Desarrollo de un método analítico por cromatografía de líquidos de alta resolución (hplc), para la determinación y cuantificación de vitamina C, ácido cítrico y ácido láctico en jarabe

El ácido ascórbico, el ácido cítrico y el ácido láctico se usan en diferentes proporciones en diferentes alimentos. Estos compuestos se encuentran presentes en jarabes medicinales. En este trabajo fue desarrollado un método analítico encromatografía líquida de alta eficiencia (HPLC)para la determinación y cuantificación de los ácidos antes mencionados. Se utilizó una fase reversa, en un equipo Agilent 1220 con una columna C18. Se determinaron las condiciones óptimas para la extracción, identificación y cuantificación los ácidos. Una vez determinados los tiempos de retención y las condiciones, fueron analizadas dos muestras de jarabes. en una mezcla de los tres ácidos, donde se pudo observar que el ácido ascórbico es el que cuenta con mayor concentración en ambas muestras de jarabe, mientras que, por otro lado, en los estándares, el ácido con mayor concentración fue el láctico.Ascorbic acid, citric acid, and lactic acid are used in different proportions in different foods. These compounds are present in medicinal syrups. In this work, a high-performance liquid chromatography (HPLC) analytical method was developed for the determination and quantification of the aforementioned acids. A reverse phase was used, in an Agilent 1220 equipment with a C18 column. The optimal conditions for the extraction, identification and quantification of the acids were determined. Once the retention times and conditions were determined, two syrup samples were analyzed. in a mixture of the three acids, where it was observed that ascorbic acid is the one with the highest concentration in both syrup samples, while, on the other hand, in the standards, the acid with the highest concentration was lactic acid

Development of Kraft Lignin Chemically Modified as a Novel Crosslinking Agent for the Synthesis of Active Hydrogels

In this research a chemical modification of kraft lignin was carried out using a basic nucleophilic substitution reaction (NSA) in order to functionalize it as a novel crosslinking agent for the synthesis of active hydrogels. The chemical modification success of the synthesized crosslinker was demonstrated by using several techniques such as volumetry probes, FTIR, 1H-NMR and DSC. Thus, the obtained materials were employed during the synthesis of acrylic acid-based hydrogels, due to its high-water absorption capacity to evaluate their retention potential of heavy metal ions. Characterization of the active hydrogels were performed by FTIR and SEM, showing the specific signals corresponding to the base monomers into the polymer skeleton and the efficiency of modified kraft lignin as a novel crosslinking agent. Additionally, to demonstrate the potential use of these hydrogels in wastewater treatment, metal ions adsorption experiments were conducted, showing adsorption percentages higher than 90% and 80% for Pb2+ and Cu2+, respectively

Estudio del hinchamiento de hidrogeles acrZapotitlánlicos terpoliméricos en agua y en soluciones acuosas de iZapotitlánn plumboso

Se prepararon hidrogeles terpoliméricos usando como monúmeros el ácido acrZapotitlánlico, la acrilamida y el ácido 2ZapotitlánacrilamidoZapotitlán2ZapotitlánmetilZapotitlán1Zapotitlánpropanosulfúnico. Los hidrogeles se sintetizaron mediante polimerizaciZapotitlánn en solución vía radicales libres, utilizando como par redox, soluciones acuosas de persulfato de potasio y de bisulfito de sodio. Como agente entrecruzante se uso el dimetacrilato de etilenglicol en proporciones de 1, 5 y 8% en peso. Se determino la capacidad de hinchamiento de los hidrogeles en agua y en soluciones acuosas con una concentración de 1000 mg LZapotitlán1 de Pb+2 (a pH de 4.0y 5.0), son una fuerza iúnica constante (I = 0.1 M)

Estudio del hinchamiento de hidrogeles acrílicos terpoliméricos en agua y en soluciones acuosas de ión plumboso

Se prepararon hidrogeles terpoliméricos usando como monómeros el ácido acrílico, la acrilamida y el ácido 2–acrilamido–2–metil–1–propanosulfónico. Los hidrogeles se sintetizaron mediante polimerización en solución vía radicales libres, utilizando como par redox, soluciones acuosas de persulfato de potasio y de bisulfito de sodio. Como agente entrecruzante se uso el dimetacrilato de etilenglicol en proporciones de 1, 5 y 8% en peso. Se determino la capacidad de hinchamiento de los hidrogeles en agua y en soluciones acuosas con una concentración de 1000 mg L–1 de Pb+2 (a pH de 4.0y 5.0), son una fuerza iónica constante (I = 0.1 M)

Experimental and theoretical thermochemical studies of imidazole, imidazole-2-carboxaldehyde and 2-aminobenzimidazole

