Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The objectives of the present work include synthesis of nanoparticles of calcium alginate by emulsion crosslinking method, their characterization by techniques such as FTIR, scanning electron microscopy (SEM), XRD, particle size and surface charge analysis, and study of removal of chromium ions from synthetic aqueous solutions. In order to study the effect of various factors like adsorbent dose, initial metal ion concentration, pH and temperature on the adsorption of chromium ions from water, a series of batch sorption experiments were conducted. The obtained results were analysed by Langmuir and Freundlich isotherm models and it was found that the adsorption of chromium more precisely follows Langmuir absorption isotherm. The metal ion removal capacity of the nanoparticles was found to depend on the chemical composition of the adsorbent, concentration of the metal ion solution, pH and temperature of the medium and speed of the suspension from wastewater before disposal.

The review article deals with theoretical aspects of Derivative UV-Spectrophotometry. The method gains significance using the first and second derivative of the transmission spectra with respect to wavelength. Generated optical derivatives are compared to the known numerical derivatives. The derivative spectra from 1st to 4th are consequently discussed. This provides valuable insight into the uses and limitations of this technique for chemical analysis. Measurement techniques and methods of obtaining derivative spectra are discussed. The degree of polynomial fit on the smoothness of derivative spectra and signal-to-noise ratio is described. Application of UV derivative spectrometry for determination of single and multicomponent analysis is shown. Derivative spectrophotometry possibly improves the selectivity and sensitivity of determination which has been illustrated.

A chiral HPLC analysis combined with time-dependent density functional theory (TD-DFT) calculations was used for the assignment of the absolute configuration (AC) of both enantiomers of the antihistamine drug chlorpheniramine. Circular dichroism and optical rotation detections coupled to the chromatographic system (HPLC-CD-OR) permitted the on-line measurement of the CD spectra and [α]670 values, while TD-DFT at the B3LYP/TZVP//B3LYP/VDZ(P) and B3LYP/ aug-cc-pVDZ//B3LYP/VDZ(P) levels of theory for CD and OR, respectively, delivered theoretical chiroptical properties in the gas and solution states. Both calculations were consistent in predicting the correct combination of CD spectra and [α]670 sign and therefore permitted the absolute configuration (AC) assignment of the optical isomers. The AC proposed using this methodology agreed with a previous X-ray study.

A stability- indicating LC method was developed and validated for the determination of risperidone in tablets.Quantitation was achieved by LC/DAD at 294 nm over the concentration range of 25.00 μg/mL to 250.00 μg/mL. Mobile phase was a mixture of water: glacial acetic acid 0.50 %: triethylamine 0.80 %: acetonitrile (65.00: 0.32: 0.52: 34.16, v/v), using a Purosphere STAR RP-18e 250 x 4.5 mm (5μ) column, and paroxetine as internal standard.The method exhibited an adequate linearity (r = 0.999), selectivity, precision (RSD ≤ 0.847 %) and accuracy (recoveries from 99.55 % to 101.35 %).Risperidone was subjected to the stress conditions of oxidative, acid, base, thermal and photolytic degradation. Risperidone was found no degrade in basic or acid stress conditions, neither in thermal stress exposition (50, 70 and 100 ºC) no at visible or UV stress conditions, during the time of the study. Only two degradation products were observed with peroxide oxidation, well resolved from analyte peak, proving the stability-indicating power of the method.The proposed method was found to be suitable for quantitative determination and the stability studies of risperidone in tablets.

 Resveratrol (RSV) is a polyphenol produced by different plant species having a variety of biological activities. Synthesis of hybrid molecules of RSV with different natural and synthetic compounds has been studied. These hybrid molecules have been prepared by using fused or merged techniques or by using some linker groups. Wittig method was mostly applied by using the appropriate ylides to prepare the RSV core. The hybrid molecules prepared by these techniques exhibited anticancer, anti-inflammatory, antioxidant, anti-alzheimer, metal chelating and enzyme inhibitory activities. These hybrid RSV molecules can serve as a lead compounds for the future design of new drug molecules. 

