Identification par couplage CG/SM des sous-produits de chloration de deux acides aminés libres, la proline et la méthionine

L'objectif de ces travaux a consiste en l'identification des sous-produits de chloration de deux acides aminés libres, la proline et la méthionine, structures reconnues pour leur grande réactivité avec le chlore.Les expériences ont été conduites a pH 8 pour un taux de chlore fixe à 8 moles de chlore par mole d'acide aminé et un temps de contact de 72 heures. Les sous-produits de chloration ont été extraits successivement par le pentane et le diethyl éther (pH acide et pH basique, extraction suivie d'une dérivation au diazométhane) et identifiés par couplage CG/SM.L'essentiel des sous-produits de chloration identifiés a été observé dans l'extrait éthéré obtenu à pH acide, que ce soit pour la proline ou la méthionine. Les acides dichloroacétique et trichloroacétique, composés retrouvés dans les eaux de surface désinfectées au chlore, ont été détectés pour les deux molécules étudiées.Les travaux effectués avec la proline ont permis d'identifier également la N- chlorodichloroacétamide et la N-chlorotrichloroacétamide. On peut noter également la formation de quelques chloroacides présentant un groupement terminal aldehyde ou nitrile caractéristique, ainsi que des composeé à structure pyrrole.En ce qui concerne la méthionine, les analyses par couplage CG/SM ont permis d'identifier quelques composés organiques chlorosoufrés comme le chlorure de méthyle sulfonyle, le chlorure de chlorométhylesulfonyle et le dichloro-1,1 diméthyle sulfonyle, ainsi que du soufre moléculaire S8.The objective of our work was to identify the chlorination byproducts of two amino acids, proline and methionine, structures that were found to be very reactive with chlorine, showing high chlorine demand and high total organohalogenated compounds (TOX) and chloroform formation potentials.Concentrated solutions of each amino acid were prepared in MilliQ water buffered with phosphate at pH 8 and chlorinated at a dose equal to 8 moles of chlorine per mole of amino acid. Chlorinated solutions were stored at 20°C (in the dark) for 72 hours before applying our extraction procedure. Two different solvents were used, pentane first, followed by diethyl ether under acidic and basic pH. After concentration (rotary evaporation, nitrogen flow) and derivatization (a few drops of diazomethane were added to the diethyl ether extracts prior to analysis), the different extracts were analyzed by gas chromatography / mass spectrometry. Most of the byproducts that were identified were analyzed from the diethyl ether extracts obtained at acidic pH. A large number of structures were detected in the extracts of the chlorinated proline solution, and only a few in the extracts from the methionine solution. Most of the identified compounds are chlorinated structures including a carboxyl function. Trichloroacetic acid and dichloroacetic acid were identified as common chlorination byproducts of the two amino acids studied. The two intermediates in the formation of these two acids, CCl3CONH2 and CHCl2CONH2, were also found.N-chlorodichloroaldimine and N-chlorotrichloroaldimine have been identified as chlorinated proline by-products. The chlorination of this amino acid also leads to the formation of chloroacids compounds which present an aldehyde or a nitrile function as a terminal group; a pyrrole structure is also proposed. The chlorination of methionine has been shown to produce several chlorosulfur compounds. The structures identified in the chlorinated methionine solution were H2CClSO2Cl, HCCl2SO2Cl and HCCl2CONH2. Molecular sulfur (S8) was also obtained

Formation des ions bromate lors de l'ozonation des ions bromures en présence de la matière organique

