CNRS Chemical Engineering Laboratory

Toulouse, France

CNRS Chemical Engineering Laboratory

Toulouse, France
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Teychene S.,CNRS Chemical Engineering Laboratory | Biscans B.,CNRS Chemical Engineering Laboratory
Crystal Growth and Design | Year: 2011

A microfluidic chip suitable for studying crystallization of organic molecules in organic solvents was developed. In this device, supersaturation can be generated either by thermal gradient (i.e., when the crystallization solvent is not miscible with the continuous phase) or by mass transfer (when the crystallization solvent is partially miscible with the continuous phase) or both. The experimental setup allows the storage of up to 2000 droplets to get nucleation statistics and crystal growth rates under static conditions. Crystallization of eflucimibe in droplets of octanol generated in water was investigated by use of this experimental device. The results show that, at lower time scale, the first nucleation events result mainly from a heterogeneous nucleation process (due to the presence of impurities or to the octanol - water interface itself). At higher time scales, the nucleation rate falls off, all the crystals appear in the droplet volume, and nucleation becomes homogeneous. This microfluidic device allows heterogeneous and homogeneous nucleation rate measurements to be performed in a single experiment. For ibuprofen crystallization in organic solvents partially miscible with water, no crystallization was observed, even at high time scales. Instead of crystallizing, the system undergoes a liquid - liquid phase separation. The liquid - liquid system obtained has a long lifetime, and contrary to what is usually observed, this metastable state does not promote nucleation of stable crystals. © 2011 American Chemical Society.

The comparative breakdown of passivity of tin by fluorides and chlorides highlight the significant slower kinetics of attack by the kosmotrope fluoride when compared to the chaotrope chloride at pH 5.7 and 10. The origin of this difference is ascribed to the predominant halide-dependent mechanism of attack, pitting with chlorides and film thinning with fluorides, which is conditioned according to the anion-specific hydration properties. © 2015 Elsevier Ltd.

Fabre P.-L.,University Paul Sabatier | Reynes O.,CNRS Chemical Engineering Laboratory
Electrochemistry Communications | Year: 2010

The electrocarboxylation of chloroacetonitrile mediated by [Co(II)(phen)3]2+ has been investigated. Cyclic voltammetry studies of [Co(II)(phen)3]2+ have shown that [Co(I)(phen)3]+, an 18 electron complex, activates chloroacetonitrile by an oxidative addition through the loss of a phenanthroline ligand to give [RCo(III)(phen)2Cl]+. The unstable one-electron-reduced complex underwent Co-C bond cleavage. In carbon dioxide saturated solution, CO2 insertion proceeds after reduction of the alkylcobalt complex. A catalytic current is observed which corresponds to the electrocarboxylation of chloroacetonitrile into cyanoacetic acid. Electrolyses confirmed the process and gave faradic yield of 62% in cyanoacetic acid at potentials that are about 0.3 V less cathodic than the one required for Ni(salen). © 2010 Elsevier B.V.

Tozlovanu M.,CNRS Chemical Engineering Laboratory | Pfohl-Leszkowicz A.,CNRS Chemical Engineering Laboratory
Toxins | Year: 2010

The OTA content of 30 roasted coffees purchased in French supermarkets was evaluated by two validated different methods: one using immunoaffinity column (IAC) clean-up after alkaline extraction; the second using toluene extraction under acidic conditions. OTA recoveries (0.5 to 5 μg/kg) ranged from 16-49% with the alkaline extraction method and 55-60% with the acidic method. OTA recoveries from prepared beverages were similar with all methods (75-80%). All samples containing OTA ranged from trace (

Trompette J.L.,CNRS Chemical Engineering Laboratory | Massot L.,CNRS Chemical Engineering Laboratory
Corrosion Science | Year: 2012

The ability of tantalum to become passive through water addition in methanol solution during chronoamperometric experiments has been investigated. The achievement of passivity was found to be modulated according to the applied electrical potential and the nature of the aggressive anions. The chronoamperometric curves were interpreted as resulting from the balance between the influence of proton mobility in solution and the building of the passive film. © 2012 Elsevier Ltd.

Angelov G.,Bulgarian Academy of Science | Gourdon C.,CNRS Chemical Engineering Laboratory
Chemical Engineering Research and Design | Year: 2012

A study on the pressure drop in pulsed extraction columns with internals of immobile discs and rings, usually called Discs and Doughnuts Columns (DDC) is carried out. The local pressure at a desired level of the column is obtained by resolving of turbulent flow model based on Reynolds equations coupled with k- e{open} model of turbulence. Consequently, the pressure drop for a column stage or for a unit of column length is determined. The results are used for development of correlations for determination of pressure drop as a function of plate free area, interplate distance and pulsation parameters - amplitude and frequency. Good correspondence to experimental data is observed. The developed quantitative relations are useful for non-experimental numerical optimization of stage geometry in view of lesser energy consumption. © 2011 The Institution of Chemical Engineers.

