Polarographic Studies of Dithiodiacetic Acid and the Uranyl-Dithiodiacetic Acid Complex

The polarographic behaviour of dithiodiacetic acid and that of U(VI) in a solution containing dithiodiacetic acid as complexing agent have been investigated. For the dithiodiacetic acid system, two waves appear over the pH range studied. The prewave is kinetic in nature and the mainwave is diffusion-controlled. However, as U(VI) is added into the dithiodiacetic acid system, the polarogram changes due to the existence of a complex. The current-potential curve of the first wave is not the normal S shape. This is due to the superposition of the first wave of the ligand and the wave due to the reduction of the U(VI) in the complex to U(V). The second wave is due to the reduction of the complex The first wave is an adsorption-controlled current and the second wave is partly diffusion-controlled and partly adsorption-controlled. We propose an electrode reaction mechanism for both systems and the complex species. The dissociation constant of the complex HASSAUO⁺₂ is found to be of the order of 10^?4.     

Solid-phase synthesis of pyrazolines and isoxazolines with sodium benzenesulfinate as a traceless linker

[reaction: see text] The preparation of pyrazoline and isoxazoline derivatives with traceless solid-phase sulfone linker strategy is described. Key steps involved in the solid-phase synthetic procedure include (i) sulfinate S-alkylation, (ii) sulfone anion alkylation, (iii) gamma-hydroxy sulfone --> gamma-ketosulfone oxidation, and (iv) traceless product release via elimination-cyclization. A library of 12 pyrazolines and isoxazolines was synthesized.     

Detailed analysis of α,ω-bis(4-hydroxybutyl) poly(dimethylsiloxane) using GPC-MALDI TOF mass spectrometry

In this study the prepolymer alpha,omega-bis(4-hydroxybutyl) poly(dimethylsiloxane), used in the formulation of oxygen permeable films, is evaluated by gel permeation chromatography (GPC) combined with matrix assisted laser desorption ionization (MALDI) time of flight (TOF) mass spectrometry (MS). Two unexpected mass distributions are observed in the mass spectra. Reaction schemes for the formation of these distributions are proposed. A solution phase trimethylsilane end group modification was performed on the prepolymer to determine whether the unexpected mass distributions occur as impurities from synthesis or as artifacts from the MS process. Evaluation of the TMS modified prepolymer indicates the unexpected mass distributions indeed occur as impurities from the synthetic procedure. Average molecular weight values are determined by traditional GPC, direct MALDI-TOF MS, and GPC-MALDI-TOF MS methods and the results are compared.     

Studies on the thermotropic liquid crystalline polymer. XII. Synthesis and properties of crosslinkable thermotropic liquid crystalline homo- and copoly(ether-ester)s

A series of crosslinkable thermotropic liquid crystalline poly(ether-ester)s and copoly(ether-ester)s was prepared. All of the polymers were crosslinked by thermal treatment or photo-irradiation upon heating. The thermal stability and thermal crosslinking reaction of these polymers were investigated. These polymers also could be crosslinked by copolymerization with vinyl monomers, such as styrene or methyl methacrylate. The crosslinked polymers exhibited thermotropic liquid crystalline behavior after softening by heating. The phase behavior of linear polymers and crosslinked polymers was studied by differential scanning calorimetry (DSC) and an optical polarizing microscope equipped with a heating stage. © 1995 John Wiley & Sons, Inc.     

离子注入修饰电极检测硝基苯

离子注入是一种新技术，可按人们的意愿和需要，将不同的离子注入不同的基本电极表面，制成具有催化活性强，稳定性高，重现性好等特点的修饰电极。作者研究了离子注入钴和注入镍的玻碳电极在０．１ｍｏｌ／ＬＨＡｃ－ＮａＡｃ缓冲溶液中硝基苯的行为及测定。     

LaC_3~n(n=-1,0,+1)分子簇的理论研究(英文)

