Revista Bases de la Ciencia. e-ISSN 2588-0764, Dec 1, 2016
Se presentan algunas contribuciones procedimentales para la extracción de vanadio (V), níquel (Ni... more Se presentan algunas contribuciones procedimentales para la extracción de vanadio (V), níquel (Ni) y azufre (S) en petrocoque. Las muestras se sometieron a varios procesos de extracción inducidos por agitación mecánica a 50°C, radiación UV y microondas, empleando como agentes extractantes: HCl:HNO3 (1:1) al 10 y 20%, H2O2 al 30%, HCl al 10%, NH4OH al 10 y 20% y H2O desionizada. La caracterización de las muestras y la cuantificación de los elementos estudiados, se realizó por análisis elemental, análisis térmico, cromatografía iónica, espectrometría de emisión atómica con plasma acoplado inductivamente (ICP-AES) y fluorescencia de rayos X (XRF). Se encontró la mayor eficiencia, induciendo la extracción con radiación microondas, obteniendo 41% para S con una solución al 20% de HCl:HNO3 (1:1) y para V de 20% con H2O2. La agitación mecánica a 50°C resultó eficiente para la extracción de Ni (2,5%) con HCl:HNO3 (1:1) al 10%. De igual manera, resultó una excelente alternativa para la extracción de S, alcanzando valores hasta de 26%. De forma similar, los procedimientos inducidos con radiación UV, también resultaron eficientes en la extracción de S, obteniendo entre 26 y 37% con las soluciones de ácidos al 20%, NH4OH al 10% y H2O2. Por otra parte, empleando la extracción Soxhlet solo con H2O desionizada, se demostró que es posible extraer hasta un 6% de V, Ni y S presentes en el petrocoque, lo que sugiere que estos elementos se encuentren disponibles en el ecosistema circundante a los depósitos de coque en las refinerías.
We present the methodological development for the spectrometric determination in the visible, ran... more We present the methodological development for the spectrometric determination in the visible, range of Ca 2+ in human blood serum by FIA. The method is based on the formation of a complex Ca 2+-Murexida in basic medium (pH 12). We used a semi-automatic system with an injection volume of 16.5 µL, reactor length of 1 m, the complex was measured at 491 nm, can process 44 samples per hour, with a linear range of 2-12 mg•L-1. We obtained a L D and L C of 0.076 mg•L-1 and 0.25 mg•L-1 , respectively, and a precision (RSD) of 1.81%. Accuracy is assessed by comparing the concentrations of Ca using the method developed by others based on spectrometric techniques. We observed no statistically significant differences (p<0.05), obtaining val
In this study, copper (Cu) and zinc (Zn) levels were determined by flame atomic absorption spectr... more In this study, copper (Cu) and zinc (Zn) levels were determined by flame atomic absorption spectrometry (FAAS) in the blood serum of patients with metabolic syndrome (MS) and controls (C) from the city of Maracaibo. Whole blood samples (N = 100; 50 for MS and 50 for C) were collected in polypropylene containers at the Endocrine Metabolic Research Center (CIEM), Faculty of Medicine at the University of Zulia. After separating the clot, each sample was centrifuged to obtain serum and stored at 4°C. Quantification of copper and zinc was performed by calibration curves prepared with concentrated aqueous standards of 0.10, 0.50, 1.00, 2.00, 4.00 and 6.00 mg Cu L-1 ; and 0.05, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.80, and 1.00 mg Zn L-1. Serum concentrations of copper and zinc in patients with MS (ca. 0.76 ± 0.24 and 1.31 ± 0.42 mg L-1 , respectively) were below those obtained for subjects in the control group (ca. 0.96 ± 0.21 and 1.04 ± 0.14 mg L-1 , respectively), demonstrating the involvement of Cu and Zn in disorders of carbohydrate and lipid metabolism in the experimental population studied.
