高效液相色谱讲座Ⅱ高效液相色谱的基本参数和基础理论（上）

色谱分离是基于样品组分在两个非互溶相间的多次反复平衡分配,利用分配中的微小差异而达到分离的目的。两个非互溶相分别称为流动相和固定相。为了描述分配过程和评价色谱柱性能,从而找出最佳分离条件,需要有一系列的色谱参数。     

色谱柱分离过程的驰豫理论基本模型的建立

根据样品分子在色谱柱分离过程中的输运特征,认为样品在系统中以跃迁的方式完成迁移,建立了色谱柱分离过程驰豫理论的基本模型。假设溶质在两相间平衡,用母函数方法研究非连续递推形式的驰豫理论输运动力学微分方程组,得到了描述组分在柱后浓度分布规律的基本流出曲线方程,并通过数值解方法模拟谱图对各输运参量与流出曲线特征的关系加以讨论。     

气相色谱过程动力学研究-柱压降对色谱流出曲线的影响

本文在色谱质量平衡模型基础上, 考虑到气相色谱过程中柱压降与载气线速的关系, 建立了考虑柱压降的气液分配色谱质量平衡模型。通过数学变换的方法, 得到了流出曲线一级矩及二级、三级中心矩的数学表达式。理论和实验均表明: 溶质的保留时间, 流出峰半峰宽与柱前压倒数近似呈线性关系; 柱压降对柱效及峰形对称性也有影响。     

气相色谱过程动力学研究-柱压降对色谱流出曲线的影响

本文在色谱质量平衡模型基础上,考虑到气相色谱过程中柱压降与载气线速的关系,建立了考虑柱压降的气液分配色谱质量平衡模型.通过数学变换的方法,得到了流出曲线一级矩及二级、三级中心矩的数学表达式.理论和实验均表明:溶质的保留时间,流出峰半峰宽与柱前压倒数近似呈线性关系;柱压降对柱效及峰形对称性也有影响.     

双柱交替循环色谱分离甘露醇山梨醇过程

本文在非线性非平衡双柱循环色谱分离过程数学模型的基础上,进行了双柱交替循环色谱分离甘露醇山梨醇的实验,对模型进行了实验验证。结果表明：采用非线性非平衡双柱循环色谱模型计算的流出曲线与实验结果相吻合。计算机模拟的结果从理论上证明了对本实验体系采用双柱交替循环色谱分离模式比采用传统的色谱分离模式能获得更高的分离产率,产率随循环次数的增加而增加,使用双柱交替循环色谱分离操作模式获得的分离效率超过使用传统长色谱柱操作模式获得的分离效率。当轴向扩散比较严重、液固两相间的传质阻力较大,或者吸附的表观选择性系数较小时,采用双柱循环色谱模式比使用传统单柱色谱模式能获得更高的产率。     

电中性溶质在反相毛细管电色谱柱上峰展宽的研究

根据溶质在色谱柱中迁移的基本特征及柱分离过程弛豫理论的一般输运方程,在平衡色谱和不单独考虑逆向流的简化情况下,得到了能够说明多种因素对半峰宽影响的流出曲线的二阶中心矩表达式。通过反相毛细管电色谱实验,讨论了电压、柱长及保留因子等因素与峰展宽之间的关系,也探讨了溶质在色谱柱内峰展宽的规律。结果表明:半峰宽随柱长的增加和保留因子的增大而线性增加,随电压的增加而呈非线性减小。     

液相色谱双保留机理动力学过程研究

本文根据质量平衡原理建立了反相色谱双保留机理的质量平衡模型, 导出了色谱流出曲线的一阶矩和二、三阶中心矩, 获得了双保留机理色谱容量因子和塔片高度的表达式. 讨论了各种色谱动力学参数对柱效和峰形的影响, 对改善色谱峰对称度和提高柱效的措施作了理论说明。     

高温二维液相色谱系统的构建及其评价

在二维液相色谱中, 第二维的分离速度是制约其发展的重要因素. 升高色谱柱温度可以有效降低流动相粘度, 加快溶质在两相间的传质速率, 有效加快分析速度. 以离子交换色谱法(WAX)为第一维分离模式和反相色谱法(RP)为第二维分离模式, 十通阀和两个捕集柱为接口, 通过将第二维色谱柱温度升高到80 ℃和提高流量到3 mL/min, 构建了高温WAX/RP二维液相色谱系统. 以4种标准蛋白的酶解物为样品评价系统的分离性能, 第一维共有33个馏分被捕集并导入到第二维分析, 高温二维液相色谱系统识别出187个色谱峰.     

