Box-Behnken响应面法优化银杏酚酸提取工艺及其抗肿瘤活性的研究

采用Box-Behnken响应面法优化微波辅助提取银杏酚酸的最佳工艺,并研究其体外抗肿瘤活性.首先以银杏酚酸为标准品建立高效液相色谱法测定银杏酚酸含量的分析方法;选取白果外种皮干粉为原料,在单因素试验基础上,以银杏酚酸总提取率为考察指标,选取3因素3水平的响应面法优化提取工艺;采用MTT法检测其抑制人源胃癌BGC823...     

响应曲面法用于高效液相色谱优化分离磺胺的研究

通过响应曲面法对高效液相色谱分离磺胺的优化过程进行了研究,分别考察了分离的3个主要因素(柱温、流动相配比、流速)对最小分离度与分离时间的影响,建立了3个因素与最小分离度和最大保留时间的目标函数,从响应曲面图可优化预测因素水平范围内的最佳分离条件.在选定优化条件下:柱温为20℃,乙腈的体积分数19%,流速1.5 mL/min,8种磺胺组分可在8 min内达到基线分离.     

Application of the response surface methodology for modeling demulsification of crude oil emulsion using a demulsifier

The main objective of this research is to determine the capability of four surface-active compounds namely poly(ethylene glycol) distearate, N,N-dimethyldodecylamine N–oxide solution, polyoxyethylene (10) tridecyl ether, and polyethylene glycol sorbitan monooleate as demulsifier agents in breaking water-in-crude oil emulsion through the bottle test method. The influence of temperature, concentration, water content, and pH on demulsification efficiency of the studied demulsifiers was investigated via the response surface methodology (RSM) and the central composite design method (CCD) was applied to design the experiments. The optimum values of input variables to obtain the maximum water separation efficiency were determined based on the developed model by analyze of variance (ANOVA). The R-squared values demonstrate that the developed models could appropriately predict the experimental results of all demulsifier agents.     

Modeling and optimizing of sonochemical degradation of Basic Blue 41 via response surface methodology

The nanocatalyst-assisted sonodegradation of Basic Blue 41 (BB41) dye in aqueous medium was modeled and optimized using response surface method (RSM) based on Box-Behnken design. The studied variables included pH, initial dye concentration, H₂O₂ concentration and sonolysis time while each factor varied at three levels: Low level (−1), Medium level (0) and High level (+1). The ultrasound -assisted degradation was well described by developing quadratic model with correlation value squared (R²) of 0.9114. Factor effects along with interaction effects were evaluated. The graphical optimization step was conducted to achieve the best experimental condition in dye removal. pH, H₂O₂ concentration and initial dye concentration of the reaction were investigated. It was recognized that at lower pH values the dye removal rate decreased. However, dye removal rate increased (82.5%) by increasing the concentration of H₂O₂ and by lowering the initial dye concentration.      

Probable mechanism for alkane oxidation with H2O2 over VS-2

Metallosilicate zeolites containing Ti and V, TS-2 and VS-2, have been synthesized using tetrabutylammonium cation as the template. Although both Ti and V exist in zeolite framework in a highly dispersed state, V easily leaches by K₂CO₃ or H₂O₂ treatments in contrast to Ti. Spin trapping experiments and relative reactivity of linear/cyclic alkanes indicate that the oxidation of alkanes over TS-2 and VS-2 proceed by different mechanisms; it is conceivable that the oxidation occurs by way of the attack of ·OH species produced from the V species in the zeolite framework with H₂O₂.     

Mixed phase Fe2O3/Mn3O4 magnetic nanocomposite for enhanced adsorption of methyl orange dye: Neural network modeling and response surface methodology optimization

In this research, a novel magnetic mesoporous adsorbent with mixed phase of Fe₂O₃/Mn₃O₄ nanocomposite was prepared by a facile precipitating method and characterized extensively. The prepared nanocomposite was used as adsorbent for toxic methyl orange (MO) dye removal from aqua matrix considering its high surface area (178.27 m²/g) with high saturation magnetization (23.07 emu/g). Maximum dye adsorption occurs at solution pH 2.0 and the electrostatic attraction between anionic form of MO dye molecules and the positively charged nanocomposite surface is the main driving force behind this adsorption. Response surface methodology (RSM) was used for optimizing the process variables and maximum MO removal of 97.67% is obtained at optimum experimental condition with contact time, adsorbent dose and initial MO dye concentration of 45 min, 0.87 g/l and 116 mg/l, respectively. Artificial neural network (ANN) model with optimum topology of 3–5–1 was developed for predicting the MO removal (%), which has shown higher predictive ability than RSM model. Maximum adsorption capacity of this nanocomposite was found to be 322.58 mg/g from Langmuir isotherm model. Kinetic studies reveal the applicability of second‐order kinetic model with contribution of intra‐particle diffusion in this process.     

