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Search Results: 1 - 10 of 335672 matches for " Gustavo S.;Salazar-Banda "
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Sonovoltammetric determination of 4-nitrophenol on diamond electrodes
Garbellini, Gustavo S.;Salazar-Banda, Giancarlo R.;Avaca, Luis A.;
Journal of the Brazilian Chemical Society , 2007, DOI: 10.1590/S0103-50532007000600002
Abstract: the sonovoltammetric determination of 4-nitrophenol was studied on a boron-doped diamond electrode. significant improvements in the analytical sensibility were observed due to electrode surface cleaning and the enhancement in the transport of species to the electrode surface provided by ultrasound. thus, for the oxidation and reduction process, the limit of detection diminished from 11.7 to 3.87 and from 6.38 to 2.57 μg l-1, respectively.
Effects of Ultrasound on the Degradation of Pentachlorophenol by Boron-Doped Diamond Electrodes
Garbellini,Gustavo S.; Salazar-Banda,Giancarlo R.; Avaca,Luis A.;
Portugaliae Electrochimica Acta , 2010,
Abstract: the beneficial effects of the ultrasound (us) like the cleaning of electrode surface and enhancement of mass transport were evaluated in association with potentiostatic electrolyses for the degradation of pentachlorophenol (pcp) at 3.0 v vs. ag/agcl, using a boron-doped diamond (bdd) electrode during 270 minutes. different decay levels of the pcp spectrum bands in 220, 251 and 321 nm, respectively, were observed after application of ultrasound without electrochemical process (18.1, 17.7 and 19.8 %), silent electrolyses (29.3, 71.6 and 70.8 %), pulsed sonoelectrolysis (31.0, 75.1 and 76.3%) and sonoelectrolyses (39.2, 80.0 and 82.6 %). for silent and sonoelectrolyses processes, cleaning/reactivation of the bdd surface by acetonitrile and/or electrochemical treatment was necessary. the pulsed sonolectrolysis were carried out purposely without cleaning/reactivation of the surface. the results showed greater pcp degradation for insonated studies than those obtained for the silent electrolyses, due to the increase of mass transport, minimization of the electrode fouling and the combined generation of hydroxyl radicals by both ultrasound and the polarized bdd surface. these tools (us and bdd), especially the pulsed sonoelectrolysis, can improve the degradation of pesticides and their metabolites in the environment and enable the use of sonoelectrochemistry for wastewater remediation.
Aplica??o do ultra-som em sistemas eletroquímicos: considera??es teóricas e experimentais
Garbellini, Gustavo S.;Salazar-Banda, Giancarlo R.;Avaca, Luis A.;
Química Nova , 2008, DOI: 10.1590/S0100-40422008000100024
Abstract: the aim of this review is to present and discuss the applications of ultrasound in electrochemical systems such as in sonoelectroanalysis and sonoelectrolysis for the electrochemical combustion of organic compounds. initially, theoretical and experimental aspects are discussed, particularly those related to the enhancement of mass transport and the surface cleaning effects. some results are included to illustrate alternative geometries for the experimental measurements and the working electrodes used in these systems. in the sequence, the available publications are presented and discussed to demonstrate that ultrasound combined with electrochemical techniques is a powerful set-up for the detection of analytes such as metals and/or organic compounds in hostile media and for the effective destruction of toxic organic substances. at the end, a table summarizes the results already published in the literature.
Determination of 5-aminosalicylic acid in pharmaceutical formulations by square wave voltammetry at pencil graphite electrodes
Uliana, Carolina V.;Yamanaka, Hideko;Garbellini, Gustavo S.;Salazar-Banda, Giancarlo R.;
Química Nova , 2010, DOI: 10.1590/S0100-40422010000400036
Abstract: an analytical method for the determination of the anti-inflammatory drug 5-aminosalicylic acid (5-asa) in pharmaceutical formulations using square wave voltammetry at pencil graphite electrodes was developed. after the optimization of the experimental conditions, calibration curves were obtained in the linear concentration range from 9.78 × 10-7 to 7.25 × 10-5 mol l-1 resulting in a limit of detection of 2.12 ± 0.05 x 10-8 mol l-1. statistical tests showed that the concentrations of 5-asa in commercial tablets and enemas obtained with the proposed voltammetric method agreed with hplc values at a 95% confidence level.
