La Revista infoANALÍTICA es una publicación semestral de la Escuela de Ciencias Químicas de la Pontificia Universidad Católica del Ecuador, cuyo objetivo es dar a conocer los resultados y análisis, fruto de la investigación en áreas relacionadas con la Química.
OBTENCIÓN DE BIODIESEL A PARTIR DE LA TRANSESTERIFICACIÓN DE ACEITE VEGETAL RESIDUAL, Jan 13, 2023
El presente trabajo muestra los resultados de la obtención de un biodiesel B100 a partir del acei... more El presente trabajo muestra los resultados de la obtención de un biodiesel B100 a partir del aceite vegetal residual de palma (obtenido) por medio de la trasesterificación empleando alcohol metílico con relación molar metanol-aceite de 6:1 y como catalizador al hidróxido de sodio 1% en peso, a diferentes tiempos de reacción y temperaturas. Se realizó una caracterización físicoquímica a cada muestra de biodiesel obtenido con el fin de determinar su calidad, así como también al aceite empleado como materia prima, estos resultados se compararon con las normas ASTM D 6 751, EN 14 214 y la NTE INEN 1640. Por medio de la caracterización físico-química se determinó que la muestra que mejor resultados presenta es la 3B con un tiempo de reacción de 50 minutos a una temperatura de 60°C. La densidad a 15°C fue de 898 kg/mᶟ, la viscosidad cinemática a 40 °C de 2,496 mm²/s, el índice de acidez de 0,561 mgKOH/g, el contenido de humedad de 0,03%. El índice de yodo de realizo en dos muestras de 30 y 60 minutos, obteniendo un valor favorable a una temperatura de 60°C. El rendimiento del biodiesel fue de 63,01 %. Esto permite concluir que se obtuvo biodiesel B100 con resultados óptimos en relación a la naturaleza del aceite empleado como materia prima.
EPOXIDACIÓN DE ACEITE DE HIGUERILLA (Ricinus communis) DE LA PROVINCIA DE MANABÍ-ECUADOR, Jan 11, 2023
El aceite de higuerilla (Ricinnus communis) atrae el interés en la industria quí-mica porque pued... more El aceite de higuerilla (Ricinnus communis) atrae el interés en la industria quí-mica porque puede emplearse como materia prima para producir productosquímicos o fuentes de energía por medio de modificaciones químicas, comoes el caso de la epoxidación. El presente estudio, de índole investigativa y ex-perimental, se enfoca en la epoxidación del aceite de higuerilla de la variedadPortoviejo-67 de la provincia de Manabí-Ecuador por medio de la reacción dePrileschajew para evaluar las características fisicoquímicas del aceite crudo yepoxidado mediante las normas ASTM D-5558, EN 14111, NTC 2366 para ín-dice de saponificación, índice de yodo e índice de acidez mediante técnicasde titulación, norma INEN 39 para contenido de humedad mediante pérdidapor calentamiento, norma ASTM D-1217 para densidad por picnometría y vis-cosidad cinemática por medio de un viscosímetro capilar mediante la normaASTM D-445 comparando los resultados con las especificaciones ASTM y DINISO 51605: 2010-09. Según los resultados, el aceite crudo y epoxidado cum-plen las especificaciones ASTM y DIN ISO 51605: 2010-09 a excepción de lahumedad y la acidez con valores superiores a 0,075 % y 2 mg KOH/g de aceite,respectivamente, representando una disminución en la calidad de los aceites,referente a la epoxidación se obtuvo una conversión del 81,34 % de las insa-turaciones y de acuerdo a la viscosidad se pudo clasificar el aceite epoxidadocon un grado ISO VG 320 ideal para lubricación de engranajes industriales. Seconcluye que se logró alcanzar una alta conversión de los dobles enlaces agrupos epoxi, siendo el proceso ideal para obtener altos rendimientos.
CARACTERIZACIÓN FÍSICA Y MECÁNICA DELADOBE DEL CENTRO HISTÓRICO DE QUITOSOMETIDO A ENVEJECIMIENTO ACELERADO, 2022
El adobe es una mezcla de suelo limo-arcillosos, fibras vegetales, materia orgánica y agua, la cu... more El adobe es una mezcla de suelo limo-arcillosos, fibras vegetales, materia orgánica y agua, la cual es endurecida al aire libre y forma unidades mampostería
DISMINUCIÓN DE CROMO Y COBRE EN AGUAS RESIDUALES UTILIZANDO CÁSCARAS DE NARANJA Y BANANO (CITRUS SINENSIS YMUSA PARADISIACA) COMO BIOADSORBENTE, 2022
Debido a la búsqueda de alternativas económicas para la disminución de contaminantes en aguas res... more Debido a la búsqueda de alternativas económicas para la disminución de contaminantes en aguas residuales, se emplea como opción el uso de las cáscaras de naranja y banano como adsorbente para remover metales pesados.
ESTUDIO TEÓRICO DE INTERACCIONES INTERMOLECULARES EN COMPUESTOS (CARBONIL) PSEUDO-HALOGENADOS, XC(O)ZY X-SCN, X: F, CL, CCL2F, CCL3Y Z: NCS, SCN, 2022
Se estudió por métodos teóricos la naturaleza de las principales interaccionesintermoleculares, a... more Se estudió por métodos teóricos la naturaleza de las principales interaccionesintermoleculares, a partir del análisis de archivos de información cristalográfica(CIF) de moléculas pseudohalogenadas CCl2FSCN*, CCl3SCN*, ClC(O)SCN*,FC(O)NCS*, FC(O)SCN*. Se estudió por el método de Hirshfeld, la contribuciónde las principales interacciones intermoleculares (gráficos 2D huellas dactilares)y las energías de interacción. Por otra parte, se realizó el análisis AIM, NCI, La-placiano de la densidad electrónica y mapas de potencial electrostático, ana-lizando varios parámetros fisicoquímicos como la lagraniana G(r), energíapotencial virial V(r), Laplaciana, Hamiltoniano de la energía cinética H(r) y el operador, que permitieron clarificar el carácter y tipo de interacción in-termolecular, complementando con el análisis NBO. Para las moléculasCCl2FC(O)NCS, CCl2FC(O)SCN, CCl3C(O)NCS, CCl3C(O)SCN, ClC(O)NCS,ClSCN y FSCN no se disponía de información cristalográfica (CIF), por lo tanto,se realizó una evaluación mediante análisis AIM, NCI, Laplaciano y mapas depotencial electrostático. Se utilizó software como Gaussian16W, MultiWfn,Crystal Explorer, Mercury, VMD y WinGx. Se evidenció interacciones N...S (cal-cógena), Cl...F (halógena) y N...Cl (halógeno) tipo agujero sigma presentes enlas moléculas de tipo XC(O)SCN y XSCN (CCl2FSCN*, CCl3SCN*, ClC(O)SCN*,FC(O)NCS* y FC(O)SCN*) estudiadas desde los archivos CIF. Por otra parte, enel análisis de los mapas de potencial electrostático y el comportamiento delLaplaciano de densidad electrónica en los átomos, sin estructura cristalina (CIF),ClSCN evidencia disminución de la densidad electrónica en el átomo de cloro,por lo tanto, muestra potencial para formar interacciones N...Cl (halógeno),mientras que FSCN, CCl2FCOSCN y CCl3COSCN sugieren la probabilidad deinteracciones N...S (calcógenas).
