电动分离统一理论

在真空、气相和液相中实施线性电动分离,创造出了质谱、离子淌度谱、电泳和毛细管电泳等,但它们却未成体系,各自发展,各有理论,互不相关。该文从牛顿力学第二定律出发结合静电学理论,推导出了它们的统一运动方程,并由此推演出并简要讨论了上述各法自己的通用运动子方程和测量模式。这些方程不仅有利于系统化这些现存方法,也可用于推导和发现新型电动分离模式。     

毛细管电泳迁移时间重现性影响因素的探讨

以电泳介质为研究对象,在毛细管区带电泳(CZE)和胶束电动毛细管色谱(MECC或MEKC)两种电泳模式下,探讨了电泳 介质中各组分浓度、冲洗程序、电泳介质在实验中发生的变化对溶质迁移时间重现性的影响。根据描述缓冲液中各组分 浓度与电渗流迁移时间和溶质迁移时间的关系式,证明利用电导值可准确地表征电泳缓冲液的浓度;通过控制缓冲液的电 导值可提高迁移时间的重现性。运行缓冲液pH值的变化影响毛细管壁上的硅羟基的电离,因此需选择合理的冲洗程序使硅 羟基的电离达到平衡,以提高迁移时间的重现性。毛细管入口端缓冲液是影响溶质迁移行为的主要因素,其在电泳中发生 的变化是影响电泳重现性的重要原因。目前在实验中可通过提高运行缓冲液的更换频率来保证迁移时间的重现性。     

毛细管区带电泳测定纳米粒子粒径分布的探索

研究了采用毛细管区带电泳测定纳米粒子粒径分布的可能性。在合适的分散条件下,聚苯乙烯(PS)纳米粒子在进样及电泳迁移过程中不发生团聚。通过选择合适的电泳操作条件,PS纳米粒子可以按照粒径大小得到分离,且迁移时间及峰面积的重现性良好。     

两种细菌的毛细管电泳分离及其与药物相互作用的研究

通过对大肠杆菌与金黄色葡萄球菌的毛细管电泳行为的研究,包括对细菌样品预处理、缓冲液、检测波长以及聚合物添加剂对分离度的改进等的考察,在优化的实验条件下,实现了大肠杆菌与金黄色葡萄球菌的快速分离,从而建立一种新的细菌辅助识别与定性的补充方法。将抗菌药物阿奇霉素与金黄色葡萄球菌混合培育,发现由于阿奇霉素抑制细菌表面蛋白合成,造成与金黄色葡萄球菌作用后,细菌表面电荷密度降低,表现为阿奇霉素对金黄色葡萄球菌的电泳淌度的影响,而且培育时间与金黄色葡萄球菌的淌度线性相关。     

高效毛细管电泳-激光诱导荧光检测生物活性肽的研究

使用毛细管电泳 -激光诱导荧光 -增强型电荷耦合器件(CE -LIF -ICCD)系统 ,用异硫氰酸荧光素(FITC)柱前衍生了亮脑啡肽、甲硫脑啡肽、血管紧张肽、P物质4种生物活性肽 ,优化了实验条件 ,在8min内 ,对它们进行了快速分离检测 ,血管紧张肽的质量检出限达到2.8×10-18 mol。     

迁移时间归一化法改善毛细管电泳表征中药大黄的重现性

探讨了迁移时间归一化法改善中药毛细管电泳分析迁移时间重现性的原理,并将其应用于实际样品的分析。迁移时间归一化法认为,在相同的操作电压、缓冲液组成和温度条件下,多次电泳实验中迁移时间产生差别的主要原因是多次电泳实验中电渗流产生了差异。迁移时间归一化法就是通过选择电泳谱图中的一个或两个峰作为标记峰,将各次电泳实验的迁移时间都归一到第一次电泳实验中的迁移时间。比较多次电泳实验中迁移时间(t)的相对标准偏差(RSD)、经单峰归一化处理的迁移时间(t′)的RSD、经双峰归一化处理的迁移时间(t″)的RSD、迁移时间比(t/tistd,istd代表所选择的标记物)的RSD,发现RSD(t″)相似文献   

