P507(K)-醇-正庚烷-水微乳液界面含醇量变化及对体系结构的影响

Ｐ５０７（Ｋ）－醇－正庚烷－水微乳液界面含醇量变化及对体系结构的影响沈兴海,高宏成（北京大学技术物理系,北京,１００８７１）关键词微乳液,２－乙基己基－２－乙基己基膦酸钾,饱和溶水量醇的性质与含量通过影响微乳液界面性质而影响其结构,而Ｗ／Ｏ型微乳液中...     

Formation of fractal porous silica by hydrolysis of TEOS in a bicontinuous microemulsion

Mesoporous silica particles have been prepared by hydrolysis of TEOS (Si(OC₂H₅)₄) in bicontinuous microemulsions containing polyoxyethylene (POE) dodecylether, isooctane and water. TEOS was dissolved in a continuous water phase and hydrolyzed by the dispersed water at around the phase inversion temperature (60°C). Undulating solid materials with layered mesostructures were produced from middle-phase microemulsions in the three phase region (o/w=0.2–0.7). On the other hand, the solids obtained from the lower aqueous phase in the three phase region were found to have a heterogeneous disordered structure. Measurements of the fractal dimensions were performed in the macropore region using a box-counting method for the outline of the SEM texture. We found that the macropore size distribution in the particles prepared from the middle-phase microemulsion follows the fractal rule with a dimension of 1.7. From the results of nitrogen adsorption/desorption curves on the silica, a steep increase in the adsorption amounts was observed at a relative pressure below 0.2, and adsorption/desorption hysteresis was also observed at a relative pressure between 0.3 and 0.5. These studies suggest that the silica synthesized in the bicontinuous microemulsion mesostructure has a very broad size range from micro to macropores with a fractal distribution.     

微乳液析相液-液萃取分光光度法测定铝

建立了TritonX100微乳液析相液液萃取法测定铝的新体系。在VTritonX100∶V正丁醇∶V正庚烷∶V水=2.7∶15∶1.5∶4微乳液介质中,铝水杨基荧光酮于72℃水浴中加热15min即被富集于微乳液层中。最大吸收波长为540nm,铝含量在0～0.5mg·L-1范围内符合比耳定律,表观摩尔吸收系数为4.3×105L·mol-1·cm-1。方法用于食品中铝的测定,结果满意。     

Bending: from thin interfaces to molecular films in microemulsions

Surfactant film rigidity is a ubiquitous general concept that is quantified into two different units. We show here how to convert the bending rigidity from reduced units of a virtual infinitely thin film (not made of molecules) into the chemical unit (kJ.mol⁻¹) of a realistic film of monomolecular thickness. In most cases, molecular lengths are not negligible versus curvature radius. Two bending constants for the elasticity of thin-shelled solids can be defined, as introduced by Gauss, whereas only one physical bending constant taking into account that the film cannot be torn has been introduced in the 1990s by Hyde and Ninham. The explicit conversion depends on the topology and is different in the quasi-planar approximation, as well as the ‘direct’ oil in water (o/w) or ‘reverse’ water in oil (w/o) case of spherical or cylindrical micelles. We show some examples for classical and nonclassical micelles and microemulsions of different compositions.     

Properties of fluoroelastomer/semicrystalline perfluoropolymer nano-blends

Properties of blends of semicrystalline perfluoropolymers in fluoroelastomers strongly depend on the size of the dispersed phase and are at the best when dispersed phase dimension is well below 0.1 μm, i.e. in the nano-scale region. This fine dispersion is obtained with an innovative mixing technology based on microemulsion polymerization. Further increase of properties can be obtained by generating chemical links between fluoroelastomer and semicrystalline fluoropolymer. Nano-blends combine the performing properties of fluoroelastomers with those of semicrystalline perfluoropolymers. For example, these nano-blends have at the same time the sealing and mechanical properties of fluoroelastomers and the exceptional thermal and chemical resistance, low permeability and low friction coefficient of semicrystalline perfluoropolymers. In addition, as dispersed phase size is below visible light wavelength, finished items made with these nano-blends are optically transparent even when they contain as much as 40 wt.% of semicrystalline perfluoropolymer.     

Quantitative analysis of sesquiterpenes and comparison of three Curcuma wenyujin herbal medicines by micro matrix solid phase dispersion coupled with MEEKC

A simple, efficient and environmental friendly method was proposed for determining five sesquiterpenoids of Curcuma wenyujin by MSPD extraction coupled with MEEKC separation. Molecular sieve was applied as a solid support for extraction of sesquiterpenoids for the first time. Various parameters affecting extraction and separation efficiency were investigated. The optimized conditions involved dispersing sample (200 mg) with 200 mg of TS‐1 for 150 s and using 1000 μL of methanol to elute five target analytes. Finally, they were well separated by using a running buffer containing 1.3% SDS, 5.0% 1‐butanol, 0.5% ethyl acetate and 10% acetonitrile in 10 mM borate buffer at pH 9.0. Consequently, the developed method was fully validated and successfully applied to determine the five sesquiterpenoids including curdine, curcumenol, germacrone, furanodiene and β‐elemene in Curcuma wenyujin origin's Chinese herbal medicines. Furthermore, hierarchical cluster analysis was performed based on the contents of target compounds for distinguishing steamed and non‐steamed drugs. The present study provided a promising method for fast investigation and discrimination of chemical difference in steam & non‐steamed Chinese medicines from Curcuma wenyujin origin.     

