M. J. Aguirre

University of Santiago, Chile, CiudadSantiago, Santiago Metropolitan, Chile

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Publications (45)92.66 Total impact

  • R. Arce, M. J. Aguirre
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    ABSTRACT: The sulfite is commonly used antiseptic wine and food. You can find free or bound to phenols , aldehydes and other organic compounds. Its concentration at high levels produces toxic effects, such as pain when breathing in asthmatic patients , hypotension and gastrointestinal problems. Therefore it is useful to determine the electrochemically concentration , and with this, to separate , by absorbing membrane system , the other impurities present in food. Sulfite (SO3-2) in aqueous solution is in equilibrium with bisulfite ( HSO3 - ) and sulfur dioxide ( SO2) , where their concentrations depend mainly on the pH. As to the electrochemical method , the cyclic voltammetry was used. This technique is widely used and is of considerable use in the study of oxide / reduction , detection of reaction intermediates and observing reactions monitoring electrode products formed in reactions . In conjunction with the cyclic voltammetry method of calibration curve is applied and thus determine how feasible it is to implement in an electrochemical analysis. The method of calibration curve represents the response of an analytical method to known concentrations of analyte . Previous studies done in the laboratory show that it is possible to find a potential range where the SO3 -2 shows an increasing response in current and potential displacement , and in addition, all the parameters are optimized for system performance membrane absorber .
    2014 ECS and SMEQ Joint International Meeting; 10/2014
  • Journal of the Chilean Chemical Society 07/2014; 59(2):2526-2528. DOI:10.4067/S0717-97072014000200029 · 0.47 Impact Factor
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    ABSTRACT: In the present work, known concentration of sulfite aqueous solutions in the presence and absence of gallic acid was measured to corroborate the validity of modified Monier-Williams method. Free and bound-sulfite was estimated by differential pulse voltammetry. To our surprise, the modified Monier-Williams method (also known as aspiration method) showed to be very inaccurate for free-sulfite, although suitable for bound-sulfite determination. The differential pulse approach, using the standard addition method and a correction coefficient, proved to be swift, cheap, and very precise and accurate.
    The Scientific World Journal 04/2012; 2012:168148. DOI:10.1100/2012/168148 · 1.73 Impact Factor
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    ABSTRACT: Anthocyanins in aged Cabernet Sauvignon red wines were studied by HPLC-MS. The major anthocyanin in 6, 7, and 8 year old red wine extracts was the dimer vitisin A produced by condensation of malvidin-3-O-glucoside mediated by pyruvic acid. In aged wine, the content of malvidin-3-O-glucoside decreased with age with a concomitant increase of vitisin A. The latter is accompanied by several condensation products with molecular weight up to 1500 m/z. Differential pulse voltammetry indicated that aged wines have lower antioxidant capacity than young wine (400 mV), but higher than malvidin-3-O-glucoside (483 mV). Tafel's plots showed that the electrochemical process occurring in aged wines is different from young wines. Six, seven and eight year old wines show similar behaviour with plots of 234, 177 and 188 mV/dec, respectively. These values are higher than the expected 120 mV/dec corresponding to a first electronic transfer but smaller compared to the 523 mV/dec corresponding to young wine.
    Food Chemistry 11/2011; 129(2):514-519. DOI:10.1016/j.foodchem.2011.05.009 · 3.26 Impact Factor
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    ABSTRACT: This paper describes the electrochemical reduction of nitrite ion in neutral aqueous solution mediated by tetraruthenated metalloporphyrins (Co(II), Ni(II) and Zn(II)) electrostatically assembled onto a Nafion film previously adsorbed on glassy carbon or ITO electrodes. Scanning electron microscope (SEM-EDX) and transmission electron microscopy (TEM) results have shown that on ITO electrodes the macrocycles forms multiple layers with a disordered stacking orientation over the Nafion film occupying hydrophobic and hydrophilic sites in the polyelectrolyte. Atomic force microscopy (AFM) results demonstrated that the Nafion film is 35nm thick and tetraruthenated metalloporphyrins layers 190nm thick presenting a thin but compacted morphology. Scanning electrochemical microscopy (SECM) images shows that the Co(II) tetraruthenated porphyrins/Nf/GC modified electrode is more electrochemically active than their Ni and Zn analogues.These modified electrodes are able to reduce nitrite at −660mV showing enhanced reduction current and a decrease in the required overpotential compared to bare glassy carbon electrode. Controlled potential electrolysis experiments verify the production of ammonia, hydrazine and hydroxylamine at potentials where reduction of solvent is plausible demonstrating some selectivity toward the nitrite ion. Rotating disc electrode voltammetry shows that the factor that governs the kinetics of nitrite reduction is the charge propagation in the film.
