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1.
The simulation of the countercurrent liquid-liquid distribution by using a microcomputer is described. The computer program that is proposed for this simulation has been made in BASIC language and its characteristics are discussed. According to the wide possibility of calculation that this program presents, several simulations of different solute mixtures have been performed. 相似文献
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F. Iskanderani K. M. Sobhi M. Ejaz 《Journal of Radioanalytical and Nuclear Chemistry》1989,132(1):159-169
Normal heptane, xylene, and a 0.01 molar solution of 4-(5-nonyl)pyridine in toluene have been investigated as extractants for selenium(IV) from nitric acid media in potassium iodide. Various parameters affecting the distribution of the element are investigated. Extraction at high aqueous to organic phase volume ratio has been studied, using a liquid-liquid extraction plant with a pulsation column. The results have been employed to measure selenium in spiked water samples. 相似文献
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Masashi Haruki Kunio NakanishiShigemitsu Mano Shin-ichi KiharaShigeki Takishima 《Fluid Phase Equilibria》2011,305(2):152-160
The phase behaviors of the hexane + polydispersed polyethylene (PE) systems were measured to clarify the effect of the molecular weight distribution (MWD) of PE on liquid-liquid (LL) phase boundaries. The weight fraction for the PE portion of a maximum LL phase separation pressure in the LL phase boundary decreased as the polydispersity of PE increased. Moreover, depression of the phase separation pressure from the maximum phase separation pressure on the higher PE weight fraction side was more drastic as the polydispersity of the PE increased. The LL phase boundaries were correlated using the Sanchez-Lacombe equation of state (S-L EOS). For the correlations, the polydispersed PEs were regarded as mixtures of 16 types of monodispersed PEs with different molecular weights, and the characteristic parameters of the S-L EOS, P*, ρ* and T*, were assigned the same values for all monodispersed PEs even though the molecular weights differed. However, the interaction parameters of the hexane-PE pairs depended on the molecular weight of the PE and the temperature. The correlated results capably reproduced the effect of the MWD of the PE on the LL phase boundaries for the hexane + polydispersed PE systems. 相似文献
5.
Liquid-vapor and liquid-liquid phase equilibria of the polarizable Brodholt-Sampoli-Vallauri water model have been investigated by Gibbs ensemble Monte Carlo computer simulations. The coexisting liquid and vapor densities and energy of vaporization of the model is found to be in a reasonable agreement with experimental data in the entire temperature range of liquid-vapor coexistence. The critical temperature and density of the model are found to be 615 K and 0.278 gcm(3), respectively, close to the experimental values of 647.1 K and 0.322 gcm(3). In the supercooled state two distinct liquid-liquid coexistence regions are observed. The existence of liquid-liquid phase separation of a polarizable water model is demonstrated for the first time. 相似文献
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We report on an observation of the phase transition between two liquid phases of supercooled confined water in simulations. The temperature of the liquid-liquid transition of water at zero pressure slightly decreases due to confinement in the hydrophobic pore. The hydrophilic confinement affects this temperature in the opposite direction and shifts the critical point of the liquid-liquid transition to a higher pressure. As a result, in a strongly hydrophilic pore the liquid-liquid phase transition becomes continuous at zero pressure, indicating the shift of its critical point from negative to a positive pressure. These findings indicate that experimental studies of water confined in the pores of various hydrophobicity/hydrophilicity may clarify the location of the liquid-liquid critical point of bulk water. 相似文献
8.