GAS PHASE DECOMPOSITION OF T-BUTYLMETHYL ETHER CATALYZED BY DIFFERENTHYDROGEN HALIDES: A DFT STUDY, 2022
The gas phase decomposition of t-butyl methyl ether catalyzed by hydrogen ha-lides is studied. Fo... more The gas phase decomposition of t-butyl methyl ether catalyzed by hydrogen ha-lides is studied. Four different hydrogen halides (fluorine, chlorine, bromine,and iodine) were evaluated to determine the electronic influence of the halogenin the reaction mechanism. To describe the mechanism, the ωB97XD/LANL2DZlevel of theory was used. The reactivity order found was F<Cl<Br<I. Interes -tingly, the activation free energy estimated for the HCl model was 133.9 kJ/mol,which is in good agreement with the experimental one (134.3 kJ/mol). Further more, a correlation above 0.804 was noticed when the electronegativity, thehydrogen-halide distance, and the pKa of the hydrogen halides were comparedto the thermodynamic parameters (activation free energy, enthalpy, and en-tropy). Analyzing the mechanism in depth through the intrinsic reaction coor-dinate, reaction force, and reaction electronic flux plots, it was observed thatthough the reaction occurs in a one-step concerted way. The mechanism couldbe divided into two events; the first one composed by a proton transfer fromthe halide to the oxygen and the carbon-oxygen bond cleavage, and the secondone being the rate-limiting event which includes the proton transfer from the t-butyl to the halide and the double bond formation.
Revista infoANALÍTICA Número Especial de Electroquímica, 2021
Microbial fuel cells are devices that convert chemical energy stored into the bonds of organic co... more Microbial fuel cells are devices that convert chemical energy stored into the bonds of organic compounds in electric energy using microorganisms. The advantages of these devices are the capability of water treatment and cleaning. We report, as proof of concept, the construction and performance of a microbial fuel cell, employing reusable and low-cost materials. Microbial Consortium was isolated from Amaluza sludge, Cuenca-Ecuador. The microbial fuel cell was tested using domestic residual water, sampled from Ubilus's neighborhood, at the canton Quito, Ecuador. A power density of ca. 40 mW/m2 and an 80 % of organic matter remotion were obtained with the final microbial fuel cell. On the concept of circular economy, nitrogen, phosphorus, and potassium were measured into the produced biomass, as possible applications in agronomy.
Revista infoANALÍTICA Número Especial de Electroquímica, 2021
Data analysis made with non-linear fitting are not very common, a possible cause is the inaccessi... more Data analysis made with non-linear fitting are not very common, a possible cause is the inaccessibility to specialized software that require license as Zview® or DigiElch. Electrochemical techniques are useful for the determination of kinetics, thermodynamic of cells parameters. The non-linear fitting can be made using Solver into a spreadsheet of Microsoft Excel. This paper present two electrochemical techniques as examples of the developed methodology. Values of area and heterogeneous electron transfer rate constant were calculated from chronoamperometry and cyclic voltammetry of hexacyanoferrate(III) onto platinum ultramicroelectrodes.
Revista infoANALÍTICA Número Especial de Electroquímica, 2021
The physicochemical aspects behind the performance of a semiconductor | electrolyte interphase ar... more The physicochemical aspects behind the performance of a semiconductor | electrolyte interphase are discussed, addressing the fact that the photoelectrochemical response depends on the juxtaposition of two fundamental phenomena: charge-carriers transfer and recombination. Such phenomena define the natural limits of the experimental behavior. Considering TiO2 nanotubes as a special case of study to illustrate the photoelectrochemical behavior of nanostructured electrodes, the analysis of the potentiodynamic response at high overpotentials in relation to Gärtner's theory shows how the incorporation of a different phase (rutile into anatase) can modulate the experimental response. The quantification of the lifetime of carriers with to photoluminescent decays at open circuit illustrates how the relationship between the kinetics of charge transfer and recombination determines the natural limitations of nanostructured photoanodes performance.
Revista InfoANALÍTICA Número Especial de Electroquímica, 2021
The food industry is one of the most environment impact industries in the world due to the high a... more The food industry is one of the most environment impact industries in the world due to the high amount of wastewater it discharges and the high content of organic matter in this water. The use of technologies to treat wastewater and generate energy simultaneously emerges as an efficient alternative to the problem of pollution. Microbial fuel cells are an effective alternative for the treatment of industrial food wastewater due to their high organic matter removal and subsequent energy generation. This work reviews the latest developments in the use of microbial fuel cells in the food industry. The main objective of this review is to describe the components and architectures used in microbial fuel cells and see how they affect the production of electricity and the efficient removal of organic matter in food industry wastewater. At the same time, the main food wastewater substrates (type of wastewater) used in the generation of higher energy efficiency are explored. In other words, it presents the future challenges and perspectives that will allow the improvement of the efficiency in the treatment of the food industry's wastewater and the use of the electrical energy that the microorganisms generate in the process of oxidation of organic matter.
