基于分离粒子随机扩散理论的色谱模拟

为了对扩散分子的轨迹实施动态追踪与模拟, 深入理解分子扩散对色谱动力学的影响, 本文利用微尺度受限空间随机行走的模拟方法对色谱填充柱中的分子扩散过程进行了模拟. 重点考察了固定相的填充率、固定相的形状和柱长对色谱动力学行为的影响. 模拟结果表明短柱和大填充率具有较高的柱效; 在相同的密堆排列下, 固定相形状对分子扩散过程影响微弱; 待分离粒子的运动表现出微尺度空间限域的扩散特征, 但粒子的流动行为会随外部压力的增大而增加. 本论文提出的模拟方法对于发展高效能色谱, 开发新型分离技术等具有参考意义.     

基于随机行走扩散模型的气相色谱分离模拟

利用粒子在受限空间内随机行走的扩散理论,构建了气相色谱毛细管柱分离的仿真模型,系统地考察了各模拟参数对粒子在色谱柱内的碰撞情况和峰宽的影响。模拟结果表明随机速度和时间步长的增加以及载气流速的降低均会加剧粒子碰撞和色谱峰展宽,而相互作用虽与碰撞行为无关,但峰宽会随着相互作用的增加而显著增大。模拟结果证实了该模型与色谱基本理论的一致性。     

控制气液色谱分离的因素

采用C_(max)/C_0作为判断色谱柱分离效能的指标及应用已获得的色谱理论的成就,研究了在氣液色谱柱上两个成分的分离问题.认为当液膜扩散是色谱区域扩张的主要因素时,应用 H_液和 F_液可以分别代表色谱柱的选择性和操作效能:     

基于布朗棘轮的单通道分离体系的模拟研究

分子在微尺度受限空间内的扩散行为是微观化学的重要研究领域. 本文利用布朗棘轮效应构建了一种微型单通道分离器件模型, 并基于随机行走理论对其中分子的扩散分离运动进行了模拟研究, 阐明了该体系的分离机理并考察了不同条件对分子扩散分离运动的影响. 模拟结果表明, 通过调节驱动力对各组分粒子的作用周期, 可以控制粒子与分离通道两端势垒发生不同程度的相互作用, 从而在单分离通道内实现粒子向不同方向的有效分离. 同时, 也给出了利用该分离体系进行分离的组分粒子本身的扩散运动与受外力驱动运动的相对大小需满足的条件. 通过调整分离器件的结构参数, 可在实现最佳分离效果的同时节约时间成本. 本文提出的模拟方法对开发微型分离器件及优化操作参数等具有参考意义.     

纳米粒子毛细管电色谱技术及其应用

纳米粒子以其较大的比表面积、良好的生物相容性而被广泛应用于分离科学领域. 纳米粒子毛细管电色谱(NPCEC)是纳米材料技术与毛细管电泳/电色谱(CE/CEC)技术相结合的产物.NPCEC技术是将不同基质的功能化纳米粒子加入电泳的运行缓冲液中,纳米粒子不仅可以通过动态吸附于毛细管壁而改变(或逆转)电渗流,还可作为准固定相(PSPs)参与样品在柱内的分配和保留,从而提高柱效和改善分离的选择性.该技术因无需填充和柱塞制备等步骤而日益受到关注.此外,NPCEC技术还可实现良好的柱更换,避免了进行复杂样品分析时所造成的柱污染.该文重点讨论在NPCEC实验中常用的几种纳米粒子的合成及应用,包括聚合物纳米粒子、二氧化硅纳米粒子、金纳米粒子、碳纳米管和树状聚合物,并对其发展前景进行了展望.     

