Abstract: In this study Methyl Isobutyl Ketone (MIBK) and acetophenone (Methyl Phenyl Ketone) are presented as suitable agents for removal of Fe(III) from concentrated hydrochloric acid solutions. An extensive study applying 4 parameters was carried out: Time (5, 10,15,20,30 and 60 minutes), Stirring rate (200, 300, 400 and 500 r.p.m), Solvent to HCl Ratio (5%, 10%, 14% and 16%), and initial concentration of Fe ions in crude HCl (95.24, 126 ppm, 330 ppm and 1955 ppm).The best Condition was found to be 30 min - 400 r.p.m - 14 %. The distilled water was used to strip Fe ions out of MIBK; In order to get most of the MIBK dissolved in both the concentrated HCl and water. Diluents were used such as benzene, kerosene and xylene. Xylene gives better recovery of about 96%.
Abstract: Deoxynivalenol (DON) is a mycotoxin that belongs to trichothecene subgroup B. Due its detrimental effects for human health, DON has been analyzed and detected by nearly all chromatographic methods. The present work reports for the first time the application of HPTLC/MS to confirm the presence of DON in wheat crops. Chromatography was performed on silica gel 60 F254 HPTLC plates using toluene - ethyl acetate - formic acid 6:3:1 (V/V/V) as mobile phase. After post-chromatographic derivatization with 10 % AlCl3, fluorescence detection was carried out at UV 366/>400 nm. Bands identity and purity was confirmed by mass spectrometry acquiring analytes directly from the sample bands by means of TLC/MS elution head-based interface. Both, sample and standard bands showed clear mass signals at m/z 341 that corresponds to the formate adduct of DON [M+HCOO]-. Thus, the presence of DON in the Chilean wheat sample was confirmed.
Abstract: In this paper, an account for determination of chlorinated byproducts by High Performance Liquid Chromatography in various tap water samples is presented. The key objective of this study was to develop an analytical method for selectively and sensitively detecting the concentration of CBPs in addition to analyze selected parameters affecting CBP formation. Concentration of targeted compounds i.e. hydrazine sulfate, Dichloroacetic acid, Bromodichloromethane and chloroform were analyzed in tap water samples collected from a low socioeconomic area in a developing country. Hydrazine sulfate, Dichloroacetic acid and chloroform were detected in four water samples i.e. T4, T7, T9 and T10 while no samples contained Bromodichloromethane. Presence of these compounds in water is associated with cancer mortality and adverse reproductive outcomes.
Abstract: In order to understand the relation between chemical composition, microscopic structure and enzymatic digestibility, different Eucalyptus globulus wood pretreated samples were examined. Pretreated materials obtained by steam explosion and autohydrolysis were compared with those obtained by organosolv and kraft processes. Chemical analyses of pretreated materials showed a decrease in the content of xylans, except in the kraft pulp. FT-IR spectra showed that the residual lignin in autohydrolysis pulp had experienced greater changes compared to those in steam explosion and organosolv pulps, whereas minor changes in lignin kraft pulp were observed. The fiber morphology indicated that autohydrolysis pretreatment was the most aggressive treatment. Reduction in the content of lignin and its redistribution on the fiber wall were confirmed through confocal laser microscopy. The formation of discrete lignin droplets deposited on the surface of the fibers was observed in all pretreatments, with a higher frequency in organosolv followed by steam explosion. A significant increase in enzymatic accessibility was achieved in organosolv, autohydrolysis and steam explosion pulps, due to xylans removal combined with lignin redistribution. Homogeneous lignin distribution and higher xylan content may be related to the low enzymatic hydrolysis efficiency in kraft pulp.
Abstract: Pentadentate Schiff base ligand(N,N-bis(2-hydroxy-1-naphthylidene) diethylenetriamine) (H2L) that exhibits a N3O2 donor set. Five rare earth complexes lanthanide (III), praseodymium (III), neodymium(III), samarium(III)and europium (III) complexes are synthesized and characterized based on elemental analyses, molar conductance, infrared, ultraviolet, thermo gravimetric, X-ray powder diffraction and mass spectral studies. Molar conductivity data suggests that the complexes are 1:1 electrolytics. Infrared spectral data suggest that the ligand binds through two naptholic oxygen atoms, two azomethine nitrogen atoms and one primary amine. IR studies reveal that the complexes contain both coordinating and ionic nitrate ligands. Thermal decomposition studies indicate the presence of two nitrate ions and two water molecules in the inner coordination sphere. Eu3+ and Sm3+ complexes exhibit luminescence properties. Further, the binding properties of these complexes with calf-thymus DNA have been investigated using absorption spectrophotometry.
