Scielo RSS <![CDATA[Journal of the Chilean Chemical Society]]> vol. 65 num. 4 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[EFFECT OF GERMINATION AND COOKING ON IRON CONTENT, PHYTIC ACID AND LECTINS OF FOUR VARIETIES OF CHILEAN BEANS ( <em>Phaseolus Vulgaris</em> )]]> ABSTRACT The family of Fabaceae has been fundamental into the traditional nutrition in South America, including Chile, however in this country has reduce consumption of legumes between children in school age. This investigation pursued establish the impact over nutritional and no nutritional composition of chilean beans ( Phaseolus vulgaris ) exposed to cook and germination. The results obtained has shown the cooked samples has decreased the contain of iron and also diminished in total minerals from ashes analysis, instead the germinated samples increased both. Total proteins determined by Kjeldahl method exhibit no change for cooked and germinated beans in relation to control without treatment, while phytic acid increased and lectins decreased with the action of cook or germination of P.vulgaris . All the analysis was supported by statistical assessment and suggest the beans germination is a good alternative to improve the variety of recipes available to prepare beans in other attractive presentations on the subject of promote the children intake. <![CDATA[REMOVAL OF OXYTETRACYCLINE BY POLYMERS. AN OVERVIEW]]> ABSTRACT Oxytetracycline (OTC) is an antibiotic belonging to the tetracycline family, widely used in veterinary medicine due to its pharmacological characteristics and adequate cost/effectiveness ratio. One of the problems presented by the therapeutic use of antibiotics such as OTC is that they do not metabolize and are expelled through animal excretions reaching the effluent of wastewater, rivers, and lagoons, causing accumulation and generating resistance to certain pathogens, mainly zoonotic bacteria. The above has presented the need and the challenge of removing this type of contaminants present in aquatic systems, using more efficient economic and eco-friendly methods than the conventional ones already known. A promising alternative is removal by using polymeric materials. Therefore, the aim of this revision is give a general revision of the application of functional polymer materials to remove these emerging organic contaminants OTC. <![CDATA[EXPERIMENTAL INVESTIGATION AND MECHANISM ANALYSIS: EFFECT OF CONCENTRATION AND TEMPERATURE ON THE VISCOSITY OF NOVEL MWCNT-MUSTARD OIL NANOFLUID]]> ABSTRACT The bio-oils as alternative lubricating fluid are potential solution for the automotive and industrial mechanical systems. The development of novel renewable and non-toxic bio-lubricants with better lubricating distinctiveness will strengthen the economy of farmers in the agricultural based countries. In the present study, different weight fractions of MWCNT-Mustard oil nanofluids are formulated and their possible effects on the dispersion stability and dynamic viscosity are experimentally investigated over the temperatures ranging from 40 to 100°C. It is observed that the dynamic viscosity and viscosity index of nanofluids were declined with temperature raise, while, it exponentially increased with the raise of MWCNT concentration. The maximum viscosity enhancement of 101.3% is achieved in comparison to the base fluid at 100°C. Further, the dynamic viscosity of nanofluids is compared with different classical semi-empirical correlations, however, the remarkable conformities were observed from multilayer feed forward Perceptron (MLP) of artificial neural network (ANN). <![CDATA[CHEMICAL CHARACTERIZATION OF LIGNANS FROM <em>Araucaria araucana</em> A NATIVE CONIFER OF CHILE AND EVALUATION OF THEIR CYTOTOXICITY AND ANTIOXIDANT ACTIVITIES]]> ABSTRACT Araucaria araucana is a native conifer of Chile commonly called Araucaria. The knots of Araucaria are extremely hard wood and highly rot-resistant, they can be found in the forest decades after that the tree has dead and decomposed. Here we report the phytochemical characterization of different parts of the Araucaria as stemwood, branch and knots, founding a remarkable difference in the content of extractables in these parts, as well as the lignan composition, which is higher in knots than in branches or stemwood. Eudesmin was isolated and crystallized from organic extract of knots, its structure was determinate by NMR; moreover, secoisolariciresinol, lariciresinol and matairesinol were identified by GCMS and HPLC in contrast to standards, and quantified in stemwood, branch