This work presents the results of the sensing analysis of Peruvian wines of known (Commercial win... more This work presents the results of the sensing analysis of Peruvian wines of known (Commercial wines) and handmade brands, using electronic noses (E-noses) which consist of an array of sensors based on tin oxide doped with Pd or Pt, and some with zeolite coating. The combinations of the sensors were performed seeking to obtain the best discrimination of the wines with the multivariate methods, with a high level of confidence and a good distribution of the results. The Principal Component Analysis (PCA), cluster and factorial results showed that the electronic noses allowed to efficiently identify wines of known brand from those of handmade brand, revealing the way in which the wines have been produced. On the other hand, the multivariate methods applied to the electronic noses made up of SnO2 sensors doped with palladium showed a clear differentiation of Borgoña-type wines from wines of handmade brand and evidenced the formation of agglomerations between red and Rosé wines. The application of PCA, cluster and factorial obtained in this study allowed to obtain good results in the differentiation of wines, even with electronic noses formed with a low number of sensors.
Traditional petroleum-derived materials like polyethylene and polypropylene are the most commonly... more Traditional petroleum-derived materials like polyethylene and polypropylene are the most commonly utilized in the field of prosthetics, but the movement toward environmental conservation necessitates the investigation of novel biocompatible and biodegradable materials. Due to its low cost, polylactic acid (PLA) is a polymer derived from natural sources that is utilized in a variety of applications, including orthopedic prosthesis. Nanoparticles of various natures can be added to improve the mechanical characteristics of PLA with the advancement of nanotechnology, although there is insufficient information. The physical and chemical characteristics of PLA, as well as the requirements for 3D printing with it, are described in this review. Nanocellulose, chitosan nanofibers, carbon nanotubes, graphene, titanium oxide, iron oxide nanoparticles, silver nanoparticles, and mesoporous silica nanoparticles are among the nanomaterials studied. The chemical, mechanical, and biocompatibility aspects of the material have been studied. As a result, some nanomaterials have been mixed with PLA, and studies comparing their mechanical characteristics reveal that nanoparticles produce better outcomes. Very few in vivo studies have been performed, only carbon nanotubes, graphene, titanium oxide, silver nanoparticles and mesoporous silica nanoparticles. The introduction of nanoparticles could possibly enhance the mechanical properties of PLA, but further research is needed, and animal models should be utilized to evaluate their effect at the tissue level and decide whether they are acceptable for combination or coating prostheses.
In this investigation, the biomass of Opuntia caracasana and a resulting material after treatment... more In this investigation, the biomass of Opuntia caracasana and a resulting material after treatment with KOH (TVM) were characterized spectroscopically, morphologically and by microanalysis. The results of the FTIR analysis indicated that the dry biomass contains functional groups that indicate the presence of lignin, cellulose, hemicellulose and pectin in the cladodes of the cactus. In addition, strong signals corresponding to the glycosidic ether of cellulose were identified in the material TVM. The morphology of the dry biomass and the material TMV were determined by Scanning Electron Microscopy coupled to an X- Ray Microanalysis Energy Dispersive Detector (SEM-EDS), the agglomerated crystals were observed on the surface of de dry biomass and the presence of cavities and fibers in the material TVM. By means of microanalysis, calcium was detected as the majority element in the dry biomass and was also detected in the material TVM. The results obtained allow us to infer that the dry biomass and the MVT material of O. caracasana have potentialities for the development of sustainable materials that can be used in the food and pharmaceutical industries and as adsorbents for pollutants in aqueous media.
In this work, the degradation of the methylene-blue dye (MB) was evaluated using TiO2 supported i... more In this work, the degradation of the methylene-blue dye (MB) was evaluated using TiO2 supported in common glass and polyethylene (PET) recycled bottles as photoreactors irradiated with solar light; also, the influence of hydrogen peroxide (H2O2) was studied. The degradation of MB (30 mg L-1) was followed by UV-Vis Spectroscopy, and its mineralization by chemical oxygen demand (COD) and total organic carbon (TOC). The results obtained show that 98.0% of MB was removed in glass bottles after four hours of sunlight exposure without H2O2, while, in the PET bottles, at least 7 hours are required to remove 87.0% of MB. On the contrary, the addition of H2O2 (30% v/v) favored the photodegradation process of MB reaching a degradation efficiency of 99.4% and 99.1% after 4 hours of solar radiation exposure, in glass bottles and PET bottles, respectively. In both processes, the kinetic of MB degradation is adapted to a pseudo-first-order kinetic model. In regard to MB mineralization, >50.0% of TOC removal was reached in glass photoreactors with and in the absence of H2O2, and a maximum degradation of COD (86.2%) was reached with the presence of H2O2 in glass photoreactors. Therefore, the photocatalytic degradation of MB is more efficient with the addition of H2O2, however, due to the formation of highly stable intermediaries’ products the complete mineralization of MB was not achieved.
In this study, the values of total phenol concentrations in aqueous extracts of ecuadorian medici... more In this study, the values of total phenol concentrations in aqueous extracts of ecuadorian medicinal plants, obtained using the spectrophotometric method developed by Folinn and Ciocalteau and by the potentiometric titration method, were compared. By the potentiometric method, the total phenols present in four medicinal plants (Ageratum conyzoides, Cnidoscolus chayamansa, Cynara scolymus y Taraxacum officinale) were quantified, which were selected for being representatives of the high, medium, intermediate, and low contents of total phenols of the twelve plants previously analyzed spectrophotometrically. The results of the quantification of total phenols by potentiometric titration had a high correlation (R2 = 0.987) with the values obtained by the spectrophotometric method, at concentrations of 0.70 to 24.0 mg/g. The use of potentiometry to quantify total phenols was environmentally friendly by using very dilute concentrations of reagents and replacing the toxic substances commonly used in spectrophotometric methods.
The current situation requires additional and urgent attention from Science, Engineering and Tech... more The current situation requires additional and urgent attention from Science, Engineering and Technology regarding environmental, climatic, and sanitary control, for the well-being and life over the planet. The scientific area that concerns this work, Electrochemenergy (EC.E), involves important contributions on this subject and there are many and varied new contributions to be made. This review presents some of these studies, some of them completed, others in progress and others to be carried out; it is important to highlight the current importance of working together with the fields of nanoscience and nanocatalysis in the scientific area.