Abstract: We report the results of theoretical mechanistic studies on PH3-assisted migration of a coordinated aryl group to a coordinated CO in the complexes RhCpI(CO) (p-XC6H4). The X-substituent effect on thermodynamic and kinetic parameters was explored. The progress of the reaction was quantitatively studied using the bond orders of the Rh-CO bond, and the percentages of bond cleavage (BCij) of Rh-CO bond at the transition state were described. This theoretical study indicates good relationships between barrier energy (ΔE), bond distances variations (Rh-CO and Rh-Ph), activation energy (ΔH‡) , activation free energy (ΔG‡) values with Hammett constants of X-substituents. Linear relationship between ln(k) and the 103Rh magnetic shielding tensors of the product was explored.
Abstract: In this study, a novel method based on floatation assistance of homogeneous liquid-liquid microextraction (FA-HLLME), combined with inductively coupled plasma-mass spectroscopy (ICP-MS) was proposed, for the determination of trace uranium in environmental water samples. As one of the miniaturized separation and extraction techniques, homogenous liquid-liquid microextraction (HLLME) has been widely applied in the field of environmental monitoring and assessment. 1,2-pyridylazo-2-naphthol (PAN) was used as the complexing agent while toluene and methanol were selected as the extraction and homogeneous solvents, respectively. The factors that influenced the extraction efficiency for uranium determination (including pH, extraction and homogeneous solvents, concentration of PAN and NaCl, extraction time) were studied statistically. Under optimum conditions (pH=7.0, 100 μL toluene, 500 μL methanol, 6.4×10-5 mol L-1 PAN, 1.5 mol L-1 NaCl and 60 sec of extraction time), the linear dynamic range for uranium determination was 1.0-500.0 ng L-1 (R²=0.9995), with a corresponding limit of detection (LOD) of was 0.27 ng L-1. The relative standard deviation (R.S.D.) (C=50.0 ng L-1, n=9) was 1.13%, with a corresponding enrichment factor of 360 for uranium extraction. The proposed method was successfully applied for the determination of uranium in different water samples.
Abstract: Stereoselective polymerization of lactide is receiving growing attention in polymer science. Herein, a five-coordinate aluminum siloxide complex, [2,2-dimethyl-1,3-propylenebis(3,5-di-tert- butylsalicylideneiminato)] (triphenyl-silanolato) aluminium (III) (1), was prepared from AlEt3, N,N'-(2,2-dimethylpropylene) bis(3,5-di-tert-butylsalicylideneimine) and triphenyl-silanol. X-ray analysis demonstrated that 1 contained a five-coordinate aluminum atom with distorted trigonal bipyramidal geometry in the solid state. ¹H NMR and 13C NMR spectra indicated that the two conformational stereoisomers of 1 tautomerizes rapidly in chloroform or toluene solution at room temperature. 1 showed high stereoselectivity (Pm = 0.84) for the ROP of rac-lactide in toluene at 100°C, and polymerized rac-lactide to crystalline polymer (Tm = 178°C). This is the first report of stereoselective polymerization of rac-lactide using aluminum siloxide as a catalyst.
Abstract: Characterizing the chemical properties of forage is critical for the production of improved pastures and livestock development. Conventional analysis methods are very time- and material-consuming, whereas near-infrared spectroscopy (NIRS) and chemometric analyses allow a fast simultaneous determination of various chemical or physical properties without the use of solvents or large sample amounts. The present research involved the development of models based on NIRS and partial least squares regression (PLS) to estimate the neutral detergent fiber (NDF), acid detergent fiber (ADF), cellulose, and crude protein (CP) contents in Brachiaria spp. forage samples. The models were constructed using spectral data in the range of 800 to 1850 nm. Different preprocessing methods were applied, such as standard normal variate and first-/second-derivative transformations. The obtained calibration models were internally cross-validated, displaying validation errors similar to those obtained for conventional methods. The predictive abilities of the developed models were evaluated for external set samples. NDF, ADF, cellulose, and CP contents were estimated with relative errors of prediction (REPs) of 1.8, 2.6, 4.1, and 8.5%, respectively. NIRS predictions are a useful and profitable tool for fast multi-sample chemical property analysis that is required for the assessment of forage quality. The obtained models are suitable for estimating the key chemical characteristics of forage quality. This research contributes a new approach to determining the quality of Brachiaria spp. forage and provides a new technological tool for the improvement of this crop.