Resumen Los ácidos grasos pueden dar origen a la formación de una especie iónica con característi... more Resumen Los ácidos grasos pueden dar origen a la formación de una especie iónica con características anfifilicas que disminuye la tensión interfacial de un sistema agua/crudo. El tipo de contraión de estas especies juega un papel fundamental en las propiedades tensoactivas del compuesto. En función a ello, se estudió la influencia del contraión de la sal del ácido hexadecanoico (C16) obten-ido al reaccionar este compuesto con NaOH y ciclohexil amina para obtener como productos hexa-decanoato de sodio (NaC16) y hexadecanoato de ciclohexil amonio (CicloC16). Se evaluó el compor-tamiento de estas especies en las propiedades de las emulsiones de agua en crudo Boscán formula-das a diferentes proporciones. En ambos tensoactivos se encontraron emulsiones estables, de fase externa crudo, polidispersas, baja viscosidad (5000 cP) con respecto a la del crudo original (100,000 cP) con un intervalo de diámetro promedio de tamaño de gota (8,04-43,46 µm) y con un alto porcentaje de crudo como fase...
Resumen Se evaluaron las posibles pérdidas de V y Ni durante el tratamiento aplicado a muestras d... more Resumen Se evaluaron las posibles pérdidas de V y Ni durante el tratamiento aplicado a muestras de crudo, asfaltenos y maltenos, para su posterior análisis por espectrometría de emisión atómica con plasma inductivamente acoplado (ICP-OES). Las muestras se calcinaron y digirieron con ácido ní-trico (HNO 3) en recipientes de politerafluoroetileno (PTFE) colocados en una carcasa de acero inoxi-dable tipo autoclave. El estudio de recuperación en crudo se realizó por dos procedimientos: (1) se agregó una cantidad de V y Ni a una muestra de crudo y se homogeneizó, tomando alícuotas de ésta para el análisis y (2) se adicionó una cantidad de los metales directamente a las alícuotas. Las recuperaciones en crudo total por el primer procedimiento dieron bajos rendimientos (76% V y 46% Ni) en comparación a las obtenidas con el segundo (98% V y 102 % Ni) razón por la cual la re-cuperación en los asfaltenos y maltenos se realizó aplicando el segundo procedimiento, arrojando valores entre 98 y 99%...
The retention behaviour of fatty acids on a reverse phase HPLC column is reported. Retention incr... more The retention behaviour of fatty acids on a reverse phase HPLC column is reported. Retention increases as the acetonitrile/methanol mobile phase becomes richer in acetonitrile. For a given solvent mixture, retention increases (linearly) with the acid chain length. Retention factor (k) is dimensionless and independent on any geometrical parameters of the column or HPLC system. It could be considered to be a thermodynamic characteristic of the adsorbent-compound -eluent system. HPLC experiments carried out at different temperatures allow to plot the variation of the ln k vs. 1/T, and to calculate the DG°, DH° and DS° of transfer of one molecule from the mobile phase to the stationary phase. According to a Van't Hoff expression, the retention decreases as temperature increases. Both DH° and DS° are negative, a result that corroborates that the adsorption of the n-alkyl chains onto the stationary phase is favourable from the energetic point of view, and that it increases the molecul...
Abstract Surfactant/oil/water systems in which the sur-face-active substance is a mixture of an u... more Abstract Surfactant/oil/water systems in which the sur-face-active substance is a mixture of an undissociated fatty acid (FA) and its sodium salt soap, exhibit the typical phase behavior and the general emulsion phenomenology pro-duced by a formulation scan. The phase ...
The development of analytical methods for routine simultaneous identification and quantification ... more The development of analytical methods for routine simultaneous identification and quantification of carboxylic fatty acids (CFAs) are required in different fields, such as, pharmaceutical cosmetics, food products and formulations of water-microemulsion-oil systems. Determination of CFAs has been developed mainly by gas chromatography (GC). As an alternative to GC, liquid chromatography (LC) has better sensitivity and selectivity. However, most CFAs show no useful absorption in ultraviolet-violet (UV-Vis) region, one of the more used detection technique in high-performance liquid chromatography (HPLC). In order to allow the use of UV-Vis detection, the use of pre-column derivatization has been reported to increase sensitivity and selectivity. Therefore, establishment of a simpler and faster on-line method with complete separation is needed for the screening of large numbers of samples. 2,4-Dinitrophenylhydrazine (2,4-DNPH.), benzoil chloride (BC), and phenylhydrazine (PH) were used for derivatization of different FAs by microwaves radiation (MW). After the on-line derivatization, products were separated and quantified by HPLC. Reactor coil was placed inside of microwaves oven at 450 W. Parameters as flow, amount of reagents, irradiation time, and chromatographic conditions were optimized. The continuous analysis using the MW-HPLC-UV system provided high sensitivity and reduced both the amount of reagent used and the analysis times. This proposed method can be used for the routine analysis of FAs contained in water-microemulsion-oil systems, to quantify the total acid fraction in each phase.
