胶束电动毛细管色谱中的双峰及其成因

研究了以十六烷基三甲基溴化铵(或十二烷基硫酸钠)为准固定相的胶束电动毛细管色谱法中的双峰及其形成原因. 指出在一定的条件下一种组分可以出现2个峰. 实验表明, 某一组分相应双峰的相对峰面积取决于该组分与表面活性剂之间的反应时间与温度以及样品中表面活性剂的浓度. 当样品中表面活性剂浓度增加时, 双峰中一个峰的相对峰面积增加, 而另一个减小; 温度可以加速反应的过程. 这意味着被分析物与表面活性剂之间的相互作用是一个慢过程, 这种相互作用可以产生一种稳定的物质, 并导致双峰的形成. 十六烷基三甲基溴化铵与间羟基苯甲酸反应产物的红外与核磁共振光谱证实了这一点.     

分光光度法研究麝香草酚蓝与吐温-80的相互作用

1　引　　言随着胶束增溶光度法的发展 ,分析工作者对显色剂和表面活性剂之间的相互作用进行了较多的研究。但现有的研究多集中于染料与电性相反的离子型表面活性剂的相互作用 ,而对胶束与显色剂的络合能力缺乏深入的定量研究。本文就上述的问题 ,研究了非离子表面活性剂Ｔｗｅｅｎ 80胶束与麝香草酚蓝 (ＴＢ)的胶束结合作用 ,测定了它们之间的结合常数 ,探讨了它们的反应机理。2　实验部分2 .1　试剂与仪器　麝香草酚蓝 (ＴＢ)为分析纯试剂 ;Ｔｗｅｅｎ 80 (上海大众制药厂 ,药典标准 ) ;不同ｐＨ硼砂 氢氧化钠缓冲溶液 ;所用试剂为分析纯 …     

卵清蛋白与离子型表面活性剂的相互作用

本文通过荧光光谱法、紫外-可见吸收光谱法和透射电镜并结合电导率测定分别研究了水中卵清蛋白与阴离子表面活性剂十二烷基硫酸钠（SDS）和阳离子表面活性剂十二烷基三甲基溴化铵（DTAB）和十六烷基三甲基溴化铵（CTAB）之间的相互作用。研究结果表明卵清蛋白可以增加SDS和CTAB的临界胶束浓度,但对DTAB的临界胶束浓度没有影响。阴离子表面活性剂可以使卵清蛋白构象完全伸展,而阳离子表面活性剂却不具备此种作用。表面活性剂单体与卵清蛋白的相互作用强于表面活性剂胶束与卵清蛋白的相互作用。     

羧甲基淀粉与十六烷基三甲基溴化铵的相互作用研究

通过电导法、粒度法、光谱及热分析等方法研究了羧甲基淀粉与十六烷基三甲基溴化铵之间的相互作用。结果表明,在较低表面活性剂浓度下,静电作用使得羧甲基淀粉与十六烷基三甲基溴化铵发生复合,这一浓度比单一表面活性剂的临界胶束浓度（cmc）低1个数量级;但随表面活性剂的增加,复合物溶液经历澄清-混浊-澄清过程,说明表面活性剂起到了...     

胶束电动力学毛细管色谱中有机调节剂对溶质容量因子的影响

将质量作用定律应用于胶束电动力学毛细管色谱中溶质、有机添加剂和胶束之间的相互作用研究,得到了溶质容是因子与各过程平衡常数及有机添加剂、表面活性剂浓度的关系的数学表达式。进一步分析表明,研究调节剂在胶束中可能有一定的溶解度,但这一过程对于胶束在电泳过程中的迁移速度几乎没有影响;有机添加剂对溶质容量因子的影响主要反映为其对表面活性剂临界胶束浓度的影响,在一级调节剂浓度不变的情况下,溶质容基因子与表面活性剂浓度之间满足很好的线性关系。     

用温度跃升法研究胶束催化

用温度跃升快速反应动力学测试仪器,研究了合成表面活性剂SDS胶束水溶液体系与生物表面活性剂脱氧胆酸钠(NaDC)胶束水溶液体系中,金属离子Ni~(2+)-2,2′-Bipyridine(Bipy)络合物形成的动力学。实验结果表明,生物表面活性剂同样表现出程度不同的胶束催化作用。又采用假相模型处理SDS胶束体系中上述反应的动力学,由动力学结果计算出可供发生反应的胶束体积。结果表明,此体积比不加电解质的胶束溶液中的反应体积增大,此现象被认为是由无机电解质的存在所造成。     

