微分倒数示波计时电位滴定

倒数示波计时电位滴定~[1]是最近提出的一种电滴定方法,它把(dE/dt)-E曲线上的切口转变为(dE/dt)~(-1)-E曲线上的峰,从而大大抑制了充电电流,提高了滴定分析的灵敏度.本文报道了微分倒数示波计时电位滴定,即对(dE/dt)~(-1)-E曲线进行一次或二次微分处理,利用示波图上去极剂峰的出现与消失指示终点,使滴定终点更易观察.     

倒数示波计时电位滴定法

提出了一种新的电滴定分析方法——倒数示波计时电位滴定法。它利用(dE/dt)~(-1)-E曲线上去极剂峰的出现或消失指示滴定终点,较经典示波滴定法灵敏,对(dE/dt)~(-1)-E曲线进行反对数非线性放大,则可以使终点峰形突变更加敏锐.     

电压反馈倒数示波计时电位滴定法

用电压反馈的(dE/dt)~(-1)-E示波图上去极剂峰的出现或消失指示滴定终点的方法称为电压反馈倒数示波计时电位滴定法。电压反馈的(dE/dt)~(-1)-E曲线使峰形更加尖锐,峰高大大增加,从而提高了分析测试的灵敏度,对所得曲线再进行一次微分和二次微分处理,则终点时去极剂峰形变化更加敏锐。     

倒数示波计时电位法

使用dE/dt的倒数对E作图的示波计时电位法,称为倒数示波计时电位法.dE/dt-E曲线上的切口在dE/dt^-1-E上变成峰,可以方便地扣除充电电流,提高分析测试的灵敏度.     

玻碳电极上的倒数示波沉淀滴定法

1 引言 近年来示波滴定技术取得了很大的发展,主要体现在两个方面,一方面各种新仪器的研制,使得滴定的灵敏度大大提高,从经典的dE/dt—E曲线发展到i_f—E曲线及倒数示波计时电位曲线;另一方面极化电极也从汞膜电极发展为固体电极,由于汞膜电极的电位仅在0～—2V之间变化,限制了其应用范围固体电极能克服     

Antilg de／dt—E曲线上的示波极谱滴定法

在示波极谱滴定中,当去极剂切口位于示波极谱图|dE/dt|的最大值附近时,利用Antilg dE/dt～E示波图来指示滴定终点能使终点变化更为敏锐。原来较难进行滴定的一些体系现在可用这种方法滴定。在50Hz的交流电频率下,用氨羧络合剂滴定了Cd~(2+)、Pb~(2+)、Zn~(2+)、Co~(2+),滴定结果符合分析要求。非线性放大还可应用于以dE/dt～E示波图的扩张或收缩来指示滴定终点的示波极谱滴定法及以荧光电位线的伸长或收缩来指示滴定终点的示波电位滴定法,以提高终点变化的敏锐性。以亚硝酸钠滴定对氨基苯磺酸为例说明了这一方法的可行性。     

交流示波极谱滴定法

用交流示波极谱曲线(dE/dt)=f(E)上切口的出现或消失来指示滴定终点的容量分析方法称为交流示波极谱滴定法,简称示波极谱滴定。     

电流反馈倒数示波计时电位滴定法

经典的示波计时电位滴定法是利用用dE/dt-E曲线上去极剂切口的出现或消失指示滴定终点,其优点是仪器简单、终点直观、准确快速,不足之处是有些去极剂在示波计时电位图上的切口不敏锐,当被测物含量较低,或用较低浓度的滴定剂进行滴定时,终点变化更不     

交流示波极谱滴定铋的研究

交流示波极谱滴定法的理论及其应用已有专文评述。示波极谱滴定铋的工作尚未见报导。我们曾经用悬汞电极为工作电极发现1毫克左右的Bi~(3+)在HAc-NaAc溶液中即能在其dE/dc=f(E)曲线上产生锐敏切口,但Bi~(3+)增加不多后切口便逐渐变钝,甚至图形有畸变倾向。本文很据恒电流交流示波极谱的特点,即汞滴面积越小则双电层电容也越小,而dE/dt的变化则越大,采用尽可能小的悬汞滴或沾汞电极,使dE/dt=f(E)曲线图得到良好的伸展,将Bi~(3+)     

三角波交流示波极谱的研究(Ⅱ)——单组分三角波交流示波极谱理论

本文提出了单组分三角波交流示波极谱理论,推导了E～t、dE/dt～E曲线的理论公式,对转移时间、切口电位、切口高度作了定量的描述。     

Nitrenium Salts in Lewis Acid Catalysis

Molecular compounds featuring nitrogen atoms are typically regarded as Lewis bases and are extensively employed as donor ligands in coordination chemistry or as nucleophiles in organic chemistry. By contrast, electrophilic nitrogen‐containing compounds are much rarer. Nitrenium cations are a new family of nitrogen‐based Lewis acids, the reactivity of which remains largely unexplored. In this work, nitrenium ions are explored as catalysts in five organic transformations. These reactions are the first examples of Lewis acid catalysis employing nitrogen as the site of substrate activation. Moreover, these compounds are readily accessed from commercially available reagents and exhibit remarkable stability toward moisture, allowing for benchtop transformations without the need to pretreat solvents.     

