Browsing by Author "Arce, Roxana"

Now showing 1 - 7 of 7
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    Electro-Reduction of Molecular Oxygen Mediated by a Cobalt(II) octaethylporphyrin System onto Oxidized Glassy Carbon/Oxidized Graphene Substrate
    (2018) Canales Oyarzo, Camila Pía; Gidi Chomalí, Leyla Denisse; Arce, Roxana; Armijo Mancilla, Juan Francisco; Aguirre, Maria J.; Ramírez Jofré, Galo
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    ELECTROCHEMICAL METHOD FOR SULFITE DETERMINATION IN WINES BY ELECTROCHEMICAL RESPONSE USING A MEMBRANE ABSORBER SYSTEM
    (SOC CHILENA QUIMICA, 2016) Arce, Roxana; Baez, Carla; Muena, J. P.; Aguirre, Maria J.; Romero, Julio
    This research demonstrates how the sulfite content can be measured by cyclic voltammetry using a previously reported membrane absorber system, which separates efficiently sulfite present in wine. Results obtained show notably similar values to those obtained for the same wine samples using modified MonierWilliams method (aspiration method) and Ripper method. The membrane absorber system allows the release of the free SO2, and can be used to determine the sulfur dioxide present in juices and other foods that contain high concentrations of phenols, polyphenols and other structurally related compounds that act as interferers in the electrochemical oxidation of sulfite. The absorber solution allows a direct measurement without change in pH or added electrolyte, facilitating the determination of great amounts of samples from diverse wines using only one calibration curve. In this way, a system that allows the detection of sulfite and that can be used in vineyards is obtained.
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    Electrodetermination of Gallic Acid Using Multi-walled Carbon Nanotube Paste Electrodes and N-Octylpyridinium Hexafluorophosphate
    (WILEY-V C H VERLAG GMBH, 2022) Gidi, Leyla; Honores, Jessica; Ibarra, Jose; Jesus Aguirre, Maria; Arce, Roxana; Ramirez, Galo
    In this work, the determination of gallic acid was performed using surface-renewable carbon paste electrodes fabricated with multi-walled carbon nanotubes (MWCNT) and a mixture of N-octylpyridinium hexafluorophosphate (OPyPF6) ionic liquid with mineral oil (MO) as binder. This system shows remarkable amperometric sensor characteristics and promotes a better electronic transfer. An electroanalytical study of gallic acid shows a linear range from 4.98 +/- 0.25 to 74.1 +/- 2.2 mu mol L-1, with R-2=0.9958 and an experiment a limit of detection of 2.70 +/- 0.08 mu mol L-1 (S/N=3), and a sensitivity of 0.029 mu A mu mol(-1) L.
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    Enhanced Electrocatalysis of the Oxygen Reduction Reaction Using Cobalt and Iron Porphyrin/Ionic Liquid Systems
    (2019) Gidi Chomalí, Leyla Denisse; Honores Sotelo, Jessica Scarlet; Arce, Roxana; Arévalo, M. C.; Aguirre, M. J.; Ramírez Jofré, Galo
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    Evidence for the Formation of a Copolymer by Simultaneous Electropolymerization of p-Tetraaminophenyl Porphyrin Cobalt (II)) and o-Phenylenediamine on Glassy Carbon
    (2012) Arce, Roxana; Río Quero, Rodrigo del; Ruiz-Leon, Domingo; Vélez Cifuentes, Jorge; Isaacs Casanova, Mauricio; Valle de la Cortina, María Angélica del; Aguirre, Maria J.
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    Extraction of sulfite for wastewater treatment and for analytical determination
    (2019) Canales , J. P.; Arce, Roxana; Madariaga, C.; García, Macarena del Pilar; Canales Oyarzo, Camila Pía; Vélez, Jorge H.; Arévalo, María del Carmen; Aguirre, María J.; Romero, Julio
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    Study of the Hydrogen Evolution Reaction Using Ionic Liquid/Cobalt Porphyrin Systems as Electro and Photoelectrocatalysts
    (MDPI, 2020) Gidi, Leyla; Honores, Jessica; Ibarra, Jose; Arce, Roxana; Aguirre, M. J.; Ramirez, Galo
    In this work, the design and manufacture of graphite paste (Gr) electrodes is carried out, including N-octylpyridinium hexafluorophosphate (OPyPF6) ionic liquid (IL) as binder and modification with Co-octaethylporphyrin (Co), in order to study the hydrogen evolution reaction (HER) in the absence and presence of light. The system is characterized by XRD and FESEM-EDX (Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy), confirming the presence of all the components of the system in the electrode surface. The studies carried out in this investigation confirm that a photoelectrocatalytic system towards HER is obtained. The system is stable, efficient and easy to prepare. Through cyclic voltammetry and electrochemical impedance spectroscopy, was determined that these electrodes improve their electrochemical and electrical properties upon the addition of OPyPF6. These effects improve even more when the systems are modified with Co porphyrin. It is also observed that when the systems are irradiated at 395 nm, the redox process is favored in energy terms, as well as in its electrical properties. Through gas chromatography, it was determined that the graphite paste electrode in the presence of ionic liquid and porphyrin (Gr/IL/Co) presents a high turnover number (TON) value (6342 and 6827 in presence of light) in comparison to similar systems reported.