Sorption of nalidixic acid onto micrometric and nanometric magnetites: experimental study and modeling

International audienceThe sorption of nalidixic acid (NA) was studied onto three kinds of magnetite characterized by different particle sizes (from micrometric to nanometric) and surface properties. Experiments were performed under static batch and dynamic flow conditions. Obtained results indicate that kinetics and extent of sorption was strongly affected by the particle size of tested magnetites. Ionic strength effect was less significant suggesting that aggregation state of the magnetite particles did not affect the sorption. During kinetic sorption experiments, apparent rate constant normalized to solid mass was faster for nanosized magnetite while an opposite trend was observed for the surface area-normalized rate constants. Infrared data suggested the possibility of similar surface interactions on both microsized and nanosized magnetites. Transport of NA in magnetite-packed column was found associated to the instantaneous sorption without any significant effect of kinetic limitation. Breakthrough curves (BC) and sorption extent in columns were calculated by using Thomas, Yan and Yoon-Nelson models. Sorption capacities predicted by Thomas or Yan model were in good agreement with that determined by integrating total area above BC. However, Thomas model failed particularly to predict an accurate concentration at lower and higher time points of the BC. These findings have strong implications in relation to the transport and removal of environmental pollutants in natural and engineered systems

Adsorption of pharmaceuticals onto activated carbon fiber cloths - Modeling and extrapolation of adsorption isotherms at very low concentrations

International audienceActivated carbon fiber cloths (ACFC) have shown promising results when applied to water treatment, especially for removing organic micropollutants such as pharmaceutical compounds. Nevertheless, further investigations are required, especially considering trace concentrations, which are found in current water treatment. Until now, most studies have been carried out at relatively high concentrations (mg L(-1)), since the experimental and analytical methodologies are more difficult and more expensive when dealing with lower concentrations (ng L(-1)). Therefore, the objective of this study was to validate an extrapolation procedure from high to low concentrations, for four compounds (Carbamazepine, Diclofenac, Caffeine and Acetaminophen). For this purpose, the reliability of the usual adsorption isotherm models, when extrapolated from high (mg L(-1)) to low concentrations (ng L(-1)), was assessed as well as the influence of numerous error functions. Some isotherm models (Freundlich, Toth) and error functions (RSS, ARE) show weaknesses to be used as an adsorption isotherms at low concentrations. However, from these results, the pairing of the Langmuir-Freundlich isotherm model with Marquardt's percent standard of deviation was evidenced as the best combination model, enabling the extrapolation of adsorption capacities by orders of magnitude

Forced degradation study of quinapril by UPLC-DAD and UPLC/MS/MS: Identification of by-products and development of degradation kinetics.

International audienceQuinapril undergoes a significant degradation in the solid state, specially in the presence of humidity, temperature and pharmaceutical excipients. Since dissolution increases the degradation, hydrolytic reactions are among the most common processes involved in drug degradation. Improving the knowledge regarding drug stability, particularly concerning the critical factors that can influence the stability of the active substance in solutions, such as the temperature, the pH and the concentration of catalytic species usually acids or bases are essential for pharmaceutical use. The aim of this study was therefore to develop a new chromatographic method for rapidly and accurately assessing the chemical stability of quinapril and to study the mechanism of quinapril degradation in acidic, neutral and alkaline media at 80°C according to the ICH guidelines. Ultra High Performance Liquid Chromatography (UPLC) coupled with electrospray ionization tandem mass spectrometry and/or diode array detector was used for the rapid and simultaneous analysis of quinapril and its by-products. Separation was achieved using a BEH C18 column and a mixture of acetonitrile-ammonium hydrogencarbonate buffer (pH 8.2; 10 mM) (65:35, v/v) at a flow rate of 0.4 mL/min as a mobile phase. This method allowed drug byproducts profiling, identification, structure elucidation and quantitative determination under stress conditions. The developed method also provides the determination of the kinetic rate constants for the degradation of quinapril and the formation of its major by-products. A complete model including degradation pathway observed under all tested conditions was proposed according to the kinetic study and the structure elucidation of by-products