We have shown from in situ synchrotron x-ray diffraction measurements that there are two thermodynamically stable liquid forms of SnI(4), depending on the pressure. Based on the liquid-liquid critical point scenario, our recent measurements suggest that the second critical point, if it exists, may be located in a region close to the point at which the melting curve of the crystalline phase abruptly breaks. This region is, unlike that of water, experimentally accessible with relative ease. 相似文献
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The phase behavior and microstructure of aqueous mixtures of n-octyl-beta-D-glucoside (C8betaG1) and triethylene glycol mono-n-octyl ether (C8E3) is presented. C8betaG1 forms a one-phase micellar solution in water at surfactant concentrations up to 60 wt %, whereas mixtures with C8E3 show a liquid-liquid phase transition at low surfactant concentration. The position of this phase boundary for mixtures can be rationally shifted in the temperature-composition window by altering the ratio of the two surfactants. Small-angle neutron scattering is used to determine the size and shape of the mixed micelles and to characterize the nature of the fluctuations near the cloud point of the micellar solutions. The C8betaG1/C8E3 solutions are characterized by concentration fluctuations that become progressively stronger upon approach to the liquid-liquid phase boundary, whereas micellar growth is negligible. Such observations confirm previous views of the role of the surfactant phase boundary in tuning attractive micellar interactions, which can be used effectively to change the nature and strength of interparticle interactions in colloidal dispersions. Colloidal silica particles were then added to these surfactant mixtures and were found to aggregate at conditions near the cloud point. This finding is relevant to current strategies for protein crystallization. 相似文献
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Sentaro Okamoto Kouichi Takano Tomohiro Ishikawa Satoshi Ishigami Akiko Tsuhako 《Tetrahedron letters》2006,47(46):8055-8058
The structure-activity relationship and behavior of N,N′-dialkylimidazolium salts as a phase transfer and/or ion-exchange catalyst in a liquid-liquid phase system were investigated for the reactions such as β-elimination reaction of alkyl halides, nucleophilic epoxidation of α,β-unsaturated carbonyl compounds, alkylation of active methylenes, and nucleophilic substitution reaction. 相似文献
11.
The interplay between liquid-liquid phase separation (LLPS) and crystallization at several compositions in statistical copolymer blends of poly(ethyleneco-hexene) and poly(ethylene-cobutene) has been examined by optical microscopy (OM), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). The phase contrast optical microscopy shows interconnected bicontinuous structures for deeply quenched LLPS, characteristic of spinodal decomposition. After a second quench to a temperature below the melting point, an overwhelming change in crystallization kinetics has been clearly observed, which is caused by the increase of the nucleation rate assisted by concentration fluctuations due to the spontaneous spinodal LLPS. We propose a new mechanism of "fluctuation assisted nucleation" in the crystallization process for such interactive process in a blend system. The experimental results from OM, AFM, and DSC measurements at various conditions are all consistent with the fluctuation assisted nucleation model. 相似文献
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Stablen-hexadecane/water andn-tetradecane/water macroemulsions containing monolayers of natural (egg yolk lecithin, EY) and synthetic (dimyristoylphosphatidylcholine,
DMPC) phospholipids at liquid-liquid interfaces were prepared. The existence of the monolayers was proved by studying the
reduction kinetics of a surface-active spin probe with ascorbate anions. Spin labeled derivatives of stearic acid in which
the nitroxide group is locared at different distances from the polar head (5-, 12-, and 16-doxylstearic acids) were used to
study the temperature dependences of the molecular ordering, rotational mobility, and local polarity in the monolayers in
emulsions and also in bilayers in liposomes obtained from the same lipids. In the EY monolayers, the degree of spin probe
solubilization is higher, while the order parameters (S) and rotational correlation times (τ) are lower than those in EY bilayers. The differences between these parameters for mono-
and bilayers increase with an increase in the distance of the reporter group from the aqueous phase. In the DMPC monolayers,
a first-order phase transition was detected by measuring the temperature dependences ofS and τ. The temperature region of the phase transition in monolayers is shifted to lower temperatures with respect to that
for bilayers and depends on the nature of the oil phase. It was concluded that the phospholipid monolayers in emulsions incorporate
hydrocarbon molecules, whose concentration in the DMPC monolayers increases on going from the low-temperature (gel) to the
high-temperature (liquid crystal) phase.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 418–425, March, 1998. 相似文献