    Electrochimica Acta 10/2011; 56(24):8484. DOI:10.1016/j.electacta.2011.07.057 · 4.09 Impact Factor
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    ABSTRACT: A new conducting film derived from the complex [Fe (diaphen)3]2+, (diaphen=5,6-diamino-1,10-phenanthroline) was electropolymerized by cyclic voltammetry onto a glassy carbon electrode. Poly-[FeII (diaphen)3] was studied by cyclic voltammetry, SEM, UV-vis and micro-Raman spectroscopy. Poly-[FeII (diaphen)3] shows electrocatalytic activity in HSO3− reduction in an ethanol/water solution. Electrocatalysis is centered at the π ring of phenanthroline. Rotating disk electrode studies showed a 0.117 V/dec Tafel slope, suggesting an EC process where the electrochemical process is the determining step. The chemical step was studied by UV-vis spectroelectrochemistry. Amperometric behavior showed a linear range between 47.5 µM to 417 µM and the LOD was 19.5 µM.
    Electroanalysis 06/2011; 23(6):1401 - 1409. DOI:10.1002/elan.201000769 · 2.50 Impact Factor
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    ABSTRACT: This paper describes the electrochemical reduction of nitrite ion in 0.1 M NaClO 4 , on glassy carbon or ITO electrodes modified with mixtures PVC-tetraruthe-nated metalloporphyrins. This electrode is able to keep the extraordinary electro-catalytic properties of the macrocycle allowing multielectronic transfers and a great stability as a consequence of the inclusion of the macrocycles into a polymeric support such as PVC. On the other hand, the electrochemical reduction of nitrite ion on these modified electrodes studied by cyclic voltammetry shows an enhancement in the current values and lower overpotential compared with the activity of the bare glassy carbon electrode. Controlled potential electrolysis experiments verify the production of ammonia, hydrazine and hydroxylamine, showing the electrocatalytic character and the stability of this modified electrode.
    Macromolecular Symposia 06/2011; 304(1):93. DOI:10.1002/masy.201150613
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    ABSTRACT: The electro-oxidation of 2-mercaptoethanol by poly-Co-tetraaminophthalocyanine (p-Co-TAPc) and poly-metal-free-tetraaminophthalocyanine (p-H2TAPc), absorbed on electrode surfaces has been investigated by UV-visible spectroelectrochemistry and electrochemical techniques. In the case of p-CoTAPc, an irreversible oxidation wave is obtained by cyclic voitammetry, whereas p-H2PcTA practically does not show activity. The foot of the oxidation, as the open circuit potential measurements indicate that the responsible redox couple is Co(II)/Co(I). The p-CoTAPc modified-electrode loses its activity after a first potential cycle. UV-visible spectroelectrochemical measurements show a charge transfer band (metal to ligand) for the p-CoTAPc between Q and Soret bands when negative potentials are applied and Co(I) is obtained. The presence of 2-mercaptoethanol promotes the appearance of the charge transfer band at open circuit potential and retain this band even at potentials as positive as +0.2V where normally the Co center is in +2 oxidation state. The permanence of a stable charge transfer band indicates the formation of a stable charge-transfer adduct between Co(I) and the thiol. This adduct would be responsible for the loss of catalytic activity for p-CoTAPc after the first oxidation cycle.
    Journal of Coordination Chemistry 03/2011; 54(3):183-191. DOI:10.1080/00958970108022634 · 2.22 Impact Factor
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    ABSTRACT: The success of Chilean wine in the international market has led to an important attention on the development of science and technology for wine differentiation, productivity, and quality. In order to report the profile of phenolic acid compounds in Chilean red wines, an SPE technique over ODS column was used followed by a reverse phase HPLC program that was developed to separate, characterize and quantify six phenolic acids (caffeic, gallic, p-coumaric, protocatechuic, syringic and vanillic acids) in four red Chilean wines varieties (Cabernet Sauvignon, Carménère, Merlot and Syrah) from grapes cultivated in the central zone of Chile. The separation was carried out on an RP C-18 column using a binary gradient elution and diode array detection.