柱吸附容量对蔗糖还原糖色谱分离过程产率和回收率的影响

本文采用了能反映流体轴向扩散的大型液相色谱分离过程数学模型,应用计算机模拟分析蔗糖和还原糖的色谱分离过程,从吸附剂吸附容量和柱装填密度两个方面;考察柱吸附容量对大型色谱分离的产率和回收率的影响。研究结果表明：在色谱柱中流体线速度恒定的条件下对多组分分离,回收率是随吸附剂吸附容量以及床层装填密度的增大而增大的;产率先随吸附剂吸附容量的增大而增大,而在出现峰值后下降;随着床层装填密度的增大,产率增加,但与此同时轴向扩散系数也增大,从而降低分离效率,导致在较高装填密度的范围内产率增力。的幅度减少。在相同的吸附剂用量下,采用短柱高装填密度的色谱柱将比长柱低装填密度色谱柱能获得更高的回收率和产率。     

液相色谱塔板高度方程的统一形式

研究了色谱分离过程中物质的径向扩散和流动相发热对柱效能的影响。从热传导方程出发,运用色谱过程动力学原理推导了包括考虑流动相径向扩散、色谱柱发热影响的液相色谱塔板高度方程：

该方程概括了高效液相色谱（HPLC）、超高效液相色谱（UPLC）、毛细管电色谱（CEC）和消滞留层液相色谱（ESFLC）塔板高度与各种因素的关系。方程最后一项代表了径向扩散和柱发热对塔板高度的贡献。当流动相线速度较低且柱内径较细时,流动相摩擦生热和径向扩散对塔板高度的贡献趋近于零,塔板高度方程还原成Horvath和Lin的方程;当流动相线速度较高时,由于流动相摩擦生热,柱轴心与边缘温差增加,导致流动相线速度径向分布差异,使得柱效率降低。柱轴心与边缘的温差与流动相线速度平方成正比。该文指出,在流动相高线速度情况下,液相色谱的柱效率与柱内径密切相关,采用细内径柱有利于实现高速与高效率;过高的流动相线速度将导致色谱柱效率崩溃。     

高温正相色谱/反相色谱(HTNPLC/RPLC)二维联用系统的构建与应用

为解决含水正相色谱与反相色谱联用过程中的谱带展宽问题,以高温正相色谱(HTNPLC)为第一维,室温反相色谱(RPLC)为第二维,分别建立了切割模式的二维液相色谱(HTNPLC-μRPLC)和全二维液相色谱(HTNPLC×RPLC)系统.样品首先在第一维(CN色谱柱)进行正相分离,第一维洗脱产物选择性地或者交替存储在十通阀上的定量环中,然后切换十通阀将定量环内存储的样品组分转移到第二维(C18色谱柱)进行反相分离.该系统降低了第一维切割组分在第二维柱头的扩散,提高了分离度以及分离效率.采用多环芳烃混合物和天然植物甘草提取液对该二维液相色谱系统进行了评价.     

径向色谱中溶质的输运特征

基于溶质在径向色谱柱内输运的质量平衡方程, 在线性分配条件下, 得到了描述分离柱效和流出曲线形状各参数的理论表达式, 也对柱效和流出曲线对称性的变化趋势加以系统讨论. 结果表明: 径向色谱中, 柱效与体积流速之间的关系与轴向色谱中柱效与流动相线速度的关系在趋势上相同; 在较高流速下运行时, 径向色谱仍可以得到高柱效. 随着溶质容量因子、进样时间的增加, 柱效单调降低. 柱直径和柱长对柱效的影响存在交叉, 设计半径较大而长度较短的色谱柱将更有利于提高分离柱效. 径向色谱适宜于大分子样品的稳定分离方法建立, 也预示其对于蛋白、DNA等样品的制备分离具有明显优势.     

线性柱色谱分离过程的递推方程

依据非平衡热力学分离理论中的局域平衡假设和流体力学的Lagrangian描述方 法，首次提出了线性柱色谱分离过程中溶质带迁移和扩散的状态递推方程，克服了 以经典动力学为基础的塔板理论不能准确预测时变控制条件下溶质扩散的局限性。 反相色谱梯度洗脱的实验数据支持递推方程的理论预测，与基于塔板理论的预测方 法比较，状态递推方程法更具优越性。状态递推方程还为采用动态优化控制柱分离 过程奠定了基础。     

