Publications

Abstract We report on the fabrication and performances of a solid-phase microextraction (SPME) fiber based on a stainless steel wire coated with a covalently attached polyacrylonitrile (PAN)/multi-walled carbon nanotubes (MWCNTs) composite. This new coating is obtained by atom transfer radical polymerization (ATRP) of acrylonitrile mixed with MWCNTs. ATRP is initiated from 11-(2-bromo-2-methylpropionyloxy)-undecyl-phosphonic acid molecules grafted on the wire surface via the phosphonic acid group. The extraction performances of the fibers are assessed on different classes of compounds (polar, non-polar, aromatic, etc.) from water solutions by headspace extraction. The optimization of the parameters affecting the extraction efficiency of the target compounds was studied as well as the reproducibility and the repeatability of the fiber. The fibers sustain more than 200 extractions during which they remain chemically stable and maintain good performances (detection limits lower than 2 mu g/l, repeatability, etc.). Considering their robustness together with their easy and inexpensive fabrication, these fibers could constitute promising alternatives to existing products.

Abstract This study focuses on the factors that affect trihalomethane (THMs) formation when dissolved organic matter (DOM) fractions (colloidal, hydrophobic, and transphilic fractions) in aqueous solutions were disinfected with chlorine. DOM fractions were isolated and fractionated from filtered lake water and were characterized by elemental analysis. The investigation involved a screening Placket-Burman factorial analysis design of five factors (DOM concentration, chlorine dose, temperature, pH, and bromide concentration) and a Box-Behnken design for a detailed assessment of the three most important factor effects (DOM concentration, chlorine dose, and temperature). The results showed that colloidal fraction has a relatively low contribution to THM formation; transphilic fraction was responsible for about 50% of the chloroform generation, and the hydrophobic fraction was the most important to the brominated THM formation. When colloidal and hydrophobic fraction solutions were disinfected, the most significant factors were the following: higher DOM fraction concentration led to higher THM concentration, an increase of pH corresponded to higher concentration levels of chloroform and reduced bromoform, higher levels of chlorine dose and temperature produced a rise in the total THM formation, especially of the chlorinated THMs; higher bromide concentration generates higher concentrations of brominated THMs. Moreover, linear models were implemented and response surface plots were obtained for the four THM concentrations and their total sum in the disinfection solution as a function of the DOM concentration, chlorine dose, and temperature. Overall, results indicated that THM formation models were very complex due to individual factor effects and significant interactions among the factors. In order to reduce the concentration of THMs in drinking water, DOM concentrations must be reduced in the water prior to the disinfection. Fractionation of DOM, together with an elemental analysis of the fractions, is important issue in the revealing of the quality and quantity characteristics of DOM. Systematic study composed from DOM fraction investigation and factorial analysis of the responsible parameters in the THM formation reaction can, after an evaluation of the adjustment of the models with the reality, serves well for the evaluation of the spatial and temporal variability in the THM formation in dependence of DOM. However, taking into consideration the natural complexity of DOM, different operations and a strict control of them (like coagulation/flocculation and filtration) has to be used to quantitatively remove DOM from the raw water. Assuming that this study represents a local case study, similar experiments can be easily applied and will supply with relevant information every local water treatment plant meeting problems with THM formation. The coagulation/flocculation and the filtration stages are the main mechanisms to remove DOM, particularly the colloidal DOM fraction. With the objective to minimize THMs generation, different unit operation designed to quantitatively remove DOM from water must be optimized.

Abstract The structure and energetics of the methoxy-derivatives of coumarin with the substituent either on the benzenic ring (5-, 6-, 7- and 8-methoxy coumarin) or on the pyrone ring (3- and 4-methoxycoumarin) is addressed on the basis of some well documented computational methods. Estimates of the enthalpies of formation are obtained using appropriate homodesmotic reactions and also atomization reactions. The condensed phase standard (p(o) = 0.1 MPa) molar enthalpy of formation for 7-methoxycoumarin was derived from the standard molar enthalpy of combustion, in oxygen, at T = 298.15 K. measured by static bomb combustion calorimetry. The standard molar enthalpy of sublimation, at T = 298.15 K, was measured by Calvet microcalorimetry. Combining these values, the enthalpy of formation in gas-phase, at T = 298.15 K. was derived: -(321.6 +/- 2.8) kJ mol(-1). The temperature of fusion, T(fusion), and fusion enthalpies, at T = T(fusion), are also reported. Good agreement between experimental and computational data is achieved. The aromaticity of these systems has been assessed through the evaluation and analysis of the Nucleus Independent Chemical Shifts (NICS) and their most significant components. NICS scan analyses have also been conducted to help clarifying the aromatic nature of the pyrone rings of these systems. (C) 2010 Published by Elsevier B.V.