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We report a Car-Parrinello molecular dynamics study of the liquid-liquid phase transition in phosphorus. We employed a gradient corrected density functional (B-LYP) to describe the electronic structure and performed simulations at constant pressure. Upon increasing pressure we observed, along the 1500 K isotherm, a structural transition converting the molecular P4 liquid into an atomic liquid with a network structure. Our calculations suggest this transition to be first order with a discontinuous density increase accompanied by an insulator into metal transition. The transition pressure is significantly higher than obtained by employing the less accurate local density functional (LDA) [Morishita, Phys. Rev. Lett. 87, 105701 (2001)], which matches the experimental value for the pressure. We argue why the LDA result should be considered fortuitous. The change of the calculated structure factor upon the transition shows the same trend as experimentally observed. Analysis of the structural changes during the phase transition revealed that a chain of linked and opened up ("butterfly") P4 molecules may serve as a seed triggering the transition from the molecular to the network phase. 相似文献
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Hélio Salvio Neto Fábio Alessandro Proença Barros Flávio Machado de Sousa Carvalho Jivaldo Rosário Matos 《Journal of Thermal Analysis and Calorimetry》2010,102(1):277-283
In the present work, the thermal behavior of prednicarbate was studied using DSC and TG/DTG. The solid product remaining at
the first decomposition step of the drug was isolated by TG, in air and N2 atmospheres and was characterized using LC-MS/MS, NMR, and IR spectroscopy. It was found that the product at the first thermal
decomposition step of prednicarbate corresponds to the elimination of the carbonate group bonding to C17, and a consequent formation of double bond between C17 and C16. Structure elucidation of this degradation product by spectral data has been discussed in detail. 相似文献
15.
Quantitation of verapamil and norverapamil in postmortem and clinical samples using liquid-liquid extraction, solid phase extraction, and HPLC 总被引:1,自引:0,他引:1
Summary A sensitive micellar electrokinetic chromatography method for the determination of impurities in SB-209247, a novel LTB4 antagonist, has been developed. Selectivity was optimised by systematic examination of the effects of the acetonitrile content
in the separation buffer. Sensitivity and resolution was enhanced by focusing effects for both charged and neutral analytes
achieved by a special sample buffer composition. Minor impurities well below 0.1% peak area ratio can be readily and reliably
detected. The validity of the method has been successfully demonstrated with respect to reproducibility of peak area ratios
and the linearity of a key impurity. A comparison with HPLC has shown the method has complementary selectivity and competitive
sensitivity. 相似文献
16.
分散液液微萃取-反相液液微萃取-扫集-胶束电动色谱法测定红酒中的3种氯酚类物质 总被引:2,自引:0,他引:2
建立了分散液液微萃取(DLLME)-反相液液微萃取(RP-LLME)-扫集-胶束电动色谱富集模型,并用于红酒中五氯酚(PCP)、2,4,6-三氯酚(TCP)和2,4-二氯酚(DCP)3种氯酚的测定。实验考察了两步微萃取的萃取参数对氯酚萃取率的影响和样品分离富集的电泳条件。最佳萃取条件DLLME为:3.5 mL红酒(pH 3.0,120 g/L NaCl),300 μL正己烷(萃取剂);RP-LLME为:25 μL 0.16 mol/L NaOH(萃取剂)。最佳电泳条件:25 mmol/L NaH2PO4,100 mmol/L十二烷基硫酸钠(SDS),30%(v/v)乙腈,pH 2.3;分离电压-15 kV;样品基质为80 mmol/L NaH2PO4;压力进样20 s×20.67 kPa(3 psi)。PCP和TCP的线性范围为0.5~100 μg/L(r≥0.9910),DCP的线性范围为1.5~80 μg/L(r=0.9851)。3种分析物的检出限(S/N=3)为0.035~0.114 μg/L,加标回收率为75.2%~104.7%,相对标准偏差≤6.17%。该方法富集倍数高、灵敏度高、重现性好、分析速度快,可为不同样品基质中痕量氯酚污染物及某些弱酸性有机污染物测定提供参考。 相似文献
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A force field model of phosphorus has been developed based on density functional (DF) computations and experimental results, covering low energy forms of local tetrahedral symmetry and more compact (simple cubic) structures that arise with increasing pressure. Rules tailored to DF data for the addition, deletion, and exchange of covalent bonds allow the system to adapt the bonding configuration to the thermodynamic state. Monte Carlo simulations in the N-P-T ensemble show that the molecular (P(4)) liquid phase, stable at low pressure P and relatively low temperature T, transforms to a polymeric (gel) state on increasing either P or T. These phase changes are observed in recent experiments at similar thermodynamic conditions, as shown by the close agreement of computed and measured structure factors in the molecular and polymer phases. The polymeric phase obtained by increasing pressure has a dominant simple cubic character, while the polymer obtained by raising T at moderate pressure is tetrahedral. Comparison with DF results suggests that the latter is a semiconductor, while the cubic form is metallic. The simulations show that the T-induced polymerization is due to the entropy of the configuration of covalent bonds, as in the polymerization transition in sulfur. The transition observed with increasing P is the continuation at high T of the black P to arsenic (A17) structure observed in the solid state, and also corresponds to a semiconductor to metal transition. 相似文献
18.