Theoretical simulation of chromatographic separation based on random diffusion in the restricted space

The diffusion behavior of particles in the chromatography is a fundamental issue of chromatographic dynamics. The understanding of the diffusion behaviors is particularly critical to optimize the operation conditions, improve the chromatographic performance and design a new separation device. Many of the present simulations focus on chromatographic thermodynamics, and very few aim at the overall diffusion and separation process. In order to dynamically trace the trajectory of the diffusing particles and to perform simulations of the whole chromatographic process, we have developed a model based on the framework of random walk in the restricted space and performed the simulation of a single particle diffusion in the gas chromatography. The simulation parameters were determined by comparing with the experimental data. The elution profiles of n-alkanes under different flow rates were accurately simulated with the method. The results show that the relative difference between the measures and the simulations are less than 2% and 10% for the retention time and the peak width, respectively. The simulation method shows great significance for the optimization of separation conditions and the development of novel technologies of chromatographic separation.     

炭化树脂色谱性能的理论探讨

本文从热力学和动力学的角度探讨二十一种炭化树脂不同分离性能的理论基础。     

厚朴酚键合硅胶液相色谱固定相的制备、表征与性能评价

通过γ-巯丙基三甲氧基硅烷(KH-590)的作用, 将具有抗菌功能的中草药厚朴的主要药用成分厚朴酚键合在硅胶表面上, 制备了厚朴酚键合硅胶液相色谱固定相. 采用红外光谱、元素分析和热重分析对该固定相进行了表征. 以苯同系物、5种吡啶、6种苯胺和8种芳香羧酸类化合物为溶质探针, 初步考察了该新型固定相的基本色谱性能, 研究了其对这些化合物的保留机理. 结果表明, 该固定相的反相色谱性能类似于十八烷基键合硅胶固定相(ODS), 分离原理与疏水性作用有关; 另外, 该固定相包含有别于疏水性作用的氢键作用、π-π电荷转移作用和偶极-偶极等作用, 多种作用力使其在分离某些可电离的碱性和酸性化合物时表现出更好的选择性和分离效果. 厚朴酚配体的多种作用位点对快速分离极性芳香化合物有重要贡献.     

Modelling of n-alkane retention and optimization of the conditions for analysis in gas adsorption chromatography with temperature programming

Summary The possibility of constructing a mathematical model of n-alkanes retention upon their separation by gas solid chromatography with temperature programming has been studied. The functional dependence between the number of the carbon atoms in n-alkane molecules, their retention in isothermal conditions and temperature of chromatographic column was used for constructing this mathematical model. It showed necessary to take into account the variance in the process temperature programming of both the carrier gas volume velocity and the column inlet pressure to obtain the adequate mathematical model of the chromatographic retention. With the use of the specific retention parameters of substances i.e. relative to the surface or the mass of sorbents the proposed model can be used not only for Silochrom C-80 but for the whole class of macroporous silica sorbents.     

Pore network modelling: determination of the dynamic profiles of the pore diffusivity and its effect on column performance as the loading of the solute in the adsorbed phase varies with time

A three-dimensional pore network model for diffusion in porous adsorbent particles was employed in a dynamic adsorption model that simulates the adsorption of a solute in porous particles packed in a chromatographic column. The solution of the combined model yielded the dynamic profiles of the pore diffusion coefficient of beta-galactosidase along the radius of porous ion-exchange particles and along the length of the column as the loading of the adsorbate molecules on the surface of the pores occurred, and, the dynamic adsorptive capacity of the chromatographic column as a function of the design and operational parameters of the chromatographic system. The pore size distribution of the porous adsorbent particles and the chemistry of the adsorption sites were unchanged in the simulations. It was found that for a given column length the dynamic profiles of the pore diffusion coefficient were influenced by: (i) the superficial fluid velocity in the column, (ii) the diameter of the adsorbent particles and (iii) the pore connectivity of the porous structure of the adsorbent particles. The effect of the magnitude of the pore connectivity on the dynamic profiles of the pore diffusion coefficient increased as the diameter of the adsorbent particles and the superficial fluid velocity in the column increased. The dynamic adsorptive capacity of the column increased as: (a) the particle diameter and the superficial fluid velocity in the column decreased, and (b) the column length and the pore connectivity increased. In preparative chromatography, it is desirable to obtain high throughputs within acceptable pressure gradients, and this may require the employment of larger diameter adsorbent particles. In such a case, longer column lengths satisfying acceptable pressure gradients with adsorbent particles having higher pore connectivity values could provide high dynamic adsorptive capacities. An alternative chromatographic system could be comprised of a long column packed with large particles which have fractal pores (fractal particles) that have high pore connectivities and which allow high intraparticle diffusional and convective flow mass transfer rates providing high throughputs and high dynamic adsorptive capacities. If large scale monoliths could be made to be reproducible and operationally stable, they could also offer an alternative mode of operation that could provide high throughputs and high dynamic adsorptive capacities.     

