Characterization of silicone oil emulsions stabilized by TiO2 suspensions pre-adsorbed SDS

To study the effects of pre-adsorbed emulsifier on Pickering emulsion stability, the preparation of silicone oil emulsions by TiO₂ suspensions pre-adsorbed sodium dodecyl sulfate (SDS) at the fixed TiO₂ concentration of 0.15 g was carried out below a fiftieth of critical micelle concentration (cmc) of SDS, where all added amounts of SDS are adsorbed on the TiO₂ particles. The stability of the Pickering emulsions incorporating TiO₂ suspensions pre-adsorbed SDS was investigated by measuring the volume fraction of emulsified silicone oil, adsorbed amounts of TiO₂ suspensions pre-adsorbed SDS, oil droplet size, and some rheological responses such as the stress-strain sweep curve and strain and frequency dependences of dynamic viscoelastic moduli. The silicone oil was almost emulsified by TiO₂ suspensions pre-adsorbed SDS above cmc/10³. Increasing in the adsorbed amount of SDS on the TiO₂ particles leads to an increase in the adsorbed amounts of TiO₂ suspensions pre-adsorbed SDS. Such silicone oil emulsions for the first time showed two yield stresses in the stress-strain sweep curve as well as the oscillatory stress-strain curve. The respective yield stresses also increase with an increase in the adsorbed amounts of TiO₂ suspensions pre-adsorbed SDS. From such characteristic rheological properties and a partial sedimentation of some TiO₂ particles remained in the dispersion medium, we proposed the formation of a three dimensional network of the flocculated TiO₂ particles pre-adsorbed SDS on the silicone oil droplets.     

High throughput screening of active pharmaceutical ingredients by UPLC

Ultra performance LC (UPLC) was evaluated as an efficient screening approach to facilitate method development for drug candidates. Three stationary phases were screened: C-18, phenyl, and Shield RP 18 with column dimensions of 150 mm x 2.1 mm, 1.7 microm, which should theoretically generate 35,000 plates or 175% of the typical column plate count of a conventional 250 mm x 4.6 mm, 5 microm particle column. Thirteen different active pharmaceutical ingredients (APIs) were screened using this column set with a standardized mobile-phase gradient. The UPLC method selectivity results were compared to those obtained for these compounds via methods developed through laborious trial and error screening experiments using numerous conventional HPLC mobile and stationary phases. Peak capacity was compared for columns packed with 5 microm particles and columns packed with 1.7 microm particles. The impurities screened by UPLC were confirmed by LC/MS. The results demonstrate that simple, high efficiency UPLC gradients are a feasible and productive alternative to more conventional multiparametric chromatographic screening approaches for many compounds in the early stages of drug development.     

超细均分散稀土化合物胶体粒子制备

利用尿素分解法制得轻、中、重稀土化合物的超细均分散胶体粒子,详细探讨了浓度、pH值、陈化温度、陈化时间及共存阴离子等因素对制备过程的影响,获得了各种粒子的最佳制备条件.     

剖析液相色谱柱技术的复杂状况(英文)

 Column packings continue to evolve as the needs of users for high efficiency, high resolution and highly sensitive high performance liquid chromatographic (HPLC) analysis drive further developments. In comparing and contrasting modern HPLC columns technologies, diameters of column packings and particle materials are covered. Some products and applications of modern HPLC columns are provided. Future directions in packing developments are predicted in this introductory article.     

Core–shell morphology as a model for the study of gas permeation in composite systems

Structured latex particles prepared by emulsion polymerization were used as a model to simulate the interphase region between two phases. Multiphase polymer films comprised of high and low permeability polymers of various compositions were used. The model system consisted of a poly(n-butyl methacrylate) (PBMA) matrix and a discontinuous phase with core and shell morphology. The structured particle had a PBMA core and a vinylidene chloride – n-butyl methacrylate (VDC–BMA) copolymer shell. The shell transport characteristics wer altered by changing the (VDC–BMA) copolymer molar ratio. The physical and transport properties for each individual component were measured. Nitrogen was the probe gas. Films used for permeation experiments were prepared by latex casting. The results showed that the morphology of a heterogeneous polymeric system and the transport characteristics of their components had a considerable effect on the magnitude of the transport properties. Experimental data also showed the dependence of the gas global permeability coefficient on the nature of the simulated interphase region, the shell, and the weight percentage of such interphase in the heterogeneous polymeric films. Upon increasing the VDC content in the VDC–BMA copolymer, the gas permeability decreased. The data were fitted to the electrical analogs of conductivity in composite systems. For the matrix filled with structured particles the overall permeability coefficient could best be described when the individual permeabilities were considered as the inverse resistances in parallel.     