Abstract Condensed phase standard (p degrees = 0.1 MPa) molar enthalpies of formation for coumarin and chromone were derived from the standard molar enthalpies of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The standard molar enthalpies of sublimation, at T = 298.15 K, were measured by Calvet microcalorimetry. Combining these values, the following enthalpies of formation in the gas phase, at T = 298.15 K, were then derived: coumarin, -(163.4 +/- 3.3) kJ(.)mol(-1), and chromone, -(126.1 +/- 2.5) kJ(.)mol(-1). The temperatures of fusion, T(fusion), and fusion enthalpies, at T = T(fusion), were also reported. Additionally, theoretical calculations were done using different methods: DFT/B3LYP, MCCM (MC-UT/3 and MC-QCISD/3), and also the more accurate G3MP2 method. Good agreement between experimental and theoretical data was achieved. Some correlations between structure and energy were also made, and the aromaticity of the compounds was evaluated by the nucleus independent chemical shifts (NICS).

Abstract Many Studies have investigated the protective effects of oleuropein and hydroxytyrosol against cell injury, but few have investigated the protective effects of oleuropein aglycones 3.4-dihydroxyphenylethanol-elenolic acid (3,4-DHPEA-EA) and 3,4-dihydroxyphenylethanol-elenolic acid dialdehyde (3,4-DHPEA-EDA). The present work Studied and compared the capacity of these four compounds, found at high concentrations in olive oil, to protect red blood cells (RBCs) from oxidative injury. The in vitro oxidative stress of RBCs was induced by the water-soluble radical initiator 2,2'-azo-bis(2-amidinopropane) dihydrochloride. RBC changes were evaluated either by optical microscopy or by the amount of hemolysis. All compounds were shown to significantly protect RBCs from oxidative damage in a dose-dependent manner. The order of activity at 20 mu M was: 3,4-DHPEA-EDA > hydroxytyrosol > Oleuropein > 3,4-DHPEA-EA. Even at 3 mu M, 3,4-DHPEA-EDA and hydroxytyrosol still had an important protective activity. However, deleterious morphological RBC changes were Much more evident in the presence of hydroxytyrosol than with 3,4-DHPEA-EDA. For the first time it was demonstrated that 3,4-DHPEA-EDA, one of most important olive oil polyphenols, may play a noteworthy protective role against ROS-induced oxidative injury in human cells since lower closes of this compound were needed to protect RBCs in vitro from oxidative mediated hemolysis.

Abstract This paper describes a novel tape platform ion sensing methodology specific to the detection of cadmium(II) ions in aqueous solution based on assisted ion transfer reactions across a polarized water vertical bar organic gel micro-interface. The tape ion sensors were constructed to incorporate the micro-water vertical bar polyvinylchloride-2-nitrophenylethyl ether (PVC-NPOE) gel interfaces referred to as ionodes. The sensors have overall thicknesses less than 300 mu m, allowing their packaging in a disposable tape format. The detection methodology is based on the selective assisted transfer of the cadmium ion in aqueous phase by ETH 1062 present in the PVC-NPOE gel layer and was first investigated using cyclic voltammetry. Quantitative analysis of cadmium(II) ions in aqueous solution using the tape sensors was then conducted under stop-flow conditions. Detection limits as low as 20 ppb (178 nM) for Cd(II) ions in very small volumes as low as a single 20 W droplet without any sample preconcentration was achieved in an analysis time of approximately 20s, which could be easily employed for the direct measurement of Cd(II) ion levels in various field applications. The tape ion sensor can also be used in a flow-cell geometry to preconcentrate Cd(H) ions from aqueous samples and further improve the detection limit.