表面活性剂与高分子链混合体系的模拟

计算机模拟了高分子链对表面活性剂胶束形成过程的影响，以及高分子链构象性质随胶束化过程的变化.结果表明,当高分子链与表面活性剂之间的相互作用强度超过临界值后，高分子链的存在有利于表面活性剂胶束的形成.临界聚集浓度（CAC）与临界胶束浓度（CMC）的比值CAC/CMC随高分子链长的增大和相互吸引作用的增强而减小.在CAC之前，高分子链与表面活性剂分子只有动态的聚集；但在CAC之后，表面活性剂胶束随表面活性剂浓度X的增加而增大，并静态地吸附在高分子链上，形成表面活性剂/高分子聚集体.随着表面活性剂分子的加入，高分子链的均方末端距和平均非球形因子先保持恒定；从X略小于CAC开始， 和快速减小，至极小值后又逐渐增大.模拟结果支持高分子链包裹在胶束表面的实验模型.     

金属胶束模拟过氧化氢酶的热动力学研究

本文以金属胶束作为过氧化氢酶的模拟模型化合物，利用热动力学半寿期法分别研究了Fe^Ⅲ-trien金属配合物和Fe^Ⅲ-trien配合物分别与CTAB、SDS、Brij35等表面活性剂形成的金属胶束催化过氧化氢分解反应的热动力学。实验结果表明：Fe^Ⅲ-trien金属配合物与CTAB形成的金属胶束对过氧化氢分解反应有催化作用，而与SDS和Brij35形成的金属胶束对反应有禁阻作用。     

咪唑衍生物的过渡金属配合物催化对硝基苯酚吡啶甲酸酯水解动力学研究

25 0±0 01℃时,研究了带有咪唑基团的配体与二价过渡金属离子生成的配合物在三种不同的表面活性剂(CTAB,Brij35和LSS)中催化对硝基苯酚吡啶甲酸酯(PNPP)水解的动力学。运用金属胶束催化的三元复合物动力学模型对所得的实验结果进行定量处理,得到了相关的动力学和热力学参数。结果表明:pH7 00时,在任何一种配合物与不同的表面活性剂生成的金属胶束溶液中,PNPP的水解速率都有较大的增加,尤其是铜(Ⅱ)配合物与两性离子表面活性剂(LSS)以及非离子表面活性剂生成的金属胶束对PNPP的水解反应表现出较高的催化活性,而在阳离子表面活性剂中,配合物催化PNPP水解反应的效率却并不高,这可能归因于阳离子表面活性剂带正电的极性头与金属离子之间的静电相斥作用;在所研究的三种配合物中,尽管Cu(Ⅱ)配合物具有最低的pKa值,但是在弱碱性条件下,Zn(Ⅱ)配合物却表现出更高的催化活性,这可能与催化剂在胶束溶液中的离子化状态以及不同配合物中活性物种的不同亲核能力有关。     

有机电解质在胶束催化聚苯乙烯氯甲基化反应中的作用

在实施聚苯乙烯氯甲基化反应的胶束催化体系中加入四丁基溴化铵 ((Bu)₄NBr, TBAB), 研究了有机电解质TBAB对胶束催化反应的影响规律. 实验结果表明, 在非离子表面活性剂NP-10及阴离子表面活性剂SDS的胶束催化体系中, TBAB的加入使聚苯乙烯氯甲基化反应的速率明显增大, 前者尤为突出；而在阳离子表面活性剂CTAB的胶束催化体系中, TBAB的加入几乎对反应速率无促进作用. 这种结果一方面归因于加入电解质TBAB会降低SDS的临界胶束浓度, 从而增强对聚苯乙烯四氯化碳溶液的增溶能力；更主要的原因是TBAB的丁基与表面活性剂碳氢链间的疏水相互作用会使季铵离子(Bu)₄N⁺嵌入SDS的胶束之中, 结合到NP-10的胶束表面, 使SDS胶束的阴离子头基对亲核取代反应(控制步骤)的禁阻作用得以减缓, 使NP-10的胶束表面携带了正电荷, 显著促进亲核取代反应的进行, 而对于CTAB的胶束, 由于静电排斥作用, 季铵离子(Bu)₄N⁺不能接近CTAB的胶束, 故TBAB的加入对聚苯乙烯氯甲基化反应不产生作用.     