The mechanism and kinetics of gas-phase pyrolysis of 4-chloro-1-butanol at DFT level were investi... more The mechanism and kinetics of gas-phase pyrolysis of 4-chloro-1-butanol at DFT level were investigated. The reaction gives as products tetrahydrofuran, formaldehyde, propene and hydrogen chloride. The molecular elimination mechanism suggests two reaction pathways. The first pathway occurs through a four-member cyclic transition state, where the theory level WB97XD/6-31G++(d,p) showed results close to experimental kinetic parameters. The second pathway occurs in two stages, the first is given by a cyclic transition state of four members and the second with a cyclical transition state of six members, the levels of theory that gave results closest to the experimental ones were B3LYP/6-31G(d,p) and WB97XD/6-31G++(d,p), for first and second stage respectively. The breakdown of the C-Cl bond, due to its polarization at the 𝐶𝛿+… 𝐶𝑙𝛿−bond, is the velocity-determining step in both reaction pathways. The NCI topological analysis was used to determine the non-covalent interactions of all structures. The variation of the strength of the bonds involved in the transitions was measured by the IBSI index, to verify the proposed mechanism
The evaluation of pollutants present in the environment is a reiterative issue at the internation... more The evaluation of pollutants present in the environment is a reiterative issue at the international level, for this reason the development of new methodologies for the extraction of analytes from matrices such as surface waters, with a low impact on the environment, is imperative. Chlorpyrifos (CP) is an organophosphate compound widely used for pest control, toxic to living beings, which can be mobilized from soils to different water sources. Dispersive liquid-liquid microextraction (DLLME) can be considered as a methodology with characteristics of green analytical chemistry, due to the low consumption of solvent and time. The objective of this work was to optimize the DLLME for the analysis of CP in water samples. For the extraction, methanol was used as a dispersing agent and CS2 as an extracting agent, evaluating five extraction times: 5, 10, 15, 20 and 25 minutes. The extracts were analyzed by gas chromatography with an electron microcapture detector (GC-μECD). The results of the evaluation of the stirring time showed that, for the stirring times of 10 and 15 minutes, a recovery percentage of CP of 108 and 88% was obtained, respectively, with a detection and quantification limit of 18, 3 and 22.4 μg / L, respectively, and a precision expressed as a relative standard deviation of less than 14.2%, acceptable for this type of extraction. It can be concluded that the DLLME methodology associated with GC-μECD is a suitable alternative for the quantification of CP in aqueous matrices with a low environmental impact.
The inappropriate use of antibiotics has led to an increase in the rate of bacterial resistance, ... more The inappropriate use of antibiotics has led to an increase in the rate of bacterial resistance, therefore, the study of new compounds with bioactive properties has been essential to face the challenge caused by the lack of effective drugs for the treatment of infections caused by a wide range of bacteria. In this sense, the present research work focuses on the computational modeling of Cruzioseptin CC-17 belonging to the family of peptides extracted from the exudate of the Cruziohyla calcarifer frog. Initially, the characterization of the peptide was carried out based on its physicochemical properties and the elucidation of its secondary structure. In addition, molecular docking was performed to analyze the activity of the different enzymes present in Escherichia coli, Staphylococcus aureus and Candida albicans and with molecules present in the bacterial cell membrane. The results show that Cruzioseptin CC-17 is a peptide which secondary structure is predominantly composed of alpha helical regions and has a net charge of +2 which gives it the basic character, has an isoelectric point of 8,6 and is composed of a 52,7% by hydrophobic amino acids, which confirms its cationic character. In the other hand, molecular docking results shows that the bioactivity of the peptide can be explained based on a concentrated attack mechanism on the bacterial cell membrane where the cell lysis occurs by the electrostatic interactions between Cruzioseptin CC-17 with the different molecules of the cell membrane.
OBTENCIÓN DE BIODIESEL A PARTIR DE LA TRANSESTERIFICACIÓN DE ACEITE VEGETAL RESIDUAL, Jan 13, 2023
El presente trabajo muestra los resultados de la obtención de un biodiesel B100 a partir del acei... more El presente trabajo muestra los resultados de la obtención de un biodiesel B100 a partir del aceite vegetal residual de palma (obtenido) por medio de la trasesterificación empleando alcohol metílico con relación molar metanol-aceite de 6:1 y como catalizador al hidróxido de sodio 1% en peso, a diferentes tiempos de reacción y temperaturas. Se realizó una caracterización físicoquímica a cada muestra de biodiesel obtenido con el fin de determinar su calidad, así como también al aceite empleado como materia prima, estos resultados se compararon con las normas ASTM D 6 751, EN 14 214 y la NTE INEN 1640. Por medio de la caracterización físico-química se determinó que la muestra que mejor resultados presenta es la 3B con un tiempo de reacción de 50 minutos a una temperatura de 60°C. La densidad a 15°C fue de 898 kg/mᶟ, la viscosidad cinemática a 40 °C de 2,496 mm²/s, el índice de acidez de 0,561 mgKOH/g, el contenido de humedad de 0,03%. El índice de yodo de realizo en dos muestras de 30 y 60 minutos, obteniendo un valor favorable a una temperatura de 60°C. El rendimiento del biodiesel fue de 63,01 %. Esto permite concluir que se obtuvo biodiesel B100 con resultados óptimos en relación a la naturaleza del aceite empleado como materia prima.