Abstract Coumarins, also known as benzopyrones, are present in remarkable amounts in plants, although their presence has also been detected in microorganisms and animal sources. The structural diversity found in this family of compounds led to the division into different categories, from simple coumarins to many other kinds of policyclic coumarins such as furocoumarins and pyranocoumarins. Simple coumarins and analogues are a large class of compounds that have attracted their interest for a long time due to their biological activities: they have shown to be useful as antitumoural, anti-HIV agents and as CNS-active compounds. Furthermore they have been reported to have multiple biological activities (anticoagulant, anti-inflammatory) although all these properties have not been evaluated systematically. In addition their enzyme inhibition properties, antimicrobial and antioxidant activities are other foremost topics of this field of research. The present work is to survey the information published from 1990 till 2008, which is mainly related to the occurrence, synthesis and biological importance of simple coumarins and some analogues such as biscoumarins and triscoumarins. Information is also highlighted concerning the development of new synthetic strategies that could help in drug design and in the work on SAR or QSAR. All rights reserved - © 2009 Bentham Science Publishers.

Abstract A new methodology for the covalent functionalization of a SAM of 11-amino-1-undecanethiol, previously adsorbed on polycrystalline Au, was successfully applied in order to immobilize a beta-CD layer on surface. A two steps synthetic strategy is proposed based on the activation of the SAM with di-(N-succinimidyl) carbonate for the further inclusion of the beta-CD. The modification of the SAM was followed by PM-FTIRRAS, AFM imaging, CV, and EIS which confirmed the introduction of beta-CD layer. The AFM images allowed the identification of homogeneously distributed beta-CD aggregates over the Au grain microstructure. The electrode was characterized in the presence of electroactive species in solution, with the ability to form inclusion complexes with the beta-CD cavity. Contrary to the reported for other thiolated CD derivative films, the results of this study showed the formation of well-packed and compact structures which strongly reduce non-specific adsorption phenomena. The redox response of the probes at the beta-CD electrode was shown to appear at higher potentials with respect to the response at bare Au. Good correlation was found between the increase of the hydroquinone oxidation peak and, both, the scan rate used in CV experiments (typical behavior of surface-confined species) and the hydroquinone concentration. In the case of dopamine, the processes seem to shifted out of the potential window of SAM stability. The results suggest that this problem could be overcome by improving the design of the device.

Abstract The kinetics and equilibrium of the adsorption of Indanthrene Olive Green (IOG) from aqueous solution onto chitosan have been investigated. The chitosan was characterised in terms of its average degree of de-acetylation (DD) and by XRD, TGA/DTG, IR, SEM and specific BET surface area methods. Batch adsorptions experiments were carried out at different pH values and dye concentrations. It was found that the adsorption process was favoured by acidic pH conditions (4.0-6.0). The adsorption followed second-order rate kinetics and the experimental equilibrium data followed the Langmuir isotherm, thereby suggesting that chemisorption might be the major adsorption mode. Such adsorption also occurred on chitosan fibres, although to a significantly lower extent than on crushed chitosan. The corresponding thermodynamic parameters (ΔG, ΔH and ΔS) were calculated. The positive values obtained for ΔH (161.7 kJ/mol) and ΔS [559.9 J/(mol K)] suggest that the adsorption process was endothermic, with the randomness of the system increasing during the adsorption process. A simplified adsorption model has also been proposed.

Abstract Mixed polymer-surfactant systems have been intensively investigated in the last two decades, with the main focus on surfactant micelles as the surfactant aggregate in interaction. The main types of phase behavior, driving forces and structural/rheological effects at stake are now fairly well understood. Polymer-vesicle systems, on the other hand, have received comparatively less attention from a physico-chemical perspective. In this review, our main goal has been to bridge this gap, taking a broad approach to cover a field that is in clear expansion, in view of its multiple implications for colloid and biological sciences and in applied areas. We start by a general background on amphiphile self-assembly and phase separation phenomena in mixed polymer-surfactant solutions. We then address vesicle formation, properties and stability not only in classic lipids, but also in various other surfactant systems, among which catanionic vesicles are highlighted. Traditionally. lipid and surfactant vesicles have been studied separately, with little cross-information and comparison, giving duplication of physico-chemical interpretations. This situation has changed in more recent times. We then proceed to cover more in-depth the work done on different aspects of the associative behavior between vesicles (of different composition and type of stability) and different types of polymers, including polysaccharides. proteins and DNA. Thus. phase behavior features. effects of vesicle structure and stability, and the forces/mechanisms of vesicle-macromolecule interaction are addressed. Such association may generate gels with interesting theological properties and high potential for applications. Finally, special focus is also given to DNA, a high charge polymer. and its interactions with surfactants, and vesicles. in particular, in the context of gene transfection studies.