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直接从原始塔板理论的级数形式色谱流出曲线表达式出发,得到了流出曲线一级原点矩及二、三级中心矩的数学表达式,并依此讨论了色谱峰的形状特征及各种因素对峰形的影响规律。本文结果直接证实原始塔板理论曲线为不对称分布,描述峰型不对称性的偏态系数与塔片数及容量因子有关,且随容量因子的增大逐渐变小。当塔片数很大时,容量因子不很小的组分流出曲线有相似的对称性。 相似文献
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在毛细管电色谱中,由于溶质在输运过程中所具有的电性质,常会产生一些特殊的现象。这些现象,如离子交换毛细管电色谱中产生超高柱效峰的现象,已经不能用一般的色谱理论加以解释。基于弛豫理论所建立的基本模型,在考虑溶质在两相中皆有可能发生正、反向迁移的情况下,得到了流出曲线一阶原点矩和二阶中心矩的理论表达式,并通过对溶质在两相中电扩散速率与电泳速率、电渗流速率关系的分析结果证实:溶质在固定相表面的电扩散行为可以使其保留变弱,出峰加快;而这种电扩散导致的超常柱效峰的出现具有不稳定性,只有在多方面因素综合影响匹配的情况下才可能出现。 相似文献
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]考虑轴向扩散的影响,导出液相色谱技术测定吸附相平衡常数和总数传质系数参数估值模型,测定葡萄糖果糖吸附相平衡常数和总传质系数,研究流速、温度对这些参数的影响。获得理论计算与色谱分离实验流出曲线相吻合结果。 相似文献
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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. 相似文献
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色谱流出曲线的二阶中心矩μ2和三阶中心矩μ3以及描述峰形非对称程度的偏态系数∑k=μ3/μ1.52是反映色谱峰形的重要参数。从液相色谱过程动力学方程出发,运用电子计算机证明了在线性非理想条件下高效液相色谱体系中不同保留值组分在柱末端峰形的分布基本一致的结论。 相似文献
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线性非理想条件下液相色谱柱末端峰形规律 总被引:2,自引:1,他引:2
色谱流出曲线的二阶中心矩μ2和三阶中心矩μ3以及描述峰形非对称程度的偏态系数∑k=μ3/μ1.52是反映色谱峰形的重要参数。从液相色谱过程动力学方程出发,运用电子计算机证明了在线性非理想条件下高效液相色谱体系中不同保留值组分在柱末端峰形的分布基本一致的结论。 相似文献
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Summary Mutual diffusion coefficients of two gases A and B can be determined in an empty gas chromatographic column by letting component B enter at an intermediate position of the column and continuously flow through a part only of it, as a carrier gas. The other component A is injected in a small amount instantaneously at the closed end of the column with the detector placed at the other end. By repeatedly stopping and then restoring after a short time the flow of B, narrow extra peaks are produced on the chromatographic elution curve, owing to diffusion of A into B. An equation is derived giving the area under the curve of each stop-peak as a function of time of the corresponding stop. Plotting the experimental data according to this equation permits the determination of the diffusion coefficient of A into B. Some results obtained by this method show negligible variations with changes in the experimental parameters. 相似文献
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The chromatographic elution has been studied from different perspectives. However, in spite of the simplicity and evident deficiencies of the plate model proposed by Martin and Synge, it has served as a basis for the characterization of columns up-to-date. This approach envisions the chromatographic column as an arbitrary number of theoretical plates, each of them consisting of identical repeating portions of mobile phase and stationary phase. Solutes partition between both phases, reaching the equilibrium. Mobile phase transference between the theoretical plates is assumed to be infinitesimally stepwise (or continuous), giving rise to the mixing of the solutions in adjacent plates. This yields an additional peak broadening, which is added to the dispersion associated to the equilibrium conditions. It is commonly assumed that when the solute concentration is sufficiently small, chromatographic elution is carried out under linear conditions, which is the case in almost all analytical applications. When the solute concentration increases above a value where the stationary phase approximates saturation (i.e. becomes overloaded), non-linear elution is obtained. In addition to overloading, another source of non-linearity can be a slow mass transfer. An extended Martin and Synge model is here proposed to include slow mass-transfer kinetics (with respect to flow rate) between the mobile phase and stationary phase. We show that there is a linear relationship between the variance and the ratio of the kinetic constants for the mass transfer in the flow direction (τ) and the mass transfer between the mobile phase and stationary phase (ν), which has been called the kinetic ratio (κ=τ/ν). The proposed model was validated with data obtained according to an approach that simulates the solute migration through the theoretical plates. An experimental approach to measure the deviation from the equilibrium conditions using the experimental peak variances and retention times at several flow rates is also proposed. 相似文献
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J. F. K. Huber 《Analytical and bioanalytical chemistry》1975,277(4):341-347
The results of the theory of chromatography are described using the mass balance model without entering into the details of mathematical treatment. The equation of the elution function describing the concentration in the column effluent as function of time is discussed with special emphasis on the theoretical plate height. The choice of the experimental parameters is discussed by means of the equation for the resolution of two components. Especially the optimation with respect to the time of separation and the dilution occurring at the separation is dealt with. 相似文献