In this study, a continuous linear alcohol derivatization is developed. Reaction of alcohol group... more In this study, a continuous linear alcohol derivatization is developed. Reaction of alcohol group (ROH) with benzoyl chloride (BC) is carried out in an on-line system with UV detection. All reaction conditions, as flow rate (FR), ROH/BC molar ratio, wavelength, temperature, microwave (MW) irradiation and reaction coil size (internal diameter and length) were optimized. 0.5 mL min −1 , 2.49 [BC]/[ROH], 230 nm, 60 • C or medium power (225 W) when MW irradiation was used and a reactor coil of 159 L (0.5 mm × 810 mm) were the optimum conditions. The on-line system with microwave irradiation was more efficient than the one with a water bath heating. The developed system reduces analysis time consumption, reagent amounts and this system was used to evaluate the composition of commercial samples of alcohols polyethoxylated (surfactants).
Photostabilizer-type HALS were analyzed by reverse-and normal-phase liquid chromatography (HPLC) ... more Photostabilizer-type HALS were analyzed by reverse-and normal-phase liquid chromatography (HPLC) using C-18, cyano, silica, and amino columns with different solvent mixtures as the mobile phase. The stabilizers analyzed were Tinuvin 770 and Chimassorb 944. The best separation was attained using a NH2-column and acetonitrile/water as the mobile phase. Also, three types of extraction procedures were performed to isolate these additives
... na Sán chez, Ger son Chá vez, Ana Cá ce res, Fredy Ysam bertt y Nel son Már quez La bo ... II... more ... na Sán chez, Ger son Chá vez, Ana Cá ce res, Fredy Ysam bertt y Nel son Már quez La bo ... II) phase be hav ior takes place in which an aque ous (re spec tively oil) surfactant-rich phase is in ... Wider knowl edge has been de vel oped on the qua ter nary sys tems wa ter/oil/sur - fac ...
El objetivo de este trabajo fue validar un metodo para la determinacion de vitamina A en leche en... more El objetivo de este trabajo fue validar un metodo para la determinacion de vitamina A en leche en polvo. Se utilizaron tres marcas de leche en polvo de distribucion masiva en la ciudad de Maracaibo, estado Zulia. Se realizaron ensayos para determinar las condiciones de extraccion y del sistema cromatografico. En el proceso de extraccion se fijo el tiempo de calentamiento de la muestra en 40 min. El contenido de vitamina A, se determino utilizando un equipo de Cromatografia Liquida de Alta Resolucion (HPLC) con una columna C18 y un detector de UV-visible. La longitud de onda se fijo en 300 nm y el flujo de la fase movil en 1,2 mL/min. Para la evaluacion estadistica de los resultados se utilizo el programa SPSS version 20.0. La selectividad del metodo se verifico empleando pruebas de degradacion artificial (termolisis, oxidacion y fotolisis) que permitieron observar los productos de degradacion de la vitamina A en los cromatogramas. Se prepararon ocho estandares de vitamina A, para el...
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia
In this work the fractions obtained by microwave-assisted oxidative degradation with hydrogen per... more In this work the fractions obtained by microwave-assisted oxidative degradation with hydrogen peroxide of two pine lignins (LAA y LKM) and its tensoactive properties were studied. The reactions were carried out using different quantities of the oxidant agent in a domestic microwave oven in closed reactors. The reaction was completed quickly with the generation of water as by-product. The oxidation products were characterized by UV and FTIR spectroscopy. When comparing them with the original lignin samples in UV analysis, the absorption decreased near the 280nmdue to the oxidation of the aromatic rings. In the analysis by FTIR the signals corresponding to the groups C=O increased among 1,700-1,720 cm1 and 1,650-1,700 cm1 attributed to the oxidation of the lateral chains and aromatic rings, respectively. This results were evidenced because of the aromatic signal C=C around the 1,600 cm1 decreased. It was proven the efficiency and versatility of the radiation microwaves to carry out...