类肝素化合物的傅立叶变换离子回旋共振-电喷雾质谱研究

采用负离子模式的电喷雾傅立叶变换离子回旋共振质谱(ESI-FTICR-MS)对3个合成的肝素类化合物DHα、THα和THβ进行了全扫描一级谱和持续非共振辐照碰撞诱导解离(SORI-CID)串联质谱分析。样品浓度10μmol/L,流动泵注射直接进样。化合物中的磺酸胺和磺酸酯结构容易在一般电喷雾条件下发生分解,失去一个或者多个SO3,一级全扫描谱图中得到的谱峰均是带有单电荷或者双电荷的准分子离子峰。在串联质谱中,部分双电荷离子发生解离时,其二级谱图中子离子由单电荷子离子和双电荷子离子共同组成。通过对谱峰的局部放大,利用同位素峰的峰间距,能直接给出子离子的带电荷情况。同时,结合FTICRMS提供的高质量精度质谱数据,能够对所选取母离子的碎裂途径进行确认。离子质荷比测量的平均误差小于3.0×10-6。为结构复杂的类肝素化合物的质谱分析提供了借鉴。     

微流控芯片上的红细胞电泳淌度研究

以单细胞成像法分别测量了 3组无农药含水质净化剂、有农药无水质净化剂及其有农药有水质净化剂处理后的杂交鲤鱼红细胞在塑料 ( polymethalmethacrylate ,PMMA)微流控芯片上的电泳淌度。其值分别为 1.138× 10 -4、0 .12 79× 10 -4和 - 0 .85 2 0× 10 -4cm2 v-1s-1。从电泳淌度的差别可以看出功夫菊酯和水质条件恶化均可使鲤鱼红细胞表面的电荷密度发生变化 ,从而引起电泳淌度的变化。同时还初步考察了细胞电泳淌度作为参数进行细胞分类的可行性 ,显示这种淌度差别有可能作为细胞分类的一项依据     

毛细管区带电泳同时分离苯二酚和硝基苯酚位置异构体

运用毛细管区带电泳模式,通过在缓冲溶液中添加有机溶剂成功地分离了邻、间、对苯二酚和邻、间、对硝基苯酚两组位置异构体。研究了缓冲溶液种类、浓度、pH值、电泳电压、温度、进样时间及有机溶剂等因素对分离的影响,得出了6种样品的标准曲线、线性范围及加样回收率。在优化条件下,10min内实现了上述6种酚类化合物的分离。该方法简便、快速、重现性好。     

泽泻乙醇提取物的HPCE分离研究

采用高效毛细管电泳的胶束电动毛细管色谱的分离模式(MEKC),对泽泻的乙醇(95％)提取物进行分离研究。以十二烷基硫酸钠(SDS)胶束为准固定相．硼砂为缓冲体系,甲醇为有机添加剂,考察了SDS浓度、硼砂浓度、pH、甲醇用量、电泳电压、电泳温度等对分离的影响。结果表明：硼砂缓冲体系为运行缓冲溶液(pH：9．18～9．20)、硼砂浓度30mmoL／L、SDS浓度45mmol／L、甲醇体积分数30％,分离电压25kv、分离温度25℃时分离效果最好。在此条件下,得到分离度和重现性均较好的泽泻乙醇提取物的HPCE色谱图。     

Identification of phosphorylation sites in phosphopeptides by positive and negative mode electrospray ionization-tandem mass spectrometry

A series of synthetic mono- and diphosphorylated peptides has been analyzed by positive and negative mode electrospray ionization-tandem mass spectrometry. The synthetic peptides are serine- and threonine-phosphorylated analogs of proteolytic fragments from the C-terminal region of rhodopsin. Use of positive and negative modes of electrospray ionization to produce ions for tandem mass spectrometry via low energy collision-induced dissociation was explored. For some of the peptides, the complementary use of experimental results allowed determination of the phosphorylation sites when either mode alone gave incomplete information. Other peptides, however, gave negative ion spectra not interpretable in terms of backbone cleavages. However, use of positive ion tandem mass spectrometry of different charge state precursor ions gave sufficient information in most cases to assign sites of phosphorylation. These results illustrate the utility of obtaining complementary information by tandem mass spectrometry by using precursor ions of different charge polarity or number.     