Preparation of micron-size monodisperse polymer particles by dispersion copolymerization of styrene with poly(2-oxazoline) macromonomer

This article describes the preparation of micron-size monodisperse polymer particles by dispersion copolymerization of styrene with a poly(2-oxazoline) macromonomer in an aqueous ethanol solution. The macromonomer acted as a comonomer as well as a stabilizer. The diameter of the particles increased as the concentration of the macromonomer decreased. The higher the molecular weight of the macromonomer, the smaller the particle size. The copolymerization in the solvent containing higher water content gave smaller polymer particles. Under the condition giving the monodisperse particles, the particles volume increased linearly with the yield of the particles. From ESCA analysis of the particle surface, poly(2-oxazoline) chains were enriched on the surface. © 1993 John Wiley & Sons, Inc.     

Kinetic investigation of the relationship between the efficiency of columns and their diameter

Many brands of packing materials made of fine particles are now available in both conventional (4.6 mm i.d.) and narrow-bore (2.1 mm i.d.) columns. It is a general observation that the efficiency of the former tends to be markedly higher than that of the latter. This report provides a detailed illustration of the characteristics of this enigma. The corrected reduced plate heights of three brands of columns packed with shell particles in 4.6 and 2.1 mm I.D. columns were measured. The brands were the 1.7 and 2.6 μm Kinetex-C(18) (Phenomenex, Torrance, CA, USA), the 2.7 μm Poroshell120-C(18) (Agilent Technologies, New Castle, DE, USA), and the 2.7 μm Halo-C(18) (Advanced Material Technologies, Wilmington, DE, USA). The extra-column contributions were minimized by optimizing the configuration of the instrument (injection volume <1.0 μL, 115 μm needle seat capillary, 80 μm connecting tubes, no heat exchanger, 0.8 μL detection cell). The correct peak variances were derived from the numerical integration of the first and second order moments of the experimental band profiles. These experimental results confirm that the kinetic performance of narrow-bore columns is inferior to that of conventional columns for all three brands of shell particles. We demonstrate that this difference is accounted for by a contribution to the column HETP of the long-range eddy diffusion term that is larger in the 2.1 than in the 4.6 mm I.D. columns. While the associated relative velocity biases are of comparable magnitude in both types of columns, the characteristic radial diffusion lengths are of the order of 100 and 40 μm in the wall regions of narrow-bore and conventional columns, respectively.     

亲/疏水不对称空心聚合物微球制备及磁性粒子装载研究

首先将(马来酸酐-醋酸乙烯酯共聚物)核/(马来酸酐-二乙烯基苯共聚物)壳微球的壳层外表面酐基烷基溴化,然后将核溶蚀、壳层内表面酐基水解,制得内表面含亲水羧基、外表面含烷基溴、具有微孔(Barrett-Joyner-Halenda平均孔径14.9nm)的空心聚合物微球.以此空心微球为微反应器,使Fe2+和Fe3+通过球壁...     

纳米膜组装介孔Al2O3：合成及Pt/Al2O3的硝基苯催化加氢性能

以"乙酸乙酯(EA)-偏铝酸钠-水"体系在室温下合成了纳米膜组装介孔Al2O3。研究发现:合成反应时间、静置前搅拌时间、NaAlO2用量、EA用量及反应温度等对合成产物的形貌有影响;另外,与用商品γ-Al2O3制备的Pt/γ-Al2O3催化剂相比,纳米膜组装介孔Al2O3制备的Pt/Al2O3催化剂含有部分易被还原的PtOx物种。在硝基苯催化加氢反应中,用合成Al2O3为载体制备的Pt/Al2O3催化剂,比用商品γ-Al2O3制备的Pt/γ-Al2O3催化剂具有更好的催化活性。     

含[AMIM]BF4的聚甲基丙烯酸甲酯基凝胶聚合物电解质的制备与改性

用两步法合成了离子液体1-烯丙基-3-甲基咪唑四氟硼酸盐（[AMIM]BF4）,将聚甲基丙烯酸甲酯(PMMA)引入离子液体[AMIM]BF4中,制备出含离子液体[AMIM]BF4的新型凝胶聚合物电解质,采用非质子溶剂、纳米SiO2等对其进行了改性。 用FT-IR、交流阻抗（AC）、TG、SEM等测试技术对其结构和性能进行了表征。 结果表明,非质子溶剂碳酸丙烯酯、碳酸二甲酯和纳米SiO2的加入使聚合物电解质的室温离子电导率增大,达5.25×10-3 S/cm;电导率与温度的关系符合Arrhenius方程;几种凝胶聚合物电解质的热分解温度均高于300 ℃,显示出良好的热稳定性。