EPOXIDACIÓN DE ACEITE DE HIGUERILLA (Ricinus communis) DE LA PROVINCIA DE MANABÍ-ECUADOR, Jan 11, 2023
El aceite de higuerilla (Ricinnus communis) atrae el interés en la industria quí-mica porque pued... more El aceite de higuerilla (Ricinnus communis) atrae el interés en la industria quí-mica porque puede emplearse como materia prima para producir productosquímicos o fuentes de energía por medio de modificaciones químicas, comoes el caso de la epoxidación. El presente estudio, de índole investigativa y ex-perimental, se enfoca en la epoxidación del aceite de higuerilla de la variedadPortoviejo-67 de la provincia de Manabí-Ecuador por medio de la reacción dePrileschajew para evaluar las características fisicoquímicas del aceite crudo yepoxidado mediante las normas ASTM D-5558, EN 14111, NTC 2366 para ín-dice de saponificación, índice de yodo e índice de acidez mediante técnicasde titulación, norma INEN 39 para contenido de humedad mediante pérdidapor calentamiento, norma ASTM D-1217 para densidad por picnometría y vis-cosidad cinemática por medio de un viscosímetro capilar mediante la normaASTM D-445 comparando los resultados con las especificaciones ASTM y DINISO 51605: 2010-09. Según los resultados, el aceite crudo y epoxidado cum-plen las especificaciones ASTM y DIN ISO 51605: 2010-09 a excepción de lahumedad y la acidez con valores superiores a 0,075 % y 2 mg KOH/g de aceite,respectivamente, representando una disminución en la calidad de los aceites,referente a la epoxidación se obtuvo una conversión del 81,34 % de las insa-turaciones y de acuerdo a la viscosidad se pudo clasificar el aceite epoxidadocon un grado ISO VG 320 ideal para lubricación de engranajes industriales. Seconcluye que se logró alcanzar una alta conversión de los dobles enlaces agrupos epoxi, siendo el proceso ideal para obtener altos rendimientos.
CARACTERIZACIÓN FÍSICA Y MECÁNICA DELADOBE DEL CENTRO HISTÓRICO DE QUITOSOMETIDO A ENVEJECIMIENTO ACELERADO, 2022
El adobe es una mezcla de suelo limo-arcillosos, fibras vegetales, materia orgánica y agua, la cu... more El adobe es una mezcla de suelo limo-arcillosos, fibras vegetales, materia orgánica y agua, la cual es endurecida al aire libre y forma unidades mampostería
DISMINUCIÓN DE CROMO Y COBRE EN AGUAS RESIDUALES UTILIZANDO CÁSCARAS DE NARANJA Y BANANO (CITRUS SINENSIS YMUSA PARADISIACA) COMO BIOADSORBENTE, 2022
Debido a la búsqueda de alternativas económicas para la disminución de contaminantes en aguas res... more Debido a la búsqueda de alternativas económicas para la disminución de contaminantes en aguas residuales, se emplea como opción el uso de las cáscaras de naranja y banano como adsorbente para remover metales pesados.
ESTUDIO TEÓRICO DE INTERACCIONES INTERMOLECULARES EN COMPUESTOS (CARBONIL) PSEUDO-HALOGENADOS, XC(O)ZY X-SCN, X: F, CL, CCL2F, CCL3Y Z: NCS, SCN, 2022
Se estudió por métodos teóricos la naturaleza de las principales interaccionesintermoleculares, a... more Se estudió por métodos teóricos la naturaleza de las principales interaccionesintermoleculares, a partir del análisis de archivos de información cristalográfica(CIF) de moléculas pseudohalogenadas CCl2FSCN*, CCl3SCN*, ClC(O)SCN*,FC(O)NCS*, FC(O)SCN*. Se estudió por el método de Hirshfeld, la contribuciónde las principales interacciones intermoleculares (gráficos 2D huellas dactilares)y las energías de interacción. Por otra parte, se realizó el análisis AIM, NCI, La-placiano de la densidad electrónica y mapas de potencial electrostático, ana-lizando varios parámetros fisicoquímicos como la lagraniana G(r), energíapotencial virial V(r), Laplaciana, Hamiltoniano de la energía cinética H(r) y el operador, que permitieron clarificar el carácter y tipo de interacción in-termolecular, complementando con el análisis NBO. Para las moléculasCCl2FC(O)NCS, CCl2FC(O)SCN, CCl3C(O)NCS, CCl3C(O)SCN, ClC(O)NCS,ClSCN y FSCN no se disponía de información cristalográfica (CIF), por lo tanto,se realizó una evaluación mediante análisis AIM, NCI, Laplaciano y mapas depotencial electrostático. Se utilizó software como Gaussian16W, MultiWfn,Crystal Explorer, Mercury, VMD y WinGx. Se evidenció interacciones N...S (cal-cógena), Cl...F (halógena) y N...Cl (halógeno) tipo agujero sigma presentes enlas moléculas de tipo XC(O)SCN y XSCN (CCl2FSCN*, CCl3SCN*, ClC(O)SCN*,FC(O)NCS* y FC(O)SCN*) estudiadas desde los archivos CIF. Por otra parte, enel análisis de los mapas de potencial electrostático y el comportamiento delLaplaciano de densidad electrónica en los átomos, sin estructura cristalina (CIF),ClSCN evidencia disminución de la densidad electrónica en el átomo de cloro,por lo tanto, muestra potencial para formar interacciones N...Cl (halógeno),mientras que FSCN, CCl2FCOSCN y CCl3COSCN sugieren la probabilidad deinteracciones N...S (calcógenas).
GAS PHASE DECOMPOSITION OF T-BUTYLMETHYL ETHER CATALYZED BY DIFFERENTHYDROGEN HALIDES: A DFT STUDY, 2022
The gas phase decomposition of t-butyl methyl ether catalyzed by hydrogen ha-lides is studied. Fo... more The gas phase decomposition of t-butyl methyl ether catalyzed by hydrogen ha-lides is studied. Four different hydrogen halides (fluorine, chlorine, bromine,and iodine) were evaluated to determine the electronic influence of the halogenin the reaction mechanism. To describe the mechanism, the ωB97XD/LANL2DZlevel of theory was used. The reactivity order found was F<Cl<Br<I. Interes -tingly, the activation free energy estimated for the HCl model was 133.9 kJ/mol,which is in good agreement with the experimental one (134.3 kJ/mol). Further more, a correlation above 0.804 was noticed when the electronegativity, thehydrogen-halide distance, and the pKa of the hydrogen halides were comparedto the thermodynamic parameters (activation free energy, enthalpy, and en-tropy). Analyzing the mechanism in depth through the intrinsic reaction coor-dinate, reaction force, and reaction electronic flux plots, it was observed thatthough the reaction occurs in a one-step concerted way. The mechanism couldbe divided into two events; the first one composed by a proton transfer fromthe halide to the oxygen and the carbon-oxygen bond cleavage, and the secondone being the rate-limiting event which includes the proton transfer from the t-butyl to the halide and the double bond formation.