The heavy crude oil presents problems in the dehydration due to the presence stable emulsions, wi... more The heavy crude oil presents problems in the dehydration due to the presence stable emulsions, with water content more than to 1.0%. In this work is proposed the application of microwaves heating (MWH) to favor the separation of emulsioned water in this crude oil, as alternative method to the standard conven-tional heating (SCH). The obtained results showed that both methods are effective for the crude oil dehy-dration since the content of water was smaller than 1.0%, nevertheless, the applied methodology in the thermal chemical methods using MWH required lower analysis time compared with the SCH, important advantage for the decrease of production costs and in the field analyses in the oil industry.
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia
The crude oil in water emulsions have been used to produce and to transport heavy hydrocarbons. M... more The crude oil in water emulsions have been used to produce and to transport heavy hydrocarbons. More stability and less viscosity than the emulsions prepared with an only surfactant was obtained for the crude oil in water emulsions prepared with non-ionic and anionic surfactant mixtures, in previous studies. The stability of these emulsions could be increased, adding short chain amines. In this work, the effect of aliphatic short chain amines in the stability and the rheological properties of heavy crude oil in water emulsions, prepared at crude oil/water relationship of 70/30, is discussed. Polyethoxylated non-ionic surfactants were used, individually or in a mixture with an anionic surfactant of aryl benzene sulfonate type. Aliphatic short chain amines of 2, 4 and 6 atoms of carbon were used as co-surfactants, so much of lineal chain and ramified chain. The results showed that the primary amines of lineal chain produce more stable emulsions and with more viscosity that the emulsio...
Revista Bases de la Ciencia. e-ISSN 2588-0764, Dec 1, 2016
Se presentan algunas contribuciones procedimentales para la extracción de vanadio (V), níquel (Ni... more Se presentan algunas contribuciones procedimentales para la extracción de vanadio (V), níquel (Ni) y azufre (S) en petrocoque. Las muestras se sometieron a varios procesos de extracción inducidos por agitación mecánica a 50°C, radiación UV y microondas, empleando como agentes extractantes: HCl:HNO3 (1:1) al 10 y 20%, H2O2 al 30%, HCl al 10%, NH4OH al 10 y 20% y H2O desionizada. La caracterización de las muestras y la cuantificación de los elementos estudiados, se realizó por análisis elemental, análisis térmico, cromatografía iónica, espectrometría de emisión atómica con plasma acoplado inductivamente (ICP-AES) y fluorescencia de rayos X (XRF). Se encontró la mayor eficiencia, induciendo la extracción con radiación microondas, obteniendo 41% para S con una solución al 20% de HCl:HNO3 (1:1) y para V de 20% con H2O2. La agitación mecánica a 50°C resultó eficiente para la extracción de Ni (2,5%) con HCl:HNO3 (1:1) al 10%. De igual manera, resultó una excelente alternativa para la extracción de S, alcanzando valores hasta de 26%. De forma similar, los procedimientos inducidos con radiación UV, también resultaron eficientes en la extracción de S, obteniendo entre 26 y 37% con las soluciones de ácidos al 20%, NH4OH al 10% y H2O2. Por otra parte, empleando la extracción Soxhlet solo con H2O desionizada, se demostró que es posible extraer hasta un 6% de V, Ni y S presentes en el petrocoque, lo que sugiere que estos elementos se encuentren disponibles en el ecosistema circundante a los depósitos de coque en las refinerías.
