Comunicaciones a congresos, Conferencias, … (Fac. de Ciencias)
Permanent URI for this collectionhttps://hdl.handle.net/10171/70279
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9 results
Results
- Electrochemical and theoretical assessment of wine by means of complexation processes with Zn and Cu(Universidad de Navarra, 2008-05-30) Santamaria-Elola, C. (Carolina); Esparza, I. (Irene); Fernandez-Alvarez, J.M. (José María); García-Mina, J.M. (José María)In the present work, an electrochemical technique DPASV will be used to follow up the evolution of ligand-metal complexes during the first sixty days of a wine fermentation. The used approach consisted in the study of the complexing capacity of natural occurring ligands on wine with respect to Zn and Cu by means of stripping voltammetry in acetate pH 4 buffered 1:5 diluted samples onto which increasing amounts of standard metals were added. The resulting titration curves allowed the ligand concentration to be estimated, and the Scatchard and/or Langmuir algorithm transformation permitted the elucidation of the predominant stoichiometries of existing complexes. This technique has proved very sensitive to detect changes in the composition of samples along fermentation time as a function of major ligand populations. Molecular modelling studies of the main polyphenols present in wine were undertaken with Hyperchem®. These studies were done in the presence of Cu and Zn in order to confirm the stoichiometry of the most energetically favourable ligand-metal complexes.
- Distinct complexing trends of chitosan with toxic metals (PO1-24)(European Chitin Society, 2009-05-23) Navarro-Blasco, I. (Iñigo); Lasheras-Zubiate, M. (María); Fernandez-Alvarez, J.M. (José María)We have been able to prove that not only adsorption but also complexation of different metals (Pb, Cd, Mo, Cu, Zn and Cr) actually takes place in acetate buffer (pH=4) with Chitosans of different molecular weights and deacetylation degrees. Depending on the different electrochemical behaviour on mercury electrode of studied metals and the nature of the resulting complexes, diverse approaches have been used. Chitosan molecular weight and concentration had been seen to play a key role in the Chitosan binding activity with Zn, Pb and Cd, as reported elsewhere[1]. Length of Chitosan chains influences the degree of complexation with both Cr and Mo, while Cu binding capacity remains independent of the molecular weight of the assayed polymers. The larger the polymer chain length the higher the number of amino group available for the retention of both Cr and Mo within the tridimensional structure of the acting ligand. This is consistent with a predominant intra-chain linkage of both metal atoms. On the contrary, in the case of Cu, an inter-layer binding mechanism is proposed as the main retention factor by Chitosan.
- A study of fractioning and heavy metal complexation in wines(Universidad de la Coruña, 2003-10-21) Santamaria-Elola, C. (Carolina); Salinas, I. (Íñigo); Calvo, M.I. (María Isabel); Esparza, I. (Irene); Fernandez-Alvarez, J.M. (José María)This work is concerned with the loss of colour observed in some of the red wines of Navarra.
- A study of heavy metal complexation in wines(NUI, Galway, 2004-06-06) Santamaria-Elola, C. (Carolina); Salinas, I. (Íñigo); Esparza, I. (Irene); Fernandez-Alvarez, J.M. (José María)DPV was used to study complexation processes of Zn in must samples, at their natural pH. Titration curves allowed the calculation of ligand concentration and stability constants, following the suitable linearization methods.
- Electrochemical and theoretical complexation studies between Zn, Cu and individual anthocyanins in wine samples(Universidad de Salamanca, 2004-09-05) Santamaria-Elola, C. (Carolina); Salinas, I. (Íñigo); Esparza, I. (Irene); Fernandez-Alvarez, J.M. (José María); García-Mina, J.M. (José María)Book of abstracts of Euroanalysis XIII 2004; PS1-280. Identification of the posible interactions between individual anthocyanins and metals was performed in selected samples of must ans wine, collected at different vinification times.
