Browsing Articles publicats (Química) by Issue Date
Now showing items 21-40 of 258
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Voltammetric lability of metal complexes at spherical micorelectrodes with various radii
(Elsevier, 2001)The size of a microelectrode can have a dramatic impact on the relative importance of the diffusional and kinetic contributions to the voltammetric current of an electroactive metal ion in a complexing medium. Decreasing ... -
Evaluation of the Koutecký-Koryta approximation for voltammetric currents generated by metal complex systems with various labilities
(Elsevier, 2002)The voltammetric response of metal complex systems with various labilities is analyzed by rigorous numerical simulation with the Finite Element Method of the time-dependent concentration profiles of the different species. ... -
Lability and mobility effects on mixtures of ligands under steady-state conditions
(Royal Society of Chemistry, 2003)Analytical solutions for the steady-state flux arriving at an active surface from a mixture (in which one active species reacts with non-active ligands in the medium) can be helpful in a variety of problems: voltammetric ... -
Acid-base properties of brown seaweed biomass considered as a Donnan gel. A model reflecting electrostatic effects and chemical heterogeneity
(American Chemical Society, 2003)Brown seaweeds are interesting materials to be used as biosorbents for heavy metals due to their high binding ability and low cost. The study of the passive biosorption of protons on this kind of materials and its ... -
AGNES: a new electroanalytical technique for measuring free metal ion concentration
(Elsevier, 2004)AGNES (absence of gradients and Nernstian equilibrium stripping) is a stripping technique consisting of two conceptual steps: (i) application of a potential program (e.g. a step at a fixed potential) generating a known ... -
Voltammetric lability of multiligand complexes: the case of ML2
(Elsevier, 2004)The voltammetric lability of a complex system, where a metal ion M and a ligand L form the species ML and ML2, is examined. Together with the rigorous numerical simulation of the problem, two limiting cases are analysed ... -
The impact of the transient uptake flux on bioaccumulation: linear adsorption and first-order internalisation coupled with spherical semi-infinite mass transport
(Elsevier, 2004)The uptake of a chemical species (such as an organic molecule or a toxic metal ion) by an organism is modelled considering linear pre-adsorption followed by a first-order internalisation. The active biosurface is supposed ... -
Affinity distribution functions in multicomponent heterogeneous adsorption. Analytical inversion of isotherms to obtain affinity spectra
(American Institute of Physics, 2004)An analytical approach for the interpretation of multicomponent heterogeneous adsorption or complexation isotherms in terms of multidimensional affinity spectra is presented. Fourier transform, applied to analyze the ... -
Gibbs-Donnan and specific ion interaction theory descriptions of the effect of ionic strength on proton dissociation of alginic acid
(Elsevier, 2004)The apparent proton dissociation constants of a commercial alginic acid have been obtained in KNO3 and NaCl at concentrations ranging between 0.01 and 2 mol·L-1. An analysis of the dependence on the ionic strength at a ... -
Volatile production, quality and aroma-related enzyme activities during maturation of ‘Fuji’ apples
(Elsevier, 2004)Production of volatile aroma compounds, and quality parameters, were monitored in relation to the activity of lipoxygenase, pyruvate decarboxylase, alcohol dehydrogenase and alcohol o-acyltransferase during maturation of ... -
Characterization of Fuji apples from different harvest dates and storage conditions from measurements of volatiles by gas chromatography and electronic nose
(American Chemical Society, 2004)Volatile compounds in Fuji apples harvested at two different maturities were measured at harvest and after 5 and 7 months of cold storage (1 °C) in four different atmospheres. When the samples were characterized by both ... -
Determination of Zn2+ concentration with AGNES using different strategies to reduce the deposition time
(Elsevier, 2005)Absence of gradient and Nernstian equilibrium stripping (AGNES) senses the free ion concentration of Zn(II) in solutions containing different ligands, being unaffected by the lack of reversibility of the Zn2+/Zn0 couple ... -
LBGK method coupled to time splitting technique for solving reaction-diffusion processes in complex systems
(The Royal society of Chemistry, 2005)A new approach to numerically solve a reaction-diffusion system is given, specifically developed for complex systems including many reacting/diffusing species with broad ranges of rate constants and diffusion coefficients, ... -
Removal of inorganic mercury from aqueous solutions by biomass of the marine macroalga Cystoseira Baccata
(Elsevier, 2005)The ability of Cystoseira baccata algal biomass to remove Hg(II) from aqueous solutions is investigated. The mercury biosorption process is studied through batch experiments at 25ºC with regard to the influence of contact ... -
Interaction of acrylic-maleic copolymers with H+, Na+, Mg2+ and Ca2+: Thermodynamic parameters and their dependence on medium
(Elsevier, 2005)Thermodynamic parameters for the interaction of two acrylic-maleic copolymers (MW = 3 and 70 kDa) with H+, Na+, Mg2+ and Ca2+ were obtained from potentiometric and calorimetric measurements. Apparent protonation constants were ... -
Biosorption of cadmium by the protonated macroalga Sargassum muticum: Binding analysis with a nonideal, competitive, and thermodynamically consistent adsorption (NICCA) model
(Elsevier, 2005)Protonated biomass of the seaweed Sargassum muticum was investigated for its ability to remove cadmium(II) from aqueous solutions. In this work, a nonideal, semiempirical, thermodynamically consistent (NICCA) isotherm was ... -
Reliability of the density functional approximation to describe the charge transfer and electrostatic complexes involved in the modeling of organic conducting polymers
(American Physical Society, 2005)Both the intermolecular interaction energies and the geometries for M ̄ thiophene, M ̄ pyrrole, M n+ ̄ thiophene, and M n+ ̄ pyrrole ͑with M = Li, Na, K, Ca, and Mg; and M n+ = Li+ , Na+ , K+ , Ca2+, and Mg2+͒ have been ... -
Lability of complexes in steady-state finite planar diffusion
(Elsevier, 2006)The analytical solution of the reaction-diffusion problem of a species forming a complex (with any association and dissociation rate constants) in solution and disappearing at an active planar surface is presented for a ... -
Conditional equilibrium constants in multicomponent heterogeneous adsorption: The conditional affinity spectrum
(American Institute of Physics, 2006)The concept of conditional stability constant is extended to the competitive binding of small molecules to heterogeneous surfaces or macromolecules via the introduction of the conditional affinity spectrum (CAS). The CAS ... -
Esterification of oleic acid catalayzed by an Aspergillus niger strain. Influence of water activity and alcohol concentration
(Facultad de Ciencias de la Universidad del Tolima, 2006)Effects of water activity and 1-propanol concentration on synthesis of propyl oleate from oleic acid using Aspergillus niger cell-bound lipases in isooctane are described. A. niger produces lipases (EC 3.1.1.3) which partly ...