Revista infoANALÍTICA Número Especial de Electroquímica, 2021
Microbial fuel cells are devices that convert chemical energy stored into the bonds of organic co... more Microbial fuel cells are devices that convert chemical energy stored into the bonds of organic compounds in electric energy using microorganisms. The advantages of these devices are the capability of water treatment and cleaning. We report, as proof of concept, the construction and performance of a microbial fuel cell, employing reusable and low-cost materials. Microbial Consortium was isolated from Amaluza sludge, Cuenca-Ecuador. The microbial fuel cell was tested using domestic residual water, sampled from Ubilus's neighborhood, at the canton Quito, Ecuador. A power density of ca. 40 mW/m2 and an 80 % of organic matter remotion were obtained with the final microbial fuel cell. On the concept of circular economy, nitrogen, phosphorus, and potassium were measured into the produced biomass, as possible applications in agronomy.
Revista infoANALÍTICA Número Especial de Electroquímica, 2021
Data analysis made with non-linear fitting are not very common, a possible cause is the inaccessi... more Data analysis made with non-linear fitting are not very common, a possible cause is the inaccessibility to specialized software that require license as Zview® or DigiElch. Electrochemical techniques are useful for the determination of kinetics, thermodynamic of cells parameters. The non-linear fitting can be made using Solver into a spreadsheet of Microsoft Excel. This paper present two electrochemical techniques as examples of the developed methodology. Values of area and heterogeneous electron transfer rate constant were calculated from chronoamperometry and cyclic voltammetry of hexacyanoferrate(III) onto platinum ultramicroelectrodes.
Revista infoANALÍTICA Número Especial de Electroquímica, 2021
The physicochemical aspects behind the performance of a semiconductor | electrolyte interphase ar... more The physicochemical aspects behind the performance of a semiconductor | electrolyte interphase are discussed, addressing the fact that the photoelectrochemical response depends on the juxtaposition of two fundamental phenomena: charge-carriers transfer and recombination. Such phenomena define the natural limits of the experimental behavior. Considering TiO2 nanotubes as a special case of study to illustrate the photoelectrochemical behavior of nanostructured electrodes, the analysis of the potentiodynamic response at high overpotentials in relation to Gärtner's theory shows how the incorporation of a different phase (rutile into anatase) can modulate the experimental response. The quantification of the lifetime of carriers with to photoluminescent decays at open circuit illustrates how the relationship between the kinetics of charge transfer and recombination determines the natural limitations of nanostructured photoanodes performance.
Revista InfoANALÍTICA Número Especial de Electroquímica, 2021
The food industry is one of the most environment impact industries in the world due to the high a... more The food industry is one of the most environment impact industries in the world due to the high amount of wastewater it discharges and the high content of organic matter in this water. The use of technologies to treat wastewater and generate energy simultaneously emerges as an efficient alternative to the problem of pollution. Microbial fuel cells are an effective alternative for the treatment of industrial food wastewater due to their high organic matter removal and subsequent energy generation. This work reviews the latest developments in the use of microbial fuel cells in the food industry. The main objective of this review is to describe the components and architectures used in microbial fuel cells and see how they affect the production of electricity and the efficient removal of organic matter in food industry wastewater. At the same time, the main food wastewater substrates (type of wastewater) used in the generation of higher energy efficiency are explored. In other words, it presents the future challenges and perspectives that will allow the improvement of the efficiency in the treatment of the food industry's wastewater and the use of the electrical energy that the microorganisms generate in the process of oxidation of organic matter.
This work presents the results of the sensing analysis of Peruvian wines of known (Commercial win... more This work presents the results of the sensing analysis of Peruvian wines of known (Commercial wines) and handmade brands, using electronic noses (E-noses) which consist of an array of sensors based on tin oxide doped with Pd or Pt, and some with zeolite coating. The combinations of the sensors were performed seeking to obtain the best discrimination of the wines with the multivariate methods, with a high level of confidence and a good distribution of the results. The Principal Component Analysis (PCA), cluster and factorial results showed that the electronic noses allowed to efficiently identify wines of known brand from those of handmade brand, revealing the way in which the wines have been produced. On the other hand, the multivariate methods applied to the electronic noses made up of SnO2 sensors doped with palladium showed a clear differentiation of Borgoña-type wines from wines of handmade brand and evidenced the formation of agglomerations between red and Rosé wines. The application of PCA, cluster and factorial obtained in this study allowed to obtain good results in the differentiation of wines, even with electronic noses formed with a low number of sensors.
Traditional petroleum-derived materials like polyethylene and polypropylene are the most commonly... more Traditional petroleum-derived materials like polyethylene and polypropylene are the most commonly utilized in the field of prosthetics, but the movement toward environmental conservation necessitates the investigation of novel biocompatible and biodegradable materials. Due to its low cost, polylactic acid (PLA) is a polymer derived from natural sources that is utilized in a variety of applications, including orthopedic prosthesis. Nanoparticles of various natures can be added to improve the mechanical characteristics of PLA with the advancement of nanotechnology, although there is insufficient information. The physical and chemical characteristics of PLA, as well as the requirements for 3D printing with it, are described in this review. Nanocellulose, chitosan nanofibers, carbon nanotubes, graphene, titanium oxide, iron oxide nanoparticles, silver nanoparticles, and mesoporous silica nanoparticles are among the nanomaterials studied. The chemical, mechanical, and biocompatibility aspects of the material have been studied. As a result, some nanomaterials have been mixed with PLA, and studies comparing their mechanical characteristics reveal that nanoparticles produce better outcomes. Very few in vivo studies have been performed, only carbon nanotubes, graphene, titanium oxide, silver nanoparticles and mesoporous silica nanoparticles. The introduction of nanoparticles could possibly enhance the mechanical properties of PLA, but further research is needed, and animal models should be utilized to evaluate their effect at the tissue level and decide whether they are acceptable for combination or coating prostheses.