    Journal of the Chilean Chemical Society 12/2010; 56(2):688-691. DOI:10.4067/S0717-97072011000200014 · 0.47 Impact Factor
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    ABSTRACT: a b s t r a c t This work describes the preparation of a new tetraruthenated porphyrin and the corresponding poly-meric film. This macromolecule consists of a Ni(II) tetrapyridylporphyrin coordinated to four [Ru(5-NO 2 -phen) 2 Cl] + moieties. The 5-NO 2 -phen ligands are reduced at À0.90 V, generating a radical anion that is able to generate polymeric coatings onto glassy carbon (GC) electrodes. These polymeric films are very stable in aqueous solutions. The polymeric films are characterized by electrochemistry, infrared spectro-electrochemistry (IR-SEC) and atomic force microscopy (AFM).
    Journal of electroanalytical chemistry 09/2010; 648(2). DOI:10.1016/j.jelechem.2010.08.007 · 2.87 Impact Factor
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    ABSTRACT: The aim of this work is to study four types of modification of a glassy carbon electrode by Fe(III)-tetrakis(p-tetraaminophenyl)porphyrin and determine the influence of the method of immobilization of the complex on glassy carbon in electrocatalytic properties for the sulfite and hydrogensulfite oxidation in ethanol–water. The first modification was deposition of a drop of solution containing the porphyrin on a glassy carbon electrode and evaporation of the solvent (dry-drop method). The second method was immersion of the electrode at 54°C in a solution of dimethylformamide containing the porphyrin for 2 h. The third method consisted of the same heating treatment but after formation of a chemical bond of 4-aminopyridine on the glassy carbon surface, which acts as an axial ligand for the first layer of porphyrin. The fourth method involves electropolymerization of the porphyrin on the electrode surface. Important differences in stability, the potential where the oxidation wave begins and selectivity of the electrode to sulfite or hydrogensulfite were observed. The behavior of the polymer-modified electrode is different in water compared to ethanol–water.
    Journal of Coordination Chemistry 09/2009; 62(17-17):2782-2791. DOI:10.1080/00958970902942982 · 2.22 Impact Factor
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    ABSTRACT: A neutral fraction (PS-SI) (0.3g/L) with MW of 74kDa, which contained galactose, arabinose, mannose, and glucose in the molar ratio of 1.0:0.6:0.4:0.2 was obtained by treatment of the whole polysaccharide extracted from red wine with cetrimide, followed by gel permeation chromatography. Spectroscopic and methylation analyses indicated that PS-SI is a mixture of neutral polysaccharides, consisting mainly of beta (1-->3)-linked galactopyranosyl residues, with side chains of galactopyranosyl residues at positions O-6. Arabinofuranosyl residues linked alpha (1-->5), alpha-mannopyranosyl and glucosyl residues appear to be components of different polysaccharides. The in vitro antioxidant capacity of fractions of wine polysaccharide was studied by hydroxyl radical scavenging and ORAC assays. Fraction PS-SI presented the strongest effect on hydroxyl radicals (IC(50)=0.21).
    Carbohydrate research 04/2009; 344(9):1095-101. DOI:10.1016/j.carres.2009.03.024 · 1.97 Impact Factor
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    ABSTRACT: The complex [Fe(II)(Imz-phen)(3)](PF(6))(2), (Imz-Phen = imidazolidine-[4,5-f]-1,10-phenanthroline) has been prepared and characterized using X-ray diffraction, UV-vis and IR spectroscopy, elemental analysis, fast atomic bombardment (FAB) mass spectrometry, and cyclic voltammetry. Its crystal lattice includes acetonitrile (pi-pi bound to phenanthroline), methanol, and water molecules. Scanning continuously between 1000 mV and 1650 mV in CH(3)CN, a modified electrode that includes the iron (II) complex is obtained; after the 25th continuous cycle a stable film is formed that is electrocatalytically active in the reduction of sulfur oxoanions. When the electrocatalytic properties are evaluated in ethanol/water solution, the current achieved from the electroreduction of these sulfur species is linearly dependent on the respective concentrations, suggesting potential application in sulfite determination. (c) 2009 Elsevier B.V. All rights reserved.