Cet article rassemble les résultats de l'étude en laboratoire des conditions de formation des ions bromate (BrO3-) lors de l'ozonation des ions bromure. Les expériences ont été réalisées en réacteur fermé, en milieu tamponné à la température ambiante, (ª23 °C) et en présence de matière organique. La concentration initiale en ions bromure a été fixée à 200 mg/L et le taux d'ozone appliqué à 5 mg/L. La matrice étudiée a été préparée à partir de différentes fractions de la matière organique extraites d'eaux naturelles (acides fulviques et acides hydrophiles) et d'une fraction synthétique (tripeptide). Les fractions ont été étudiées individuellement ou en mélange dans des proportions compatibles avec la matière organique naturelle. L'étude a porté sur l'impact de la matière organique, du pH, de l'azote ammoniacal, de l'alcalinité et du peroxyde d'hydrogène sur la formation des ions bromate. L'analyse de BrO3- a été effectuée par chromatographie ionique après 24 heures de temps de réaction (ozone résiduel négligeable) ; la limite de détection de la mesure est de 2 mg/L.The objective of our work was to evaluate the importance of various parameters (natural organic matter, pH, ammonia, bicarbonate, hydrogen peroxide) affecting the formation of bromate during the ozonation of natural waters containing bromide. Bench scale experiments were carried out on synthetic solutions prepared in phosphate buffer (10-2 - 10-3 M). Bromate concentrations were determined by ion chromatography after the complete consumption of the added ozone (24 h contact time); the ion chromatograph was equipped with a suppressed conductivity detection system (DIONEX) with a detection limit of ca. 2 µg BrO3-/L.The impact of organic matter was evaluated with model organic compounds: fulvic acid and hydrophilic acids (FA and HyA) isolated from a river water with XAD8 and XAD4 resins, and a tripeptide (Tyr-Gly-Gly). These different organic compounds were studied individually or as a mixture (60% FA, 30% HyA, 10% tripeptide). All solutions were spiked with 200 mg/L of bromide and the applied ozone dose was 5 mg O3/L; the DOC content varied from 0 to 5 mg C/L.For given experimental conditions, bromate formation varies depending on the origin and nature of the organic matrix (natural organic matter or tripeptide), probably due to their respective ozone consumption. For a particular ozone dose, an increase in DOC results in decreasing bromate production. In fact, ozone consumption by the natural organic matter reduces the available ozone and somewhat inhibits the efficiency of bromate formation reactions.More bromate is formed with increasing pH, for the relative proportion of hypobromite increases in relation to hypobromous acid. In the presence of ammonia and natural organic matter, bromate formation is lowered because ammonia diverts part of the HOBr to form organobrominated compounds, and thus participates indirectly in ozone consumption.Bicarbonate addition favors molecular ozone type reactions by scavenging free radicals. Ozone is stabilized in the medium and thus more bromate is formed than in the absence of any scavenger. The reaction of OH radicals leading to bromate formation needs the presence of BrO-. Thus the use of hydrogen peroxide with an excess of ozone, or ozonation prior to hydrogen peroxide addition, may lead to the production of high bromate concentrations. This experiments shows that the higher the available ozone, the higher the bromate production. The use of ozone for disinfection purposes involves maintaining a residual ozone concentration during a due time in order to achieve the required C. t for bacterias and viruses inactivation. This increasing C. t may result in high bromate formation

Analyse par HPLC et CG/SM des constituants du carbone organique dissous (COD), du COD biodégradable (CODB) et des composés organohalogénés (TOX) d'un perméat de nanofiltration

