乙二醇在铂电极上吸附和氧化过程的现场FTIR反射光谱研究(Ⅰ)──酸性介质

运用循环伏安法和现场FTIR反射光谱研究了酸性介质中乙二醇在铂电极上的吸附和氧化行为,指出乙二醇电催化氧化是通过解离吸附产物和反应中间体双途径机理进行的。经FTIR反射光谱检测,解离吸附产物为CO,反应中间体主要有CH₂OH─COOH和HOOC─COOH等。本文还在分子水平上解释了铂电极上乙二醇吸附和氧化循环伏安特征的内在原因。     

A quick and green ionic liquid-mediated approach for the synthesis of high-performance, organosoluble and thermally stable polyimides

Three diamine monomers with different derivatives of imidazole heterocyclic ring and meta-linked aryl ethers were synthesized and used in polycodensation reaction with various commercial dianhydrides for preparation of a series of novel poly(ether-imide) (PEI)s. The polycodensation reactions were carried out by using conventional method and in a green medium of ionic liquid (IL) without using NMP-pyridine-acetic anhydride. The PEIs were obtained in good yields (80% 96%) with moderate viscosity (0.48 0.66 dL/g) in a shorter reaction time (10 h) in IL as compared with the conventional method (36 h). All of the polymers were amorphous in nature, showed excellent solubility in amide-type polar aprotic solvents with ability to form tough and flexible films, and excellent thermal stability with Tgs in the range of 212 340 ℃ and 10% weight loss temperature (T10) up to 570℃ in N 2 and 528 ℃ in air.     

Direct determination of residual Pluronic F-68 in in-process samples from monoclonal antibody preparations by high performance liquid chromatography

A simple and sensitive high performance liquid chromatography (HPLC) method was developed to determine residual Pluronic F-68 (PF-68) in in-process samples of monoclonal antibody (MAb) preparations. The method permits the direct injection of proteinaceous samples after simple sample dilution and is able to quantitate as low as 50 mg/L of PF-68 in the presence of up to approximately 30 g/L of protein. The PF-68 molecule was separated on a restricted access reversed phase column using a step gradient and then measured by an evaporative light scattering detector (ELSD). The method was successfully applied to demonstrate PF-68 clearance in MAb purification processes. A modified colorimetric method using liquid-liquid extraction and cobalt thiocyanate to derivatize PF-68 is also described. The results obtained by both the HPLC and colorimetric methods were compared. In addition to its ease of use and simplicity, the HPLC method had better accuracy and higher throughput than the colorimetric method.     

Studies on the Thermodenaturation Behavior of Bacillus subtilis α‐Amylase on Chromatographic Media

The thermodenaturation behavior of Bacillus subtilis α‐amylase on some chromatographic media was studied by determining their adsorption parameters with frontal analysis. The experimental results show that on a RP‐C₁₈ reversed‐phase medium, a Chelating Sepharose Fast‐Flow chelated by Zn²⁺ affinity medium and a WCX‐1 cation‐exchange medium, a stable conformation of α‐amylase molecule separately exists below or over 30 °C; while on a PEG‐400 hydrophobic medium and a modified PEG‐400 medium, a stable conformation of α‐amylase molecule separately exists below 40 and 30 °C, and when the experimental temperatures are separately over 40 and 30 °C, a drastically conformational change of α‐amylase molecules can continuously take place. And by combining the intrinsic fluorescence emission spectrum and thermal inactivation profile of α‐amylase in free solution and on the PEG‐400 and modified PEG‐400 hydrophobic media, it can be concluded that in liquid chromatographic procedure, chromatographic media can induce the conformational change of α‐amylase molecules and promote their thermodenaturation; and in hydrophobic interaction chromatography, the higher the hydrophobicity of chromatographic medium, the lower the conformational change temperature of α‐amylase molecules on the chromatographic medium.     

I型和II型结构气体水合物的记忆效应

利用水合物二次生成实验装置, 采用“定容法”对I型(甲烷、二氧化碳)和II型(丙烷)结构气体水合物的二次生成进行了实验, 研究了不同结构水合物(I型、II型)彼此间的记忆效应, 发现水合物生成过程存在明显的诱导期, I型结构水合物间在二次生成过程中存在着记忆效应. I型与II型结构水合物之间在相互二次生成过程中存在着显著的记忆效应.     