In this investigation, the biomass of Opuntia caracasana and a resulting material after treatment... more In this investigation, the biomass of Opuntia caracasana and a resulting material after treatment with KOH (TVM) were characterized spectroscopically, morphologically and by microanalysis. The results of the FTIR analysis indicated that the dry biomass contains functional groups that indicate the presence of lignin, cellulose, hemicellulose and pectin in the cladodes of the cactus. In addition, strong signals corresponding to the glycosidic ether of cellulose were identified in the material TVM. The morphology of the dry biomass and the material TMV were determined by Scanning Electron Microscopy coupled to an X- Ray Microanalysis Energy Dispersive Detector (SEM-EDS), the agglomerated crystals were observed on the surface of de dry biomass and the presence of cavities and fibers in the material TVM. By means of microanalysis, calcium was detected as the majority element in the dry biomass and was also detected in the material TVM. The results obtained allow us to infer that the dry biomass and the MVT material of O. caracasana have potentialities for the development of sustainable materials that can be used in the food and pharmaceutical industries and as adsorbents for pollutants in aqueous media.
In this work, the degradation of the methylene-blue dye (MB) was evaluated using TiO2 supported i... more In this work, the degradation of the methylene-blue dye (MB) was evaluated using TiO2 supported in common glass and polyethylene (PET) recycled bottles as photoreactors irradiated with solar light; also, the influence of hydrogen peroxide (H2O2) was studied. The degradation of MB (30 mg L-1) was followed by UV-Vis Spectroscopy, and its mineralization by chemical oxygen demand (COD) and total organic carbon (TOC). The results obtained show that 98.0% of MB was removed in glass bottles after four hours of sunlight exposure without H2O2, while, in the PET bottles, at least 7 hours are required to remove 87.0% of MB. On the contrary, the addition of H2O2 (30% v/v) favored the photodegradation process of MB reaching a degradation efficiency of 99.4% and 99.1% after 4 hours of solar radiation exposure, in glass bottles and PET bottles, respectively. In both processes, the kinetic of MB degradation is adapted to a pseudo-first-order kinetic model. In regard to MB mineralization, >50.0% of TOC removal was reached in glass photoreactors with and in the absence of H2O2, and a maximum degradation of COD (86.2%) was reached with the presence of H2O2 in glass photoreactors. Therefore, the photocatalytic degradation of MB is more efficient with the addition of H2O2, however, due to the formation of highly stable intermediaries’ products the complete mineralization of MB was not achieved.
In this study, the values of total phenol concentrations in aqueous extracts of ecuadorian medici... more In this study, the values of total phenol concentrations in aqueous extracts of ecuadorian medicinal plants, obtained using the spectrophotometric method developed by Folinn and Ciocalteau and by the potentiometric titration method, were compared. By the potentiometric method, the total phenols present in four medicinal plants (Ageratum conyzoides, Cnidoscolus chayamansa, Cynara scolymus y Taraxacum officinale) were quantified, which were selected for being representatives of the high, medium, intermediate, and low contents of total phenols of the twelve plants previously analyzed spectrophotometrically. The results of the quantification of total phenols by potentiometric titration had a high correlation (R2 = 0.987) with the values obtained by the spectrophotometric method, at concentrations of 0.70 to 24.0 mg/g. The use of potentiometry to quantify total phenols was environmentally friendly by using very dilute concentrations of reagents and replacing the toxic substances commonly used in spectrophotometric methods.
The current situation requires additional and urgent attention from Science, Engineering and Tech... more The current situation requires additional and urgent attention from Science, Engineering and Technology regarding environmental, climatic, and sanitary control, for the well-being and life over the planet. The scientific area that concerns this work, Electrochemenergy (EC.E), involves important contributions on this subject and there are many and varied new contributions to be made. This review presents some of these studies, some of them completed, others in progress and others to be carried out; it is important to highlight the current importance of working together with the fields of nanoscience and nanocatalysis in the scientific area.
The mechanism and kinetics of gas-phase pyrolysis of 4-chloro-1-butanol at DFT level were investi... more The mechanism and kinetics of gas-phase pyrolysis of 4-chloro-1-butanol at DFT level were investigated. The reaction gives as products tetrahydrofuran, formaldehyde, propene and hydrogen chloride. The molecular elimination mechanism suggests two reaction pathways. The first pathway occurs through a four-member cyclic transition state, where the theory level WB97XD/6-31G++(d,p) showed results close to experimental kinetic parameters. The second pathway occurs in two stages, the first is given by a cyclic transition state of four members and the second with a cyclical transition state of six members, the levels of theory that gave results closest to the experimental ones were B3LYP/6-31G(d,p) and WB97XD/6-31G++(d,p), for first and second stage respectively. The breakdown of the C-Cl bond, due to its polarization at the 𝐶𝛿+… 𝐶𝑙𝛿−bond, is the velocity-determining step in both reaction pathways. The NCI topological analysis was used to determine the non-covalent interactions of all structures. The variation of the strength of the bonds involved in the transitions was measured by the IBSI index, to verify the proposed mechanism
The evaluation of pollutants present in the environment is a reiterative issue at the internation... more The evaluation of pollutants present in the environment is a reiterative issue at the international level, for this reason the development of new methodologies for the extraction of analytes from matrices such as surface waters, with a low impact on the environment, is imperative. Chlorpyrifos (CP) is an organophosphate compound widely used for pest control, toxic to living beings, which can be mobilized from soils to different water sources. Dispersive liquid-liquid microextraction (DLLME) can be considered as a methodology with characteristics of green analytical chemistry, due to the low consumption of solvent and time. The objective of this work was to optimize the DLLME for the analysis of CP in water samples. For the extraction, methanol was used as a dispersing agent and CS2 as an extracting agent, evaluating five extraction times: 5, 10, 15, 20 and 25 minutes. The extracts were analyzed by gas chromatography with an electron microcapture detector (GC-μECD). The results of the evaluation of the stirring time showed that, for the stirring times of 10 and 15 minutes, a recovery percentage of CP of 108 and 88% was obtained, respectively, with a detection and quantification limit of 18, 3 and 22.4 μg / L, respectively, and a precision expressed as a relative standard deviation of less than 14.2%, acceptable for this type of extraction. It can be concluded that the DLLME methodology associated with GC-μECD is a suitable alternative for the quantification of CP in aqueous matrices with a low environmental impact.