- Picloram and Thiram: 2 pesticides acting as heavy metals carriers portrayed by DPASV(ISE, 2008-09-07) Santamaria-Elola, C. (Carolina); Valle, E.M.A. (Eliana M.A.); Machado, S.A.S. (Sergio A.S.); Fernandez-Alvarez, J.M. (José María)Comunicación presentada en el Program of the 59th Annual Meeting of the International Society of Electrochemistry, Seville, 2008, S10-P085:Page 141. Picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxilic acid) is a herbicide widely used, alone or in combination with other herbicides to control of weeds in crops of sugar cane, rice, pasture and wheat1. It can stay active for long time, depending on the type of soil, moisture and temperature. Thiram (N,N-dimethildithiocabamate) is a fungicide used for a control of a variety diseases in the crops of fruits, vegetables and ornamentals2. From an electrochemical point of view, the study of the redox behaviour of both pesticides on modified electrodes has been reported recently3. However, few works reported the interactions between metallic ions and pesticides and their properties in the environment, although these molecules usually present functional groups that can act as ligands. In this work, we studied the interaction between heavy metals (Zn, Cu, Pb and Cd) and the pesticides (picloram and thiram) using the Differential Pulse Anodic Stripping Voltammetry technique on Hg electrode (DPASV) which has shown efficient in the evaluation of the formation of complexes in natural samples4 through the competing role of Hg for metals with respect to ligands. Electrochemical measurements provided a simple means to evaluate the stoichiometry of the complexes, and Scatchard and Langmuir algorithms allowed the calculation of the conditional complexation constants for both systems in an acetate pH 4 buffered solutions. Studies carried out for both Zn and Cu with Picloram have shown that 1:1 complexes were formed in all instances. Calculated conditional stability constants are quite close (log K’ ~ 6) for both metallic species, Cu consistently yielding highest values.
- Voltammetric evaluation of chitosan as an effective complexing ligand for the removal of toxic heavy metals(ISE, 2008-09-07) Navarro-Blasco, I. (Iñigo); Lasheras-Zubiate, M. (María); Fernandez-Alvarez, J.M. (José María)Program of the 59th Annual Meeting of the International Society of Electrochemistry, 2008:138: The aim of this study is to evaluate de complexation of toxic heavy metals such as Pb, Zn, Cd and Cu by three commercial chitosans with different molecular weights. For this purpose, the complexation capacity of chitosan was evaluated through competitive deposit of the metals onto the HMDE from ligand-containing solutions and subsequent voltammetric measurement of the anodic stripping signal. Chitosan and spiked metal solutions were dissolved in an acetic-acetate buffer solution (pH=3,5). The complexation capacity was also evaluated at different concentrations of chitosans. Up to now, preliminary results indicate that chitosan complexes more effectively Zn than Pb, probably due to the lower size of Zn which allows its inclusion into the available linking sites of chitosan. Besides, Zn stripping peak shows a marked decrease in its intensity and a displacement towards less negative potentials, proving the high affinity of chitosan for Zn.
- An etherified derivative of chitosan as an improved complexing agent for solidification/stabilisation of heavy metals into cementitious matrices(2010-06-20) Alvarez-Galindo, J.I. (José Ignacio); Bessard, B. (Benjamin); Navarro-Blasco, I. (Iñigo); Lasheras-Zubiate, M. (María); Fernandez-Alvarez, J.M. (José María)Book of abstracts of the13th International Conference on Electroanalysis ESEAC, 2010; PIN50:357: Chitosan is a natural widely available biopolymer and increasingly used for most diverse applications. Different chitosans of various molecular weight and deacetylation degrees have been previously checked as for their complexing activity towards selected target heavy metals, such as Zn, Pb, Cd, Cu, Mo and Cr [1,2]. Some rheological properties of cementitious matrices have been seen to improve upon incorporation of those biopolymers, such as water retention, setting time and consistency (through the flow table test). In this paper we report the different complexing patterns found for Zn and Pb when a chitosan derivative is used. These results will be discussed by comparison with the behaviour of the aforementioned non-modified chitosans.
- Assessment of the effect of pH values on the complexing ability of two etherified derivatives of chitosan with a view to improving retention of heavy metals into cement mortars(2010-06-20) Alvarez-Galindo, J.I. (José Ignacio); Bessard, B. (Benjamin); Navarro-Blasco, I. (Iñigo); Lasheras-Zubiate, M. (María); Fernandez-Alvarez, J.M. (José María)Book of abstracts of the13th International Conference on Electroanalysis ESEAC, 2010; PIN50:358: Removal of heavy metals from polluted aqueous systems (industrial and waste waters) may be accomplished by complexing and sequestering them into inert matrices. A suitable matrix can be cement mortars, owing to the fact that they have the capability of immobilise and stabilise the complexes, reducing heavy metal leaching. The complexing ligand has to be properly chosen so that it presents high affinity for the metal and a good performance of the formed complex in the largely alkaline medium of the cement mortar. Our research interest is focused on chitosans and its derivatives as a model ligand that fulfills both demands. The complexing ability of unmodified chitosans for several target heavy metals has been checked in acetated buffer (pH = 4) [1]. In this contribution we will take advantage of the fact that some etherified chitosans are soluble in alkaline pH mimicking the cement mortar conditions. Retention of Zn and Pn in alkaline media by the etherified chitosans will be related to the heavy metal concentrations found in the leaching coming from polymer modified mortars.