    Inorganic Chemistry Communications 03/2009; 12(5):392-395. DOI:10.1016/j.inoche.2009.02.017 · 2.06 Impact Factor
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    ABSTRACT: A comparison is made of the behavior of three Cu(II)-porphyrins (with the amino substituents in different positions on the periphery of the ligand) electropolymerized on glassy carbon electrodes in HCl as solvent. The electropolymerized films show a certain degree of demetallation but the Cu amount of porphyrin in each case is sufficient to catalyze the oxidation of sulfite and hydrogensulfite in ethanol–water solutions. The ligands of the porphyrins are almost inactive in the electrocatalysis of the sulfite. The oxidation processes are favored at low scan rates. The foot of the oxidation waves depends on the positions. The most active porphyrin bears the substituents with the amino groups in para position, the oxidation occurring at low positive potentials. All the modified electrodes can be used as amperometric sensors for sulfite; they show linear relationships between the current and sulfite concentration in the range in which sulfites are present in red wines. The modified electrodes are stable and all of them promote the oxidation of sulfite to sulfate.
    Collection of Czechoslovak Chemical Communications 01/2009; DOI:10.1135/cccc2008173 · 1.14 Impact Factor
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    ABSTRACT: Low molecular weight carbohydrates (LMW) were determined in a Chilean Cabernet Sauvignon red wine by the Dubois method, a specifc method for the determination of carbohydrates. Dialysis treatment of red wine allowed the separation of pentoses, hexoses, reducing and non-reducing oligosaccharides and glycosides (LMW) from the polysaccharides fraction (HMW) fraction. The total sugar content of red wine by Dubois method was 5.55 g/L. The content of LMW sugars determined by Dubois method (3.63 g/L) is higher than the sugar content of the polysaccharides fraction (1.78 g/L). Analysis of twenty more samples of Cabernet Sauvignon red wines showed that the high molecular weight fraction content is quite iterative (mean value 2.50 g/L). The advantage of the Dubois method in relation to Fehling method is that the former does not need prior decolouration of the sample and there is not interference of aldehydes. The method developed in this work may be a complementary method for the determination of carbohydrates in wine industry.
    Journal of the Chilean Chemical Society 01/2009; 54(4). DOI:10.4067/S0717-97072009000400018 · 0.47 Impact Factor
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    ABSTRACT: This article describes the electrochemical reduction of sulfite in water–ethanol mixtures under acidic conditions on a glassy carbon electrode modified with a conducting film formed by Co(II) tetra-3-aminophenyl porphyrin. Rotating disc electrode experiments show a kinetic limitation related with the formation of an adduct between the reduced porphyrin and the sulfur compound. UV–Visible spectroelectrochemical data suggest that Co(I) is not stabilized; thus the adduct should involve a radical species of the porphyrin. However, the resulting modified electrode is stable and shows a linear relationship between current and concentration of the sulfur species at pH 1. The detection range of sulfite by the modified electrode goes from 12 to 150 mg L−1. The detection limit is 4.15 mg L−1.
    Journal of Coordination Chemistry 01/2009; 62(1-1):130-140. DOI:10.1080/00958970802474839 · 2.22 Impact Factor
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    ABSTRACT: A study of glassy carbon electrodes modified with poly-Cu-x-tetraaminophenylporphyrin (TAPP) (x=2, 3, and 4) toward the electrooxidation of nitrite is reported. The position of the amino group influences the degree of electropolymerization and the response toward the electrooxidation of nitrite. The influence of pH on the electrocatalytic oxidation of nitrite was also studied, finding that the activity is strongly pH-dependent. For each system (polymeric porphyrins, poly-Cu-2-TAPP, poly-Cu-3-TAPP, and poly-Cu-4-TAPP), the behavior of the modified electrode as amperometric nitrite sensor was studied at the best pH response, finding a linear correlation over a wide range of concentrations for poly-Cu-3-TAPP. With poly-Cu-2-TAPP, the range is smaller, and there is no linear relationship for poly-Cu-4-TAPP. The plot of Ip vs. the square root of the scan rate shows a linear relationship for all the polymer systems, indicating that the electrooxidation of nitrite in the modified electrodes is a process controlled by diffusion. The Tafel slope was calculated, indicating that the determining step in the electrooxidation of nitrite varies depending on the position of the substituent, showing a dramatic change in the nature of the active sites.