Pfohl-Leszkowicz A.,CNRS Chemical Engineering Laboratory | Manderville R.A.,University of Guelph
Chemical Research in Toxicology | Year: 2012

Ochratoxin A (OTA) is a naturally occurring chlorophenolic fungal toxin that contaminates a wide range of food products and poses a cancer threat to humans. The mechanism of action (MOA) for OTA renal carcinogenicity is a controversial issue. In 2005, direct genotoxicity (covalent DNA adduct formation) was proposed as a MOA for OTA-mediated carcinogenicity [Manderville, R. A. (2005) Chem. Res. Toxicol. 18, 1091 - 1097]. At that time, inconsistent results had been published on OTA genotoxicity/mutagenicity, and conclusive evidence for OTA-mediated DNA adduction had been lacking. In this update, published data from the past 6 - 7 years are presented that provide new hypotheses for the MOA (Figure presented) of OTA-mediated carcinogenicity. While direct genotoxicity remains a controversial issue for OTA, new findings from the Umemura and Nohmi laboratories provide definitive results for the mutagenicity of OTA in the target tissue (outer medulla) of male rat kidney that rules out oxidative DNA damage. These findings, coupled with our own efforts that provide new structural evidence for DNA adduction by OTA, has strengthened the argument for involvement of direct genotoxicity in OTA-mediated renal carcinogenesis. This MOA should be taken into consideration for OTA human risk assessment. © 2011 American Chemical Society.

Falk L.,CNRS Chemical Engineering Laboratory | Commenge J.-M.,CNRS Chemical Engineering Laboratory
Chemical Engineering Science | Year: 2010

The present paper proposes a detailed comparison of mixing efficiency of different mixers that have been characterized by the Villermaux/Dushman test reaction. Considering simple relations of mixing in laminar flow, it is shown how to obtain the theoretical mixing time and how to relate it with operating parameters as the Reynolds number of the flow and the specific power dissipation per mass unit of fluid. The comparison of the experimental and of the theoretical mixing times indicates that only a few percents of the total mechanical power transmitted to the fluid is effective for mixing. © 2009 Elsevier Ltd. All rights reserved.

Muzzarelli R.A.A.,Marche Polytechnic University | Boudrant J.,CNRS Chemical Engineering Laboratory | Meyer D.,Sensus Inc. | Manno N.,University of Padua | And 2 more authors.
Carbohydrate Polymers | Year: 2012

Two hundred years ago, Henri Braconnot described a polysaccharide containing a substantial percent of nitrogen, later to be called chitin: that discovery stemmed from investigations on the composition of edible mushrooms and their nutritional value. The present interdisciplinary article reviews the major research topics explored by Braconnot, and assesses their importance in the light of our most advanced knowledge. Thus, the value of fungi, seafoods and insects is described in connection with the significance of the presence of chitin itself in foods, and chitinases in the human digestive system. The capacity of chitin/chitosan to depress the development of microbial pathogens, is discussed in terms of crop protection and food preservation. Other topics cherished by Braconnot, such as the isolation of pectin from a large number of plants, and inulin from the Helianthus tubers, are presented in up-to-date terms. Acids isolated from plants at that early time, led to enormous scientific advancements, in particular the glyoxylic acid and levulinic acid used for the preparation of soluble chitosan derivatives that paved the way to a number of applications. An opportunity to trace the origins of the carbohydrate polymers science, and to appreciate the European scientific heritage. © 2011 Elsevier Ltd. All rights reserved.

Trompette J.L.,CNRS Chemical Engineering Laboratory
Corrosion Science | Year: 2014

The comparative aggressiveness of NaF and NaCl solutions on the breakdown of passivity of iron has been investigated once the passivating borate buffer solution has been removed. The results highlight the inhibitive action of borate anions towards the less aggressive kosmotrope fluorides. Without borates, the kinetics of attack by fluorides is slower as the prepassivation is longer, and it is considerably retarded when compared to the case with the chaotrope chlorides. The high positive viscosity B coefficient value of borate anion argues in favor of its use as an inhibitor or as an efficient electrolyte for anodization baths. © 2014 Elsevier Ltd.

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