Standard addition method for the determination of pharmaceutical residues in drinking water by SPE-LC-MS/MS

International audienceThe study of the occurrence and fate of pharmaceutical compounds in drinking or waste water processes has become very popular in recent years. Liquid chromatography with tandem mass spectrometry is a powerful analytical tool often used to determine pharmaceutical residues at trace level in water. However, many steps may disrupt the analytical procedure and bias the results. A list of 27 environmentally relevant molecules, including various therapeutic classes and (cardiovascular, veterinary and human antibiotics, neuroleptics, non-steroidal anti-inflammatory drugs, hormones and other miscellaneous pharmaceutical compounds), was selected. In this work, a method was developed using ultra performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) and solid-phase extraction to determine the concentration of the 27 targeted pharmaceutical compounds at the nanogram per litre level. The matrix effect was evaluated from water sampled at different treatment stages. Conventional methods with external calibration and internal standard correction were compared with the standard addition method (SAM). An accurate determination of pharmaceutical compounds in drinking water was obtained by the SAM associated with UPLC-MS/MS. The developed method was used to evaluate the occurrence and fate of pharmaceutical compounds in some drinking water treatment plants in the west of France

Analysis of chlordecone by LC/MS-MS in surface and wastewaters

International audienceChlordecone (also known as Kepone) was used extensively in the French West Indies until 1993. This persistent pollution raises the question of the faith of this pesticide through water treatment plants and its eventual release in the environment. To address this issue, a two-step methodology is herein proposed. First, a complete description of the analysis of \CLD\ is given using liquid chromatography with mass spectrometry (LC/MS-MS). The reliability of this analytical methodology was demonstrated in ultrapure water as well as in the presence of organic and/or inorganic compounds (groundwater, river water and nutritive solutions). The limits of quantification were decreased to 1.5 μg L−1. In a second part, the removal of \CLD\ is considered via the sorption onto activated sludge. Kinetics and isotherms of sorption were determined. Very short times (less than 5 min) were observed to reach the equilibrium. Moreover, a linear relationship was determined for the sorption equilibrium, which led to the conclusion that the solid/liquid partition coefficient was 7600 L kg−1, i.e. log KOC of 3.88, very close to the values encountered for the sorption of \CLD\ in soils

Effects of UV-dechloramination of swimming pool water on the formation of disinfection by-products: A lab-scale study.

International audienceUV dechloramination has become a very popular process for reducing the concentration of chloramines in public swimming pool water. As the effects of this process on the formation of disinfection by-products (DBPs) remain a controversial issue, a bench-scale study has been undertaken to examine the impact of UV dechloramination on the formation of various DBPs. Four pool water samples were exposed to UV radiation at 254 nm in the presence of free chlorine ([Cl2]0 = 3 mg L-1) and then chlorinated in the dark for 24 h ([Cl2]0 = 3 mg L-1). High UV doses (up to 47 kJ m-2) were used to simulate cumulative UV doses received by real pool waters. The data showed that UV irradiation led to a 90 % photodecay of free chlorine for UV doses ranging from 13 to 20 kJ m-2, to the formation of chlorate ion (0.05-0.11 mole of chlorate/mole of free chlorine decomposed) and to a significant increase in the chlorine demand of pool water during the post-chlorination step. UV exposure followed by post-chlorination did not significantly affect the formation of haloacetic acids, led to a small increase in the concentrations of adsorbable organic halogen (AOX) and of chloral hydrate and markedly increased the formation of trihalomethanes (chloroform, bromodichloromethane, chlorodibromomethane), dichloroacetonitrile, 1,1,1-trichloropropanone and chloropicrin

Determination of hydrogen peroxide by differential pulse polarography in advanced oxidation processes for water treatment