色谱柱分离过程弛豫理论——流出曲线的动力学本质

在分析型线性色谱中,流出曲线一般表现为拖尾的形式,这种现象可以采用多种机理加以解释。模仿动力学弛豫理论的假设条件,认为溶质在柱过程中的迁移以跃迁形式完成,得到了浓度分布曲线的数学表达式。分别探讨跃迁次数、两相间跃迁速率及溶质在流动相中的轴向跃迁对峰形的影响,进一步说明了色谱流出曲线的动力学本质     

毛细管电色谱柱重复性考察及实验条件的选择

成功地研制了７５μｍ内径偶联式和７５,１００μｍ内径非偶联式毛细管电色谱柱。在自制电色谱柱上获得了小于２．１２％的保留时间ＲＳＤ值,考察了ｐＨ值、有机溶剂浓度对保留行为的影响,并用以指导实验条件的选择。比较了两种方式电色谱柱的峰形。     

国内光催化研究进展简述

分1975~1985, 1985~1995和1995~2012三个时期简要介绍了国内光催化研究进展, 主要侧重于光催化材料及其改性、应用和反应机理方面的研究进展, 并指出了当前光催化领域存在的一些重要问题和未来的发展趋势, 涉及到光解水、CO₂还原、环境净化和选择性有机合成等方面.     

青蒿素研究进展

青蒿素是目前治疗疟疾的特效药。本文对自青蒿素发现以来的最新研究进展进行了比较详尽的综述。内容包括: 青蒿素的发现及历史, 青蒿素的来源, 青蒿素的全合成,青蒿素的生物合成, 青蒿素衍生物以及植物组织培养生产青蒿素。     

Reactions in droplets in microfluidic channels

Fundamental and applied research in chemistry and biology benefits from opportunities provided by droplet-based microfluidic systems. These systems enable the miniaturization of reactions by compartmentalizing reactions in droplets of femoliter to microliter volumes. Compartmentalization in droplets provides rapid mixing of reagents, control of the timing of reactions on timescales from milliseconds to months, control of interfacial properties, and the ability to synthesize and transport solid reagents and products. Droplet-based microfluidics can help to enhance and accelerate chemical and biochemical screening, protein crystallization, enzymatic kinetics, and assays. Moreover, the control provided by droplets in microfluidic devices can lead to new scientific methods and insights.     

Interpretation of inorganic arsenic metabolism in humans in the light of observations made in vitro and in vivo in the rat

The toxicity of inorganic trivalent arsenic for living organisms is reduced by in vivo methylation of the element. In man, this biotransformation leads to the synthesis of monomethylarsonic (MMA) and dimethylarsinic (DMA) acids, which are efficiently eliminated in urine along with the unchanged form (As_i). In order to document the methylation process in humans, the kinetics of As_i, MMA and DMA elimination were studied in volunteers given a single dose of one of these three arsenicals or repeated doses of As_i. The arsenic methylation efficiency was also assessed in subjects acutely intoxicated with arsenic trioxide (As₂O₃) and in patients with liver diseases. Several observations in humans can be explained by the properties of the enzymic systems involved in the methylation process which we have characterized in vitro and in vivo in rats as follows: (1) production of As_i metabolites is catalyzed by an enzymic system whose activity is highest in liver cytosol; (2) different enzymic activities, using the same methyl group donor (S-adenosylmethionine), lead to the production of mono- and di-methylated derivatives which are excreted in urine as MMA and DMA; (3) dimethylating activity is highly sensitive to inhibition by excess of inorganic arsenic; (4) reduced glutathione concentration in liver moderates the arsenic methylation process through several mechanisms, e.g. stimulation of the first methylation reaction leading to MMA, facilitation of As_i uptake by hepatocytes, stimulation of the biliary excretion of the element, reduction of pentavalent forms before methylation, and protection of a reducing environment in the cells necessary to maintain the activity of the enzymic systems.     

