نشریه شیمی کاربردی روز
پیاپی 38 (بهار 1395)

Food colors a group of natural or synthetic additives that are being prepared. Colors usually used for beautiful, the shape and cover defects in food products. Food colors can cause illness like asthma, immunosuppression or even have carcinogenic effects. The aim of this study is preconcentration and determination of trace amounts of ponceua 4R artificial colors in food samples. Modified nanosorbent with cationic surfactant cetyl bromide (CTAB) in this study, as a new sorbent for the extraction and preconcentration food dye was used. After praparation of modified nanoabsorbent, influencing parameters on the extraction of ponceua 4R by nanosorbent such as: pH, adsorbent dosage, extraction time, solvent type, effect sample valume has been studied and figures of merit including precision, limit of detection, concentration factor and enrichment factor achieved with good results. The calibration graph of this method for ponceua 4R was linear in the range of 0.2 to 50 μg.ml-1 with a detection limit 0.07 μg.ml-1, relative standard deviation %1.9 and concentration factor 20. The proposed method has been applied to the determination of the ponceua 4R at level of microgram in food samples such as cherries, Smart, tomato paste, ketchup, jelly, jam and water samples such as pomegranate juice, barberry juice, cranberry juice, cranberry juice and red grape juice with satisfactory results.

Magnetic nano-Fe3O4@TiO2/Cu2O core-shell composite had been successfully applied as catalyst for cross-coupling reaction of various aryl halides and phenols. All the reactions proceed under optimum conditions using DMF as solvent at 140ºC in the presence of 30 mg of nano-magnetic catalyst and completed in good to high yields. The catalyst was conventionally recovered using an external magnet and was reused at least in four successive runs, without appreciable loss of activity.

In this research, structural, electronic and vibrational properties of cubic BaHfO3 are investigated by using pseudopotential method, within the framework of density functional theory (DFT) and with two local density approximation (LDA) and generalized-gradient approximation (GGA). Implementation of calculations in quantum-espresso package shows that the band structure of BaHfO3 including a direct band gap of 3.67 eV and 3.88 eV at G point (center of reciprocal lattice) for LDA and GGA respectively which valence electrons of Ba atom play the most important role at the lowest bands and those of O atom at the top of the valence band and also, those of Hf atom at the bottom of the conduction band. Also, from the study of charge density contours is deduced that the bond formed between Ba and O atoms has ionic character, whereas the bond between Hf and O atoms has ionic-covalent character. The vibrational spectrum of BaHfO3 shows that the number of the vibrational bands at the range of 0-400 cm-1 is more than those of higher frequencies, and also, the most frequency degeneracies are devoted to G, R and M points which modes with the higher frequencies play the most important role in the optical behavior of crystal. Cubic symmetry of structure casing to be diagonalized dielectric (4.482) and polarization (22.392) tensors which are the dynamic response of material to external fields applied. The difference between the Born effective charge of atoms participated (in compound) and those nominal ionic values confirms the results of the charge density calculations (based on the ionic-covalent character of BaHfO3).

Three-dimensional molecularly imprinted polymers (MIPs) network was formed by radical polymerization reaction in the present of the Catechin (), Acrylic acid (AA), Trimethylolpropanetrimethacrylate (TRIM) (in ratio 1:20:80) as a template, functional monomer, cross-linker, respectively in Acetonitrile porogen. In extraction procedure by eluent, the template was removed and therefore nanoporous imprinted polymeric network was prepared which enable to adsorb Catechin bioactive, selectively. In this research, the molecularly imprinted polymers were synthesized and the binding capacity 304.0 mg/g as adsorbent of Catechin is reported. This polymer had the binding capacity 4.0 mg/g for Quercetin (similar structure of Catechin) that indicates high selectivity for the synthesized polymers. Evaluating of the polymers by adsorption-desorption with N2 gas, show that the specific surface area of the MIPs was 488.4 m2/g while it was 461.8 m2/g for the Non-Imprinted polymers (NIPs). Polymer particles have been evaluated by Atomic Force Microscope, too.

In this study, solvent-assisted dispersive solid phase extraction (SADSPE) method was developed and applied for separation, preconcentration, and spectrophotometric determination of Hg (II) in natural water samples. Dithizone was used as a chelating and chromogenic agent. Several variables that affect the efficiency and sensitivity of extractive-spectrophotometric procedure such as type and amount of sorbent, type and volume of dispersive solvent, sulfuric acid concentration, dithizone concentration, and salt concentration were investigated and optimized. After optimization of the complexation and extraction conditions, an enrichment factor of 15 was obtained. The calibration curve was linear in the range of 5–250 µg L–1 and the limit of detection was 1.5 µg L–1. The relative standard deviation for 100 µg L–1 of Hg (II) was lower than 2.5%. The proposed method was applied to the determination of Hg (II) in several natural water samples with satisfactory results.