Magnetically separable polyoxometalate catalyst for the oxidation of dibenzothiophene with H2O2

Two types of polyoxometalate-functionalized magnetic nanoparticles catalysts consisting of H(3)PW(12)O(40) supported on surface-modified Fe(3)O(4) magnetite nanoparticles were prepared using an easy synthetic route and successfully applied for the oxidation of dibenzothiophene. The magnetic catalysts showed a catalytic performance in the oxidation of dibenzothiophene in acetonitrile with hydrogen peroxide, and high conversions were obtained. The catalysts could be easily separated from the reaction solution by applying an external magnetic field and recycled several times.     

Hybrid platinum nanoparticle ensemble for the electrocatalytic oxidation of H2O2: Toward nanostructured biosensor design

This paper reports the electrocatalysis of H₂O₂ oxidation by Langmuir–Blodgett (LB) thin films based on polymer-grafted platinum nanoparticles (PtNPs). 4-mercaptoaniline-functionalized PtNPs have been chemically modified to obtain poly(methacrylic acid)-grafted platinum nanoparticles (PMAA-PtNP) via surface-ATRP. These elementary bricks are used to form mixed LB films consisting of controlled mixtures of PMAA-PtNP and a redox-inactive fatty acid molecule to tune the PtNP surface density. Nanostructures are formed in which the number of layers and the number of particles in each layer may be varied. The nanostructure morphology strongly depends on the amount of PtNP. High Pt content leads to quite large nanoparticle domains whereas low content gives small domains with a finely divided nanostructure. The H₂O₂ oxidation current increases when the PMAA-PtNP surface density decreases. This result is discussed in terms of electrocatalyst accessibility modification related to the nanostructure of the films.     

Statistical optimizing of electrocoagulation process for the removal of Cr(VI) using response surface methodology and kinetic study

Optimization of electrocoagulation (EC) using copper electrode in terms of Cr(VI) removal from simulated waste water was executed by applying surface methodology and kinetic study. In this research, electrocoagulation process was applied to evaluate the outcome of operational parameters such as initial Cr(VI) concentration, pH, electrode distance, current density and supporting electrolyte (NaCl) concentration for the removal of Cr(VI). The experimental results showed that current density of 41.32 A/m², electrode distance of 1.4 cm, initial pH of 5.65, time of electrocoagulation of 40 min and initial conductivity 0.21 ms are the optimal operating parameters to attain 93.33% removal efficiency of Cr(VI) ions from simulated waste water. The high value of R² = 98.15 and R²_adj = 96.49 show that fitted model confirms a good agreement with the real and predicted Cr(VI) removal percentage. It was concluded that Cr(VI) ion removal follows the first-order kinetic model by kinetic study of EC process.     

Heats of transfer in the diffusion layer before the surface and the surface temperature for a catalytic hydrogen oxidation (H2 + (1/2)O2 --> H2O) reaction

The surface temperature and surface mole fractions are calculated for a catalytic hydrogen oxidation reaction over a Pt/Al2O3 catalyst pellet. The thermodynamics of irreversible processes was used in order to ensure the correct introduction of coupled heat and mass transfer. Two pathways, one using the 4 x 4 resistivity matrix and the other using a simplified effective conductivity matrix, were proven to yield equivalent results. By using expressions for the thermal diffusion coefficients, heats of transfer, and the Maxwell-Stefan diffusion coefficients given in the literature, available experimental data could be reproduced. The Dufour effect was found to be negligible for the prediction of the surface temperature. Neglecting the Soret effect would increase the predicted value of the surface temperature significantly-more than 30 K out of an average of about 400 K. It is found that the reaction rate can be used to predict the surface temperature.     