International audienceKnowing the concentration of hydrogen peroxide (H2O2) is crucial for the monitoring and optimizing the Fenton reaction in advanced oxidation processes. Several analytical methods exist to determine these concentrations, but their applications can be difficult because of low selectivity (interaction with other metals), the use of toxic compounds, or low concentrations (mu mol LmmolL(-1)). To overcome these problems, we developed a differential pulse polarographic (DPP) method at the dropping mercury electrode (DME) with the following conditions: tg = 1.0 s, Delta E = -100 mV and v = 10 mV s(-1). Calibration curves had very high correlation coefficients (R-2 > 0.999). The limits of detection and quantification were evaluated respectively at 13 and 21 mu mol L-1 with peak area measurements of hydrogen peroxide reduction (Ap). The DPP method was compared with other analytical methods (iodometric titration and spectrophotometry) for determining at low concentrations of H2O2 (in the order of mmol L (1) to mu mol L-1) in Fenton and electro-Fenton processes. The method developed here allows measure low concentrations of hydrogen peroxide in Fenton and electro-Fenton processes in acidic solutions (similar to 3) and the presence of interfering species such as Fe3+ and dissolved oxygen

Etude de la décomposition de la monochloramine en milieu aqueux et réactivité avec des composés phénoliques

Cette étude a eu pour but d'étudier la réactivité de la monochloramine sur des composés phénoliques simples en solution aqueuse. Les expériences ont été réalisées à température ambiante, à pH compris entre 5 et 14, et en utilisant des rapports de concentrations Chlorure d ammonium/Chlore (N/Cl) compris entre 1,08 et 31,2 mol/mol pour la préparation des solutions de monochloramine. Une étude préliminaire effectuée en absence de composés organiques a permis de proposer un modèle cinétique capable de décrire les cinétiques de décomposition de la monochloramine, dans l'eau ultrapure non tamponnée et tamponnée (tampon phosphates) et de modéliser les évolutions des concentrations en monochloramine, dichloramine et en chlore libre dans une large gamme de valeurs de pH et de rapport N/Cl. L'étude de la réactivité de la monochloramine sur six composés phénoliques (phénol, catéchol, résorcinol, hydroquinone, pyrogallol et phloroglucinol) et de quelques matières organiques extraites d'eaux naturelles, a permis de déterminer des demandes en monochloramine et de montrer l'influence du rapport N/Cl sur les rendements de formation de chloroforme, d'acides chloroacétiques, de composés organochlorés totaux (AOX) ainsi que sur l'évolution du Carbone Organique Total (COT). Une étude cinétique détaillée a permis de déterminer les constantes cinétiques absolues de réaction de la monochloramine sur les trois formes acido-basique du résorcinol et de ses premiers sous-produits de réaction. La modélisation cinétique a permis de démontrer que le chlore libre, issu de l'hydrolyse de la monochloramine, contribue d'une manière importante à l oxydation du résorcinol aux faibles valeurs de rapport N/Cl.The reactivity of monochloramine with model phenolic coumpounds in aqueous solution has been investigated. Experiments were carried out at ambient temperature, at pH within 5 to 14, and by using ammonia-to-chlorine ratios (N/Cl) ranging from 1.08 to 31.2 mol/mol for the preparation of monochloramine solutions. A preliminary study of the autodecomposition of monochloramine in organic-free solutions showed that the rate of decomposition of monochloramine in non-buffered and in phosphate-buffered ultra-pure water could be accurately simulated by a kinetic model. This model could also simulate the concentration-time profiles of monochloramine, dichloramine and free chlorine under a wide range of pH values and N/Cl molar ratios. The monochloramine demands of six phenolic compounds (phenol, catechol, resorcinol, hydroquinone, pyrogallol and phloroglucinol) and of Natural Organic Matter have been determined at neutral pH. The effects of N/Cl on the yields of formation of chloroform, chloroacetic acids and Total Organochlorinated byproducts and on the decay of Total Organic Carbon have been examined. The absolute second-order rate constants for the reaction of monochloramine with the three protonated forms of resorcinol and chlororesorcinols were determined. Kinetic modeling of the resorcinol/chlorine/chloramines system evolution underlined the key role played by free chlorine (liberated from monochloramine hydrolysis) in the mechanisms of resorcinol degradation at low N/Cl molar ratios.POITIERS-BU Sciences (861942102) / SudocSudocFranceF