Pour limiter la formation de composés organohalogénés des eaux traitées et la reviviscence bactérienne des réseaux, il est important d'éliminer la majeure partie du carbone organique dissous (COD) et du carbone organique dissous biodégradable (CODB) contenus dans les eaux naturelles. Des travaux récents nous ont permis de montrer que la nanofiltration est une technologie de choix pour répondre à ces contraintes.L'objectif de cet article est de présenter à partir de travaux de laboratoire un inventaire détaillé du carbone organique résiduel d'un perméat prélevé le 21/04/93 sur le prototype industriel de nanofiltration de Méry/Oise en banlieue parisienne. Pour atteindre cet objectif il a été nécessaire de mettre en œuvre des 'techniques analytiques impliquant l'utilisation de la chromatographie liquide haute performance (CLHP) et de la chromatographie en phase gazeuse (CG) soit équipée d'un détecteur à ionisation de flamme (FID) ou d'un détecteur à capture d'électrons (ECD), soit couplée à la spectrométrie de masse (SM).Les résultats obtenus ont montré que le COD du perméat étudié est constitué d'environ 60% d'acides aminés libres et combinés, de 7% d'aldéhydes et de 10 à 20% de composés divers identifiables en CG/SM. Ces derniers composés comprennent majoritairement des acides gras aliphatiques et des acides aromatiques de faibles masses. La concentration de chacun de ces composés a été estimée à 0,3 µg l-¹ C. On peut raisonnablement penser, d'après la bibliographie que les hydrates de carbone (non analysés dans cette étude) représenteraient une part importante de COD du perméat. En outre, cette étude a montré que la part prise par les acides aminés totaux dans le CODB du perméat est importante.Seul le tiers des potentiels de formation d'organohalogénés totaux (PFTOX) a été identifié comme étant des trihaloméhanes (THM) et des acides haloascétiques. Toutefois, étant donné que les acides aminés totaux représentent à eux seuls la quasi totalité de la demande en chlore du perméat, les autres sous-produits de chloration non identifiés seraient probablement des nitriles chlorés, des chloramines et des chloroaldéhydes qui sont parmi les principaux intermédiaires réactionnels de la coloration des acides aminés.Removal of dissolved organic carbon (DOC) and biodegradable dissolved organic carbon (BDOC) is one of the most important means to prevent disinfection by-products (DBPs) formation during water treatment and bacterial regrowth in distribution systems. In previous investigations, the authors have shown that nanofiltration, over nine months of operation at industrial scale in Paris suburbs, was an effective technology to meet the new guidelines concerning chlorine DBPs.This paper reports laboratory investigations aimed to identify and quantify the main organic components included in the low DOC, BDOC and TOXFP (Total - Organohalides Formation Potential) residuals of a nanofiltration permeate sampled on April 21, 1993.Details on DOC, BDOC, organohalides, amino acids and aldehydes analysis procedures were described elsewhere (AGBEKODO et al., 1994). Chlorination was undertaken in potential conditions k: 2.5 mg Cl2/mg DOC, pH=7.5 (phosphate buffer), 72 hours contact time, in dark at 20°C. Haloacetic acids determination consisted (after chlorination in potential conditions) in liquid-liquid extraction, methylation with diazomethane and gas chromatography analysis. Extraction procedure based on XAD8/XAD4 adsorption prior to gas chromatography/Mass Spectrometry (GC/MS) analysis (Fig. 3), allowed a 19000 fold concentration of the permeate. To prevent possible contamination of the permeate, the extraction system consisted of four glass columns and teflon materials. The flow through the columns was performed under high purity nitrogen gas pressure.Analysis involving high performance liquid chromatography (HPLC) and gas chromatography (GC) in combination with Mass Spectrometry (MS), showed that the studied permeate DOC (- 0.15 mg l-¹ c) consisted of amino acids at an average of 60% of DOC, aldehydes (7%) and 10 to 20% of several other compounds (analyzed in GC/MS) including primarily fatty and aromatic acids of low molecular weight (Table 4a and Table 4b). The maximum concentration of each compound (identified hy GC/MS) has been roughly assessed to 0.3 µg l-¹ C. According to literature, sugars represent probably an important portion of the remaining DOC of the permeate. Moreover, the authors have shown that amino acids represented a large portion of permeate BDOC.Only 34% of the total organohalide potentials were identified as trihalomethanes and haloacetic acids. However, since amino acids represent almost the entire chlorine demand of the permeate, the non- identified chlorination DBPs are likely chlorinated nitriles, chloramines and chloraldehydes which are known as the main reactionnal intermediates of aminoacid chlorination

Recherche et identification des premiers sous-produits d'oxydation de l'isoproturon par le système ozone/peroxyde d'hydrogène

