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Tauler R.,CSIC - Institute of Chemical and Environmental Research | Da Silva J.C.G.E.,University of Porto
Journal of Fluorescence | Year: 2011

The performance of multivariate curve resolution (MCR-ALS) to decompose sets of excitation emission matrices of fluorescence (EEM) of nanocomposite materials used as analytical sensors was assessed. The two fluorescent nanocomposite materials were: NH 2-polyethylene glycol (PEG200) functionalized carbon dots, sensible to aqueous Hg(II) (CD); and, CdS quantum dots attached to the dendrimer DAB, sensible to the ionic strength of the aqueous medium (CdS-DAB). The structures of these sets of EEM, obtained as function of the Hg(II) concentration and ionic strength, are characterized by collinear properties (CD) and non-linear spectral variations (CdS-DAB). MCR-ALS was able to detect that the source of the collinearities is the presence of different size CD that show similar affinity towards Hg(II). Moreover, MCR-ALS was able to model the non-linear spectral variations of the CdS-DAB that are induced by varying ionic strength. The chemometric pre-processing of the fluorescent data sets using soft-modelling multivariate curve resolution like MCR-ALS is a critical step to transform these nanocomposites with interesting fluorescent proprieties into analytical useful nanosensors. © 2011 Springer Science+Business Media, LLC.

Ruckebusch C.,University of Lille Nord de France | Sliwa M.,University of Lille Nord de France | Pernot P.,University Paris - Sud | de Juan A.,University of Barcelona | Tauler R.,CSIC - Institute of Chemical and Environmental Research
Journal of Photochemistry and Photobiology C: Photochemistry Reviews | Year: 2012

Nowadays, time-resolved spectroscopy data can be routinely and accurately collected in UV-vis femtosecond transient absorption spectroscopy. However, the data analysis strategy and the postulation of a physically valid model for this kind of measurements may be tackled with many different approaches ranging from pure soft-modeling (model-free) to hard-modeling, where the elaboration of a parametric spectro-temporal model may be required. This paper reviews methods that are used in practice for the analysis of femtosecond transient absorption spectroscopy data. Model-based methods, common in photochemistry, are revisited, and soft-modeling methods, which originate from the chemometrics field and that recently disseminated in the photo(bio)chemistry literature, are presented. These soft-modeling methods are designed to suit the intrinsic nature of the multivariate (or multi-way) measurement. Soft-modeling tools do not require a priori physical or mechanistic models to provide a decomposition of the data on the time and wavelength dimensions, the only requirement being that these two (or more) dimensions are separable. Additionally, Bayesian data analysis, which provides a probabilistic framework for data analysis, is considered in detail, since it allows uncertainty quantification and validation of the model selection step. © 2011 Elsevier B.V.

Garcia J.,Polytechnic University of Catalonia | Rousseau D.P.L.,UNESCO-IHE Institute for Water Education | Morato J.,Polytechnic University of Catalonia | Lesage E.,Ghent University | And 2 more authors.
Critical Reviews in Environmental Science and Technology | Year: 2010

The main contaminant removal processes occurring in subsurface-flow constructed wetlands treating wastewater are reviewed. Redox conditions prevailing in the wetlands are analyzed and linked to contaminant removal mechanisms. The removal of organic matter and its accumulation in the granular medium of the wetlands are evaluated with regard to particulate and dissolved components and clogging processes. The main biological processes linked to organic matter transformationaerobic respiration, denitrification, acid fermentation, sulfate reduction, and methanogenesisare reviewed separately. The processes of removal of surfactants, pesticides and herbicides, emergent contaminants, nutrients, heavy metals and faecal organisms are analyzed. Advances in wetland modeling are presented as a powerful tool for understanding multiple interactions occurring in subsurface-flow constructed wetlands during the removal of contaminants. Copyright © 2010 Taylor and Francis Group, LLC.

Guitart C.,CSIC - Institute of Chemical and Environmental Research | Guitart C.,CSIC - Institute of Marine Sciences | Garcia-Flor N.,CSIC - Institute of Chemical and Environmental Research | Miquel J.C.,IAEA Marine Environment Laboratories | And 2 more authors.
Journal of Marine Systems | Year: 2010

