Solubilité de la p. nitroaniline dans les mélanges eau + urée et eau + urées substituées et fonctions de transfert de l’eau vers ces mélanges

Les mesures de solubilité par spectrophotométrie à 380 nm de la p.nitroaniline dans l’eau et dans les mélanges eau + urée et eau + urées méthyl-substituées à plusieurs températures, ont permis d’obtenir l’enthalpie libre standard et l’entropie standard de transfert de la p.nitroaniline de l’eau vers ces différents solvants mixtes aqueux.Pour ces différents solvants mixtes aqueux on constate que le transfert de la p.nitroaniline est spontané ([math] < 0), et que les variations de l’entropie de transfert [math] en fonction de la concentration en cosolvant confirment le caractère briseur de structure de l’urée, et le caractère hydrophobe donc promoteur de structure des urées méthyl-substituées, lequel augmente avec le nombre des substitutions sur l’urée

Solubilité de la P. nitroaniline dans les mélanges eau + hexamethylphosphorotriamide (HMPT) et fonctions de transfert de l’eau vers ces melanges

Les mesures de solubilité par spectrophotométrie à 380 nm du non-électrolyte p.nitroaniline dans l’eau et dans les mélanges eau + hexaméthylphosphorotriamide à sept températures (10-40°C) ont permis d’obtenir l’enthalpie libre standard et l’entropie standard de transfert de la p.nitroaniline de l’eau vers les mélanges eau + HMPT.Le transfert de la p.nitroaniline est spontané [maths], et les courbes de l’entropie standard de transfert [maths] en fonction de la composition du solvant mixte passent par un maximum, et confirment l’existence du maximum de structure de l’eau pour une fraction molaire voisine de 0,05 en HMPT, résultat obtenu dans une étude antérieure

Solubilité de la N,N-dimenthylaniline dans les mélanges eau + hexamethylphosphorotriamide (HMDT) et fonctions de transfert de l’eau vers ces mélanges

Dans un article précédent nous avons déterminé les différentes fonctions standards de transfert de la p. nitroaniline dans les mélanges eau + hexaméthylphosphorotriamide (HMPT). Il était nécessaire de mettre en évidence l’importance relative des contributions autres que celles résultant de la modification de la structure du solvant. En effet la présence du groupe nitré et de la fonction amine pouvait conduire à des interactions chimiques par liaison hydrogène avec le cosolvant HMPT. Les effets observés étaient la somme des contributions de solvatation électrostatiques, de solvatation par liaison hydrogène des groupements NO2 et NH2 avec l’eau et le HMPT et de solvatation par interaction hydrophobe. Nous avons donc mesuré les différentes fonctions standards de transfert de la N,N- diméthylaniline dans les mélanges eau + HMPT, à partir de la solubilité de la N,N-diméthylaniline déterminée par spectrophotométrie à 245 nm et à quatre températures (10-40 °C).Le transfert de la N,N-diméthylaniline est spontané ([math] < 0) et la variation de l’entropie standard de transfert confirme le maximum de structure du solvant mixte lorsque sa composition est voisine de 0,05 (fraction molaire en HMPT). De plus on constate la très faible influence des groupements NO2 et NH2 de la p. nitroaniline, dans les valeurs des fonctions de transfert

Safety evaluation of plastic food contact materials by appropriate analytical methodologies coupled with chemometric tools

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Safety evaluation of plastic food contact materials using analytical fingerprinting methodologies coupled with chemometric tools

Safety evaluation of plastic food contact materials using analytical fingerprinting methodologies coupled with chemometric tools.Research issue : Transport phenomena and reactivity in dense polymeric material

Chemometric tools to highlight non-intentionally added substances (NIAS) in polyethylene terephthalate (PET)