F Priego-Capote 《Analytica chimica acta》2003,489(2):223-232
An automated flow injection (FI) manifold based on iterative change of the flow direction has been designed to carry out continuous liquid-liquid extraction without phase separation and hydrolysis both with ultrasound-assistance. The dynamic approach has been applied to suppositories from which paracetamol has been extracted in this way into an aqueous phase and hydrolysed prior to reaction with o-cresol in the alkaline medium used as extractant. The three linked reactions, extraction-hydrolysis-derivatisation, cause displacement of the balance to completeness. The strategic location of the photometric flow-cell in the flow-injection manifold enables monitoring of the overall process and the obtaining of a characteristic multipeak recording. The influence of ultrasounds on the different steps was investigated. The indophenol blue dye formed was monitored at 620 nm. The limits of detection (LOD) and quantification (LOQ) of the method are 0.38 and 0.64 μg ml−1, respectively, with a linear range from 0.64 to 50 μg ml−1; a within-laboratory reproducibility between 2.07 and 4.66% and repeatability from 2.01 to 4.63%, both expressed as relative standard deviation. The results obtained with the proposed method are in excellent agreement with those provided by the official method, but with a shorter analysis time, lower sample and reagent consumption and less analyst involvement. 相似文献
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Soulin Lin Qin Shuai Haiou Qiu Zhiyong Tang 《Spectrochimica Acta Part B: Atomic Spectroscopy》1996,51(14):1769-1775
A new versatile phase separator for flow injection solvent extraction has been designed and its analytical performance investigated. Manifolds for various instrumentation and the corresponding operating procedures have been established. Experimental results show that the newly designed phase separator possesses several advantages over the existing ones, such as long term stability, robustness, sufficient phase separation and integral in situ collection of the solvent extracts at different phase flow rate ratios. The detection limits for cobalt, gold, iodide, iron, lead, nickel, nitrate and tungsten were 1.4, 0.45, 70, 1.9, 160, 0.9, 137 and 23 ng ml−1, and the relative standard deviations 2.5, 1.3, 2.2, 2.9, 4.8, 3.6, 1.4 and 3.3%, respectively. 相似文献
20.
Preparation of DNA-loaded polysulfone microspheres by liquid-liquid phase separation and its functional utilization 总被引:1,自引:0,他引:1
DNA-loaded polysulfone (PSf) microspheres were fabricated by means of a liquid-liquid phase separation technique. The porous microspheres were then used to remove DNA-binding intercalating materials--ethidium bromide, acridine orange, and endocrine disruptors. The DNA-loaded PSf microspheres are stable in water. The stability of the DNA-loaded microspheres and/or the release rate of DNA from the microspheres can be controlled by manipulating the microsphere structure. Increasing the polymer concentration, which causes lower porosity and smaller pores on the outer surface of the microspheres, led to increased stability of the microspheres and decreased release rate of DNA. Additionally, the drying temperature also affected the stability of the microspheres. The DNA-loaded PSf microspheres could effectively accumulate harmful DNA-intercalating pollutants and endocrine disruptors, such as ethidium bromide, acridine orange, biphenyl, dibenzofuran, and dibenzo-p-dioxin. The amount of pollutants removed by the microspheres is dependent on the amount of incorporated DNA and on the microsphere structure. The DNA-loaded microspheres have the potential to be used in environmental applications. 相似文献