and knots. The results showed that secoisolariciresinol is the main lignan with 45.77 mg g−1, followed by eudesmin with 22.68 mg g−1, lariciresinol 4.57 mg g−1 and matairesinol with 1.19 mg g−1. The antioxidant activity in terms of DPPH assay showed that knotwood extract displays the higher activity, meanwhile that eudesmin did not displays activity in DPPH assay. The cytotoxic activity against SHSY5Y neuroblastoma and P3X myeloma cell lines, revelated a moderate activity of extracts, while eudesmin did not showed activity. <![CDATA[REMOVAL OF REACTIVE RED 198 FROM AQUEOUS SOLUTIONS USING MODIFIED CLAY: OPTIMIZATION, KINETIC AND ISOTHERM]]> ABSTRACT Dyes are large group of environmental pollutions with complex molecular structure and resistant to biodegradation. The entrance of these compounds into the water sources causes health problems in humans and many aquatic organisms. Therefore, colored effluents have to be adequately treated before discharging into the environment. This study aimed to evaluated efficiency of adsorption process of modified clay by cetyltrimethylammonium bromide (CTAB) in removal of Reactive Red 198 (RR 198) from aqueous solution. The modified clay was prepared and its characterization was accomplished by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influences of major operational parameters on the efficiency of adsorption process were investigated and optimized. Kinetic and isotherm of adsorption were determined. The results revealed that increasing pH, initial concentration, ionic strength and temperature decrease rate of dye removal and increasing adsorbent dosage increases the dye removal efficiency. The maximum removal efficiency (99.61%) of RR 198 with modified clay was at pH; 3, time; 60 min, adsorbent dosage; 0.1 g/L and initial concentration; 20 mg/L. The experimental data fitted well to the Langmuir isotherm model and exhibited a maximum adsorption capacity (qmax) of 25.84 mg/g, which followed the pseudo-second-order equation. The adsorption process shows an intra-particle diffusion mechanism. According to the results, modified montmorillonite clay can be considered as an effective and promising adsorbent for the removal of RR 198 from aqueous solutions. <![CDATA[DEVELOPMENT OF A SIMPLE LC METHOD FOR QUANTIFICATION OF LAMOTRIGINE IN HUMAN SERUM]]> ABSTRACT A liquid chromatographic (LC) method for quantitative analysis of lamotrigine in human serum was developed using liquid –liquid extraction with ethyl acetate. Quantitation was achieved over the concentration range of 1.0 to 40.0 µg/mL (r = 0.999), using a mixture of acetonitrile: phosphate buffer (0.5 M) of pH 4.5 (69:31 v/v) as mobile phase, with a flow of 1 mL min− 1. Column was C18 (150 mm x 4.6 mm, 5 cm; Merck), chloramphenicol was used as internal standard, and UV detection at α 306 nm. The intra-assay variation was between 1.22 % and 1.85 % and the inter-assay was between 1.72 % and 2.91 %. The detection limit was 0.14 µg/mL, and the quantification limit was 0.42 µg/mL. The method proved to be accurate, with a recovery between 94.02 % and 109.95 %, with RSD not higher than 2.91 % and was selective for lamotrigine (Rs between lamotrigine and chloramphenicol was 4.9). This method was successfully applied to quantify lamotrigine in patient serum samples. In conclusion, the method is precise, accurate, reproducible and selective for the analysis of lamotrigine in human serum. Therefore, it could be an important tool to evaluate drug level in this matrix and, of this way, to obtain a better drug effect. <![CDATA[AMINO-FORMALDEHYDE RESINS. PROPERTIES AND APPLICATION TO REMOVE CONTAMINANT METAL IONS. AN OVERVIEW]]> ABSTRACT The global production of formaldehyde urea resins (UF) for 2019 was 6 million ton/year, being the largest use in the forestry industry in the production of MDP and MDF boards. It is in the resin industry's interest to develop other applications of these polymers. The possible metal ion separation properties of commercial resins of the type urea-formaldehyde resins (UF), melamine-urea-formaldehyde resins (MUF), and formaldehyde melamine (MF) are achieved by modifying with functional groups. The metal retention properties are determined by batch method in aqueous phase where the purified and sieved solid resin is put into contact with the metal ions at different pH, controlling temperature and ion force. The most studied metal ions are metal ions like Cu(II), Co(II), Cd(II), Zn(II), Cr(III), Hg(II) and Cr(VI). The aim to contribute with this overview, is demonstrate the use of these