We present the methodological development for the spectrometric determination in the visible, ran... more We present the methodological development for the spectrometric determination in the visible, range of Ca 2+ in human blood serum by FIA. The method is based on the formation of a complex Ca 2+-Murexida in basic medium (pH 12). We used a semi-automatic system with an injection volume of 16.5 µL, reactor length of 1 m, the complex was measured at 491 nm, can process 44 samples per hour, with a linear range of 2-12 mg•L-1. We obtained a L D and L C of 0.076 mg•L-1 and 0.25 mg•L-1 , respectively, and a precision (RSD) of 1.81%. Accuracy is assessed by comparing the concentrations of Ca using the method developed by others based on spectrometric techniques. We observed no statistically significant differences (p<0.05), obtaining val
In this study, copper (Cu) and zinc (Zn) levels were determined by flame atomic absorption spectr... more In this study, copper (Cu) and zinc (Zn) levels were determined by flame atomic absorption spectrometry (FAAS) in the blood serum of patients with metabolic syndrome (MS) and controls (C) from the city of Maracaibo. Whole blood samples (N = 100; 50 for MS and 50 for C) were collected in polypropylene containers at the Endocrine Metabolic Research Center (CIEM), Faculty of Medicine at the University of Zulia. After separating the clot, each sample was centrifuged to obtain serum and stored at 4°C. Quantification of copper and zinc was performed by calibration curves prepared with concentrated aqueous standards of 0.10, 0.50, 1.00, 2.00, 4.00 and 6.00 mg Cu L-1 ; and 0.05, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.80, and 1.00 mg Zn L-1. Serum concentrations of copper and zinc in patients with MS (ca. 0.76 ± 0.24 and 1.31 ± 0.42 mg L-1 , respectively) were below those obtained for subjects in the control group (ca. 0.96 ± 0.21 and 1.04 ± 0.14 mg L-1 , respectively), demonstrating the involvement of Cu and Zn in disorders of carbohydrate and lipid metabolism in the experimental population studied.
Resumen Los ácidos grasos pueden dar origen a la formación de una especie iónica con característi... more Resumen Los ácidos grasos pueden dar origen a la formación de una especie iónica con características anfifilicas que disminuye la tensión interfacial de un sistema agua/crudo. El tipo de contraión de estas especies juega un papel fundamental en las propiedades tensoactivas del compuesto. En función a ello, se estudió la influencia del contraión de la sal del ácido hexadecanoico (C16) obten-ido al reaccionar este compuesto con NaOH y ciclohexil amina para obtener como productos hexa-decanoato de sodio (NaC16) y hexadecanoato de ciclohexil amonio (CicloC16). Se evaluó el compor-tamiento de estas especies en las propiedades de las emulsiones de agua en crudo Boscán formula-das a diferentes proporciones. En ambos tensoactivos se encontraron emulsiones estables, de fase externa crudo, polidispersas, baja viscosidad (5000 cP) con respecto a la del crudo original (100,000 cP) con un intervalo de diámetro promedio de tamaño de gota (8,04-43,46 µm) y con un alto porcentaje de crudo como fase...
Resumen Se evaluaron las posibles pérdidas de V y Ni durante el tratamiento aplicado a muestras d... more Resumen Se evaluaron las posibles pérdidas de V y Ni durante el tratamiento aplicado a muestras de crudo, asfaltenos y maltenos, para su posterior análisis por espectrometría de emisión atómica con plasma inductivamente acoplado (ICP-OES). Las muestras se calcinaron y digirieron con ácido ní-trico (HNO 3) en recipientes de politerafluoroetileno (PTFE) colocados en una carcasa de acero inoxi-dable tipo autoclave. El estudio de recuperación en crudo se realizó por dos procedimientos: (1) se agregó una cantidad de V y Ni a una muestra de crudo y se homogeneizó, tomando alícuotas de ésta para el análisis y (2) se adicionó una cantidad de los metales directamente a las alícuotas. Las recuperaciones en crudo total por el primer procedimiento dieron bajos rendimientos (76% V y 46% Ni) en comparación a las obtenidas con el segundo (98% V y 102 % Ni) razón por la cual la re-cuperación en los asfaltenos y maltenos se realizó aplicando el segundo procedimiento, arrojando valores entre 98 y 99%...