Bethe ansatz of electrons as a mean-field wavefunction for chemical systems

Eigenvectors of a Hamiltonian solvable by a Bethe ansatz (BA) are employed as a variational trial wavefunction for electrons. Energy expressions are developed showcasing the methods of BA. Numerical results are presented for atomic systems as well as molecular dissociations, which are numerically identical with the restricted Hartree-Fock (HF) results. The present contribution serves as a bridge between HF and other BA wavefunctions to be employed as mean-field methods for strongly correlated electrons.     

Structure and growth of self-assembling monolayers

The structural phases and the growth of self-assembled monolayers (SAMs) are reviewed from a surface science perspective, with emphasis on simple model systems. The concept of self-assembly is explained, and different self-assembling materials are briefly discussed. A summary of the techniques used for the study of SAMs is given. Different general scenarios for structures obtained by self-assembly are described. Thiols on Au(1 1 1) surfaces are used as an archetypal system to investigate in detail the structural phase diagram as a function of temperature and coverage, the specific structural features on a molecular level, and the effect of changes of the molecular backbone and the end group on the structure of the SAM. Temperature effects including phase transitions are discussed. Concepts for the preparation of more complex structures such as multi-component SAMs, laterally structured SAMs, and heterostructures, also with inorganic materials, are outlined. The growth and ways to control it are discussed in detail. Solution and gas phase deposition and the impact of various parameters such as temperature, concentration (in solution) or partial pressure (in the gas phase) are described. The kinetics and the energetics of self-assembly are analyzed. Several more complex issues of the film formation process including non-equilibrium issues are discussed. Some general conclusions are drawn concerning the impact of various molecular features on the growth behavior and concerning the relationship between growth and structural phase diagram. Finally, the potential of self-assembly as a route for the preparation of monolayers with pre-designed properties and SAMs as building blocks in heterostructures as well as application strategies are discussed.     

Chemical reaction and Soret effects on MHD convective flow of second grade fluid through an absorbent medium with ramped wall temperature as well as ramped surface concentration

In the present paper, the heat generating and/or absorption as well as thermo-diffusion on the unsteady free convection MHD gyrating flow of radiation and chemical reactive second grade fluid past an unbounded perpendicular plate during absorbent medium have been discussed. Here, it is assumed that, the confining plate has the ramped wall temperature with ramped surface concentration and isothermal temperature with ramped surface concentration. The analytical solutions for the governing equations are found by utilization of Laplace transformation methodology. The velocity, temperature and concentration profiles are analyzed with quite few figures. It is determined that, velocity, temperature and concentration distribution sketches in case of ramped temperature as well as ramped surface concentration are not as much of as those of isothermal temperature as well as ramped surface concentration. In addition to the idioms of skin friction, Nusselt number as well as Sherwood number are achieved and characterized numerically with tabular format.     

Hydrophobins: Proteins that self assemble at interfaces

Hydrophobins are surface active proteins that are produced by filamentous fungi. They are interesting from a Surf Sci point of view because some of their properties as surface active proteins are quite spectacular. In this review, recent advances in understanding these properties will be surveyed. We will attempt to define what the properties are that make them unique. As an understanding of both structure and function of hydrophobins is emerging we see that this is paving the way for industrial applications as well as an understanding of their biological functions.

Major recent advances

Recently there has been a clear increase in attempts to use hydrophobins in applications. We are starting to understand their unique properties as surfactants and especially applications related to the stability and development of foams and various surface treatments are emerging. There are several new reports on molecular structures as well on mechanisms of self-assembly. Hydrophobins have functions in biology that are far from understood, but also here techniques are developing and a broader understanding is emerging.     

Eka-elements as chemical pure possibilities

From Mendeleev’s time on, the Periodic Table has been an attempt to exhaust all the chemical possibilities of the elements and their interactions, whether these elements are known as actual or are not known yet as such. These latter elements are called “eka-elements” and there are still some of them in the current state of the Table. There is no guarantee that they will be eventually discovered, synthesized, or isolated as actual. As long as the actual existence of eka-elements is predicted, they cannot be considered as actual but only as purely possible. Given that eka-elements are chemical pure possibilities, a possibilist approach, entitled “panenmentalism,” can gain support as well as an important implication.     

锂离子电池有机硅电解液

有机硅电解液具有优良的热稳定性、低可燃性、无毒性、高电导率和高分解电压等优点,近年来成为了锂离子电池新型电解液的研究热点。本文综述了有机硅电解液的研究进展,重点介绍了聚醚有机硅电解液的设计合成、物理化学性能、与电解质盐和电极材料的匹配性关系及其在电池中的性能表现;简述了有机硅功能化电解液添加剂的研究进展,如成膜添加剂、阻燃添加剂、吸酸吸水添加剂等;最后对有机硅电解液的进一步研究趋势和应用前景进行了展望。     

肉类食品中杂环胺检测的样品前处理及分析方法的研究进展

杂环胺是畜禽、鱼肉等食品在高温烹饪过程中生成的一类致癌、致突变化合物,高效、高选择性的样品前处理方法和高灵敏的分析方法是食品中痕量杂环胺分析检测的关键。本文综述了近年来溶剂萃取、固相萃取和固相微萃取等样品前处理方法,以及液相色谱、液相色谱-质谱等分析方法在食品中痕量杂环胺检测中的应用,结合现有研究对其发展趋势进行了展望。共引用文献51篇。