Gemini表面活性剂合成进展

系统总结了近百种Gemini表面活性剂的合成路线和方法,并且按照其结构特点分门别类地进行比较和归纳,对今后Gemini表面活性剂的合成发展方向提出了一些看法,这对促进此类新颖表面活性剂的工业化进程将具有指导意义。     

Recent Advances in Analytical Methodology for in vivo Electrochemistry in Mammals

Electrochemistry is one of the most advanced techniques for monitoring neurochemical activities in the living brain because electrochemical approaches bear the advantageous features of high spatial and temporal resolutions, which facilitate its tremendous potential in investigating the highly spatially heterogeneous brain system and the fast dynamics of neurochemical activities. On the other hand, since brain is the most complicated organ in the sense of its numerous kinds of neurochemical species, high selectivity is always required for any analytical methods that approach the brain. In this review, we will discuss various electrochemical methodologies to achieve selective detection of neurochemicals in mammalian brain and the strategies developed mainly by our group towards selective monitoring of both electrochemically active and inactive neurochemicals. At the end, we will discuss possible solutions towards brain mapping of neurochemical species and combination of neurochemical detection strategy with electrophysiology as the direction of future development of electroanalysis in living brain.     

乙基香兰素研究前景

报导了近几十年来国内外关于乙基香兰素的研究进展与动态,并简单介绍了本文作者在该方面所取得的研究成果,参考文献33篇。     

Trends in education in analytical chemistry

Summary At the session of the WPAC of Fechem on education in analytical chemistry it was concluded that it is now essential to include chemometrics and basic knowledge of computers in all courses on analytical chemistry.

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Tendenzen in der analytisch-chemischen Ausbildung

Zusammenfassung Bei einer Tagung der WPAC über die Lehre auf dem Gebiet der analytischen Chemie wurde bei der Betrachtung neuer Aspekte festgestellt, daß vor allem Chemometrie und Grundkenntnisse in Computertechnik in die Ausbildung aufgenommen werden sollten.

     

钙与人体及临床

钙是宏量元素，是人体中含量较高的元素之一，体内99％的钙构成骨骼和牙齿以及维持骨骼结构，1％的钙调节人体重要生理功能。钙的含量过高或过低都与许多疾病有关，只有保持一种平衡状态，才能使机体处于正常环境。     

AGET ATRP in the Presence of Air in Miniemulsion and in Bulk

Summary: The recently developed initiation system, activators generated by electron transfer (AGET), is used in atom transfer radical polymerization (ATRP) in the presence of a limited amount of air. Ascorbic acid and tin(II ) 2‐ethylhexanoate are used as reducing agents in miniemulsion and bulk, respectively. An excess of reducing agent consumes the oxygen present in the system and, therefore, provides a deoxygenated environment for ATRP. ATRP of butyl acrylate is successfully carried out in miniemulsion and in the presence of air. During polymerization the radical concentration remains constant. The polymerization reaches over 60% monomer conversion after 6 h, which results in polymers with a predetermined molecular weight = 14 000 g · mol⁻¹ and a low polydispersity ( = 1.23). AGET ATRP of styrene is also successful in bulk in the presence of air, as evidenced by linear semi‐logarithmic kinetics, which leads to polystyrene with an of 13 400 g · mol⁻¹ and a low polydispersity index ( = 1.14).

Appearance of miniemulsion before and after the reducing agent ascorbic acid was added (left); and GPC traces representing molecular weights during the AGET ATRP of BA in miniemulsion in the presence of air (right).