Comunicaciones a congresos, Conferencias, … (Fac. de Ciencias)
Permanent URI for this collectionhttps://hdl.handle.net/10171/70279
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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.
- Estudio de la interacción quitosano-metales pesados y su inmovilización en matrices cementicias(Universidad de Navarra, 2008-05-30) Navarro-Blasco, I. (Iñigo); Lasheras-Zubiate, M. (María); Fernandez-Alvarez, J.M. (José María)La quitina es un biopolímero natural segundo en abundancia tras la celulosa. El quitosano es su principal derivado y se obtiene mediante desacetilación. La presencia de los grupos amino en la cadena polimérica hace del quitosano un material versátil y con múltiples aplicaciones prácticas entre las que desataca su eficacia como retenedor y fijador de metales pesados. Se ha determinado el grado de desacetilación de tres quitosanos comerciales de distinto peso molecular a través de distintas metodologías (potenciometría, espectrofotometría UV, espectrofotometría UV de primera derivada, resonancia magnética nuclear y espectrometría de infrarrojos) Por otro lado, se ha realizado un estudio voltamperométrico de la complejación de diversos metales pesados (Cd, Pb y Zn) por parte de quitosanos de distinto peso molecular y a distintas concentraciones. Los resultados muestran que el método de determinación del grado de desacetilación tiene una influencia determinante en el valor obtenido, de modo que es imprescindible especificarlo al proporcionar un resultado. Asimismo, se concluye que el quitosano compleja efectivamente cadmio, plomo y zinc, mostrando la máxima capacidad de retención para el zinc, seguido del plomo y en menor medida en cadmio. Se observa que la capacidad complejante aumenta a medida que disminuye la concentración de quitosano y aumenta su peso molecular.
- Evaluación de la capacidad complejante del quitosano para la eliminación de metales tóxicos(Universidad de Navarra, 2009-04-03) Navarro-Blasco, I. (Iñigo); Lasheras-Zubiate, M. (María); Fernandez-Alvarez, J.M. (José María)En el presente estudio se ha evaluado el comportamiento electroquímico de diversos metales (Pb, Cd, Mo, Cu, Zn y Cr) en presencia de quitosanos con distintos pesos moleculares y grados de desacetilación. Se demuestra que –efectivamente- se produce la complejación de los metales señalados, presentando distintos comportamientos en función de la naturaleza del complejo formado. Tanto el peso molecular como la concentración juegan un papel determinante en la capacidad complejante de Zn, Pb y Cd. La longitud de las cadenas tiene una elevada influencia en la complejación de Cr y Mo, no manifestándose su repercusión en el caso del Cu. Se propone un mecanismo de inclusión dentro de las cadenas de quitosano para los metales Cr y Mo, mientras que en el caso del Cu el mecanismo principal supone la incorporación del metal entre las capas formadas por las cadenas del polímero.
- Thiram: un fungicida atrapador de metales. Caracterización electroquímica(Universidad de Navarra, 2008-05-30) Santamaria-Elola, C. (Carolina); Valle, E.M.A. (Eliana M.A.); Fernandez-Alvarez, J.M. (José María)El thiram es un fungicida, de la familia de los ditiocarbamatos, muy utilizado en los cultivos de frutas y verduras, tanto para proteger las cosechas en el campo como para prevenir su deterioro durante los periodos de almacenamiento y transporte. En su estructura hay grupos funcionales que son capaces de formar enlaces con iones metálicos como el cobre, plomo y cadmio que están presentes en el medio ambiente libres o formando complejos con diversas moléculas orgánicas. La unión de estos metales con el thiram puede modificar las características contaminantes del fungicida, por lo que se considera de elevado interés conseguir una metodología capaz de cuantificar algunas de las propiedades de estos complejos. En el presente trabajo, se pretende evaluar esta interacción metal-fungicida, utilizando una técnica electroquímica como es la voltametría de redisolución anódica por pulso diferencial y la espectroscopía ultravioleta/visible. El empleo de estas dos técnicas permitirá confirmar la formación de complejos entre ciertos metales y thiram, así como cuantificar la fuerza de esta unión a través de las constantes condicionales de formación respectivas. El thiram presenta un comportamiento electroquímico que se ve alterado cuando se estudia en presencia de alguno de los metales anteriormente mencionados, lo que permite verificar la formación de un complejo entre ambas especies. Del mismo modo esta diferencia es visible por espectroscopía, donde después de la adición del metal se registran bandas adicionales a las observadas sólo para el thiram, que también sugieren la formación del complejo.
- 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.
- Effect of frosts on the mortality of common and cornwall forms of Oxalis latifolia Kunth(Association Française de Protection des Plantes, 2004) Royo-Esnal, A. (Aritz); Lopez, M.L. (María Luisa)Oxalis latifolia Kunth is not reported as a weed in those regions where the first centimetres of the soil get frozen in winter. The objective of this study is to evaluate the incidence of freezing temperatures on the mortality of common and cornwall form bulbs of O.latifolia in field conditions. 30 bulbs, 15 of each form, were planted 1 cm depth in two pots in April 2001 and they were placed outdoors in Azkoitia (northern Spain). Bulbs grew normally throughout the growing season and were harvested in January 2002. The lowest temperature reported in this period was -10ºC in December 2001. At the harvest all the found apical bulbs, whether they were common or cornwall, were dead. Among the lateral bulbs, 82% and 94% of common and cornwall form died because of frosts. The difference of mortality between the forms is explained by their morphology: common form bulbils grow over stolons some of which can bury the bulbils deeper in the soil and protect them from frosts; meanwhile, cornwall form bulbils are sessile and they have no choice of being buried and protected.
- 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.
- A colour study in the early stages of fermentation of a Vitis vinifera Tempranillo grape must: a comparative assessment under different climatic conditions(Université Montpellier 1, 2005-07-07) Santamaria-Elola, C. (Carolina); Calvo, M.I. (María Isabel); Esparza, I. (Irene); Fernandez-Alvarez, J.M. (José María)Program and abstracts of the In Vino Scientia 2005; Poster 59, page 113. Vinifera Tempranillo grapes were collected in two consecutive crops (2002 and 2003) and monitored in their early stages of fermentation undel real cellar production conditions at EVENA (the Station of Viticulture and Enology of Navarra). Parameters such as pluviometry, day-night contrast temperatures, pH, density, polyphenols, metals (Fe, Cu, Zn and Mn) and several colour variables were measured. A similar pattern was observed for both polyphenols and metals contents evolutions in the two years study, although different absolute values were obtained which correlate to the diverse climatic conditions occurring along the grape growing stages. Spectrophotometric analysis were carried out of the samples at different fermentation times, and changes in colour were monitored after exogenous addition of certain metals. Metals such as Fe and Cu showed a concentration profile vs. fermentation time that resembles closely those of "blue" and "yellow" absorbances in the same period of feermentation. Shiftings of the maximum wavelenghts took place and the influence of polyphenols over the "brightness" and "red" parameters was checked.