A reusable and cost-effective magnetic graphite oxide (Fe3O4NPs@GO) nanocomposite was fabricated and applied for pre-purification of paclitaxel from leaf-derived crude extract of Taxus baccata. Furthermore, the potential roles of three crucial criteria (i.e., adsorbent dosage, sorption temperature and agitation/shaking power) on the two responses [i.e., efficiency of plant pigments removal (EPPR) and efficiency of taxol purity (ETP)] were examined and simultaneously optimized through response surface methodology. The nanocomposite was accurately characterized using TEM, AFM, BET, FT-IR, Raman and VSM. Moreover, for both proposed second-degree polynomial regression models, highly significant correlations were achieved between the experimental and predicted data (p < 0.0001). Meanwhile, the optimum conditions to simultaneously acquire the maximum EPPR (94.0 %) and ETP (11.4 %) were recorded as adsorbent dosage of 37.7 g L−1, sorption temperature of 30.7 °C and agitation power of 153.1 rpm; and the predictive results were confirmed using experimental rechecking survey. Interestingly, upon five consecutive treatments, the nanocomposite still exhibited substantial potency in eliminating large amounts of plant pigments and impurities (up to 90 %), without significant reduction on sorption capacity and magnetism thereof. Our results demonstrated that the current nanocomposite, as SPE sorbent for MSPE, could be a simple, fast and reusable approach for HPLC-based purification studies of paclitaxel, and probably other plant secondary metabolites.
Synthesis of tetrasubstituted pyrroles by the three-component condensation reaction of acid chlorides, dialkyl acetylenedicarboxylates,
and amino acids in the presence of various room-temperature ionic liquids (RTILs) as catalysts in water is reported. Among
the ionic liquids used, the basic functionalized ionic liquid, butyl methyl imidazolium hydroxide [bmim]OH, was the most effective
catalyst. The influence of reaction temperature, reaction time, and amount of ionic liquid on the reaction was investigated.
The [bmim]OH/H2O catalyst system could be reused for at least five recycles without appreciable loss of efficiency. 相似文献
A new micelle-mediated extraction method for preconcentration of ultra-trace quantities of beryllium and aluminum as a prior step to their simultaneous spectrophotometric determination has been developed. Chrome Azurol S (CAS), cetyltrimethylammonium bromide (CTAB) and Triton X-114 were used as chelating agent, cationic surfactant for extraction and co-extraction agent, respectively. Mean centering (MC) of ratio spectra has been used for simultaneous analysis of beryllium and aluminum. The optimal extraction and reaction conditions were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 5-40 ng mL−1 of beryllium and 3-100 ng mL−1 of aluminum. The detection limit of the method is 0.98 and 0.52 ng mL−1 for beryllium and aluminum, respectively. The interference effect of some anions and cations was also tested. The method was applied to the simultaneous determination of beryllium in water samples. 相似文献
The aim of this study is to introduce the application of some acidic ionic liquids (ILs) as an electrolyte additive in lead-acid
batteries. A family of alkylammonium hydrogen sulfate ILs, which are different in the number of alkyl chain, is investigated
with the aim to compare their effects on the electrochemical behavior of Pb–Sb–Sn alloy in sulfuric acid solution. The hydrogen
and oxygen gas evolution potential and anodic layer characteristics were investigated employing cyclic and linear sweep voltammetric
methods. The morphological changes of the PbSO4 layer that formed on the electrode surface were confirmed using scanning electron microscopy. Also, potentiodynamic polarization
curves, electrochemical impedance spectroscopy, and an equivalent circuit analysis were used to evaluate the corrosion behaviors
of the Pb–Sb–Sn alloy in the presence of ILs. The obtained results indicate that hydrogen and oxygen evolution overpotential
of lead–antimony–tin alloy increases in the solution containing IL and mainly depends on the number of alkyl chain in alkylammonium
cation. It is clearly observed that the morphology of PbSO4 layer changes under the influence of ILs. The corrosion studies show an increase in corrosion resistance of lead alloy in
the presence of some ILs. Also, the electrochemical effects of ILs in conversion of PbSO4 to PbO2 and vice versa were investigated by carbon-PbO paste electrode. Cyclic voltammogram of carbon-PbO electrode shows that in
the presence of ILs, oxidation and reduction peak currents increase, while reversibility decreases. 相似文献