Pseudo Peak Phenomena in Micellar Electrokinetic Capillary Chromatography by Using Ionic Surfactant

The origin of pseudo peak was studied by means of micellar electrokinetic capillary chromatography with cetyltrimethylaminium bormide as the pseudo stationary phase.It has been pointed that two peaks may appear for one component under certain conditions.Experiments showed that the relative areas of the two peaks of analyte depended on the time and the temperature of reaction between analyte and surfactant,and the concentration of surfactant in the sample solution.It means that the interaction between the analyte and the surfactant is a slow process,and a stable substance can be produced from the interaction.It is the substance and the analyte that may lead to the formation of two peaks.The fast interaction mechanism between the solute and the micellar should be queried from the experiment result.     

Two-peak phenomena and formation origin in micellar electrokinetic capillary chromatography

Since Terabe et al.[1] developed micellar electrokinetic capillary chromatography (MECC) in 1984, a great number of important advances about separating neutral compounds have been achieved. In MECC mode, micellar of an ionic surfactant can form so-called pseudo stationary phase in the buffer solution when it is above the critical micelle concentration, and some portions of the solute may be distributed into the micellar phase when they are mobilized into the buffer solution from sample zone…     

Ion Interaction: The Energetics and Mechanism of The Competitive Behavior BEtween Two Similarly Charged Molecules. 2. Temperature Effect and Energetics

Abstract

The competition between two molecules of similar polarity for adsorption sites on the stationary phase is discussed in light of the effects of temperature, acetonitrile and surfactant (cyclohexylaminopropane sulfonic acid, CAPS) concentration on the retention of the thyroid hormones (3,5-diiodo-thyronine, T2; 3,3′,5-trillodo-thyronine, T3 and thyroxine, T4). The data are analyzed using a second-order polynomial from which the enthalpy, entropy and heat capacity can be evaluated. The molecular motion of the analyte is reduced with an increase in surfactant concentration as determined from entropy and heat capacity calculations. This effect does not result from micelle formation but rather from molecular interaction between the analyte and a few surfactant molecules. A reduction in enthalpy from competitive and interactive behaviour is proposed. The compensation temperature is half of what is normally observed, which is related to the heat capacity effect and the data treatment.     

Steric repulsion between internal aqueous droplets and the external aqueous phase in double emulsions

A theoretical model for analyzing the steric repulsion energy between internal aqueous droplets and the external aqueous phase in double emulsions, which results from the steric interaction between the surfactant molecules adsorbed at the two interfaces, has been established. The steric interaction is dependent on the separation distance between the internal aqueous droplets and the external aqueous phase, the thicknesses of the two adsorbed surfactant layers, and the size of the internal aqueous droplets and the oil globules, all of which determine the extent of the compression of the adsorbed surfactant molecules. The thickness of each of the two surfactant layers have the same effect on the steric repulsion, and stronger steric interaction can be achieved with thicker adsorbed layers, which can effectively prevent coalescence between the internal aqueous droplets and the external aqueous phase. Increasing the internal aqueous droplet size can produce stronger steric repulsion; however, larger oil globules will weaken the steric repulsion, indicating that a more stable double-emulsion system can be achieved by preparing the system with smaller oil globules and larger internal aqueous droplets.     

Shape-specific detection based on fluorescence resonance energy transfer using a flexible water-soluble conjugated polymer

We present the detection of the shape-specific conformation of DNA based on the fluorescence resonance energy transfer (FRET) by using a novel flexible water-soluble cationic conjugated polymer (CCP). The flexible backbone of CCP has more conformational freedom with the potential to be responsive to analyte shape by electrostatic interaction between flexible CCP and negatively charged DNA. The analyte shape dependent recognition is accomplished by structural changes that compressed or extended the flexible CCP. The morphology-dependent spectral properties of the novel flexible polymer related to the analyte shapes are investigated in detail, where two types of chromophores, referred to as "isolated" segment and "packed" segment aggregates, within the flexible polymer are identified by means of ensemble and single molecule measurements upon binding with different geometric DNA. The change in fluorescence intensity upon binding with shape-specific DNA without obvious color shifts makes this novel flexible polymer a suitable CCP donor for FRET measurements. The results provide insights for understanding the spectral properties of flexible water-soluble CCP and CCP/DNA interaction related to the geometry of target analyte.     