The retention behaviour of fatty acids on a reverse phase HPLC column is reported. Retention incr... more The retention behaviour of fatty acids on a reverse phase HPLC column is reported. Retention increases as the acetonitrile/methanol mobile phase becomes richer in acetonitrile. For a given solvent mixture, retention increases (linearly) with the acid chain length. Retention factor (k) is dimensionless and independent on any geometrical parameters of the column or HPLC system. It could be considered to be a thermodynamic characteristic of the adsorbent-compound -eluent system. HPLC experiments carried out at different temperatures allow to plot the variation of the ln k vs. 1/T, and to calculate the DG°, DH° and DS° of transfer of one molecule from the mobile phase to the stationary phase. According to a Van't Hoff expression, the retention decreases as temperature increases. Both DH° and DS° are negative, a result that corroborates that the adsorption of the n-alkyl chains onto the stationary phase is favourable from the energetic point of view, and that it increases the molecul...
Abstract Surfactant/oil/water systems in which the sur-face-active substance is a mixture of an u... more Abstract Surfactant/oil/water systems in which the sur-face-active substance is a mixture of an undissociated fatty acid (FA) and its sodium salt soap, exhibit the typical phase behavior and the general emulsion phenomenology pro-duced by a formulation scan. The phase ...
The development of analytical methods for routine simultaneous identification and quantification ... more The development of analytical methods for routine simultaneous identification and quantification of carboxylic fatty acids (CFAs) are required in different fields, such as, pharmaceutical cosmetics, food products and formulations of water-microemulsion-oil systems. Determination of CFAs has been developed mainly by gas chromatography (GC). As an alternative to GC, liquid chromatography (LC) has better sensitivity and selectivity. However, most CFAs show no useful absorption in ultraviolet-violet (UV-Vis) region, one of the more used detection technique in high-performance liquid chromatography (HPLC). In order to allow the use of UV-Vis detection, the use of pre-column derivatization has been reported to increase sensitivity and selectivity. Therefore, establishment of a simpler and faster on-line method with complete separation is needed for the screening of large numbers of samples. 2,4-Dinitrophenylhydrazine (2,4-DNPH.), benzoil chloride (BC), and phenylhydrazine (PH) were used for derivatization of different FAs by microwaves radiation (MW). After the on-line derivatization, products were separated and quantified by HPLC. Reactor coil was placed inside of microwaves oven at 450 W. Parameters as flow, amount of reagents, irradiation time, and chromatographic conditions were optimized. The continuous analysis using the MW-HPLC-UV system provided high sensitivity and reduced both the amount of reagent used and the analysis times. This proposed method can be used for the routine analysis of FAs contained in water-microemulsion-oil systems, to quantify the total acid fraction in each phase.
In this study, a continuous linear alcohol derivatization is developed. Reaction of alcohol group... more In this study, a continuous linear alcohol derivatization is developed. Reaction of alcohol group (ROH) with benzoyl chloride (BC) is carried out in an on-line system with UV detection. All reaction conditions, as flow rate (FR), ROH/BC molar ratio, wavelength, temperature, microwave (MW) irradiation and reaction coil size (internal diameter and length) were optimized. 0.5 mL min −1 , 2.49 [BC]/[ROH], 230 nm, 60 • C or medium power (225 W) when MW irradiation was used and a reactor coil of 159 L (0.5 mm × 810 mm) were the optimum conditions. The on-line system with microwave irradiation was more efficient than the one with a water bath heating. The developed system reduces analysis time consumption, reagent amounts and this system was used to evaluate the composition of commercial samples of alcohols polyethoxylated (surfactants).
Photostabilizer-type HALS were analyzed by reverse-and normal-phase liquid chromatography (HPLC) ... more Photostabilizer-type HALS were analyzed by reverse-and normal-phase liquid chromatography (HPLC) using C-18, cyano, silica, and amino columns with different solvent mixtures as the mobile phase. The stabilizers analyzed were Tinuvin 770 and Chimassorb 944. The best separation was attained using a NH2-column and acetonitrile/water as the mobile phase. Also, three types of extraction procedures were performed to isolate these additives
... na Sán chez, Ger son Chá vez, Ana Cá ce res, Fredy Ysam bertt y Nel son Már quez La bo ... II... more ... na Sán chez, Ger son Chá vez, Ana Cá ce res, Fredy Ysam bertt y Nel son Már quez La bo ... II) phase be hav ior takes place in which an aque ous (re spec tively oil) surfactant-rich phase is in ... Wider knowl edge has been de vel oped on the qua ter nary sys tems wa ter/oil/sur - fac ...