modified resins to remove metal ions and also the potential application to use them as support to include new functional groups to increase the efficiency and affinity, Moreover, it is motivated by the production in our country of these resins and investigate possible applications in this research field. <![CDATA[SMART POLYMER NANOCOMPOSITES: RECENT ADVANCES AND PERSPECTIVES]]> ABSTRACT Nanocomposite polymers have received considerable interest in research for the last three decades. Those nanocomposite polymers that are sensitive to a stimulus such as pH, temperature, magnetism, and electricity, among others, called smart or intelligent nanocomposite polymers had received even greater attention due to their potential technological applications. Applications of these polymers include flexible electronic devices, sensors, self-healing polymers, shape-memory materials, etc. The sensitivity of the material can come from both the polymer that acts as a matrix and the nanofiller, resulting in a material that combines properties of each of its components and that each one will not have separately. This mini-review aims to provide an update on the most recent and significant applications in the area of stimuli-responsive polymer nanocomposites, emphasizing the most innovative applications in biomedicine and catalysis developed in the last three years. <![CDATA[BIPHASIC HYDROGENATION OF EUGENOL WITH RUTHENIUM AND RHODIUM NANOPARTICLES STABILIZED IN IONIC LIQUIDS]]> ABSTRACT The purpose of this study was to evaluate on the catalytic activity nanostructured systems of ruthenium and rhodium stabilized in ionic liquids derived from imidazole: IL1= butylmethyllimidazole tetrafluoroborate [BMIM][BF4] and IL2= butylmethylimidazole hexafluorophosphate [BMIM][PF6] in the biphasic hydrogenation of eugenol under mild reaction conditions T= 80°C, P= 100psi during 4 hours. The metallic nanoparticles (NPs-M) were synthesized using the ligand hydrogenation displacement reaction for the ruthenium III tris(acetylacetonate), [Ru(acac)3], and bis-μ-cloro-di(1,5-ciclooctadieno) dirhodium(I), [Rh(COD)Cl]2, showing a mean particle size between (2.0±_0.2) nm and (4.0±0.2) nm. The nanostructured systems Rh/IL2, Ru/IL2 and Ru/IL1 show similar activities and different from the Rh/IL1 system. On the other hand, the systems stabilized in the IL1 were more selective towards the formation of the 2-methoxy-4-propylphenol than the systems stabilized in the IL2. Nevertheless, in general, the catalysts were good for hydrogenating eugenol, resulting in Rh/IL1 nanoparticles less reactive than Rh/IL2, Ru/IL1 and Ru/IL2. <![CDATA[SURFACE MODIFICATION OF RUBBER FROM END-OF-LIFE TIRES FOR USE IN CONCRETE: A DESIGN OF EXPERIMENTS APPROACH]]> ABSTRACT A large amount of discarded tire waste generated year after year has encouraged the scientific community to seek alternatives for recycling or reusing this waste. The cross-linked nature and the high number of additives in tires make recycling significantly difficult. Thus, the use of particulate rubber as filler for other materials such as concrete has emerged as an attractive alternative. However, the hydrophobic nature of the rubber and hydrophilic particles of cement decreases the compatibility at the cementitious matrix-rubber interface, affecting the concrete's final performance. This work presents a method based on hydrogen peroxide and Fenton for the oxidation of rubber particles from end-of-life tires to introduce hydrophilic groups on the surface of the particles to improve compatibility at the interface. The method was studied from an experimental design approach based on the infrared spectroscopy response and using a Rechtschaffner Resolution V design, PCA and PLSR in order to evaluate variables such as time, temperature and reactants. The concentration of H2O2 and reaction temperature was shown to increase the oxidation, while Fenton reduces the time of oxidation. <![CDATA[MECHANICAL AND MORPHOLOGICAL PROPERTIES OF POLY(3-HYDROXYBUTYRATE)-THERMOPLASTIC STARCH/CLAY/EUGENOL BIONANOCOMPOSITES]]> ABSTRACT Food packaging for traditional foods mainly serves to isolate foods from external environmental. For this reason, it is a growing interest in developing active packaging materials that can extend foodstuff shelf-life. Also, it could counteract the level of contamination by plastic in the environment using biodegradable polymers. For this purpose, poly(3-hydroxybutyrate) (PHB)-thermoplastic starch (TPS)/ organically modified montmorillonite (OMMT)/eugenol bionanocomposites were prepared by