Potencialidades do uso de ultrassom na determina??o do pesticida carbaril empregando eletrodos de diamante
Garbellini, Gustavo S.;Avaca, Luis A.;Salazar-Banda, Giancarlo R.;
Química Nova , 2010, DOI: 10.1590/S0100-40422010001000039
Abstract: the potentiality of the use of ultrasound radiation in association with a boron-doped diamond electrode was evaluated on the voltammetric determination of the pesticide carbaryl. improvements in the sensitivity, limit of detection and reproducibility of the measurements were observed due to both, the enhancement of mass transport and the cleaning of the electrode surface provided by ultrasound. satisfactory recovery levels for carbaryl in pure water (96-98%) and pineapple juice (89-92%) for quiescent and sonovoltammetric methodologies were obtained. these methodologies can be alternative tools for the analyses of pesticides in fruit samples, mainly the insonated condition that improve the analytical performance and dispense intermediary cleanings of the electrode surface.
Metodologias eletroanalíticas para a determina??o de herbicidas triazínicos por voltametria de onda quadrada e técnicas de deconvolu??o
Garbellini, Gustavo S.;Pedrosa, Valber A.;Salazar-Banda, Giancarlo R.;Avaca, Luis A.;
Química Nova , 2007, DOI: 10.1590/S0100-40422007000800039
Abstract: this work describes the development of electroanalytical methodologies for the determination of atrazine, ametrine and simazine by square wave voltammetry on a mercury electrode. for pure atrazine and pure ametrine, the detection limits (dl) were 3.7 and 4.3 μg l-1, respectively, while they increased to 4.8 and 6.5 μg l-1 in the presence of 3.0 x 10-6 mol l-1 of the other component (a mathematical deconvolution program was used in the mixture cases). the voltammetric response for simazine could not be separated from that of atrazine and measurements were carried out only in pure simazine solutions (dl: 7.5 μg l-1).
Effects of Ultrasound on the Degradation of Pentachlorophenol by Boron-Doped Diamond Electrodes
Gustavo S. Garbellini,Giancarlo R. Salazar-Banda,Luis A. Avaca
Portugaliae Electrochimica Acta , 2010,
Abstract: The beneficial effects of the ultrasound (US) like the cleaning of electrode surface and enhancement of mass transport were evaluated in association with potentiostatic electrolyses for the degradation of pentachlorophenol (PCP) at 3.0 V vs. Ag/AgCl, using a boron-doped diamond (BDD) electrode during 270 minutes. Different decay levels of the PCP spectrum bands in 220, 251 and 321 nm, respectively, were observed after application of ultrasound without electrochemical process (18.1, 17.7 and 19.8 %), silent electrolyses (29.3, 71.6 and 70.8 %), pulsed sonoelectrolysis (31.0, 75.1 and 76.3%) and sonoelectrolyses (39.2, 80.0 and 82.6 %). For silent and sonoelectrolyses processes, cleaning/reactivation of the BDD surface by acetonitrile and/or electrochemical treatment was necessary. The pulsed sonolectrolysis were carried out purposely without cleaning/reactivation of the surface. The results showed greater PCP degradation for insonated studies than those obtained for the silent electrolyses, due to the increase of mass transport, minimization of the electrode fouling and the combined generation of hydroxyl radicals by both ultrasound and the polarized BDD surface. These tools (US and BDD), especially the pulsed sonoelectrolysis, can improve the degradation of pesticides and their metabolites in the environment and enable the use of sonoelectrochemistry for wastewater remediation.
AFM studies and electrochemical characterization of boron-doped diamond surfaces modified with metal oxides by the Sol-Gel method
Suffredini Hugo B.,Salazar-Banda Giancarlo R.,Tanimoto S?nia T.,Calegaro Marcelo L.