The use of ionic liquids as novel solvents for the synthesis of aromatic copoly(ester-amide)s, containing a 9,10-anthraquinone moiety in the main chain, from the polycondensation reaction of terephthaloyl chloride and various ratios of p-phenylenediamine and 1,4-dihydroxyanthraquinone is reported. 1,3-Dialkylimidazolium-based ionic liquids are suitable reaction media for the synthesis of copoly(ester-amide)s. These copolymers exhibit color characteristics and thermal stability. The presence of the amide groups in the backbone of these polymers enhances their thermal stabilities. Inherent viscosities of the polymers obtained in 1,3-dialkylimidazolium bromide range from 0.28 to 0.42 dL/g. 相似文献
We have performed the molecular dynamics simulation to obtain energy, pressure, and self-diffusion coefficient of helium at
different temperatures and densities using Lennard–Jones (LJ), Hartree–Fock dispersion-Individual damping (HFD-ID) potential,
and the HFD-like potential which has been obtained with an inversion of viscosity data at zero pressure supplemented by quantum
corrections following the Feynman–Hibbs approach. The contribution of three-body interactions using an accurate simple relationship
reported by Wang and Sadus between two-body and three-body interactions has been also involved for non-effective potentials
(HFD-ID and HFD-like) in simulation. Our results show a good agreement with corresponding experimental data. A comparison
of our simulated results with other molecular simulations using different potentials is also included. 相似文献
Both of experimental and numerical investigations were performed to understand unsteady natural convection from outer surface of helical coils. Four helical coils with two different curvature ratios were used. Each coil was mounted in the shell both vertically and horizontally. The cold water was entered the coil and the hot water in the shell was cooling by unsteady natural convection. A CFD code was developed to simulate natural convection heat transfer. Equations of tube and shell are solved simultaneously. Statistical analyses have been done on data points of temperature and natural convection Nusselt number. It was revealed that shell-side fluid temperature and the Nusselt number of the outer surface of coils are functions of in-tube fluid mass flow rate, specific heat of fluids and geometrical parameters including length, inner diameter of the tube and the volume of the shell, and time. 相似文献
In this work, the excess thermodynamic properties, namely excess molar Gibbs energy, excess molar enthalpy, excess molar entropy, excess molar internal energy, and excess molar Helmholtz energy for four polymer mixtures and blends at different temperatures, pressures, and compositions have been calculated using the GMA equation of state. We have also calculated the activity coefficient for these polymeric mixtures using the GMA equation of state. The values of statistical parameters between experimental and calculated properties show the ability of this equation of state in reproducing and predicting the excess thermodynamic functions and activity coefficients for studied polymeric mixtures. 相似文献
2-(5-H/methyl-1H-benzimidazol-2-yl)-4-bromo/nitro-phenol (HLx:X=1–4) ligands and their iron(III) nitrate complexes have been synthesized and characterized. In all of the complexes, the
ligands are bidentate, via one imine nitrogen atom and a phenolate oxygen atom. The coordination is completed with a bidentate nitrate anion, and a
water molecule. Elemental analysis, molar conductivity, magnetic susceptibility, FT-Raman, FT-IR (mid i.r., far i.r.), UV–visible
and as well as quantum chemical calculations performed with CACHE are in agreement with a 1:1 electrolyte structures that
are mononuclear, and distorted 5-coordinate square pyramidal. The antimicrobial activities of free ligands, their hydrochloride
salts and the complexes were evaluated using the disk diffusion method in dimethyl sulfoxide (DMSO) toward nine bacteria,
each with multiple, fresh clinical isolates, and the results are compared with those for penicillin-g, ampicillin, cefotaxime,
vancomycine, oflaxacin and tetracycline. Antifungal activities were reported for Kluyveromyces fragilis, Rhodotorula rubra, Candida albicans, Hanseniaspora Guilliermondii and Debaryomyceshansenii yeasts, each with multiple isolates, and the results were referenced against nystatin, ketaconazole and clotrimazole antifungal
agents. In most cases, the compounds tested showed broad-spectrum (Gram+ and Gram−) activities that were either more active or as potent as the references particularly as antifungal agents. 相似文献