9 pags., 2 figs., 11 tabs.Here were determined the molar standard enthalpies of formation, ΔH (s), at T = 298.15 K of imidazole, imidazole-2-carboxaldehyde and 2-aminobenzimidazole from their respective molar standard energies of combustion, obtained by static combustion calorimetry. Enthalpies of sublimation, ΔH, at T = 298.15 K were obtained by thermogravimetry measurements. Using data for ΔH (s) and ΔH, the gas phase enthalpies of the two imidazole-derived compounds were calculated. The enthalpy increases due to certain functional groups attached to the imidazole (IM) molecule, and were analyzed that change in the enthalpies using the experimental gas phase enthalpy of formation data. By using theoretical methods, namely G3 and G4, the enthalpies of formation of the compounds under study were obtained and were compared with the experimental ones. In addition, the purity, the melting temperature, the enthalpy of fusion and the heat capacity of the compounds were determined by differential scanning calorimetry.Carmen Salomón and Gastón Perdomo thank CONACyT for their grants (registration numbers: 327677 and 321454, respectively)

Study on the Degradation of a Semi-Synthetic Lignin–Acrylic Acid Hydrogel with Common Bacteria Found in Natural Attenuation Processes

In this study, lignin was chemically modified to promote hydrogel degradation as a source of carbon and nitrogen for a bacterial consortium consisting of P. putida F1, B. cereus and, B. paramycoides. A hydrogel was synthesized using acrylic acid (AA), acrylamide (AM), and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and cross-linked with the modified lignin. The structural changes and mass loss in the hydrogel, as well as its final composition, were evaluated as functions of the growth of the selected strains in a culture broth with the powdered hydrogel. The average loss was 18.4% wt. The hydrogel was characterized using FTIR spectroscopy, scanning electronic microscopy (SEM), elemental analysis (EA), and thermogravimetric analysis (TGA) before and after bacterial treatment. FTIR showed that the carboxylic groups present in both the lignin and the acrylic acid of the hydrogel decreased during bacterial growth. The bacteria showed a preference for the biomaterial components of the hydrogel. SEM demonstrated superficial morphological changes in the hydrogel. The results reveal that the hydrogel was assimilated by the bacterial consortium while preserving the water retention capacity of the material and that the microorganisms carried out a partial biodegradation of the hydrogel. The results of the EA and TGA confirm that the bacterial consortium not only degraded the biopolymer (lignin), but also used the synthetic hydrogel as a carbon source to degrade its polymeric chains and modified original properties. This modification with lignin as a crosslinker (which is a waste product of the paper industry) is therefore proposed to promote hydrogel degradation

Synthesis and Evaluation of Antifungal and Antibacterial Abilities of Carbon Nanotubes Grafted to Poly(2-hydroxyethyl methacrylate) Nanocomposites

Developing nanomaterials with the capacity to restrict the growth of bacteria and fungus is of current interest. In this study, nanocomposites of poly(2-hydroxyethyl methacrylate) (PHEMA) and carbon nanotubes (CNTs) functionalized with primary amine, hydroxyl, and carboxyl groups were prepared and characterized. An analysis by Fourier-transform infrared (FT-IR) spectroscopy showed that PHEMA chains were grafted to the functionalized CNTs. X-ray photoelectron spectroscopy suggested that the grafting reaction was viable. The morphology of the prepared nanocomposites studied by field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) showed significant changes with respect to the observed for pure PHEMA. The thermal behavior of the nanocomposites studied by differential scanning calorimetry (DSC) revealed that the functionalized CNTs strongly affect the mobility of the PHEMA chains. Tests carried out by thermogravimetric analysis (TGA) were used to calculate the degree of grafting of the PHEMA chains. The ability of the prepared nanocomposites to inhibit the growth of the fungus Candida albicans and the bacteria Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli was evaluated. A reduced antifungal and antibacterial capacity of the prepared nanocomposites was determined

Heats of combustion representative of the carbohydrate mass contained in fruits, vegetables, or cereals

The obtainment of suitable values for metabolizable energy requires the previous knowledge of accurate and precise values of the heat of combustion of the different macronutrients. Thus, in this work, the heats of combustion of six carbohydrates (glucose, fructose, sucrose, maltose, starch, and cellulose) were experimentally measured, and such values were statistically compared with equivalent bibliographic values collected in a parallel work (Heats of combustion of the main carbohydrates in vegetable foods: a bibliographic approach, 2019), proposing, for each carbohydrate, an “overall interval” and an actualized representative value, which were estimated considering jointly the bibliographic and experimental information. Besides, a numerical methodology that used such parameters and the relative content of the different carbohydrates in selected foods was proposed, to estimate the global heat of combustion producible by the carbohydrate mass contained in such foods. The results estimated for 68 foods were globalized to propose the following generalized heats of combustion: (a) for fruits: 3.88 kcal/g, (b) for vegetables: 3.98 kcal/g and, and (c) for cereals: 4.13 kcal/g. These results demonstrated that the use of the Atwater's value (4.2 kcal/g of carbohydrate of vegetable source) involves a clear overestimation of the heat of combustion of the carbohydrate mass contained in vegetable source foods