Journal of the Brazilian Chemical Society , 2006,
Abstract: Continuing previous investigations, direct surface modifications of boron-doped diamond (BDD) electrodes with metal oxides (PtOx, RuO2, IrO2 and PbO2) and with some mixed composites were carried out by the Sol-Gel technique. The materials were studied by atomic force microscopy (AFM) to determine their surface topologies and by electrochemical techniques to establish the catalytic activity towards the oxygen evolution reaction (OER) and also, for the PtOx and PtOx-RuO2 composites, the ethanol oxidation reactions in acid media. The stability of PtOx coating covered by a Nafion film was also tested by long-term operation. The AFM results indicated sites of heterogeneous deposition and the electrochemical studies demonstrated that the active surface area changed considerably with the proposed method of modification. The IrO2/BDD electrode showed the best performance to the OER with the onset of the oxidation current at ~1.4 V, a value 200 mV lower than for the PtOx/BDD electrode. The enhanced stability of PtOx/BDD electrodes achieved by the application of a Nafion film and already reported in acid media was further proved using the ethanol oxidation reaction. Only a small loss of activity (6%) was observed after 4-hours electrolysis while one-thousand voltammetric cycles left the surface practically unchanged. In addition, preliminary studies for the same reaction on PtOx/BDD and PtOx-RuO2/BDD electrodes demonstrated the excellent activity of these mixed Sol-Gel coatings on the BDD surface and the possibility of further investigations for practical applications.
AFM studies and electrochemical characterization of boron-doped diamond surfaces modified with metal oxides by the Sol-Gel method
Suffredini, Hugo B.;Salazar-Banda, Giancarlo R.;Tanimoto, S?nia T.;Calegaro, Marcelo L.;Machado, Sergio A. S.;Avaca, Luis A.;
Journal of the Brazilian Chemical Society , 2006, DOI: 10.1590/S0103-50532006000200007
Abstract: continuing previous investigations, direct surface modifications of boron-doped diamond (bdd) electrodes with metal oxides (ptox, ruo2, iro2 and pbo2) and with some mixed composites were carried out by the sol-gel technique. the materials were studied by atomic force microscopy (afm) to determine their surface topologies and by electrochemical techniques to establish the catalytic activity towards the oxygen evolution reaction (oer) and also, for the ptox and ptox-ruo2 composites, the ethanol oxidation reactions in acid media. the stability of ptox coating covered by a nafion? film was also tested by long-term operation. the afm results indicated sites of heterogeneous deposition and the electrochemical studies demonstrated that the active surface area changed considerably with the proposed method of modification. the iro2/bdd electrode showed the best performance to the oer with the onset of the oxidation current at ~1.4 v, a value 200 mv lower than for the ptox/bdd electrode. the enhanced stability of ptox/bdd electrodes achieved by the application of a nafion? film and already reported in acid media was further proved using the ethanol oxidation reaction. only a small loss of activity (6%) was observed after 4-hours electrolysis while one-thousand voltammetric cycles left the surface practically unchanged. in addition, preliminary studies for the same reaction on ptox/bdd and ptox-ruo2/bdd electrodes demonstrated the excellent activity of these mixed sol-gel coatings on the bdd surface and the possibility of further investigations for practical applications.
Improved stability of PtOx sol-gel-modified diamond electrodes covered with a Nafion? film
Salazar-Banda, G.R.;Suffredini, H.B.;Avaca, L.A.;
Journal of the Brazilian Chemical Society , 2005, DOI: 10.1590/S0103-50532005000600003
Abstract: the modification of boron-doped diamond (bdd) electrodes with platinum oxide particles deposited by the sol-gel method and using several pre- and post-treatments of the surface is described. the electrochemical stability of the resulting catalytic coatings was evaluated by cyclic voltammetry in acid medium and was much greater than those previously reported in the literature for others deposition methods. a thermal pre-treatment of the bdd surface yielded electrodes that retained 91.6% of the coated material after 1000 voltammetric cycles carried out between the water decomposition reactions. the application of a nafion? film on top of the coating preserved integrally the deposited platinum oxide. the use of such modified electrodes for practical applications is now feasible under the present experimental conditions.
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