melt blending. Morphology, thermal, and mechanical properties were determined by comparing the concentration influence of eugenol and clay on the PHB-TPS blend and PHB. X-ray diffraction measurements revealed the existence of exfoliated morphology in the bionanocomposites. Atomic force microscopy imaging (AFM) showed the difference in morphological characteristics of the pure PHB and the prepared bionanocomposites. Roughness analysis from the AFM data indicates that the presence of clay and TPS increases the roughness with respect to PHB. Dynamic mechanical thermal analysis (DMTA) showed that bionanocomposites have an improved storage module. Finally, properties such as hardness and elastic modulus studied by nanoindentation showed a decrease with respect to PHB. The presence of eugenol in the bionanocomposites does not show a significant effect on the different properties. <![CDATA[EFFECT OF THE MONOMERS RATIO IN THE ELECTROSYNTHESIS OF POLY(ANILINE- <em>CO</em> - <em>O</em> -METHOXYANILINE) ON STEEL CORROSION PROTECTION]]> ABSTRACT In this work, the synthesis of poly(aniline- co - o -methoxyaniline) was carried out on AISI 304 steel, by voltammetric or potentiostatic method. Electropolymerization was achieved from different ratios of 0.4 mol·L−1 aniline/ o -methoxyaniline monomers in 1.0 mol·L−1 H2SO4. Homo- and copolymers were characterized by cyclic voltammetry, infrared spectroscopy, and scanning electron microscopy. Furthermore, the electrodeposits were studied with a view to their use as corrosion protectors, for which their polarization curve was measured in NaCl 3% and, after 168 h, the surface of the steel was also evaluated by optical microscopy. It was observed that the reactivity that the o -methoxy group gives to the aniline ring reduces the protection against corrosion due to the excessive inclusion of N-phenyl-1,4-benzo quinone-di-imine oligomers and/or with an oxazine structure. On the other hand, the optical images confirm the surface damage of the steel, correlating with SEM images that show morphological changes associated with the progress of synthesis and the o -methoxy group. Nevertheless, under optimal conditions, poly(aniline- co - o -methoxyaniline) modifies the corrosion potential of AISI 304 steel, displacing it by 0.283 V. Furthermore, the presence of small pits and the absence of surface oxide was observed, indicating a significant delay in the oxidation of AISI-304 steel. <![CDATA[BIOPOLYMERS APPLIED TO REMOVE METAL IONS THROUGH ULTRAFILTRATION. A REVIEW]]> ABSTRACT This manuscript is an overview of the versatile biopolymer materials alginic acid, carboxymethyl cellulose, and quaternized chitosan which contain different functional groups to remove hazardous inorganic species. These bioadsorbents are completely water-soluble and have a high versatility to achieve a higher sorption capacity and efficiency under different experimental conditions in combination with ultrafiltration membranes through the liquid-phase polymer-based retention (LPR) technique. In general, thesebioadsorbents are friendly with the environment and have a higher biodegradability compared with those more employed synthetic polymers. <![CDATA[OPTIMIZING THE STRUCTURE OF AMPHIPHILIC INVERTIBLE POLYMERS (AIPs) MADE OF PEGs AND FATTY COMPOUND SEGMENTS TO OBTAIN A SINGLE CRITICAL MICELLE CONCENTRATION]]> ABSTRACT Amphiphilic biopolyesters containing hydrophilic segments (PEGs) and hydrophobic blocks (silicon fatty from a castor oil derivative) showed the ability to self-assembly in inverted micelles. Due to their capability to form also direct micelles, these biopolyesters could be classified as amphiphilic invertible polymers AIPs. The micellar concentrations CMC and ICMC corresponding to the direct and inverted micelles respectively precisely correlated with PEG length. The methodology used in this investigation allowed to determine the PEG length needed to obtain the adequate structural biopolyester able to self-assembly in direct and inverted micelles from a unique concentration. Inverted micelle diameters, determined by DLS analysis, increased as the molecular polarity of the biopolyesters decreased. No individual inverted micellar were observed by TEM technique due to the concentration change during the sample preparation, however micellar macromolecular aggregations were revealed. <![CDATA[VIBRATIONAL SPECTRUM CHARACTERIZATION OF OUTER SURFACE OF <em>HELICOBACTER PYLORI</em> BIOFILMS BY FUNCTIONALLY-ENHANCED DERIVATIVE SPECTROSCOPY (FEDS)]]> ABSTRACT Mid-infrared spectroscopy in conjunction