The halloysite nanotubes (HNTs) are naturally found in New Zealand, China, Brazil, America, and France. Halloysite nanotubes have unique physical, chemical, and electrochemical properties. Due to their non-hazardous nature and easy availability, they are used in various fields of science. To improve halloysite nanotubes’ interactions, these can be functionalized by different modification methods like covalent functionalization, non-covalent functionalization, etc. The chemical formula of halloysite nanotubes is Al2Si2O5(OH)4.2H2O. HNTs have a nanotubular geometry which exhibit its dimensions on nanoscale. This nanotubular array of HNTs varies with different regions. In this review, we have tried to reiterate the key properties and various methods to modify halloysite nanotubes.

The purpose of this study was to determine the antioxidant and antiradical activities in aqueous and ethanol extracts of Crataegus meyeri Pojark leaf, additionally, to examine some vitamins (A, E, C), trace elements (Cu, Zn, Mn, Se, Cr, Co). In this study, vitamin C, antioxidant and antiradical properties were determined using spectrophotometer. The results are compared with the reference antioxidants such as trolox, a-tocopherol and BHT. Levels of vitamin (A, E) measured using HPLC method. Trace elements were carried out using method of dry ashing with ICP-MS. The results of this study showed that C. meyeri leaf has a high antioxidant capacity and vitamin levels. C. meyeri is thought to be used as additives for food products and pharmaceutical industries with appropriate antioxidant properties and an antioxidant in future studies of experimental animal models, against free radicals generated in response to oxidative stress.

In order to deepen understanding the interactions between ionic liquid and chitin/chitosan/ cellulose at the molecular level, we have performed a study on the electronic structures, topological properties, nonconvalent interactions between 1-ethyl-3-methyl imidazolium chloride and chitin/chitosan/cellulose by using density functional theory. The results indicate that interactions between chitin/chitosan/cellulose and 1-ethyl-3-methyl imidazolium chloride are stronger that the intra-interaction of chitin/chitosan/cellulose, implying that chitin/ chitosan/ cellulose can dissolve in 1-ethyl-3-methyl imidazolium chloride.

Carbon paste electrodes modified with a family of ionic liquids (as binders) derived from N-octyl-pyridinium hexafluorophosphate, (composite-ionic liquid electrodes (CILEs)) were studied toward the oxidation of sulfite as an inner-sphere probe reaction and compared to a conventional carbon paste electrode (CPE) in which the binder was mineral oil. The ionic liquids were modified at para-position with substituents that are electron withdrawing: -CN (CILE/CN) and –CF3 (CILE/CF3) and substituents that are electron donating: -CH3 (CILE/CH3) and –OCH3 (CILE/OCH3), and compared with the ionic liquid without substituents (CILE/OPy). The results showed that CILEs are capable of catalyzing the sulfite oxidation, shifting the oxidation potential to more negative values compared to CPE. Also, they showed linear correlations between increasing sulfite concentration and increasing current density. The best system in terms of sensitivity was the electrode modified with the 4-methyl-N-octylpyridiniumhexafluorophosphate CILE/CH3 and, then, that modified with the non-substituted ionic liquid CILE/OPy measured by amperometry. In terms of potential, the best systems are the CILEs modified with ILs with inductive-substituents, -CH3 and –CF3 and OPy, indicating that the delocalization of the charge of the cation produced by the mesomeric-substituent (-OCH3, -CN) diminishes the electrocatalytic behavior of these binders for that oxidation. On the other hand, the analytical parameters of all the amperometric sensors studied here (all CILEs excepts CILE/OCH3) are good enough to be applied in food industry for samples without polyphenols at concentrations higher than ca. 1mM of sulfite. Their stability is very high (at least 100 cycles after obtaining a stable response without changing its current, exposed to air and humidity) and they can be used to remove sulfite from wastewaters. Finally, to our knowledge, there are not comparative studies about the effect of changing the substituent of the cation in electrocatalysis of modified IL-electrodes.

Inorganic-organic hybrid structures based on metal-complexes particularly, octahedral bis-2,2’:6’,2’’- terpyridine metal complexes provide an advantages of increased symmetry and in the case of ruthenium(III)/ruthenium(II) complexation an entrance to a directed complexation Method. The Ru (II) terpyridine methane thiolate protected gold nanoparticle was synthesized through covalent bonding of Ru terpyridine methane thiolates over gold nanoparticles surfaces. The ligand terpyridine methanethiolate was synthesized successfully in good percentage of yield. The structures were confirmed and characterized by different physical, analytical, spectral data like FTIR, UV, SEM and Cyclic voltammetry. All the data are shown the expected results.