Several measurements of polycyclic aromatic hydrocarbons (PAHs) in coastal marine compartments (viz. atmosphere, sea surface microlayer, subsurface seawater, sinking particles and sediments), made nearly simultaneously at two stations in the north-eastern Mediterranean, were used to estimate the transport fluxes of individual and total PAHs through the air-seawater-sediment system. Diffusive air-sea exchange fluxes were estimated using both subsurface water (SSW) and sea surface microlayer (SML) concentrations. The air-SML fluxes ranged from 411 to 12,292 ng m- 2 d- 1 (absorption) and from - 506 to -13,746 ng m- 2 d- 1 (volatilisation) for total PAHs (Σ15). Air-seawater column transport of particle-associated PAHs was estimated from the analysis of particulate atmospheric and sediment interceptor trap materials. Air-sea particle deposition fluxes of total PAHs ranged from 13 to 114 ng m- 2 d- 1 and seawater particle settling fluxes (upper 5 m water column) ranged from 184 to 323 ng m- 2 d- 1. The results of this study indicate that both the magnitude and the direction of the calculated air-sea diffusive fluxes change when PAH concentrations in the SML are considered. As a result, PAHs accumulation in the SML could produce the so-called "flux capping effect". However, the high variability in the coastal air-sea PAHs flux estimations, mainly due to the parameters uncertainty, requires further experimental approaches, including improvement of parameterisations. © 2009 Elsevier B.V. All rights reserved.

Freire C.,University of Granada | Ramos R.,University of Granada | Lopez-Espinosa M.-J.,University of Granada | Lopez-Espinosa M.-J.,Center for Public Health Research | And 5 more authors.
Environmental Research | Year: 2010

The main source of human exposure to mercury is the consumption of fish contaminated with methylmercury, which may adversely affect early neurodevelopment. This study assessed mercury levels in hair of preschoolers in Spain, where fish consumption is elevated, with the aim of investigating the influence of their fish intake and other factors on mercury exposure, and evaluating their association with cognitive development. A population-based birth cohort from Granada (Spain) was studied at the age of 4 yr. Total mercury (T-Hg) levels were determined in children's hair, and daily fish intake was assessed by a food frequency questionnaire. The McCarthy Scales of Children's Abilities (MSCA) were used to assess children's motor and cognitive abilities. Complete data were gathered on 72 children, and multivariate analyses were performed to evaluate the influence of mercury exposure and fish intake on MSCA outcomes. Mean concentration of T-Hg in hair was 0.96 μg/g (95% confidence interval=0.76; 1.20 μg/g). T-Hg levels were associated with higher frequency of oily fish consumption, place of residence, maternal age, and passive smoking. After adjustment for fish intake, T-Hg levels ≥1 μg/g were associated with decrements in the general cognitive (-6.6 points), memory (-8.4 points), and verbal (-7.5 points) MSCA scores. Higher mercury exposure in children from this Mediterranean area was associated with cognitive development delay. Studies on the putative benefits of fish intake during early development should consider mercury exposure from different fish species. © 2009 Elsevier Inc. All rights reserved.

Kuligowski J.,University of Valencia | Quintas G.,Leitat Technological Center | Tauler R.,CSIC - Institute of Chemical and Environmental Research | Lendl B.,Vienna University of Technology | De La Guardia M.,University of Valencia
Analytical Chemistry | Year: 2011

The use of multivariate curve resolution-alternating least-squares (MCR-ALS) in liquid chromatography-infrared detection (LC-IR) is troublesome due to the intense background absorption changes during gradient elution. Its use has been facilitated by previous removal of a significant part of the solvent background IR contributions due to common mobile phase systems employed during reversed phase gradient applications. Two straightforward background correction approaches based on simple-to-use interactive self-modeling mixture analysis (SIMPLISMA) and principal component analysis (PCA) are proposed and evaluated on reversed phase gradient LC-IR data sets obtained during the analysis of carbohydrate and nitrophenol mixtures. After subtraction of the calculated background signal, MCR-ALS provided improved signal-to-noise ratios, removed remaining mobile phase and background signal contributions, and resolved overlapping chromatographic peaks. The present approach tends to enable easy-to-use background correction to facilitate the use of MCR-ALS in online LC-IR, even in challenging situations when gradient conditions are employed and only poor chromatographic resolution is achieved. It, therefore, shows great potential to facilitate the full exploitation of the advantages of simultaneous quantification and identification of a vast amount of analytes employing online IR detection, making new exciting applications more accessible. © 2011 American Chemical Society.

