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101.
102.
L. A. Kartsova A. M. Popova A. A. Sidorova O. I. Markova 《Journal of Analytical Chemistry》2007,62(2):179-183
The possibility of evaluating stability constants in the analyte-macrocycle system by capillary zone electrophoresis was exemplified in the separation of a mixture of acids (homovanillic acid, vanilmandelic acid, 5-hydroxyindole-3-acetic acid, and 3,4-dihydroxyphenylalanine) or bases (adrenalin, noradrenalin, dopamine, serotonin, and metanephrine) with the addition of β-cyclodextrin or 18-crown-6, respectively, to the buffer electrolyte. The information content of the constants obtained in the separation of biologically important mixtures for the determination of optimum concentrations of the complex-forming agents in the running buffer is discussed. 相似文献
103.
The effect of the addition of 18-crown-6 to the water–methanol and water–acetonitrile mobile phase on the selectivity of the separation of different derivatives of phenol, aniline, and benzoic acid by reversed-phase high-performance liquid chromatography was studied. It was demonstrated that the retention of compounds with the protonated primary amino group is increased in the presence of 18-crown-6 in the eluent, which can be explained by complexation between analyte compounds and macrocycles. For compounds containing the hydroxyl group (phenol and its derivatives), the addition of 18-crown-6 to the mobile phase leads to some decrease in retention. It was demonstrated that the selectivity of 18-crown-6 can change depending on the nature of the positional isomer (ortho, meta, orpara) of the analyte and the nature of the solvent increasing or decreasing the complexing ability of the sorbate with the macrocycle. The effect of the concentration of crown ether on the retention of compounds with the protonated amino group was revealed, and the complexation mechanism was suggested. 相似文献
104.
基于密度泛函理论(DFY)的第一性原理计算方法,对氢原子在过渡金属(Sc、Ti、Cr、Mn、Fe、Co、Ni、Cu、V、Zn)修饰的Mg(0001)表面扩散性能进行了研究.研究发现过渡金属元素Sc、Ti、V、Cr、Mn、Fe、Co、Ni和Cu选择替代在镁表面第二层稳定,而Zn则选择替代在第一层稳定.当镁表面掺杂Zn和Cu时,氢原子选择停留在表面稳定;当掺杂Sc、Ti、V、Cr、Mn、Fe、Co和Ni时,氢原子选择进入镁块体内部.值得一提的是氢原子通过从过渡金属顶部通道扩散进入镁块体内部的势垒大大降低,笔者用差分电荷密度分析后发现氢原子与过渡金属原子成键使扩散势垒降低.当氢原子进入镁块体内部后靠近Sc、Ti、V、Cu和Zn原子时,将与这些过渡金属原子成键,从而阻碍了氢原子继续向内部扩散;而氢原子靠近Cr、Mn、Fe、Co、Ni原子时,选择离开过渡金属从而促进了氢原子向块体内扩散,可以大幅改善镁基储氢材料的吸氢动力性能. 相似文献
105.
106.
Kimmo A Michelsen Daniël LA van den Hove Christoph Schmitz Olivier Segers Jos Prickaerts Harry WM Steinbusch 《BMC neuroscience》2007,8(1):107
Background
Both prenatal stress (PS) and postnatal chronic mild stress (CMS) are associated with behavioral and mood disturbances in humans and rodents. The aim of this study was to reveal putative PS- and/or CMS-related changes in basal spine morphology and density of pyramidal neurons in the rat medial prefrontal cortex (mPFC). 相似文献107.
To improve the sensitivity of the UV-detection for the determination of trace amounts of albumin by capillary zone electrophoresis (CZE), five on-line preconcentration techniques, including field-amplified sample stacking (FASS), head-column field-amplified sample stacking (HC-FASS), stacking with a polymer solution, dynamic pH junction and large volume sample stacking (LVSS) with reversed polarity, were compared. Sensitivity enhancement factor and reproducibility were two factors that were used to assess the suitability of each method. To minimize protein adsorption on the capillary wall, capillaries were covalently modified with anionic polymer, poly(sulfopropylmethacrylate) coating. All used methods have good reproducibility. The maximum sensitivity enhancement factor (about 67-fold in terms of peak heights) was achieved with LVSS technique. The concentration limit of detection (LOD) (S/N=3) for the human serum albumin obtained with the optimized LVSS approach was 15 microg/ml with UV-detection. The method was further evaluated for the analysis of urine samples with gel-filtration-based sample-desalting procedure. 相似文献
108.
目的对青海省唐古特铁线莲质量控制标准进行研究。方法采用薄层色谱法对唐古特铁线莲进行定性鉴定,展开剂为氯仿与丙酮(95:5),显色剂为10%硫酸甲醇;采用HPLC(Lc-2010HT)法测定唐古特铁线莲中齐墩果酸的含量,色谱柱为PhenomenexLunaCt8(250mm×4.6mm,5Ixm),流动相为y(乙腈)+V(0.2%磷酸水溶液)=35+65,流量为1mL/min,柱温为室温(25℃),检测波长为205nm。结果薄层色谱鉴定中,供试品色谱与对照品色谱相应的位置上,显示出相同颜色的荧光斑点;齐墩果酸在0.0233—0,7000mg/mL范围内呈良好的线性关系,线性回归方程为Y=2×10-6+360803,r。=0.9917,RSD为1.61%,并对青海省野生和栽培唐古特铁线莲中齐墩果酸进行了定量分析,结果显示前者平均值为0.1184%、RSD为2.5113%,后者平均值为0.0651%、RSD为2.92%。结论该法操作简单、快速、准确、灵敏、重现性好,可有效控制青海省唐古特铁线莲的质量。 相似文献
109.
采用密度泛函理论(DFT)B3LYP方法和非迭代三激发电子相关耦合簇CCSD(T)方法研究了二重态和四重态势能面上由Pt+(2D,4F)催化H2O和CH4产生水煤气的循环反应.采用分子轨道(MO)理论和自然键轨道(NBO)理论对最低能量路径的反应势能面作了详细的分析说明.应用Kozuch撰写的能量跨度模型(energetic span model)确定了决定循环反应速率的决速过渡态(TDTS)和决速中间体(TDI),最后计算了催化剂的转化频率(TOF)以评价催化剂的性能. 相似文献
110.
V. E. Potolitsyna L. A. Kartsova E. A. Bessonova 《Journal of Analytical Chemistry》2013,68(11):981-985
Capillary electrochromatography (CEC) is actively used for biomedical studies. Therefore, the search for new materials for stationary and pseudostationary phases for CEC that allow the control of the selectivity of separation, modification of quarts capillary walls, an increase in efficiency, and the reduction of the limits of analyte detection is a promising line of research. PLOT columns in this work have been synthesized using new dendritic polymers that are water soluble oligosaccharide derivatives of hyperbranched polyethyleneimine (PEI-Mal). The obtained coating has been characterized by the value of electroosmotic flow (EOF), and the influence of the composition and pH of a buffer electrolyte on the separation of proteins under CEC conditions with PLOT columns has been studied. 相似文献