A new Schiff base system (H2L) were synthesized and characterized by using of 2-hydroxy-1-naphthaldehyde and 2,6-diaminopyridine. The influence of metal cations Cr3, Mn2, Co2, Cs, Al3, K, Zn2, Ni2, Hg2, Ba2, Cu2, Mg2, Na, Ag, Cd2, Pb2, Fe2 and Fe3 on the spectroscopic properties of the Schiff base (H2L) in ethanol (1µM) were investigated by means of absorption and emissions spectrophotometry. When increasing concentrations of Al3 ions were introduced, the fluorescent emission of (H2L) was drastically increased. This special change was not observed when other metal ions were used. The Schiff base (H2L) was found to be as an effective fluorescence sensor for Al3 ions.

In this project, epoxidation of olefins using nanocluster polyoxomolybdate, (NH4)12[Mo36(NO)4O108(H2O)16] in presence of tert- butyl hydroperoxide (TBHP) were studied. The reactions were optimized according to the oxidation of cyclooctene through the investigation of the influence factors of epoxidation, such as solvent, amount of catalyst and reaction temperature. High yields and selectivities with high turnover numbers are the advantages of this catalytic system.

Unidirectional Pure and NaCl-doped triglycine sulfate (TGS) crystals were grown by Sankaranarayanan–Ramasamy (SR) method. The grown crystals were then studied by atomic absorbtion, optical transmission and Fourier Transform Infrared (FTIR) spectroscopy techniques, microhardness and surface etching techniques. The NaCl-doped TGS crystal showed higher transmission than the pure crystal in the entire UV-Vis. region. It was observed that the NaCl additive caused the growth rate of TGS crystal in the [001] direction to increase.

In this study, we investigate the direct electron-transfer reactivity of immobilized hemoglobin (Hb) onto the surface of a carbon paste electrodes (CPE) modified with nanocomposite consist of iron-nickel alloys and multi-walled carbon nanotubes. Fe-Ni nanocrystals were synthesized by a simple chemical method and then by various methods such as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) have been characterized. The simultaneous presence of nanocrystals of nickel-iron (Fe@Ni) and multi-walled carbon nanotubes (MWCNT) in structure of modified electrode provides a unique structure for reliable and effective interaction of Hb whit surface of electrode. The immobilized Hb maintains its bioactivities and displays an excellent electrochemical behavior. The biosensor was used to catalyze the reduction of hydrogen peroxide. The electrochemical behavior of modified electrode by various techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were evaluated. The electrocatalytic response showed a linear dependence on the H2O2 concentration ranging widely from 5.0 to 250.0 µM with a detection limit of 1.43 µM.

This study was aimed to survey the feasibility application of Red mud as adsorbent for the removal of Acid red 88 dye. The efficiency of the adsorbent in removal of dye was studied by investigation of the impact of different parameters such as pH, adsorbent dosage, contact time, initial dye concentration, mixing rate and solution temperature. The experimental data was explained by adsorption isotherms and kinetics. The results indicated that increasing of contact time from 10 to 75 min and adsorbent dosage from 2 to 6 gr/L are led to increase the dye adsorption from 48% to 99.5% and 44% to 99.5%, respectively. The pH value of 3, contact time of 75 min, adsorbent dosage of 6 g/L, dye concentration of 25 mg/L and mixing rate of 200 rpm were determined as optimum conditions. The equilibrium data is best fitted on Langmuir isotherm and the adsorption kinetic model follows pseudo-second model.

A facile and efficient one-pot synthesis of polyhydroquinoline derivatives using LaMnO3 perovskite nanoparticles as a heterogeneous catalyst with high catalytic activity and reusability in solvent-free conditions was reported. This method consistently has the advantages of short reaction times, high yields, little catalyst loading, easy workup, and reusability of the catalyst.

Essential oils are volatile aromatic compounds that are found in herbal plants. Extraction method of plant essential oils can extraction yield, percentage and type of chemical compounds extant in the change. In this research, essential oil product from Trachyspermum ammi (T. ammi) seeds was extracted using subcritical water and further analyzed by GC and GC-MS for determination of chemical compositions. The effect of various parameters on SWE such as temperature, water flow rate and mean particle size were investigated using Taguchi experimental design method. The optimum conditions were obtained from S/N ratio analysis, respectively, at temperature of 175 °C, flow rate 2 mL/min and mean particle size 0.25 mm.