A generalized equation describing isotope exchange kinetics at solid-liquid interface

A generalization of the kinetic equation for the isotope exchange at solid—liquid interface is presented. The generalized equation may be used to describe kinetics of the isotope exchange process limited by surface reactions and diffusion without assumption of spherical symmetry of solid particles.

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Eine generalisierte Gleichung für die Kinetik des Isotopenaustausches an Fest-Flüssig-Phasengrenzen

Zusammenfassung Es wird eine generalisierte kinetische Gleichung angegeben, die die Kinetik des Isotopenaustausches an Fest-Flüssig-Phasengrenzen beschreibt, wobei der Austauschprozeß durch Oberflächenreaktionen und Diffusion ohne der Annahme sphärischer Symmetrie für die festen Partikel begrenzt ist.

     

Synthetische und NMR-spektroskopische Untersuchungen der Benzylaminaddition an N-Maleyl-aminosäurederivate

Summary During the addition of amines to maleylamino acids in general -amino derivatives are formed. In order to change the reactivity within the vinylogous maleyl system we introduced the -benzylester group into the starting compound N-(cis--carboxyacryloyl)-phenylalanine methylester1. The obtained benzylester2 is adding benzylamine in -position yielding N-benzyl--aspartyl(-benzyl)-phenylalanine methylester4. The addition reaction was investigated by¹H-NMR-spectroscopy. The structures of the compounds have been confirmed by elemental analysis, IR,¹H-NMR and¹³C-NMR spectroscopy.

     

一类2(1H)-喹喔啉衍生物的电子轰击质谱分析

以邻苯二胺为原料合成表征了一类喹喔啉衍生物；1-烷基-3-甲基-2（1H）-喹喔啉-2-酮（1-alkyl-3-methly-2(1H)-quinoxalin-2-one，简称AMQ，其中alky=H、CH3、Et、n-C3H5、n-C5H11、n-C16H33)。用电子轰击电离质谱（EI-MS）和核磁共振谱图（^1H-NMR)鉴定了AMQ，研究了不同取代基对这类化合物EI-MS谱图的影响，分析得到一些裂解规律。结果表明：所有样品谱图中均有芳香化合物的特征CnHn^ 系列峰m/z78，65，52，39和（或）m/z77、76、64、63、51、50、38、37。对于末取代的样品及低级烷烃取代的样品，谱图中的基峰为分子离子峰，对于取代基中碳数大于等于3的样品。谱图中的基峰不是分子离子峰，分子离子峰强度随着碳数的增加而降低。这些样品一般容易发生骨架重排，丢失一分子CO，生成1-烷基-2-甲基苯并哒唑正离子。此外，还讨论了谱图中其它的一些碎片离子峰。这对于研究和指导喹喔啉衍生物 的合成，探讨它们在药效及结构特征与生理活性的关系等方面具有重要的应用价值和理论意义。     

QuEChERS/超高效液相色谱-串联质谱法同时测定水产品中四溴双酚A与六溴环十二烷

建立了同时测定水产品中四溴双酚A(TBBPA)和六溴环十二烷(HBCD)的超高效液相色谱-串联质谱方法。样品前处理采用QuEChERS方法,均质生物样品用水分散后加乙腈提取,经C_(18)分散固相萃取净化。采用CORTECS~?C_(18)色谱柱(4.6 mm×100 mm×2.7μm)分离,以甲醇-水为流动相进行梯度洗脱,流速为0.7 mL/min。采用电喷雾离子源,在负离子模式下以多反应监测(MRM)方式检测。结果表明,TBBPA和3种HBCD单体在0.5～500μg/L范围内线性良好,相关系数(r)大于0.998,检出限(LOD,S/N=3)和定量下限(LOQ,S/N=10)分别为0.04～0.16μg/kg和0.12～0.55μg/kg。在5、20、50μg/kg加标水平下的平均回收率为74.0%～121%,相对标准偏差(RSD)为0.20%～23%。该方法操作简单、快速、重现性好,适用于水产品中TBBPA和HBCD的快速检测。     

A Convenient Synthesis of Phosphorines and Phospholidins by <Emphasis Type="Italic">Lawesson</Emphasis>’s Reagent and Microwave Irradiation

Summary. A new and simple method for the synthesis of 1,3,2-diazaphosphorines and 1,3,2-oxazaphosphorine was developed based on the reactions of Lawessons reagent with -aminopropionitriles and -hydroxypropionitrile. In addition, a rapid and facile synthesis of 1,3,2-diazaphospholidin-4-ones by the reaction of P(NEt₂)₃ with hindered diamino substrates under microwave irradiation was also achieved. The prepared phosphorines show herbicidal activity to some extent in the preliminary bioassays.     

