play a crucial role—under the present conditions, gradient and core–shell particles are obtained if the feed order is St/MMA (St fed first), but not if the feed order is reversed. These findings illustrate that thermodynamic factors are important, given that thermodynamically it is more favorable for MMA‐rich chains to occupy the oil–water interface to reduce the interfacial tension. Systems where St is the second stage monomer lead to mixed structures rather than the targeted core–shell or gradient morphology with St‐rich chains at the particle surface. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2513–2526     

A Cobalt Film Electrode for Nitrite Determination in Natural Water

In this study a cobalt film electrodeposited on a copper disk (Ø=3.1 mm) was tested as electrode to measure nitrite ions in raw water. This electrode was able to determine the nitrite ions concentration in nondeaerated synthetic media and in natural water. The electrode reached a detection limit of 0.2 μmol L^?1 and has a linear concentration range of 0.4 to 2 μmol L^?1 NO₂^?. The influence of several ions such as NO₃^?, Cl^?, SO₄^2?, Mg²⁺, HCO₃^? and NH₄⁺ was also tested. The electrode was used to determine the concentration of nitrite ions in a real sample.     

Diastereoselective synthesis of polyfunctionalized piperidines as precursors of dopamine transporter imaging agents

The design and synthesis of a new kind of precursors of radiolabelled tracer agents for dopamine transporters imaging is described. The concept is based on the possibility of introducing the radioelement far from the sites of recognition and on the fact that only the labelled marker could cross the blood brain barrier to reach the dopamine transporters. For this purpose, a polyfunctionalized piperidine was synthesized bearing two aldehyde functions in the configuration allowing the formation of a tropane analog after the introduction of complexing moieties and complexation of a radioactive metal.     

Thermal hardening and structure of a phosphorus containing cementitious model material

The reaction of phosphoric acid with wollastonite has been studied for reaction mixtures with a molar ratio r=P/Ca from 0.39 up to 2.9. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) reveal the formation of the crystalline products brushite (when r is smaller than 1.4) and monetite and calcium dihydrogenphosphate monohydrate (when r is above 1). Magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) and FTIR show that amorphous silica is also formed which contains some residual calcium and hydroxyl groups. The proposed reactions are confirmed by the evolution of the reaction enthalpy measured with differential scanning calorimetry (DSC). The reaction was monitored with temperature modulated DSC (TMDSC) and dynamic mechanical analysis (DMA). The sharp increase of the elasticity modulus coincides with the onset of decrease in heat capacity. The setting of the reaction mixture does not slow down the reaction rate.     

Matching and multiscale expansions for a model singular perturbation problem

We consider the Laplace–Dirichlet equation in a polygonal domain which is perturbed at the scale ε near one of its vertices. We assume that this perturbation is self-similar, that is, derives from the same pattern for all values of ε. On the base of this model problem, we compare two different approaches: the method of matched asymptotic expansions and the method of multiscale expansion. We enlighten the specificities of both techniques, and show how to switch from one expansion to the other. To cite this article: S. Tordeux et al., C. R. Acad. Sci. Paris, Ser. I 343 (2006).