Optimizing the degradation of dichlorvos in aqueous solution using nZVI DTPA+H2O2 and its detection using ac conductivity measurement with the help of response surface methodology

Degradation of organic pollutants in wastewater is a common subject of discussion under advanced oxidation process. To detect the degradation of colourless organic pollutants conventional analytical techniques are available but their sophistication makes it difficult to pursue in all form of chemical laboratories. In the present study it was found that during degradation of Dichlorvos using diethylene triamine pent acetic acid (DTPA) stabilized nano zero valent iron (nZVI), COD removal and ac conductivity change has been done simultaneously. In this degradation study the heterogeneous Fenton type oxidation method was employed and an LCR circuit (which contains inductor, capacitor and resistor) was used to measure the ac conductivity. This study aims to find out a correlation between ac conductivity and COD removal using simple response surface methodology (RSM) so that the degradation of colourless pollutants can be estimated easily and also to identify the best processing parameters to optimise Dichlorvos degradation. It was found that COD removal in most of all cases, was more than 60% when the change in final ac conductivity more than 600% with respect to initial value. All of the experimental results were in good accord with the projected outcome.     

Multi-wall carbon nanotube-supported manganese(III) porphyrin: An efficient and reusable catalyst for the oxidation of alkenes with H2O2 under ultrasonic irradiation

A manganese complex of meso-tetrakis(p-hydroxyphenyl)porphyrin immobilized onto functionalized multi-wall carbon nanotubes has been synthesized and characterized. The catalytic activity of this heterogeneous catalyst was investigated in the oxidation of various olefins with hydrogen peroxide under ultrasonic irradiation. The role of the stoichiometric amounts of acetic anhydride/or acetic acid as an activator that introduces in situ peracetic acid is discussed. This heterogeneous catalyst was highly reusable in the oxidation reactions and reused several times without significant loss of its catalytic activity.     

High temperature oxidation of HP40 alloy under H2–H2O and air atmospheres: a surface study

In the present work, high temperature oxidation of HP40 alloy was carried out at 1050 °C under H₂–H₂O and air atmospheres; the influence of atmosphere on surface morphology and composition was studied. Octahedral crystals with considerable spalled regions are present on the surface of alloy oxidized under air, the oxide scale composes of MnCr₂O₄, Cr₂O₃ and (Fe, Ni)Cr₂O₄ and spalled regions exhibit base alloy and SiO₂‐rich regions. The surface of alloy oxidized under H₂–H₂O is fully covered by small granular crystals and blade‐type structures without spallation, and the oxide scale composes of MnCr₂O₄ and Cr₂O₃. Moreover, X‐ray photoelectron spectroscopy analysis shows considerable difference in chemical valence states of Mn, Cr and O elements on both alloy surfaces, and hydroxyl compounds exist on the alloy oxidized under H₂–H₂O atmosphere. Copyright © 2017 John Wiley & Sons, Ltd.     

Optimizing ultrasonic ellagic acid extraction conditions from infructescence of Platycarya strobilacea using response surface methodology

The infructescence of Platycarya strobilacea is a rich source of ellagic acid (EA) which has shown antioxidant, anticancer and antimutagen properties. Response surface methodology (RSM) was used to optimize the conditions for ultrasonic extraction of EA from infructescence of P. strobilacea. A central composite design (CCD) was used for experimental design and analysis of the results to obtain the optimal processing parameters. The content of EA in the extracts was determined by HPLC with UV detection. Three independent variables such as ultrasonic extraction temperature (°C), liquid:solid ratio (mL/g), and ultrasonic extraction time (min) were investigated. The experimental data obtained were fitted to a quadratic equation using multiple regression analysis and also analyzed by appropriate statistical methods. The 3-D response surface and the contour plots derived from the mathematical models were applied to determine the optimal conditions. The optimum ultrasonic extraction conditions were as follows: ultrasonic extraction temperature 70 °C, liquid:solid ratio 22.5, and ultrasonic extraction time 40 min. Under these conditions, the experimental percentage value was 1.961%, which is in close agreement with the value predicted by the model.     

GC-MS analysis of water-soluble organics in atmospheric aerosol: response surface methodology for optimizing silyl-derivatization for simultaneous analysis of carboxylic acids and sugars

This paper describes the development of a derivatization procedure — silylation using N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA) — for the simultaneous GC–MS analysis of a wide range of water-soluble organics in atmospheric aerosols. The reaction operating conditions were optimized using the response surface methodology (RSM) including central composite design (CCD) in order to achieve the highest response for a large number of dicarboxylic acids and sugars. The factors considered were: (i) reaction temperature (50–90 °C), (ii) the reaction duration (60–120 min), (iii) reagent concentrations (10–100% of the total solution volume) and (iv) pyridine concentration (0–50% of the derivatization reagent). On the basis of RSM and experimental evidence, the optimum derivatization conditions were defined as reaction temperature of 75 °C, reaction duration of 70 min, BSTFA reagent concentration of 55% and pyridine concentration of 35%. The optimized protocol was extended to a broader range of 22 target analytes that are relevant chemical markers, i.e., 15 carboxylic acids and 7 sugars. In addition, the applicability of the optimized procedure was verified in environmental matrices from PM filters collected under different conditions, i.e., different seasons (summer vs. winter), different sampling sites (urban vs. rural), different particle size dimensions (PM_2.5 vs. PM₁).     

