核苷与碱基的苯胺甲基键合硅胶固定相高效液相色谱分离

建立苯胺甲基键合硅胶固定相(PAMS)高效液相色谱分离核苷与碱基的方法；研究流动相有机溶剂浓度、磷酸缓冲液pH值、离子强度对核苷和碱基在该键合固定相上的色谱保留及分离选择性的影响，用磷酸缓冲液(pH＝4)为流动相快速分离了部分核苷与碱基。     

Modification of silica surfaces for CZE by adsorption of non-ionic hydrophilic polymers or use of radial electric fields

Polyvinylalcohols (PVA) and hydroxyethylcelluloses (HEC) have been used as additives in cyclodextrin-modified capillary zone electrophoretic chiral separations of aromatic amines such as tocainide and its analogs in unpretreated 50 μm i.d. fused silica capillaries. The additives were used at low concentrations (<0.05%) in common buffers, together with the γ-cyclodextrin as chiral selector. They reduce the electroosmotic flow, i.e. increase the migration times of the analytes in these chiral separations, and, moreover, considerably improve both peak symmetry and the widths of the peaks relative to migration time. In terms of the chromatographic theory of efficiency, more than 200000 theoretical plates can be achieved with unpretreated fused silica capillaries. This enhancement of efficiency arises because adsorptive “dynamic” coating with the hydroxylic modifier molecules suppresses adsorption of the analyte molecules by the capillary walls. The influence of field strength and buffer composition on the separation efficiency attainable with and without modifier in the buffers has also been investigated. Alternative experiments on the influence of analyte adsorption on efficiency have been performed by superimposing radial electric fields on the capillary to modify the ζ potentials. Although the EOF could be freely adjusted, it was not possible to obtain an improvement in efficiency comparable with that furnished by coating the adsorptive surface with PVA or HEC.     

固体酸催化剂SO4^2-／SiO2-TiO2的制备及其催化酯化性能

分别以机械混合法和浸渍法制备了SO42-/SiO2-TiO2固体酸催化剂,以乙醇和乙酸的酯化反应为模型反应考察了不同SiO2含量及不同温度焙烧的催化剂的活性.结果表明,机械混合法制备的400℃焙烧的SO42-/40%SiO2-TiO2催化剂活性最高,部分回流时,乙酸几乎全部转化,全回流反应100min时,其乙酸转化率达到84%.X射线衍射分析表明,SiO2抑制了硫酸氧钛的形成;催化剂的活性组分包括一定量的四方晶锐钛矿型TiO2、正交晶硫酸氧钛、少量立方晶金属钛和高比表面积的SiO2.红外光谱分析表明,添加SiO2后催化剂形成Ti-O-Si键,进而使SO42-与样品表面产生强相互作用;结合的SO42-主要以无机螯合状双配位和有机硫酸酯两种结构形式存在.热重-示差扫描量热分析表明,SiO2的添加使SO42-不易脱除,同时使锐钛矿TiO2向金红石相的转变温度降低.     

表面氧浓度对负载型金属催化剂活化甲烷反应性能的影响

 利用脉冲－质谱在线分析技术考察了无气相氧条件下负载型金属催化剂上脉冲CH4的反应结果表明，对于Rh／SiO2催化剂，不管是氧化态还是还原态，除第1次脉冲生成较多的CO2外，从第2次脉冲开始，只有CO生成；对于Ru／SiO2催化剂，无论是氧化态还是还原态，每次脉冲均有一定量的CO2生成．这可能是由于Rh和Ru两种金属对氧的亲合力不同所致．甲烷在负载型催化剂表面的活化以及产物的选择性主要受催化剂表面活性氧物种覆盖度的影响．     

Synthesis of Nano Silica Particles for Polishing Prepared by Sol–Gel Method

In order to produce an excellent abrasive, a fabrication method for cocoon shaped silica particles has been studied. The particles are prepared from TMOS, water, ammonia and methanol by a sol–gel method. The method is to add the methanol solution of TMOS at a constant supply rate to a mixture of water, ammonia and methanol. Effects of various reaction conditions such as temperatures, supply rates of TMOS, and amounts of TMOS are studied on the diameter and shape of the particles. The diameter and shape are resulted in depending strongly on temperatures. High temperature makes particles with the high aspect ratio and the small diameter. And the mechanism of forming the cocoon shaped particle is also discussed. It is concluded that the primary particles are generated at the beginning stage of reaction and two of them become the cocoon shaped particle. For the polishing efficiency, particles have high polishing efficiency with the diameter between 40 nm and 210 nm. As a result, best diameter of particles for abrasive is 40–100 nm with respect to polishing efficiency and surface finish.     