用密度泛函方法研究了ＬａＣ３ｎ（ｎ＝－１，０，＋１）分子簇的结构和稳定性，对这个四原子体系，提出了５种可能构型，其中３种具有Ｃ２ｖ对称性，２种为Ｃ∞ｖ对称性．在Ｃ２ｖ对称性结构中，其中１个为Ｌａ接在弯曲的Ｃ３链上，第２个是Ｌａ通过２个键与Ｃ３环相链，第３个是Ｌａ通过１个键与Ｃ３环相连；在Ｃ∞ｖ对称性中，第１个Ｌａ接在Ｃ３链的一端，而在第２个构型中，Ｌａ被插入在Ｃ３链中．结果表明，环状结构当Ｌａ接在弯曲的Ｃ３链上的是局域极小值并且最稳定     

对氟苯酚-过氧化氢-辣根过氧化物酶体系酶联荧光免疫分析研究──Ⅰ.对氟苯酚直接法及铝-钙指示剂偶合法测定人血清中乙肝表面抗原和表面抗体

对氟苯酚在辣根过氧化物酶（HRP）的催化下可被H2O2氧化，生成本酚及F-。测定对氟苯酚荧光猝灭程度及用铝－钙指示剂荧光体系检测酶促反应释放的F－，可分别建立HRP及其标记物的两种分析方法。铝－钙指示剂偶合法测定HRP的线性范围为0．031～31U／L，检测限（3δ）为0．0093U／L。两种方法分别用于测定人血清中乙肝表面抗原及抗体，结果令人满意。     

铜（Ⅱ）锌（Ⅱ）－氟哌酸体系电化学行为及示波极谱法研究

铜（Ⅱ）和锌（Ⅱ）分别在０．１ｍｏｌ／ＬＫＨ＿２ＰＯ＿４－Ｎａ＿２ＨＰＯ＿４缓冲溶液（ｐＨ６．５）和０．２５ｍｏｌ／ＬＮＨ＿４Ｃｌ溶液中，与氟哌酸形成良好的络合吸附波，峰电位分别为－０．２６Ｖ和－１．２８Ｖ（ｖｓ；ＳＣＥ）；络合比分别为１：３和１：２；峰电流与铜（Ⅱ）和锌（Ⅱ）的浓度均在４．０×１０￣（－７）～５．０×１０￣（－６）ｍｏｌ／Ｌ范围内呈线性关系，检测限分别为７．０×１０￣（－８）和５．０×１０￣（－８）ｍｏｌ／Ｌ。用线性扫描和循环伏安法等手段研究体系的行为，表明均具吸附性，而铜（Ⅱ）－氟哌酸体系属络合物中铜（Ⅱ）的两电子还原的可逆过程。     

Chromatographic characterization of molecularly imprinted microspheres for the separation and determination of trimethoprim in aqueous buffers

Molecularly imprinted microspheres (MIMs) against trimethoprim (TMP), prepared by aqueous microsuspension polymerization, bound strongly to TMP, by electrostatic and other non-covalent interactions. The effects of pH, kind and ionic strength (I) of buffer on capacity factors (k') have been discussed in detail. The capacity factors for TMP increased with increasing pH of both acetate and phosphate buffers. The effects of ionic strength on capacity factors were very substantial and the linear relationship between logk' and logI was described by the equation logk'=0.3162-0.4420logI with R=-0.9995. The results showed that pH 3.5 acetate buffer (0.05 mol L(-1)) containing 0.1 mol L(-1) sodium chloride and a 1:9 ratio of buffer to methanol were the optimum conditions for separation and determination of TMP. The calibration plot of peak area against concentration was linear with R=0.9979.     

A unique spherical molecular host with D2d symmetry. A novel intramolecular kinetic equilibrium in metal ion complexation between two crown ethers

[formula: see text] A spherical host with D2d symmetry consisting of a tetrathia[3.3.3.3]paracyclophane and two 18-crown-6 moieties was synthesized. Its crystal structure shows a central cavity with a diameter of 1.96 A and a depth of 6.75 A. A Na+ ion could rest in the cavity center but prefers core binding to external binding in one of the crown units. An intramolecular kinetic equilibrium was reached with the Na+ ion switching between the two crown units with an energy barrier of 14.1 +/- 3 kcal/mol.