Abstract: The influence of the background concentration of ZnCl2 on the selectivity of Zn(NCS)4(2-)−SE based on QAS to SCN- is studied. The introduction of ZnCl2 into a solution fixes zinc released from the membrane in the form of thiocyanate complex. A high selectivity of the Zn(NCS)4(2-)−SE to SCN- ions is due to the formation of better extractable complexes between zinc and SCN- compared to acidocomplexes of competitive anions. An introduction of 5.0 M ZnCl2 into a solution increases selectivity to SCN- ions by 5 orders of magnitude in the presence of interfering CKO4- ions and more than 4.5 orders of magnitude in the presence of interfering NO3- ions.
Abstract: A simple analytical procedure, magnetic solid phase extraction combination to HPLC, has been developed for the analysis of gemifloxacin in human plasma and breast milk. Before chromatographic separation, magnetic solid phase extraction has been applied for sample preparation which is currently preffered extraction technique accordingly its simple, fast and efficient procedure. Fe3O4 magnetic nanoparticles have been used as magnetic adsorbents, the adsorption process has been optimized. RP C18 column has been used with mobile phase composed of acetonitrile-10 mM orthophosphoric acid including 1 mL/L triethylamine (60:40) by isocratic elution with flow rate of 1.3 mL/min. Calibration curve is linear over the range of 0.5-30 μg/mL and 0.5-20 μg/mL for plasma and breast milk, respectively. LOD and LOQ has been found to be 0.15 and 0.5 μg/mL for both matrices. Intraday and interday RSD values are less than 3.57% for both assays. Moreover, the newly developed method provides fast, simple, cost reduced and sensitive assay for gemifloxacin.
Abstract: A simple and precise stability indicating RP-HPLC method was developed for simultaneous analysis of drug nortriptyline and pregabalin using BDS (250mm x 4.6 mm, 5μ) C18 column at 210 nm of UV detection. Perchloric acid (0.1%) and acetonitrile in the ratio of 55:45 was used as the mobile phase with a flow rate of 1.0 ml/min and linearity response was established over the concentration range of 5-30 μg/ml for nortriptyline and 37.5-225 μg/ml for pregabalin. The active pharmaceutical ingredients recovered for nortriptyline and pregabalin are in the range of 100.60-101.65% and 100.59-101.74% respectively. The method was validated and was found to be stability indicating and can be successfully utilized for the quantitative analysis of pharmaceutical tablet dosage formulations containing nortriptyline and pregabalin.
Abstract: Two novel 1,2-diol containing azo dyes have been synthesized for application on polymeric textile substrates. We used multistep synthesis scheme which involved selectively bonding azo chromophore with glycerol moiety such that only one alcohol out of the three gets bonded to the chromophore while rest two remain unchanged. The 1,2-diol moiety, common in both dyes, is responsible for forming hydrogen bonds with polar sites on a polymeric substrate. The molecular structure of the final molecule and synthesized intermediates were elucidated by UV/Vis, FT-IR, MS (EI, ESI, and CI) and ¹H-NMR spectroscopic techniques. Dyes were applied to polyester and nylon 66 fabrics as disperse dyes by exhaust dyeing method and furnished good to excellent fastness properties on both of them.
Abstract: Imidation of various anhydrides employing solvent-free grindstone technique using smectite clays as recyclable and green catalysts was examined and obtained excellent yields.