Formal Mathematical Analysis of the Existence of the Common Intersection Point in Relation to Determining the Parameters Describing Ion Adsorption at the Oxide/Electrolyte Interface: Comparison of the Triple and Four-Layer Models

For most oxide/electrolyte systems potentiometric titration curves measured for different ionic strengths have a Common Intersection Point (CIP) which corresponds to the Point of Zero Charge (PZC). However, there are systems where a CIP exists but the surface charge at this point does not equal zero (PZC CIP). In this paper theoretical analysis of the systems in which the PZC and CIP do not coincide is presented. It is based on the well-known 2-pK surface charging approach and Triple Layer Model (TLM) as well as the Four Layer Model (FLM) of the electric double layer. The appropriate mathematical criterion for CIP existence was applied with detailed derivations, both for TLM and FLM. Having determined in this manner the parameter values, one can draw proper conclusions about the features of oxide/electrolyte adsorption systems, in which PZC and CIP do not coincide. The values of adsorption parameters are found by fitting simultaneously the obtained theoretical expressions to both of the experimental titration isotherms, and to the individual isotherms of electrolyte cation adsorption measured using radiometric methods.     

离子敏感场效应晶体管及其应用

离子敏感场效应晶体管具有若干不同于寻常传感器的特点：超小型、全固态、集成化和自身阻抗变换等。它是一种很有发展前途的传感器。本文了讨论了离子敏感场效应晶体管的分类、结构和性能；评述了１９８９年以来其在临床医学和流动注射分析等方面的应用。引参考文献６７篇。     

Polyfluorinated hydrazones in organic syntheses

The reaction of poly- and perfluoroaldehyde hydrazones with hydrazine hydrate was studied. A new preparative method for obtaining the hitherto inaccessibleN,N-unsubstituted bis-hydrazones of polyfluorinated -oxoaldehydes was developed based on this reaction.For Part 2, seeIzv. Akad. Nauk, Ser. Khim., 1995, 2465 [Russ. Chem. Bull, 1995,44, 2360 (Engl. Transl.)].Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2526–2527, December, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grant No. 94-03-08548) and the International Science Foundation (Grant Nos. NDL 000 and NDL 300).     

Changes in molecular ordering associated with alkali treatment and vacuum drying of cellulose

Carbon-13 NMR methods were used to monitor changes in the proportions of crystalline and non-crystalline cellulose, and the exposure of chains on crystallite surfaces, in samples of alkali-treated kraft pulp and regenerated cellulose. A large increase in the amount of disorderd cellulose, as a result of conversion to cellulose II, is the major effect of alkali treatment with kraft pulp. Removal of small crystallites is the major effect with regenerated cellulose. Samples were examined never-dried, or were vacuum-dried prior to remoistening for characterization. Changes in molecular ordering consistent with pore collapse and coalescence of crystallite surfaces accompanied the removal of water.     

Application of Kirkwood-Buff theory to electrolyte solutions. III. Activity coefficients of aqueous NaCl between 273.15 and 573.15 K

Using a theory recently developed for the interpretation of activity coefficients of 1:1 electrolytes up to high concentrations in aqueous solution at 25°C, we have analysed available data for aqueous sodium chloride solutions up to saturation in the temperature range 273.15–573.15 K. The approach, which is based on Kirkwood-Buff theory and uses the truncated Poisson-Boltzmann equation to obtain the required information about the various ion-ion radial distributions, is able to fit the results to high accuracy with minimum of parameters, viz, three, of which one is the distance of closest approach, the other two relate to ion-solvent interactions and/or higher order terms in the ion-ion interaction.