    Electroanalysis 12/2008; 20(24). DOI:10.1002/elan.200804369 · 2.50 Impact Factor
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    ABSTRACT: A modified synthetic route for the complexes [Cu(II)5,7,12,14-tetramethyldinaphtho [b,i][1,4,8,11]tetraaza[14]annulene], [Cu(II)tmdnTAA], and [Cu(II) 5,7,12,14-tetramethyl-6,13-dichloro-dinaphtho[b,i][1,4,8,11]tetraaza[14]annulene], [Cu(II)dCltmdnTAA], is presented in this work. The electrochemical characterization of both complexes and their precursors, [bis(2,4-pentanedionato)copper(II)], [Cu(II)(acac)2] and [bis(3-chloro-2,4-pentanedionato)copper(II)], [Cu(II)(3-Cl-acac)2], respectively, under nitrogen and carbon dioxide is also presented. The voltammetric response of [Cu(II)(acac)2] and [Cu(II)(3-Cl-acac)2] are different compared to [Cu(II)tmdnTAA] and [Cu(II)dCltmdnTAA] under nitrogen. Precursors show the reduction of Cu(I) to Cu(0) and the tetraazadinaphtho[14]annulene complexes do not. The chlorine substituted complex has a lower reduction potential than the unsubstituted homologue under nitrogen atmosphere. However, the contrary response is obtained in the presence of carbon dioxide: the unsubstituted complex is more catalytic in terms of potential because the current discharge appears 270 mV shifted to the anodic region. These facts can be explained in terms of electronic and steric effects. The modified electrode obtained by oxidative electropolymerization of [Cu(II)tmdnTAA] over glassy carbon electrode presented a suitable amperometric response for the sulfite reduction in acidic medium (pH = 2.7). A linear correlation was observed for the catalytic current and sulfite concentration between 0.6–6.0 mM range.
    Journal of Coordination Chemistry 02/2008; 61(4-4):479-489. DOI:10.1080/00958970701370559 · 2.22 Impact Factor
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    ABSTRACT: 5,15-Bis(veratryl)porphyrin (1), 5,10,15-tris(veratryl)porphyrin (2), and 5,10,15,20-tetrakis(veratryl)porphyrin (3), C36H30N4O4, C44H38N4O6, and C52H46N4O8 were synthesized by an acid-catalyzed, one-pot reaction of meso-dipyrromethane, 3,4- di-OCH3-benzaldehyde (veratraldehyde), and trifluoroacetic acid (TFA). These three different products were obtained as a result of scrambling reactions. The molecular structures have been characterized by elemental analysis, ESI mass spectra, 1D and 2D NMR techniques (1H and 13C), and UV-visible spectroscopy.
    Synthetic Communications 11/2007; 37(12-12):2001-2009. DOI:10.1080/00397910701356496 · 0.98 Impact Factor
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    ABSTRACT: Reactions of photochemically or radiolytically generated radicals with tetrakis(x-aminophenyl)porphyrin, tapp2−, initiate the polymerization of the porphyrin complexes Mtapp, where M=Ni or Zn. In the photochemical process, the porphyrin-centered excited state of Mtapp reacts with the ground state to generate oxidized and reduced radical species. The cationic radical, M(tapp+), appears to be the initiator of the porphyrin polymerization. An electron transfer reaction between the excited state of Mtapp and a Co(III) complex generates also the cation radical and initiates the polymerization process. Pulse radiolytically generated Cl2- and OH radicals were also able to initiate the polymerization of the porphyrin complexes.
    Inorganica Chimica Acta 04/2006; 359(7):2281-2284. DOI:10.1016/j.ica.2005.08.036 · 2.04 Impact Factor

Publication Stats

460 Citations
92.66 Total Impact Points

Institutions

  • 1994–2014
    • University of Santiago, Chile
      • • Departamento de Química de los Materiales
      • • Facultad de Química y Biología
      • • Facultad de Ciencia
      CiudadSantiago, Santiago Metropolitan, Chile
  • 1992
    • Universidade Federal de São Carlos
      • Departamento de Química (DQ)
      São Carlos, Estado de Sao Paulo, Brazil