Suarez-Serrano A.,IRTA - Institute of Agricultural-Alimentary Research and Technology | Alcaraz C.,IRTA - Institute of Agricultural-Alimentary Research and Technology | Ibanez C.,IRTA - Institute of Agricultural-Alimentary Research and Technology | Trobajo R.,IRTA - Institute of Agricultural-Alimentary Research and Technology | And 2 more authors.
Ecotoxicology and Environmental Safety | Year: 2010

In the Ebro River basin, point and diffuse pollution of heavy metals stems mainly from industry and agriculture. Bioaccumulation patterns were examined under different pollution sources (point and diffuse) using levels of heavy metals (As, Cd, Cr, Cu, Hg, Pb and Zn) in abdominal muscle tissue of Procambarus clarkii. P. clarkii captured under point source effects presented the highest concentrations of Hg, Pb and As; and were related with distance to the source of industrial waste sediments. Mean Hg levels in crayfish exposed to point sources of metals significantly exceeded legal allowed values established by the European Union legislation. In the Ebro Delta, high levels of As, Cr, Cu and Zn were associated with traditional agriculture activity (diffuse pollution) as well. These results demonstrate the potential of P. clarkii to bioaccumulate heavy metals from both point and diffuse sources and hence potentially transfer these metals to higher trophic levels. © 2009 Elsevier Inc.

Ladokhin A.S.,University of Kansas Medical Center | Fernandez-Vidal M.,University of California at Irvine | White S.H.,CSIC - Institute of Chemical and Environmental Research
Journal of Membrane Biology | Year: 2010

Circular dichroism (CD) spectroscopy is an essential tool for determining the conformation of proteins and peptides in membranes. It can be particularly useful for measuring the free energy of partitioning of peptides into lipid vesicles. The belief is broadly held that such CD measurements can only be made using sonicated small unilamellar vesicles (SUVs) because light scattering associated with extruded large unilamellar vesicles (LUVs) is unacceptably high. We have examined this issue using several experimental approaches in which a chiral object (i.e., peptide or protein) is placed both on the membrane and outside the membrane. We show that accurate CD spectra can be collected in the presence of LUVs. This is important because SUVs, unlike LUVs, are metastable and consequently unsuitable for equilibrium thermodynamic measurements. Our data reveal that undistorted CD spectra of peptides can be measured at wavelengths above 200 nm in the presence of up to 3 mM LUVs and above 215 nm in the presence of up to 7 mM LUVs. We introduce a simple way of characterizing the effect on CD spectra of light scattering and absorption arising from suspensions of vesicles of any diameter. Using melittin as an example, we show that CD spectroscopy can be used to determine the fractional helical content of peptides in LUVs and to measure their free energy of partitioning of into LUVs. © The Author(s) 2010.

Fernandez-Vidal M.,University of California at Irvine | Fernandez-Vidal M.,CSIC - Institute of Chemical and Environmental Research | White S.H.,University of California at Irvine | Ladokhin A.S.,University of Kansas Medical Center
Journal of Membrane Biology | Year: 2011

The free energy of transfer of nonpolar solutes from water to lipid bilayers is often dominated by a large negative enthalpy rather than the large positive entropy expected from the hydrophobic effect. This common observation has led to the idea that membrane partitioning is driven by the "nonclassical" hydrophobic effect. We examined this phenomenon by characterizing the partitioning of the well-studied peptide melittin using isothermal titration calorimetry (ITC) and circular dichroism (CD). We studied the temperature dependence of the entropic (-TΔS) and enthalpic (ΔH) components of free energy (ΔG) of partitioning of melittin into lipid membranes made of various mixtures of zwitterionic and anionic lipids. We found significant variations of the entropic and enthalpic components with temperature, lipid composition and vesicle size but only small changes in DG (entropy-enthalpy compensation). The heat capacity associated with partitioning had a large negative value of about -0.5 kcal mol-1 K-1. This hallmark of the hydrophobic effect was found to be independent of lipid composition. The measured heat capacity values were used to calculate the hydrophobic-effect free energy ΔGhΦ, which we found to dominate melittin partitioning regardless of lipid composition. In the case of anionic membranes, additional free energy comes from coulombic attraction, which is characterized by a small effective peptide charge due to the lack of additivity of hydrophobic and electrostatic interactions in membrane interfaces [Ladokhin and White J Mol Biol 309:543-552, 2001]. Our results suggest that there is no need for a special effect - the nonclassical hydrophobic effect - to describe partitioning into lipid bilayers. © The Author(s) 2010.

Platikanov S.,CSIC - Institute of Chemical and Environmental Research | Tauler R.,CSIC - Institute of Chemical and Environmental Research | Rodrigues P.M.S.M.,Polytechnic Institute of Guarda | Antunes M.C.G.,University of Trás os Montes e Alto Douro | And 2 more authors.
Environmental Science and Pollution Research | Year: 2010

Background, aim, and scope: 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. Materials and methods: 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). Results: 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. Discussion: 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. Conclusions: 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. Recommendations and perspectives: 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. © 2010 Springer-Verlag.

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