QTAIM charge-charge flux-dipole flux models for the infrared fundamental intensities of the fluorochloromethanes

The molecular dipole moments, their derivatives, and the fundamental IR intensities of the fluoro-, chloro-, and fluorochloromethanes are determined from QTAIM atomic charges and dipoles and their fluxes at the MP2/6-311++G(3d,3p) level. Root-mean-square (rms) errors of 0.01 D and 5.6 km mol(-1) are found for the dipole moments and fundamental IR intensities calculated using QTAIM parameters when compared with those obtained directly from the MP2/6-311++(3d,3p) calculations and 0.04 D and 23.1 km mol(-1) when compared with the experimental values. Charge, charge flux, and dipole flux contributions are calculated for all the normal vibrations of these molecules. A large negative correlation coefficient of -0.92 is calculated between the charge flux and dipole flux contributions and indicates that electron transfer from one side of the molecule to the other during vibrations is accompanied by relaxation with electron density polarization in the opposite direction. The CF, CCl, and CH stretching normal modes of these molecules are shown to have characteristic sets of charge, charge flux, and dipole flux contributions. Although the FCF and ClCCl deformation normal modes can also be discriminated from one another based on the sizes and signs of these contributions, some HCH deformations have contributions that are similar to those for some of the ClCCl deformations.     

Molecular electronegativity in density functional theory(Ⅷ)——Charge polarization modes in a closed system

Based on the density functional theory and the atom-bond electronegativity equalization model (ABEEM), a method is proposed to construct the softness matrix and to obtain the electron population normal modes (PNMs) for a closed system. Using this method the information about the bond charge polarization in a molecule can be obtained easily. The test calculation shows that the PNM obtained by this method includes all the modes about the bond charge polarization explicitly. And the bond charge polarization mode characterized by the biggest eigenvalue, which is the softest one of all modes related with chemical bonds, can describe the charge polarization process in a molecule as exquisitely as the corresponding ab initio method.     

Infrared intensity analysis of hydroxyl stretching modes in carboxylic acid dimers by means of the charge–charge flux–dipole flux model

The Charge‑Charge Flux‑Dipole Flux (CCFDF) model in terms of multipoles from the quantum theory of atoms in molecules (QTAIM) was used to investigate the variations in infrared intensities of hydroxyl (O H) stretching modes during the dimerization of carboxylic acids. The hydrogen bond formation in these systems results into bathochromic shifts of vibrational frequencies for all the O H stretching modes along with huge infrared intensity increments for some of them. These bands become more intense on dimerization due mainly to changes in the cross-term contribution between charge and charge flux. In addition, interaction energies for the pair of atoms directly involved in individual hydrogen bonds (O…H) are linearly correlated to electron densities at their bond critical points (BCPs). Therefore, the hydrogen bonds between the carbonyl group (CO) of acetic acid and the hydroxyl group of halogenated monomers show the largest electron density values at their BCPs. The formation of these intermolecular interactions is also accompanied by ionic character enhancements of O H bonds and electron density decrements at their BCPs. We finally noticed that the hydrogen atom belonging to the hydroxyl group loses electronic charge, while the oxygen from the CO end becomes more negatively charged during dimerization. © 2019 Wiley Periodicals, Inc.     

Molecular electronegativity in density functional theory(VIII) Charge polarization modes in a closed system

Based on the density functional theory and the atom-bond electronegativity equalization model (ABEEM), a method is proposed to construct the softness matrix and to obtain the electron population normal modes (PNMs) for a closed system. Using this method the information about the bond charge polarization in a molecule can be obtained easily. The test calculation shows that the PNM obtained by this method includes all the modes about the bond charge polarization explicitly. And the bond charge polarization mode characterized by the biggest eigenvalue, which is the softest one of all modes related with chemical bonds, can describe the charge polarization process in a molecule as exquisitely as the correspondingab initio method.     

