PS-PBA粒子分散系的介电弛豫谱解析——同、反离子对弛豫的影响及表界面电参数的计算

制备了近纳米级的聚苯乙烯-丙烯酸丁酯(PS-PBA)复合微球粒子,并在40Hz～110×106Hz的宽频范围测量了该粒子分散在9种电解质中时的介电弛豫谱,发现了与PS微球粒子分散系不同的特异介电弛豫:低频弛豫对反离子种类具有敏感性而高频弛豫则与电解质种类几乎无关;根据Shilov-Dukhin模型和M-W-O模型分别分析了高、低频率的弛豫机制,并通过对介电谱的Cole-Cole拟合获得了各体系的介电参数.进一步利用Hanai方法由介电参数计算获得了所有体系的相参数;详细分析了体系的内部参数受PS-PBA微球自身结构以及电解质种类影响的原因;讨论了离子扩散系数对介电参数的影响,从而得出了低、高频的弛豫特征时间分别由同离子的扩散系数和反离子的扩散系数所决定之结论.最后,结合Grosse宽频介电理论计算了粒子表面的以及双电层的主要电参数,并分析了电解质种类差异对这些电参数的影响.     

Pitzer model parameters for sparingly soluble salts from solubility measurements. The systems TlCl+SrCl2+H2O and TlCl+BaCl2+H2O at 25°C

The solubility of thallium(I) chloride has been determined in aqueous solutions of strontium chloride and barium chloride at concentrations up to 1.5 mol kg^–1. The data were analyzed using Pitzer's equations without making explicit assumption of association to ion pairs by assuming =3 instead of =2, with the ⁽¹⁾ term for TlCl being equivalent to the ⁽²⁾ term for 2-2 electrolytes. Best values of ⁽⁰⁾ and ⁽¹⁾ for TlCl are recommended together with K _s , the activity solubility product. These were used to fit the present solubility data and derive the Pitzer model mixture parameters relevant to the systems, _fTIN and _fTINCl (N=Sr, Ba). Mixture parameters for TlCl+MCl+H₂O systems are also derived to complete the parameter base. The fit of the experimental data was found to be worse when higher-order terms for asymmetrical mixing were included in the analysis. Activity coefficients for thallium(I) chloride in the mixtures are derived.     

析氢反应动力学的交流阻抗法研究

利用交流阻抗法测定析氢电化学动力学参数，得到与极化曲线法一致的结果，为确定复杂析氢过程速率的决定步骤提供了判据。     

Improvement of some pharmaceutical properties of nocloprost by β- and γ-Cyclodextrin Complexation

Inclusion complexation of nocloprost, a potent antiulcer prostaglandin derivative, with -, -, and -cyclodextrins (CyDs) in aqueous solutions has been studied by the solubility method and¹³C-NMR spectroscopy. The steric requirement of host-guest interaction was reflected in the magnitude of the stability constants and the thermodynamic parameters of the inclusion complexes. Solid complexes of nocloprost with - and -CyDs in a molar ratio of 1 : 2 were obtained on the basis of aBs-type phase solubility diagram. The X-ray diffraction data suggested that nocloprost is included in the cylindrical channel formed by coaxial alignment of -CyD molecules to give a channel type structure. Release and thermal behavior of the solid complexes was examined and compared with nocloprost itself. The results indicated that the -CyD complex may have great utility among the three CyDs, being a rapid dissolving form of nocloprost with improved thermal stability.     

Retention prediction of phenylthiohydantoin amino acid derivatives in reversed-phase liquid chromatography

Summary The concept of retention prediction for the separation of phenylthiohydatoin-amino acid derivatives in isocratic reversed-phase liquid chromatography is described. A novel retention-solubility parameter, R, is defined, for the retention prediction strategy and the performance of this R value is evaluated by comparing measured and predicted retention data. Excellent agreement between these values were observed. It is concluded that the R value has a very high potential in describing the retention of phenylthiohydantopinamino acid derivatives withdifferent types of separation systems consisting of C-18, C-8 and phenethyl bonded stationary phases and various mobile phases.     

脲和盐酸胍诱导的卵清溶菌酶分子去折叠过程中各稳定构象态的分布和过渡

以内源荧光光谱和荧光相图法研究了脲和盐酸胍诱导的卵清溶菌酶分子的去折叠过程,结果表明,当变性液中脲和盐酸胍的浓度分别约为4.0和3.0 mol/L时,卵清溶菌酶分子的去折叠过程均存在一个折叠中间态,这两个去折叠过程均符合"三态模型".在卵清溶菌酶分子"三态"去折叠过程的基础上,通过变性剂分子和卵清溶菌酶分子之间的缔合一...     

反气相色谱法测定环氧树脂的表面张力和溶解度参数

采用反气相色谱(IGC)测定了环氧E51树脂在30、40、50和60 ℃下的表面张力和溶解度参数。采用Schultz法,以正癸烷、正壬烷、正辛烷和正庚烷为非极性溶剂探针,计算了不同温度下环氧E51树脂的色散表面张力。根据Good-van Oss方程,以甲苯为碱性探针,二氯甲烷为酸性探针,计算得到环氧E51树脂的极性表面张力。结果表明,环氧E51树脂的色散表面张力和极性表面张力均随着温度的升高而线性降低。根据不同溶剂探针与树脂间的Flory-Huggins相互作用参数,采用DiPaola-Baranyi和Guillet方法计算得到环氧E51树脂在不同温度下的溶解度参数,其在30、40、50和60 ℃下分别为11.78、11.57、11.48和11.14 MPa1/2。根据表面张力、内聚能和溶解度参数的相互关系,计算得到不同温度下溶解度参数的色散和极性分量。结果发现,环氧E51树脂的溶解度参数的色散分量大于极性分量,且均随着温度的升高而降低。     

DFT Study on the Correlation between Thermodynamical Property and Molecular Structure of Polybromo-phenoxathiin

Complete optimization was conducted for 136 polybromo-phenoxathiin congeners(PBPTs) on the B3LYP/6-31G* level with Gaussian 03 program.The structural parameters and thermodynamical parameters of each molecule were obtained under the standard state of 298.15 K and 1.013×105 Pa.Reverse linear regression was employed to establish the quantitative structure-property correlation models between heat capacity at constant volume(CVθ),entropy(Sθ),standard heat of formation(△fHθ) and standard free energy of formation(△fGθ) of PBPTs and the structural parameters(the most negative atomic charge(q-) and molecular average polarizability(α)).These models presented better correlations(r20.97).And they were validated by variance inflation factor(VIF) and t-test,which can better explain the regularity of thermodynamical property of PBPTs,and has good stability and great prediction ability.     

Tutorial review on validation of liquid chromatography–mass spectrometry methods: Part I

This is the part I of a tutorial review intending to give an overview of the state of the art of method validation in liquid chromatography mass spectrometry (LC–MS) and discuss specific issues that arise with MS (and MS/MS) detection in LC (as opposed to the “conventional” detectors). The Part I briefly introduces the principles of operation of LC–MS (emphasizing the aspects important from the validation point of view, in particular the ionization process and ionization suppression/enhancement); reviews the main validation guideline documents and discusses in detail the following performance parameters: selectivity/specificity/identity, ruggedness/robustness, limit of detection, limit of quantification, decision limit and detection capability. With every method performance characteristic its essence and terminology are addressed, the current status of treating it is reviewed and recommendations are given, how to determine it, specifically in the case of LC–MS methods.