Une solution aqueuse tamponnée par des phosphates (pH initial - 8) dopée en isoproturon (N- (isopropyl-4-phényl)-N-N'-diméthylurée) (~ 20 mg 1-1), a été oxydée par le système perozone, combinant l'ozone et le peroxyde d'hydrogène dans un rapport molaire de 0,5 à 0,6 moles de H2O2 par mole d'ozone. Les disparitions du composé parent, du carbone organique total (COT), du carbone total (CT) et de la consommation d'ozone, ont été suivies au cours de l'oxydation. Les premiers sous-produits d'oxydation, ceux susceptibles de conserver une formulation moléculaire proche de celle du composé initial, et par conséquent de posséder encore une activité toxique, ont été isolés et caractérisés par chromatographie gazeuse couplée à la spectrométrie de masse.Il a été trouvé que l'isoproturon requiert un taux d'oxydation molaire de 10 moles d'ozone par mole d'isoproturon introduit, pour obtenir une élimination complète de cet herbicide. En revanche, le COT n'est pratiquement pas minéralisé, même avec de très forts taux d'ozone, ce qui indique la présence dans le milieu de sous-produits rémanents.La plupart des premiers sous-produits d'oxydation détectés conservent le cycle aromatique dans leur structure, et au moins un atome d'azote, et sont présents à des concentrations significatives. Ces composés semblent aussi réactifs que l'isoproturon vis-à-vis de la perozonation puisqu'ils disparaissent lorsqu'on prolonge l'oxydation. De plus, l'identification de ces sous-produits laisse supposer que l'attaque des radicaux hydroxyles générés par le procédé perozone, entraîne la rupture d'une liaison C-N ou d'une liaison C-H, conduisant à la formation de composés oxygénés.The goal of our study was to identify the initial oxidation by-products (IOBP) of isoproturon (N-(isopropyl 4 phenyl)-N-N'-dimethylurea) formed during a combined ozone/hydrogen peroxide (peroxone system) treatment. Solution of isoproturon (20 mg · l-¹ or 10[sup]4 M) were prepared in ultrapure water buffered with phosphate ions (45.9 mg · l-¹ KH2PO4 + 457.2 mg · l-¹ Na2HPO4) at an initial pH dose to 8 and an ionic strength of about 10-2 mol · l-¹, and in the absence of radical scavengers (bicarbonate ions) and organic matter. Each experiment was conducted in a glass semi-continuous reactor (bubble column, capacity: 2.81, ID=40 mm, H=2 m) with recirculation of the aqueous phase (60-651 · h-¹) counter current to the gaseous phase. Ozonized air produced in the laboratory (TRAILIGAZ Labo 76 apparatus) was applied at the bottom of the column through a porous glass frit (porosity: 15 to 40 µm) at a flow rate of about 2.81 · h-¹ (ozone concentration in gas: 76 to 124 mg l-¹). The hydrogen peroxide solution (dilution from a 30 % solution FLUKA) was introduced at the level of the ozonized air entrance. The applied hydrogen peroxide/ozone molar ratio was equal to about 0.5 (or 0.4 g/g). In the first phase of our work, primary experiments were conducted to determine the efficiency of peroxone oxidation (combined O3/H2O2) in removing isoproturon and carbon. For these experiments, the analysis of isoproturon was performed by HPLC on a SUPELCOSIL C8 column (15 cm x 4.6 mm) with UV detection at 236 nm (WATERS Model 500 pump with SPECTROMONITOR 3100 detector), using a methanol/water carrier phase (50/50 v/v, 1 ml · min-¹). Each five minute during the oxidation, total organic carbon (TOC) and total carbon (TC=TOC + mineral carbon) were controlled with DOHRMANN DC80 carbon analyser. The pH and ozone concentrations were also monitored (ozone introduced and in the off-gas by potassium iodure method, and dissolved ozone by indigotrisulfonate method). Calculation of consumed ozone was obtained by the following equation: consumed O3=introduced O3 - O3 in off-gas - dissolved O3. The results are expressed as curves showing removals of isoproturon, TOC, TC versus the oxidation dosage (as moles of introduced ozone per mole of initial isoproturon). Their interpretation has shown that the complete disappearance of isoproturon is achieved in 12 minutes and requires about 10 moles of ozone per mole of pesticide. However, TOC was removed to only 50% for a three times higher ozone dose (27 moles per mole reached in 30 minutes). The presence of this remaining TOC (65 mg · l-¹) for such high ozone dose indicates that some by-products remain in the solution. These by-products visualised on the HPLC chromatograms for the isoproturon dosage (4 well-separated and significant peaks) seem to be as reactive as pesticide itself because of their disappearance during oxidation.In a second phase of our work, a similar experiment was conducted over a period of 7 minutes for having up to 90% removal of isoproturon. A 1.5 litre of oxidized isoproturon solution was collected for liquid-liquid extraction with methylene dichloride ((50 ml (2 min), 25 ml (2 min), 25 ml (2 min)) after adding acid (HCI to pH 2) and salt (NaCl). After desiccation on anhydrous sodium thiosulphate (Na2SO4) and concentration under nitrogen flow, the methylene dichloride extract (extract A) was analysed by gas chromatography/mass spectrometry (VARIAN 3300 coupled with a FINNIGAN ITS 40, on-column injector: 280°C, carrier gas: helium) on DB5 capillary column (50°C to 250°C at 3°C · min), for structural identification of the oxidation by-products. Two other extracts were obtained by the same way and analysed as blanks: the initial isoproturon solution not oxidized (extract B), and the buffer solution without isoproturon oxidized under the same conditions as the pesticide solution (extract C). These two blanks have allowed to distinguish the peaks really appeared after oxidation of those either present before oxidation or produced by the oxidation/extraction of the buffer. The GC/MS chromatogram of extract A has revealed 15 peaks really issued from the oxidation of isoproturon. The molecular weights given by the mass spectra have been correlated by chemical ionisation. The identified oxidation by-products (7 on the 15) are phenylated and/or nitrated compounds which are: 4-isopropylaniline, 4-amino-benzaldehyde, paraquinon, 4-isopropylnitrobenzene, 4-isopropylbenzene-N-for-mamide, N-(4-phenol)-N-N'-dimethylurea or « oxoisoproturon » and N-(isopropyl-4-phenyl)-N-N'- (methyl-formyl) urea. Mechanisms are suggested for the formation of these products from isoproturon. It seems that the hydroxyl radicals (OH) generated by the peroxone system attack either a C-N bond (as in the case of atrazine) or a C-H bond. The subsequent attacks (OH· or O3, O2) lead to the formation of oxygenated molecules (alcohol, carboxyl groups)