El objetivo de este trabajo fue validar un metodo para la determinacion de vitamina A en leche en... more El objetivo de este trabajo fue validar un metodo para la determinacion de vitamina A en leche en polvo. Se utilizaron tres marcas de leche en polvo de distribucion masiva en la ciudad de Maracaibo, estado Zulia. Se realizaron ensayos para determinar las condiciones de extraccion y del sistema cromatografico. En el proceso de extraccion se fijo el tiempo de calentamiento de la muestra en 40 min. El contenido de vitamina A, se determino utilizando un equipo de Cromatografia Liquida de Alta Resolucion (HPLC) con una columna C18 y un detector de UV-visible. La longitud de onda se fijo en 300 nm y el flujo de la fase movil en 1,2 mL/min. Para la evaluacion estadistica de los resultados se utilizo el programa SPSS version 20.0. La selectividad del metodo se verifico empleando pruebas de degradacion artificial (termolisis, oxidacion y fotolisis) que permitieron observar los productos de degradacion de la vitamina A en los cromatogramas. Se prepararon ocho estandares de vitamina A, para el...
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia
In this work the fractions obtained by microwave-assisted oxidative degradation with hydrogen per... more In this work the fractions obtained by microwave-assisted oxidative degradation with hydrogen peroxide of two pine lignins (LAA y LKM) and its tensoactive properties were studied. The reactions were carried out using different quantities of the oxidant agent in a domestic microwave oven in closed reactors. The reaction was completed quickly with the generation of water as by-product. The oxidation products were characterized by UV and FTIR spectroscopy. When comparing them with the original lignin samples in UV analysis, the absorption decreased near the 280nmdue to the oxidation of the aromatic rings. In the analysis by FTIR the signals corresponding to the groups C=O increased among 1,700-1,720 cm1 and 1,650-1,700 cm1 attributed to the oxidation of the lateral chains and aromatic rings, respectively. This results were evidenced because of the aromatic signal C=C around the 1,600 cm1 decreased. It was proven the efficiency and versatility of the radiation microwaves to carry out...
The heavy crude oil presents problems in the dehydration due to the presence stable emulsions, wi... more The heavy crude oil presents problems in the dehydration due to the presence stable emulsions, with water content more than to 1.0%. In this work is proposed the application of microwaves heating (MWH) to favor the separation of emulsioned water in this crude oil, as alternative method to the standard conven-tional heating (SCH). The obtained results showed that both methods are effective for the crude oil dehy-dration since the content of water was smaller than 1.0%, nevertheless, the applied methodology in the thermal chemical methods using MWH required lower analysis time compared with the SCH, important advantage for the decrease of production costs and in the field analyses in the oil industry.
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia
The crude oil in water emulsions have been used to produce and to transport heavy hydrocarbons. M... more The crude oil in water emulsions have been used to produce and to transport heavy hydrocarbons. More stability and less viscosity than the emulsions prepared with an only surfactant was obtained for the crude oil in water emulsions prepared with non-ionic and anionic surfactant mixtures, in previous studies. The stability of these emulsions could be increased, adding short chain amines. In this work, the effect of aliphatic short chain amines in the stability and the rheological properties of heavy crude oil in water emulsions, prepared at crude oil/water relationship of 70/30, is discussed. Polyethoxylated non-ionic surfactants were used, individually or in a mixture with an anionic surfactant of aryl benzene sulfonate type. Aliphatic short chain amines of 2, 4 and 6 atoms of carbon were used as co-surfactants, so much of lineal chain and ramified chain. The results showed that the primary amines of lineal chain produce more stable emulsions and with more viscosity that the emulsio...
Manual de acompañamiento del estudiante, parte 2, volumetría ácido-base. En este documento se tie... more Manual de acompañamiento del estudiante, parte 2, volumetría ácido-base. En este documento se tiene algunos ejercicios realizados en la aplicación del equilibrio acido-base
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