Molecular electronegativity in density functional theory(VIII)

Based on the density functional theory and the atom-bond electronegativity equalization model (ABEEM), a method is proposed to construct the softness matrix and to obtain the electron population normal modes (PNMs) for a closed system. Using this method the information about the bond charge polarization in a molecule can be obtained easily. The test calculation shows that the PNM obtained by this method includes all the modes about the bond charge polarization explicitly. And the bond charge polarization mode characterized by the biggest eigenvalue, which is the softest one of all modes related with chemical bonds, can describe the charge polarization process in a molecule as exquisitely as the correspondingab initio method.     

Saturation of the electron-withdrawing capability of the NO2 group in nitroaromatic anions: spectroscopic and quantum-chemical evidence

The electronic (UV-vis) and resonance Raman (RR) spectra of the anionic species derived from 4-nitrophenol (pNP) and 4-nitroaniline (pNA) are reported. The interpretation of the electronic transitions in the visible, near-UV region was supported by quantum-mechanical calculations, allowing a consistent analysis of the enhancement patterns observed in the RR spectra, which show substantial differences in relation to those observed for the neutral species. The removal of the proton of the donor groups (OH and NH2) leads to additional charge density at the oxygen atoms of the electron-withdrawing group (NO2). On the other hand, when the RR spectra of [pNP]- and [pNA]- are compared, a drastic difference concerning the enhancement of modes related to the NO2 moiety is noticed. In particular, in the case of [pNA]-, the RR enhancement pattern involving the NO2 moiety is at variance with those observed for nitroaromatics in general, because the corresponding normal modes involve a more complex composition. Such results are in accordance with the quantum-chemical calculations, which indicate, in the case of [pNA]-, a saturation of the charge density at the N-O bonds, even in the ground state (i.e., the charge density is very similar in the ground and excited-state, which precludes large geometric variations of the NO2 moiety in the two electronic states). Conversely, in this case the most enhanced bands have significant participation of ring modes, which suggests that the charge in the excited-state is now much more distributed in the molecule as a whole.     

Chemical reactivity concepts in charge sensitivity analysis

Recent reactivity concepts formulated within charge analysis (CSA ) are outlined. The charge stability criteria of equilibrium states in open and closed systems are conveniently characterized in terms of the condensed reactant hardness quantities of reactants; their implications for catatytic systems are examined. A use of characteristics associated with selected collective charge displacement modes, including the populational normal modes and minimum-energy coordinates, as diagnostic tools in the theory of chemical reactivity is proposed. The importance of the mapping relations between modes defined in the electron population and nuclear position spaces, respectively, as the unifying concept linking the conjugate charge and geometry displacements, is commented upon. Recent results for model catalytic clusters are used to illustrate some of the concepts introduced. Finally, the relevant contributions to the quadratic interaction energy between reactants are reexamined and expressed in terms of relevant charge sensitivities. © 1995 John Wiley & Sons, Inc.     

Characterization of charge neutralization reaction in aqueous solution using the membrane separation method

Colloid titration and streaming current detector are two popular techniques used to determine the charge density of dissolved and colloidally dispersed polyelectrolytes. However, both techniques are based on some assumptions that may not be valid under some circumstances. In this paper, a membrane separation technique developed to determine the charge density and characterize a charge neutralization reaction is described. The technique characterizes the reaction between cationic and anionic charge carriers by measuring the counterions released during reaction or the unreacted small molecule charge carriers. Membranes with selected cutoff pore size were used to separate the species of interest from the bulk of the reaction mixture. Three different charge determination techniques were also compared.     

常压下能量与电荷在分子间的传递机制

离子源是质谱仪的心脏,制备待测物的离子是质谱分析的首要前提.如何有效地电离含有复杂基体的实际样品中的痕量待测物分子是制约实际样品直接质谱分析的重要瓶颈.本文提出了用电子云模型帮助理解能量与电荷传递和中性分子电离过程的关系,从分子的基本物性参数、能量耦合方式等角度讨论了能量与电荷在不同相态、组成和维度的复杂基体样品分子间传递的过程,着重阐述了能荷传递过程中分子的电子云变化规律及其对分子电离的影响,并简要讨论了这些影响在质谱分析中的应用.