Influence of the seed polymer on the chromatographic properties of size monodisperse polymeric separation media prepared by a multi-step swelling and polymerization method

Monodisperse polymer particle-based separation media were prepared by a multi-step swelling and polymerization method with two pairs of monomers and two porogenic solvents. Their chromatographic properties were compared to those of beads prepared by a corresponding suspension polymerization method without the use of seed polymer to ascertain the influence of the seed polymer on their porous structures. A large change in porous structure was observed when the swollen particle consisting of monomers and porogenic solvents contained at least one good solvent for the polystyrene seed polymer, allowing it to remain in the polymerizing medium. In contrast, when the polystyrene seed particle was excluded from the swollen oil droplets, due to its poor solubility in the monomers and the porogenic solvents, there was no difference in the chromatographic properties such as pore volume, pore size, pore size distribution, or retention selectivity between the multi-step swelling and polymerization method and the suspension polymerization method. Since the only difference between the multi-step swelling and polymerization method and the suspension method is the use of the seed polymer, it appears that a very small amount (< 1% v/v) of seed polymers in the enlarged swollen droplets plays an important role as a porogen and affects the porous structure as well as the chromatographic properties of the monodisperse polymer particle-based separation media. © 1993 John Wiley & Sons, Inc.     

Interpretation of NMR Relaxation as a Tool for Characterising the Adsorption Strength of Liquids inside Porous Materials

Nuclear magnetic resonance (NMR) relaxation times are shown to provide a unique probe of adsorbate–adsorbent interactions in liquid‐saturated porous materials. A short theoretical analysis is presented, which shows that the ratio of the longitudinal to transverse relaxation times (T₁/T₂) is related to an adsorbate–adsorbent interaction energy, and we introduce a quantitative metric e_surf (based on the relaxation time ratio) characterising the strength of this surface interaction. We then consider the interaction of water with a range of oxide surfaces (TiO₂ anatase, TiO₂ rutile, γ‐Al₂O₃, SiO₂, θ‐Al₂O₃ and ZrO₂) and show that e_surf correlates with the strongest adsorption sites present, as determined by temperature programmed desorption (TPD). Thus we demonstrate that NMR relaxation measurements have a direct physical interpretation in terms of the characterisation of activation energy of desorption from the surface. Further, for a series of chemically similar solid materials, in this case a range of oxide materials, for which at least two calibration values are obtainable by TPD, the e_surf parameter yields a direct estimate of the maximum activation energy of desorption from the surface. The results suggest that T₁/T₂ measurements may become a useful addition to the methods available to characterise liquid‐phase adsorption in porous materials. The particular motivation for this work is to characterise adsorbate–surface interactions in liquid‐phase catalysis.     

Study of the retention behavior of iodinated X‐ray contrast agents in hydrophilic interaction liquid chromatography,comparing bare silica and zwitterionic stationary phases

Iodinated X‐ray contrast media are the most widely used pharmaceuticals for intravascular administration in X‐ray diagnostic procedures. The increasing concern of the fate of these compounds into the environment has led to the development of analytical methods to determine them. However, these methods present problems due to the polar character of these analytes. In this paper, hydrophilic interaction LC is presented as an alternative technique. The retention of iodinated X‐ray contrast media was studied in two bare silica phases with different particle designs (i.e. porous and Fused Core?) and a zwitterionic sulfoalkylbetaine phase. The effect of the most important parameters of the mobile phase was studied for each stationary phase. It was observed that optimal mobile phase conditions included buffers with a high buffering capacity. Additionally, the retention mechanisms involved were studied in order to provide some insight into the possible occurring interactions. The contributions of partition and adsorption and the effect of the temperature on the retention of analytes were evaluated on all of the stationary phases.     

<Emphasis Type="Italic">AB initio</Emphasis> quantum chemical study of the reaction mechanism of ethynide ion formation in the C<Subscript>2</Subscript>H<Subscript>2</Subscript>/MOH/DMSO system (M = Li,Na, K)

The reaction mechanism of the formation of alkali metal ethynides C₂H₂ + MOH → C₂HM + H₂O (M = Li, Na, K) is studied for the gas phase (MP2/6-311++G**//RHF/6-31+G*) and also with regard to the solvent effect of dimethyl sulfoxide (DMSO) included within the continuum model. Among all acetylene complexes with alkali metal hydroxides considered (C₂H₂·MOH (M = Li, Na, K)), only the complex with KOH is thermodynamically stable in DMSO solution. The formation of this structure results in activation of the acetylene molecule towards electrophilic attack. The formation of alkali metal ethynide in solution is also thermodynamically favorable only in the system with potassium hydroxide of a whole series of metals considered. Further, the ethynide ion can interact in KCCK·HOH systems.     

Novel,efficient,and green procedure for the synthesis of 1,5-benzodiazepines catalyzed by MgBr_2 in aqueous media

MgBr_2 performs as a novel catalyst for the synthesis of various 1,5-benzodiazepine derivatives from wide range of substituted ophenylenediamines and various ketones in good to excellent isolated yields(93-98%)using water as solvent at ambient temperature.Several solvents were examined for this reaction;however,in terms of reaction yield and time,water was found to be the optimum solvent.The remarkable advantages offered by this method are easily and inexpensive available catalyst,simple procedure,mild c...