Polymerisation of styrene in microemulsion with catanionic surfactant mixtures

The use of aqueous catanionic surfactant mixtures in the oil-in-water (o/w) microemulsion polymerisation of styrene is reported. Catanionic surfactant mixtures of dodecyltrimethylammonium bromide 1 and sodium dodecylsulfate 3, or decanediyl-1,10-bis(dimethyldodecylammonium bromide) 2, a gemini surfactant, and the anionic surfactant 3 were used. Phase behaviour and polymerisation properties of the microemulsions were studied as a function of the total surfactant concentration and the cationic/anionic surfactant ratio. Single-phase o/w microemulsions were only formed if either the cationic or anionic surfactant were present in large excess. Upon -irradiation, polymer nanoparticles were obtained. Using dynamic light scattering, the particle radii were determined to be 10 to 20 nm, the size depending on the total surfactant concentration, the cationic/anionic surfactant ratio and the surfactant/styrene ratio. Size exclusion chromatography indicated molecular weights of polystyrene of between 3×10⁵ and 1.4×10⁶ Daltons. Catanionic 1/3 and 2/3 mixtures differ in their styrene solubilizations. In a 1- or 3-rich system, the solubilization efficiency can be improved by increasing the concentration of the oppositely charged minor surfactant component, while in a 2-rich system the addition of 3 only diminishes the efficiency. Possible reasons for the different behaviours are discussed.     

Comparison of microemulsion electrokinetic chromatography and solvent modified micellar electrokinetic chromatography on rapid separation of heroin, amphetamine and their basic impurities

Microemulsion electrokinetic chromatography (MEEKC) and solvent modified micellar electrokinetic chromatography (MEKC) were investigated with the goal of the rapid separation of complex heroin and amphetamine samples. The rapid simultaneous separation of 17 species of heroin, amphetamine and their basic impurities and adulterants was performed within about 10 min using MEEKC for the first time, whereas solvent modified MEKCs were unable to resolve all the components. The comparisons between MEEKC and solvent modified MEKC proved internal lipophilic organic phase in microemulsions played an important role in improving the separation performance with respect to efficiency. However, the role of internal lipophilic organic phase in MEEKC was disgusted at high concentrations of cosurfactant, and the separations of MEEKC and 1-butanol modified MEKC became similar at high concentrations of 1-butanol. The evaluation of reproducibility, linearity and detection limit of optimized MEEKC method provided good results for all the analytes investigated, thus allowing its application to real controlled drug preparation analysis.     

Chiral separations in microemulsion electrokinetic chromatography. Use of micelle polymers and microemulsion polymers

In this study, microemulsions of the chiral surfactant polysodium N-undecenoyl-D-valinate (poly-D-SUV) was utilized for enantiomeric separation by investigating two approaches using polymeric chiral surfactant in microemulsion electrokinetic chromatography (MEEKC). In the first approach, poly-D-SUV was used as an emulsifier surfactant along with 1-butanol and n-heptane. Enantioseparation of anionic or partially anionic binaphthyl derivatives, anionic barbiturates, and cationic paveroline derivatives were achieved by varying the mass fraction of 1-butanol, n-heptane and poly-D-SUV. For anionic or partially anionic analytes, relatively lower mass fractions of n-heptane, and poly-D-SUV were found to give optimum chiral separations as compared to that for cationic solutes. In the second approach, the chiral microemulsion polymer was prepared by polymerizing mixtures of 3.50% (w/w) of sodium N-undecenoyl-D-valinate (D-SUV) and 0.82% (w/w) of n-heptane (core phase) at varying concentration of 1-butanol. After polymerization, the n-heptane and 1-butanol were removed to yield solvent free microemulsion polymers (MPs) which were then utilized for the separation of anionic binaphthyl derivatives and anionic barbiturates. When MPs of D-SUV were utilized for chiral separation, 1.00% (w/w) 1-butanol and 3.50% (w/w) 1-butanol was optimum for enantioseparation of (+/-)-BNP and (+/-)-BOH, respectively. On the other hand, for anionic (+/-)-barbiturates very low concentration of butanol (0.25%, w/w) provided optimum resolution. Compared with micellar electrokinetic chromatography (MEKC), the use of micelle polymers or microemulsion polymers in MEEKC showed dramatic enhancement for resolution of (+/-)-BNP, while this enhancement was less dramatic for other binaphthyls [(+/-)-BOH, (+/-)-BNA] as well as for (+/-)-barbiturates and (+/-)-paveroline derivatives. However, higher separation efficiency of the enantiomers was always observed with MEEKC than in MEKC.     

Immobilization of trypsin on porous glycidyl methacrylate beads: effects of polymer hydrophilization

The immobilization of trypsin at porous glycidyl methacrylate (GMA-GDMA) beads was investigated. In particular, the effects of surface modification of the beads through hydrophilic polymers on the amount protein immobilized and on the extent of retained activity after immobilization were adressed. Furthermore, immobilization at unmodified and hydrophilized beads from aqueous solution was compared to that from a water-in-oil microemulsion. It was found that the amount trypsin immobilized at the unmodified GMA-GDMA beads was significantly higher than that at hydrophilized GMA-GDMA beads. However, also the extent of specific activity loss after immobilization was larger for the unmodified than for the hydrophilized beads. Despite the latter, however, the total activity displayed by the hydrophilized beads was comparable to the unmodified beads at best. On the other hand, by peforming the immobilization from the microemulsion a high immobilization yield can be reached even for the hydrophilized beads, which also results in a higher degree of retained activity in the latter case than obtained for immobilization at the unmodified beads. Using this approach therefore resulted in the highest total activity of the trypsin-activated GMA-GDMA beads.