Abstract: In this paper a novel adsorbent was prepared from Nigella sativa L. waste and used for the removal of Coomassie Brilliant Blue dye from wastewater. The preparation of Nigella sativa waste carbon (NSWC) was achieved by adding concentrated sulfuric acid to the precursor material at an impregnation ratio (1: 1) and the mixture was left overnight. The resulting material was washed with sodium bicarbonates and finally oven dried. The kinetics of coomassie brilliant blue adsorption onto NSWC was investigated by three kinetic models. The pseudo-second order model (R² = 0.99) was the best model fitted the experimental data. The equilibrium results revealed that Freundlich model was the best isotherm model fitted (R²= 0.994). Also the value of the Freundlich exponent (n) was found to be 1.174 suggesting the favorable dye adsorption onto NSWC. The thermodynamics results indicated negative values of ΔG proving the spontaneous nature of Brilliant Blue dye adsorption on NSWC. The exothermic nature of the adsorption was also confirmed by the negative value of change in enthalpy ΔH°. Also, the negative value of the activation entropy ΔS° demonstrates the decreased randomness at the solid-solution interface during adsorption. The present study results suggest the possible use of a waste such as Nigella sativa L. waste as a precursor for the development of a new cheap and efficient adsorbent that could be used in dyes removal from wastewater.
Abstract: This paper presents a discussion of the processing and characterization of alloy Co87Nb46B15 produced by rapid solidification, in which characterization techniques such as X-Ray Diffraction (XRD), scanning electron microscopy and spectroscopy Dispersion Energy (SEM / EDS) and magnetic properties were used, with the study of hysteresis curve. Several researches have been making on nanocrystalline materials, especially cobalt-base alloys, because of their thermodynamic stability, characterization and processing. Amorphous alloys have a structure of ultrafine, homogeneous grains with small crystal clusters in amorphous phase.
Abstract: Glassy carbon electrode modified with COOH- and NO2-functionalized polyspyrophosphazenes were used to study the redox process of a electroactive probe (ferrocene) in non-aqueous electrolyte. The electrochemical behavior of polyphosphazenes substituted with COOH and NO2 groups has been studied using cyclic voltammetry. Their blocking properties depend on the substituent group and on the substitution/nitration degree. The oxoreduction of the couple Fc/Fc+ occurs with rapid redox kinetic at the modified glassy carbon electrode with high nitration degree NO2−functionalized polyspyrophosphazene. The polymers were immobilized on the glassy carbon surface at different concentrations to study surface charge density effect. In this report were studied the reproducibility, repeatability and stability of the modified electrodes.
Abstract: Electrocoagulation is a promising technique for the treatment of wastewater like the produced by the textile industry, which generates large volumes of water containing dyes. Thus, synthetic samples of the textile dye acid black 194 (AB194, CI 22910) were treated by this method using iron anodes at two different initial pH values. Tafel studies in the presence and absence of the dye were performed. The complete removal of AB194 from 1.0 L of solution in a static cell was achieved, at short electrolysis times, applying low-density currents at two different initial pH values. In addition, the operating costs by mass consumed anode, per cubic meter electocoagulated and per TOC unit, were assessed to help determine the most efficient conditions, considering a future application of the method in the industry.
Abstract: Hydrogen peroxide (H2O2) plays an important role as an intermediary in different biological, chemical and environmental systems. It has been widely used as an oxidizing and antimicrobial agent, in germicides production and textile and paper bleaching. However, it is well known, that H2O2 is a possible responsible in many diseases and is a chemical agent that threatens the environment, so it becomes important to detect peroxide with high accuracy. In this study, carbon paste electrode (CPE), modified with Co2SnO4 was synthesized and tested. It was successfully obtained a non-enzymatic H2O2 detection type sensor, based on Co2SnO4/ CPE composite, showing good linear response in concentration of H2O2 in the range of 88 - 605.9 μM.