with Functionally-Enhanced Derivative Spectroscopy (IR+FEDS) is a powerful analytical tool for the improvement of analysis of microorganism IR spectra. The objective of this research is to characterize the outer surface of two Helicobacter pylori strains by IR+FEDS. This work is a key stage for the study of cell-cell and cell-surface interactions between microorganisms, as well as, for polymicrobial biofilm characterizations where H. pylori species are involved. Artificial bacterial biofilms were deposited on ultrafiltration cellulose membranes covalently modified by insertion of one spectral marker and used as sensing surface for analysis of bacterial biolayers. Biolayers were analyzed using an infrared spectrophotometer with ATR. Data were analyzed by classic procedures and by deconvolution based on FEDS transform. It is concluded that, for correct application of technique is required a minimum amount of noise in the working spectra which can be achieved by simple smoothing algorithms; in addition, reproducibility must be warranted by the implementation of standardized protocols and the use of an appropriate number of samples. It is concluded that in addition to typical signals associated with the IR spectrum of microorganisms, by FEDS, a better and more detailed description of the outer membrane of H. pylori biofilms can be performed. In particular, it is concluded that the detecting and monitoring of cysteine-rich proteins can be satisfactorily performed by IR+FEDS. <![CDATA[ELECTRODE MODIFIED WITH A POLYMER OF ANILINE AND 3-HEXYLTHIOPHENE TO BE ASSAYED IN THE SELECTIVE DETERMINATION OF NITRATE]]> ABSTRACT In this work, platinum electrodes are modified with poly[4-(3-hexyl-2-thiophene)-aniline], PTANIr2, and characterized by cyclic voltammetry. In the presence of nitrate in the electrolytic medium, an oxidation signal at 0.6 V vs . SCE is recorded, so the response of this modified electrode, Pt|PTANIr2, is evaluated to determine its relationship with the concentration of the anion. Thus, it is verified that the best response is achieved by chrono-amperometry, obtaining a directly proportional relationship between the charge and the concentration, in an interval between 5 and 100 mg L−1 of the anion, with r2 = 0.996. Furthermore, it is found that the response of Pt|PTANIr2 is quite selective for nitrate, since there is no response for anions such as HPO4−, PO42-, ClO4−, F−, Cl−, Br−, I−, and NO2−, thereby contributing significantly to solving the main problem of devices of this type proposed so far. Finally, the surfaces were characterized by atomic force microscopy, showing a strong anion-polymer layer interaction. Thus, this material can be proposed to be tested as a columbimetric nitrate sensor, highlighting the possibility of varying the area of the electrode and/or the thickness of the deposited polymeric layer and with it, the sensitivity of the device. <![CDATA[PHOTOCATALYTIC DEGRADATION/ADSORPTION OF CARCINOGENIC AZO DYE DISPERSE RED 176.1 BY NANOCAGE CU<sub>2</sub>O AS A DUAL FUNCTION CATALYST ON THE VISIBLE-LIGHT]]> ABSTRACT Refining and disposal of wastewater is an important concern of textile industries due to the presence of carcinogenic azo dyes. The monoazo dye Disperse Red 167.1 (DR167.1) is used in dyeing polyester and cotton fibers. In this study, Cage Cu2O particles was synthesized by using non-toxic and inexpensive materials as a bi-functional material that can mineralize this pollutant under light irradiation and dark media. The samples were characterized by FESEM, XRD, BET / BJH, FTIR, and DRS techniques. The crystallite size was almost 24.3 nm by the Williamson-Hall. Direct band gap energy was equal to 2.08 eV by Kubelka-Munk. It revealed a greater photocatalytic performance in visible light than UV-C and it absorbed 49% of the dye within 10 minutes in the darkness. The oxidation results indicated that at pH equal to 6.44 without the presence of H2O2, 0.75 mg.L−1 of cage Cu2O and of 94 mg.L−1 dye concentration yielded 91 % removal and mineralization during 10 min. Removal under the visible light irradiation increased to 93% upon increasing the time to 40 min. as dye concentration rose from 94 to 340 mg.L−1, with a slight reduction in the efficiency of the photocatalytic degradation process, the efficiency was obtained as 91%. Koble Corrigan model was found as the best isotherm model. Reaction kinetics followed the pseudo-second order model. Overall, due to its absorption and removal of dyes in a short time, it can be a good candidate for textile wastewater treatment.