In an effort to identify non-intentionally added substances (NIAS), which is still a challenging task for analytical chemists, PET pellets, preforms and bottles were analyzed by an optimized headspace solid phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME/GC-MS). Fingerprints obtained by the proposed method were analyzed by three chemometric tools: Principal Components Analysis (PCA), Independent Components Analysis (ICA) and a multi-block method (Common Components and Specific Weights Analysis CCSWA) in order to extract pertinent variations in NIAS concentrations. Total ion current (TIC) chromatograms were used for PCA and ICA while extracted ion chromatograms (EIC) were used for CCSWA, each ion corresponding to a block. PCA managed to discriminate pellets and preforms from bottles due to several NIAS. Volatiles like 2-methyl-1,3-dioxolane, ethylene glycol, ethylbenzene and xylene were responsible for the discrimination of pellets and preforms. Less volatile compounds like linear aldehydes and phthalates were responsible for the discrimination of bottles. ICA showed more specific discriminations especially for bottles and pellets while CCSWA managed to discriminate preforms. The proposed methodology, combining HS-SPME/GC-MS with chemometric tools proved its efficiency in highlighting NIAS in PET samples in a relatively simple and fast approach compared to classical techniques

Safety evaluation of plastic food contact materials using analytical fingerprinting methodologies coupled with chemometric tools

Safety evaluation of plastic food contact materials using analytical fingerprinting methodologies coupled with chemometric tools.Research issue : Transport phenomena and reactivity in dense polymeric material

Empirical models to predict the effect of sterilisation and storage on bisphenols migration from metallic can coatings into food simulants

International audienceBased on response surface methodology, empirical models were built to predict the influence of can processing (heat treatment) and storage conditions (time and temperature) on the migration of bisphenol compounds from the inner lacquer of tinplate cans (4 brands) into several food simulants. Analysis using liquid chromatography revealed the presence of BADGE.2H(2)O and BPA in all samples. Models were significant in fitting the levels of these two bisphenols in food simulants depending on the input variables, with excellent adjusted coefficients of determination. Their prediction performance was validated through running new data sets. Further comparison of predicted values with bisphenols levels measured in canned vegetables revealed that the proposed models are conservative. By the desirability of the response output, the models are capable of proposing the range of can processing and storage conditions that limit migration for further compliance with the regulation. The proposed approach could be a convenient tool for the industries to control processing conditions in order to ensure the conformity of canned foods

Application of 2D correlation spectroscopy on olive stones acid hydrolysates: Effect of overliming

In order to valorize olive stones we are studying their dilute-acid hydrolysate (DAH) composition, and trying to highlight the effect of the overliming process on DAH composition in order to perform an effective treatment that maximize sugars concentrations (xylose) and minimizes the amount of toxic materials (FF and HMF). An 2(2)3(1) experimental design was established to describe the effects of three controlled factors with distinct levels: pH (10 and 12), temperature (25 and 60 degrees C) and detoxification time (15,30 and 60 min) on the concentration of xylose, FF and HMF. A better understanding of this overliming process was possible by exploring the chromatograms obtained with 2D Correlation Spectroscopy (2DCOS). 2D correlation spectroscopy gave information about the relations that exist between chromatographic peaks and chromatograms. The order in which the constituents vary can be deduced from the sign of peaks in the synchronous and asynchronous matrices, facilitating the interpretation of kinetic studies. (c) 2011 Published by Elsevier B.V

Experimental design approach in the synthesis of molecularly imprinted polymers specific for iprodione fungicide

International audienceAn experimental design (ED) approach was applied to study the weight of three factors in the synthesis of a molecularly imprinted polymer (MIP) specific for iprodione fungicide. The objective was to obtain a high specific polymer with the best performance of iprodione binding. Thirteen iprodione-imprinted polymers and 13 non-imprinted polymers (NIP) were synthesized according to ED having 3 influencing factors: the polymerization method, the crosslinker nature and the functional monomer type. For each factor, two levels were studied: bulk and precipitation polymerization for the first factor, trimethylolpropane trimethacrylate (TRIM) and ethylene glycol dimethacrylate (EGDMA) for the second factor, and methacrylamide (MAM) alone or with styrene for the third factor. The ED responses were: the imprinting factor, the site number and the apparent affinity constant. They were determined after studying the interactions between iprodione and each MIP and NIP in hydro-alcoholic medium. The best polymer of the ED was synthesized using MAM as functional monomer, EGDMA as crosslinker and precipitation polymerization. It has an imprinting factor of 2.4, a site number of 1172 and an affinity constant of 19.36. The best MIP was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Nitrogen sorption isotherms. The best MIP has a mesoporous structure with a high specific surface area of 407 m(2).g(-1). Molecularly imprinted solid phase extraction (MISPE) was successfully applied, using the best MIP, to preconcentrate iprodione from a white wine containing two competing fungicides. (C) 2015 Elsevier B.V. All rights reserved