Direct deposition of gold nanoparticles onto polymer beads and glucose oxidation with H2O2

Gold nanoparticles (Au NPs) were deposited directly from aqueous solution of diethylenediaminegold(III) complex onto polymer beads commercially available, such as poly(methyl methacrylate) (PMMA), polystyrene (PS), and polyaniline (PANI) without surface modification. The dropwise addition of NaBH4 to reduce Au(III) was found to be very effective to obtain small Au0 NPs with a narrow size distribution except for PANI. The catalytic performance of Au NPs deposited on polymer beads for H2O2 decomposition and glucose oxidation with H2O2 were more significantly affected by the kinds of polymer supports than by the size of Au NPs. The equimolar oxidation of glucose with H2O2 could be operated by controlling the decomposition rate of H2O2 over Au/PMMA.     

A computational chemist approach to gas sensors: modeling the response of SnO2 to CO, O2, and H2O gases

A general bottom-up modeling strategy for gas sensor response to CO, O(2), H(2)O, and related mixtures exposure is demonstrated. In a first stage, we present first principles calculations that aimed at giving an unprecedented review of basic chemical mechanisms taking place at the sensor surface. Then, simulations of an operating gas sensor are performed via a mesoscopic model derived from calculated density functional theory data into a set of differential equations. Significant presence of catalytic oxidation reaction is highlighted.     

Drastic increase of selectivity for H2O2 formation in direct oxidation of H2 to H2O2 over supported Pd catalysts due to their bromination

Incorporation of bromide anions (1.0 wt%) in supported Pd catalysts (viz. Pd supported on Al2O3, ZrO2, SiO2, H-beta or Ga2O3) leads to a drastic increase in their selectivity for H2O2 formation in the direct oxidation of H2 to H2O2 by O2(at room temperature) in an aqueous acidic (0.03 M H3PO4) reaction medium; the selectivity increase is accompanied by a large decrease in the H2O2 decomposition activity of the catalysts.     

Decolorization and mineralization of yellow 5 (E102) by UV/Fe2+/H2O2 process. Optimization of the operational conditions by response surface methodology

In this study, the optimization and implementation of a homogeneous photo-Fenton process for the decolorization and mineralization of a wastewater containing highly concentrated yellow 5 (E102) dye, resulting from an industry placed in the suburbs of Medellin (Colombia), is presented. Response surface methodology was applied as a tool for the optimization of operational conditions such as initial dyestuff concentration, H₂O₂ concentration, and UV-radiation power (number of lamps). The decolorization, degradation and mineralization efficiencies were used as response variables. The following conditions were found to be optimal for decolorization and mineralization of yellow 5: UV radiation of 365 nm (4 W, one lamp), dye concentration of 200 mg/L, Fe²⁺ concentration of 1.0 mM, H₂O₂ concentration of 1.75 mL/L, treatment time of 180 min, Fe²⁺ concentration of 1 mM and pH = 3. Under these conditions (180 min), the photo-Fenton process allowed us to reach ca. 100% of color dye degradation, 99% of COD degradation, and 85% of mineralization (TOC). The scavenging effect of the Cl^– anion on the photodegradation process was also confirmed.     

Hydrogenase enzymes: Application in biofuel cells and inspiration for the design of noble-metal free catalysts for H2 oxidation

While hydrogen is often considered as a promising energy vector and an alternative to fossil fuels, the rise of the hydrogen economy is ever and ever postponed. This is mainly due to the high costs of the materials required for the elaboration of fuel cells, these wonderful systems that release the energy contained in the H₂ molecule in the form of electrical power. Indeed, scarce and precious platinum is required as a catalyst at both electrodes of fuel cells. A solution may be found in nature with metalloenzymes involved in hydrogen metabolism, called hydrogenases. These natural catalysts can be used directly in biofuel cells or serve as an inspiration to chemists for the elaboration of bio-inspired electrocatalytic materials.