Abstract: This work reports the degradation of methylene blue (MB) on Ti/TiO2 and Ti/TiO2/Fe-allophane electrodes in a pH 3 using 0.1 M Na2SO4 as support electrolyte. SEM micrographs show a homogeneous distribution of TiO2 over the whole electrode surface forming nanotubes and nanopores. Fe-allophane modified electrode shows the formation of large-grains agglomerate on the electrode surface due to allophane, which provides a greater surface area to the electrode due to meso and micropore structures. Preliminary cyclic voltammetry show that Ti/TiO2 has the typical voltammetric response due to Ti(III)/Ti(IV) pair. Diffusional problems were observed through of the film when the electrode is modified with Fe-allophane modifying the quasi-reversible process Ti(III)/Ti(IV). Different kind of methodologies in the degradation process were used: Electrochemistry (EC), Photochemistry (PC), Photoelectrochemistry (PEC) and Adsorption (Ads). These methods were developing to discard any reaction or interaction that is not of interest. On Ti/TiO2 with PC and Ads methodologies was not observed any activity to MB degradation showing that is not photosensitive and that the interaction between this and surface electrode is low. But with EC and PEC degradation to 55% is reached after 3 hours of electrolysis. With Ti/TiO2-Fe-allophane electrodes are observed a higher activity for all methodologies. The PC and Ads methods show that the MB degradation reaches to ~20 % of the initial concentration. As mentioned above, the PC and Ads processes no show degradation on Ti/TiO2, therefore the degradation it only due to the adsorption of MB in/on allophane coat behaving as concentrator matrix. A lower improvement is observed with EC process when is incorporated Ti/TiO2-Fe-allophane is due to the barrier of the electrode surface by oxidation products. With PEC is reached the higher degradation value of ~88 %, showing an improvement of the degradation with the presence of Fe-allophane. The results indicate that the main role of Fe-allophane on the electrode is similar to a concentrator matrix.
Abstract: The molecular structure of the title compound [iupac name: 13-epi-8-hydroxy-3-isopropyl-5a,8-dimethyl-2,3,4,5,5a,6,7,8,10a,10b-decahydrocyclohepta[e] indene-3a(1H) acid] is similar to the structure of the known compound mulinolic acid.The structure of this mulinolic acid epimer consists of a mulinane skeleton and the isopropyl, methyl group, carboxylic acid and the hydroxyl group at C3, C8, C5, C13, respectively, which are ß-oriented, whereas the methyl group at C13 are a-oriented. The cyclopentane (A), ciclohexane (B) and cicloheptene (C) rings are trans (A/B) and (B/C) cis fused, and are in an envelope, chair, and twist chair conformation respectively. In the crystal the molecules are linked by two strong intermolecular O-H···O hydrogen bond forming bidimensional supramolecular structures with graph-set notation (12) and (46).The absolute configuration of the title compound which has been determined from the refinement of the Flack parameter16. On this basis the absolute configuration was assigned as C3R, C5S, C8S, C9S,C10S and C13S.
Abstract: An optimized spectroscopic methodology for the quantification of urea using p-dimethylaminobenzaldehyde (DMAB) as a derivatizing reagent is proposed to avoid changes in reproducibility caused by aging of acidic DMAB solutions, and the unintended use of different solvents. Four solvents; ethanol, methanol, 2-propanol and acetonitrile are evaluated. Acetonitrile has never been reported for the determination of urea with DMAB, and it is found to be the best medium for the quantification of urea due to its aprotic nature. The use of acetonitrile allows a more stable reaction system, which results in a faster urea quantification, less acid consumption and a more sensitive spectroscopic method. Taking into account that polymer matrices of chitosan are being used recently to develop controlled release fertilizers of urea, a complementary study is carried out to determine any interference by released chitosan macromolecules with different molecular mass and degree of deacetylation in the optimized system. The results show no appreciable changes in the sensitivity and accuracy of the methodology being other available application of this work.
Abstract: Last decade has witnessed enormous changes in the studies of impurity profiling of drugs which can be reflected from pharmacopoeia and regulatory guidelines. The present review article is an attempt to provide comprehensive knowledge about various aspects and details about the impurity profiling in context with regulatory guidelines. Article also focused on isolation, separation and characterization techniques of impurities. It gives preliminary idea about applicability of virtual software used for studies on safety limit for impurities. The comprehensive information related to residual solvents, residual metals and genotoxicity studies of isolated impurities have also been incorporated into present article.
Abstract: Methacrylic monomers with pyrylium salt derivatives are widely used to detect nucleophilic species. A new synthesis method has been used to obtain a pyrylium salt that is trisubstituted with phenyl groups at positions 2,4, and 6. The phenyl group of the 4-position has a metacrylate group in the para-position. The new synthesis method implies the esterification of 4-hydroxybenzaldehyde, using methacrylic anhydride. The formed compound react with acetophenone to form the pyrylium derivative. The yields of both reactions are greater than those previously reported in the literature.
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