The inappropriate use of antibiotics has led to an increase in the rate of bacterial resistance, ... more The inappropriate use of antibiotics has led to an increase in the rate of bacterial resistance, therefore, the study of new compounds with bioactive properties has been essential to face the challenge caused by the lack of effective drugs for the treatment of infections caused by a wide range of bacteria. In this sense, the present research work focuses on the computational modeling of Cruzioseptin CC-17 belonging to the family of peptides extracted from the exudate of the Cruziohyla calcarifer frog. Initially, the characterization of the peptide was carried out based on its physicochemical properties and the elucidation of its secondary structure. In addition, molecular docking was performed to analyze the activity of the different enzymes present in Escherichia coli, Staphylococcus aureus and Candida albicans and with molecules present in the bacterial cell membrane. The results show that Cruzioseptin CC-17 is a peptide which secondary structure is predominantly composed of alpha helical regions and has a net charge of +2 which gives it the basic character, has an isoelectric point of 8,6 and is composed of a 52,7% by hydrophobic amino acids, which confirms its cationic character. In the other hand, molecular docking results shows that the bioactivity of the peptide can be explained based on a concentrated attack mechanism on the bacterial cell membrane where the cell lysis occurs by the electrostatic interactions between Cruzioseptin CC-17 with the different molecules of the cell membrane.
RESUMEN En el desarrollo de este trabajo de investigación se han sintetizado y caracteri-zado nan... more RESUMEN En el desarrollo de este trabajo de investigación se han sintetizado y caracteri-zado nanocompositos en base de halloysita con nanopartículas de sulfuro de bismuto. La halloysita, es un filosilicato que se encuentra en forma de nanotu-bos de multicapas y constituye una alternativa de morfología similar a los na-notubos de carbono; sin embargo, posee características químicas distintas en la superficie externa e interna. La síntesis se llevó a cabo utilizando un método de impregnación de los precursores en nanotubos de halloysita para el posterior crecimiento de las nanopartículas in situ. La caracterización incluyó espectroscopias de absorción electrónica (UV-visible) y difracción de rayos X, en polvos. La morfología de los nanocompositos preparados se evidenció utilizando microscopía de barrido electrónico (SEM) y microscopía de transmisión electrónica (TEM); además se utilizó espectroscopia de energía dispersiva (EDS) para identificar elementos particulares y su distribución en la muestra. Los resultados indican que las nanopartículas de Bi2S3 (Bi2S3 NPs), de morfología esférica, se depositaron de manera uniforme sobre los nanotubos de halloysita (HNTs). Las partículas en el nanocomposito presentaron mayor diámetro que las partículas sintetizadas sin HNTs. Este cambio se evidencia en la reducción del ancho del pico en los patrones de difracción y en la disminución de valor de energía de la brecha energética. La formación del nanocomposito contribuyó a mantener las nanopartículas dispersas de manera homogénea sobre halloysita, evitando su aglomeración. Además, se evidenció el control de tamaño y morfología cuando se utiliza los nanotubos como soporte.
RESUMEN La presente investigación tuvo como finalidad determinar el valor nutricional, así como i... more RESUMEN La presente investigación tuvo como finalidad determinar el valor nutricional, así como identificar los tipos de ácidos grasos que componen la grasa de los chontacuros de la especie Rhynchophorus palmarum L. Estos fueron recolec-tados en los mercados de la ciudad del Puyo de la provincia de Pastaza, siendo el mercado de los Plátanos y el mercado Mariscal donde se los encuentra con mayor frecuencia. Se consideró también el tipo de palma de la cual provienen los chontacuros y se encontró que la palma chonta y la palma morete son las
RESUMEN Se reporta el valor nutricional y caracterización del contenido lipídico del catzo de la ... more RESUMEN Se reporta el valor nutricional y caracterización del contenido lipídico del catzo de la especie Platycoelia lutescen, recolectado en los cantones Cayambe y
RESUMEN La zeína es una proteína no polar que tiene un elevado contenido de prolina y leucina, se... more RESUMEN La zeína es una proteína no polar que tiene un elevado contenido de prolina y leucina, se puede obtener fácilmente de los granos de maíz y por su composi-ción puede formar una matriz proteica de nanopartículas para encapsular co-lorantes polares. A partir de zeína USP decolorada, se sintetizaron nanopar
RESUMEN En este artículo de revisión se da a conocer el principio de funcionamiento de dos técnic... more RESUMEN En este artículo de revisión se da a conocer el principio de funcionamiento de dos técnicas nucleares modernas: el análisis de reacción nuclear (NRA) y la emisión de rayos γ inducidos por partículas (PIGE). También se mencionan ven-tajas como la alta sensibilidad y desventajas como la dificultad de interpretar sus espectros. Además, se revisan aplicaciones en donde varios autores han de-sarrollado trabajos de investigación y se da un resumen sobre lo que se espera de la técnica dentro de los próximos años. Todo esto, con el objetivo de sinte-tizar los aspectos más importantes de ambas. Así, sirve de ayuda para aquellos que desconocen NRA y PIGE o que se encuentran evaluando la posibilidad y
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de naranja y banano como adsorbente para remover metales pesados.
de naranja y banano como adsorbente para remover metales pesados.
de absorción electrónica (UV-visible) y difracción de rayos X, en polvos.
La morfología de los nanocompositos preparados se evidenció utilizando microscopía
de barrido electrónico (SEM) y microscopía de transmisión electrónica
(TEM); además se utilizó espectroscopia de energía dispersiva (EDS) para
identificar elementos particulares y su distribución en la muestra. Los resultados
indican que las nanopartículas de Bi2S3 (Bi2S3 NPs), de morfología esférica, se
depositaron de manera uniforme sobre los nanotubos de halloysita (HNTs). Las
partículas en el nanocomposito presentaron mayor diámetro que las partículas
sintetizadas sin HNTs. Este cambio se evidencia en la reducción del ancho del
pico en los patrones de difracción y en la disminución de valor de energía de
la brecha energética. La formación del nanocomposito contribuyó a mantener
las nanopartículas dispersas de manera homogénea sobre halloysita, evitando
su aglomeración. Además, se evidenció el control de tamaño y morfología
cuando se utiliza los nanotubos como soporte.