Structural Models of Dense Gels

The structural models of gels typically reported concentrate either on the solid space or the pore space of the system. The models described in this paper present a connection between grain and pore spaces, applicable to dense gels with uniform particulate microstructure. The gel structure is depicted as a hierarchy at several levels by means of models built up using the Monte-Carlo technique, on the basis of random close packing (RCP) premises. The pore volume distributions are calculated from the largest sphere radius inscribed within the interstices. These distributions are compared to the pore volume distributions of various RCP classic models and to the pore volume distributions of a series of xerogels measured by means of the Brunauer-Emmett-Teller method. Data on the pore volumes associated with different hierarchical levels (e.g., micro-, meso-, or macropores), the local density of the i-th aggregation level and packing of the successive levels are obtained.     

Ceramic Micro-Particles Synthesised using Emulsion and Sol–Gel Technology: An Investigation into the Controlled Release of Encapsulants and the Tailoring of Micro-Particle Size

Controlled release technologies have many applications in such diverse fields as the pharmaceutical, agricultural, cosmetic and food industries, where tailored release rates and protection of the active molecule for delivery at a specific site or time are advantageous. Silica microspheres, with controlled diameters of 10–50 m and containing Orange II dye as a model encapsulant, have been synthesised by combining water-in-oil (w/o) emulsion technology with sol–gel chemistry. The average particle size may be controlled by the microemulsion parameters, including the surfactant and solvent concentrations, and by the sol–gel processing parameters, particularly water-to-silicon alkoxide ratio, pH, temperature, ageing and mixing conditions. Physical properties of the SiO₂ microspheres, which modulate the release rates of the encapsulated molecule (including pore size and tortuosity), are also controlled by the sol–gel process parameters.The effect of synthesis parameters, including surfactant concentration, sol–gel solution pH and drying temperature, on the morphology of the SiO₂ microspheres produced will be discussed. The effect of such parameters on the corresponding release rates of the model encapsulants will also be presented.     

劣化变压器油中硅胶吸附物的分离分析

利用红外光谱法、气相色谱法（GC）和色－质联用（GC-MS)技术分析测定了投运一年后的劣质变压器油中硅胶吸附物的呈色成分，分析了硅胶吸附变色的原因。     

纳米SiO_2粒子锚固偶氮引发剂及接枝聚甲基丙烯酸甲酯

对纳米SiO2 粒子锚固偶氮引发剂 ,进而引发甲基丙烯酸甲酯聚合而制备聚甲基丙烯酸甲酯(PMMA) 纳米SiO2 复合粒子进行了研究 .纳米SiO2 先用环氧型硅烷偶联剂处理 ,再与偶氮二氰基戊酸发生缩合反应而锚固上偶氮引发剂 ,通过差示扫描量热和元素分析证明了引发剂在纳米SiO2 表面的锚固 .通过改性纳米SiO2 存在下MMA的乳液聚合 ,制备得到了接枝率为 2 3 2 %、接枝效率为 36 1%的PMMA 纳米SiO2 复合粒子 .经乳液聚合后 ,纳米SiO2 粒子团聚程度减小 ,在水相中分散稳定 .     

Separation and determination of neuraminic acids in nanogram quantities by liquid chromatography — A comparative study with different amino phases

Summary Neuraminic acid derivatives were separated easily by liquid chromatography on amino phases and using acetonitrile/15 mM phosphate buffer, pH 5.2 as mobile phase. Detection at 200 nm allowed determination of substances in the nanomole range. All solvent systems were used isocratically at room temperature. The separation did not depend on ion-exchange but on a partition mechanism, the solutes being separated according to their polarity. Thus, it was possible to optimize the resolution by varying the stationary phase and the composition of the eluent.Part of this work has been presented at the 15th International Symposium on Chromatography, Nürnberg, October 1–5, 1984.