基于随机扩散理论的色谱模拟辅助化学教学研究

为了满足当今教学的信息化发展趋势,本研究基于随机扩散理论建立了气相色谱仿真模型并开发了相关的计算模拟软件Stochastic Diffusion-Chroma。以混合组分分别在气相色谱填充柱和毛细管柱中的扩散分离模拟为例,探究了随机扩散理论模型在色谱理论教学和实验教学方面的应用。基于随机扩散理论的仿真教学改变了传统的教学模式,将学生较难理解的抽象色谱动力学基本理论转变为动态的具体形象,激发了学生的学习兴趣,提高教学质量。     

Computer-assisted method development and optimization in high-performance liquid chromatography

This paper reports the use of DryLab, a computer simulation software package, to assist in the development and optimization of a reversed-phase high-performance liquid chromatographic (HPLC) method for the separation of a model drug candidate and its degradation products. Prior to the optimization process, columns with various bonded phases are evaluated for their chromatographic performance using the sample of interest. Simultaneous optimization of two separation variables and the use of resolution maps to predict the optimal conditions are illustrated. Options to optimize column conditions (column length and flow-rate) to further reduce run time are briefly discussed. The accuracy of DryLab-predicted retention times and resolution is compared with experimental values. The DryLab software used in this study provided satisfactory predictions for the selected model, with average errors of less than 3.5 and 11.8% for retention time and resolution, respectively.     

小鼠血清IgG的蛋白G灌注亲和色谱行为的研究

通过实验考察了小鼠血清ＩｇＧ的蛋白Ｇ灌注亲和色谱行为,虽然未发现非特异性吸附,但在通常情况下对ＩｇＧ存在不可逆性吸附。洗脱液组成及ｐＨ的不同决定ＩｇＧ在灌注亲和色谱柱上具有不同的解离常数ＫＤ,产生不同的色谱行为。流动相的流速对ＩｇＧ与蛋白Ｇ的结合／解离动力学过程产生一定的影响。结果表明,对于小鼠血清中的ＩｇＧ灌注亲和色谱的分离,由于解离速率影响到传质过程,使之在高流速下的分离受到一定的限制。     

Partitioning and adsorption in gas-liquid-solid chromatography: Models of temporal moments for retention and variance

Summary The resolution of gaseous chemical species in gasliquid-solid chromatography is influenced by absorption (partitioning) in the liquid and adsorption at the liquid-solid interface. We consider fundamental mass transfer models with adsorption and partitioning effects for solid chromatographic supports covered with thin films of stationary liquid. The dynamic models, based on mass-balance partial-differential equations, include the significant phenomena: convection, axial dispersion, gas-liquid mass transfer, intraparticle diffusion, and liquid-solid adsorption. Expressions for retention time and band variance (first and second temporal moments) are presented and evaluated for four distinct models: (1) capillary tube with inner surface covered with a uniform-thickness liquid film, (2) column of nonporous spheres covered with a uniform-thickness liquid film, (3) porous spherical particles with intraparticle pores covered with a uniform-thickness liquid film, (4) porous spherical particles with intraparticle pores completely filled with liquid.