Mycolactone as Analgesic: Subcutaneous Bioavailability Parameters

is the bacillus responsible for Buruli ulcer, an infectious disease and the third most important mycobacterial disease worldwide, after tuberculosis and leprosy. infection is a type of panniculitis beginning mostly with a nodule or an oedema, which can progress to large ulcerative lesions. The lesions are caused by mycolactone, the polyketide toxin of . Mycolactone plays a central role for host colonization as it has immunomodulatory and analgesic effects. On one hand, mycolactone induces analgesia by targeting type-2 angiotensin II receptors (ATR), causing cellular hyperpolarization and neuron desensitization. Indeed, a single subcutaneous injection of mycolactone into the mouse footpad induces a long-lasting hypoesthesia up to 48 h. It was suggested that the long-lasting hypoesthesia may result from the persistence of a significant amount of mycolactone locally following its injection, which could be probably due to its slow elimination from tissues. To verify this hypothesis, we investigated the correlation between hypoesthesia and mycolactone bioavailability directly at the tissue level. Various quantities of mycolactone were then injected in mouse tissue and hypoesthesia was recorded with nociception assays over a period of 48 h. The hypoesthesia was maximal 6 h after the injection of 4 μg mycolactone. The basal state was reached 48 h after injection, which demonstrated the absence of nerve damage. Surprisingly, mycolactone levels decreased strongly during the first hours with a reduction of 70 and 90% after 4 and 10 h, respectively. Also, mycolactone did not diffuse in neighboring skin tissue and only poorly into the bloodstream upon direct injection. Nevertheless, the remaining amount was sufficient to induce hypoesthesia during 24 h. Our results thus demonstrate that intact mycolactone is rapidly eliminated and that very small amounts of mycolactone are sufficient to induce hypoesthesia. Taken together, our study points out that mycolactone ought to be considered as a promising analgesic

IL-34 and macrophage colony-stimulating factor are overexpressed in hepatitis C virus fibrosis and induce profibrotic macrophages that promote collagen synthesis by hepatic stellate cells