Micellar electrokinetic chromatography of proteins

Micellar electrokinetic capillary chromatography (MECC) of proteins is a high resolution capillary electrophoretic (CE) analysis method that utilizes the hydrophobic and electrostatic interaction of protein analytes with surfactant micelles present in the buffer medium to facilitate separation. Through the manipulation of the protein-micelle interaction by the adjustment of variables such as surfactant concentration, solution pH, ionic strength, the presence of an organic modifier and the use of coated capillaries, MECC analyses of a wide variety of proteins have been optimized. MECC has been demonstrated to provide resolution of mixtures consisting of proteins with minor structural variations and also has provided the successful quantitative analysis of protein present in complex matrices. The adoption of protein MECC as a routine analytical technique may be dependent upon the successful interface of MECC with detection methodology, such as mass spectrometry, which can provide analyte characterization information.     

Solute-solvent interactions in micellar electrokinetic chromatography: V. Factors that produce peak splitting

The experimental conditions that produce analyte peak splitting in micellar electrokinetic capillary chromatography (MEKC) have been systematically investigated. The system studied was a neutral phosphate buffer and sodium dodecyl sulfate (SDS) micelles as pseudostationary phase. A number of analytes showing a wide variety of hydrophobicity values and several organic solvents as sample diluents have been tested. Peak splitting phenomena are mainly due to the presence of organic solvent in the sample solution. They increase with the hydrophobicity of the analyte and decrease with the increase of the surfactant concentration. When hydrophobic compounds are analyzed the suggested ways to avoid split peaks are: (i) the use of 1-propanol or 1-butanol as sample diluent instead of methanol or acetonitrile or (ii) the use of high concentration of surfactant in the separating solution when the analyte must be dissolved in pure methanol or acetonitrile.     

DEA与SDS/n-C5H11OH/H2O微乳液的相互作用

以循环伏安法研究了N,N-二乙基苯胺（DEA）与十二烷基硫酸钠（SDS）/正戊醇（n-C5H11OH）/H2O体系O/W和W/O结构微乳液的相互作用.结果表明,DEA在SDS/n-C5H11OH/H2O体系微乳液中有两种定位方式:其一,DEA分子在微乳液液滴膜相中定位于表面活性剂和助表面活性剂的极性基团附近;其二,DEA分子在微乳液液滴膜相中定位于表面活性剂疏水基团一侧.两种定位的分布与微乳液的结构和组成相关.     

Electromigration peak dispersion of isotachophoretic protein zones during capillary zone electrophoresis

The relationships between electromigration dispersion (EMD) and on-line isotachophoresis-capillary zone electrophoresis (ITP-CZE) are described for several basic model proteins and interleukin-6 (rhIL-6). During CZE separation of the highly concentrated analyte zones which were generated during the initial ITP step EMD evolves from intrinsic differences in conductivity between the focused ITP zones and the leading electrolyte. Nearly triangular peaks with a sharp front and diffuse rear side were observed. An electromigration dispersion factor (F_EMD) was introduced to measure peak asymmetry. EMD of individual peaks was shown to increase with the absolute amount of the respective analyte injected and with analyte mobility. Good linearity was observed when F_EMD was plotted against protein mobility (r > 0.95). The slope of the graphs describing this relationship increased with the amount of analyte injected. The influence of EMD on the separation efficiency of neighboring peaks appeared to be less pronounced than expected. Consecutive release from the ITP-stack during transition from ITP to CZE might be an explanation for this observation.     

Capillary zone electrophoretic separation of neutral species of chloro-s-triazines in the presence of cationic surfactant monomers

Chloro-s-triazines are difficult to separate by capillary zone electrophoresis (CZE), due to their low pKa values. However, these analytes can be effectively separated by CZE in the presence of cationic surfactant monomers, such as tetradecylammonium bromide (TTAB) and dodecyltrimethylammonium bromide (DTAB). The separation mechanism based on a 1:1 binding of analytes to cationic surfactant monomers is proposed. The binding constants of chloro-s-triazines to cationic surfactant monomers are estimated. The results show that the strength of the interactions of these analytes with TTAB monomers is considerably strong, whereas that of the corresponding analyte with DTAB monomers is about 12- to 14-fold weaker. A linear correlation of binding constants with log P(ow) (the logarithm of the partition coefficient of analytes between 1-octanol and aqueous phases) indicates that the migration order of these chloro-s-triazines depends primarily on their hydrophobicity. Moreover, the skewed peaks of chloro-s-triazines observed may reveal the occurrence of adsolubilization of these analytes in the adsorbed cationic surfactant layer on the capillary surface.