Chronic hepatitis C virus (HCV) infection is characterized by progressive hepatic fibrosis, a process dependent on monocyte recruitment and accumulation into the liver. The mediators expressed in chronically injured liver that control the differentiation of human monocytes into profibrotic macrophages (Mφ) remain poorly defined. We report that chronically HCV-infected patients with high fibrosis stages have higher serum levels of macrophage colony-stimulating factor (M-CSF) and interleukin (IL)−34 than HCV-infected patients with lower fibrosis stages and healthy subjects. Immunohistochemistry reveals an intense expression of IL-34 and M-CSF by hepatocytes around liver lesions. In addition, HCV infection and inflammatory cytokines enhance the in vitro production of IL-34 and M-CSF by hepatocytes. We next analyzed the acquisition of profibrotic properties by Mφ generated with M-CSF (M-CSF-Mφ) or IL-34 (IL-34-Mφ). M-CSF and IL-34 up-regulate the expression, by differentiating monocytes, of chemokine (C-C motif) ligand (CCL)2, CCL4, C-C chemokine receptor (CCR)1, and CCR5, which are involved in monocyte recruitment/Mφ accumulation in liver lesions. M-CSF-Mφ and IL-34-Mφ also express the hepatic stellate cell (HSC) activators, platelet-derived growth factor, transforming growth factor beta, and galectin-3. IL-34-Mφ and M-CSF-Mφ induce type I collagen synthesis by HSCs, the main collagen-producing cells in liver fibrosis. IL-13, whose expression correlates with the fibrosis stage in HCV-infected patients, decreases the expression of the collagenase, matrix metalloproteinase 1, by IL-34-Mφ and M-CSF-Mφ, thereby enhancing collagen synthesis. By inhibiting the production of interferon-gamma (IFN-γ) by activated natural killer cells, IL-34-Mφ and M-CSF-Mφ prevent the IFN-γ-induced killing of HSCs. Conclusion: These results identify M-CSF and IL-34 as potent profibrotic factors in HCV liver fibrosis

Tensions in the periphery: Dependence and the trajectory of a low-cost productive model in the Central and Eastern European automotive industry

This article analyses the productive strategy adopted by Renault for its Dacia plant in Romania. It proposes a detailed analysis of the conditions for the success of the Logan project – Renault’s radical approach to the concept of the low-cost automobile. We look into both market- and production-related aspects that have made the Logan work and highlight the tensions sparked by Renault’s drive to capitalize on its favourable market situation as well as the success achieved by Dacia’s workers in defending their interests. In particular, we emphasize the company governance compromises that have shaped industrial relations at Dacia over the past decades and show how in recent years the maintaining of such a compromise has come increasingly into question due to threats by automation and relocation in a context of constantly rising wages and improving working conditions. Finally, we discuss the strategic dilemmas facing both management and labour and their possible resolutions, as well as the relevance of the Dacia case for understanding the future of Central and Eastern Europe as a peripheral region attracting automotive foreign direct investments

Electrochemical methodology to study labile trace metal/natural organic matter complexation at low concentration levels in natural waters

A new electrochemical methodology to study labile trace metal/natural organic matter complexation at low concentration levels in natural waters is presented. This methodology consists of three steps: (i) an estimation of the complex diffusion coefficient (DML), (ii) determination at low pH of the total metal concentration initially present in the sample, (iii) a metal titration at the desired pH. The free and bound metal concentrations are determined for each point of the titration and modeled with the non-ideal competitive adsorption (NICA-Donnan) model in order to obtain the binding parameters. In this methodology, it is recommended to determine the hydrodynamic transport parameter, α, for each set of hydrodynamic conditions used in the voltammetric measurements. The methodology was tested using two fractions of natural organic matter (NOM) isolated from the Loire river, namely the hydrophobic organic matter (HPO) and the transphilic organic matter (TPI), and a well characterized fulvic acid (Laurentian fulvic acid, LFA). The complex diffusion coefficients obtained at pH 5 were 0.4 ± 0.2 for Pb and Cu/HPO, 1.8 ± 0.2 for Pb/TPI and (0.612 ± 0.009) × 10−10 m2 s−1 for Pb/LFA. NICA-Donnan parameters for lead binding were obtained for the HPO and TPI fractions. The new lead/LFA results were successfully predicted using parameters derived in our previous work

High pressure membrane foulants of seawater, brackish water and river water: Origin assessed by sugar and bacteriohopanepolyol signatures

The present work aimed to study the origin of foulant material recovered on membranes used in water treatment. Firstly, sugar signatures were assessed from the monosaccharide composition. As results were not conclusive, a statistical approach using discriminant analysis was applied to the sugar data set in order to predict the origin of the foulant material. Three groups of various origins (algal, microbial, continental dissolved organic matter) were used as sugar references for the prediction. The results of the computation showed that the origin of reverse osmosis (RO) seawater foulant material is influenced by both the location of the water sources and the season. RO brackish water and nanofiltration river water foulant materials had a terrestrial origin. Secondly, bacteriohopanepolyol signatures indicated that RO seawater foulant material had a marine signature, RO brackish water foulant material had both a marine and a terrestrial origin and the nanofiltration river water foulant material contained only a terrestrial signature