1.涡流扩散项He He = 2ldP 上式的含义及对峰扩展的影响同气相色谱 2.纵向扩散项Hd Hd ∝ Dm u Hd = Cd Dm u Due to very little diffusion coefficient of the molecules in liquid phase, when linear velocity is higher than 0.5cm.s-1 ， contribution of longitudinal diffusion term to peak broadening is neglectable
1.涡流扩散项He He = 2ldP 上式的含义及对峰扩展的影响同气相色谱 2.纵向扩散项Hd Hd ∝ Dm u Hd = Cd Dm u Due to very little diffusion coefficient of the molecules in liquid phase, when linear velocity is higher than 0.5cm.s-1 ， contribution of longitudinal diffusion term to peak broadening is neglectable
3. 传质阻力项 ●Stationary phase mass transfer resistance term 固定相传质过程：试样分子从流动相进入固定液进行质量交换 Hs = Cs df 2 Ds u Cs is a coefficient depending on k How to eliminate or reduce peak broadening induced by mass transfer of stationary phase ?
3. 传质阻力项 ●Stationary phase mass transfer resistance term 固定相传质过程：试样分子从流动相进入固定液进行质量交换 Hs = Cs df 2 Ds u Cs is a coefficient depending on k How to eliminate or reduce peak broadening induced by mass transfer of stationary phase ?
▲ Use thin layer of stationary phase for liquid-liquid partition chromatography ▲Use small grains with a little radii (小颗粒）as filling materials(填料）for adsorption, size-exclusion and ion-exchange chromatography ▲Use the stationary liquid with a big diffusion coefficient ▲Reduce rate of mobile phase However, too low mobile phase rate will deduce enhancement of molecular diffusion term and prolonging(延长）of analytical time. ▲ Improve mass transfer to quicken desorption of solute molecules on stationary phase
▲ Use thin layer of stationary phase for liquid-liquid partition chromatography ▲Use small grains with a little radii (小颗粒）as filling materials(填料）for adsorption, size-exclusion and ion-exchange chromatography ▲Use the stationary liquid with a big diffusion coefficient ▲Reduce rate of mobile phase However, too low mobile phase rate will deduce enhancement of molecular diffusion term and prolonging(延长）of analytical time. ▲ Improve mass transfer to quicken desorption of solute molecules on stationary phase
●Mass transfer resistance term of mobile phase Mass transfer in moving mobile phase Mass transfer in retardation(滞留） mobile phase Hm = Cm dp 2 Dm u Cm = constant depending on k , diameter and shape of applied column and structure of filling materials packed. Hm ∝ dp 2 Dm u Mass transfer resistance term Hm Flow rate of mobile phase is not identical on whole column, slower near packing particles
●Mass transfer resistance term of mobile phase Mass transfer in moving mobile phase Mass transfer in retardation(滞留） mobile phase Hm = Cm dp 2 Dm u Cm = constant depending on k , diameter and shape of applied column and structure of filling materials packed. Hm ∝ dp 2 Dm u Mass transfer resistance term Hm Flow rate of mobile phase is not identical on whole column, slower near packing particles
Mass transfer resistance term in retardation mobile phase column Solute molecule Stationary phase particle Mobile phase Due to porosity of stationary phase particles, some mobile phase stays in the aperture(孔），and these stationary phase usually do not move(滞留区的流动 相通常是不动的）. Solute molecules must diffuse into these holes(滞 留区） to carry out mass transfer with stationary phase (试样分子必须先扩散到滞留区才能完成质量 交换） The smaller and deeper the holes, the lower the rate of mass transfer, the more remarkable the influence on peak broadening(微孔越深和越小，传 质速率越慢，对峰扩展的影响越显著）. The smaller the grain of stationary phase and the bigger the aperture(孔径）， the shorter the distance of mass transfer, the faster the mass transfer rate and the higher the column efficiency(固定相粒度越小，微孔孔径越大，传质途径越小， 传质速率越高，柱效越高）
Mass transfer resistance term in retardation mobile phase column Solute molecule Stationary phase particle Mobile phase Due to porosity of stationary phase particles, some mobile phase stays in the aperture(孔），and these stationary phase usually do not move(滞留区的流动 相通常是不动的）. Solute molecules must diffuse into these holes(滞 留区） to carry out mass transfer with stationary phase (试样分子必须先扩散到滞留区才能完成质量 交换） The smaller and deeper the holes, the lower the rate of mass transfer, the more remarkable the influence on peak broadening(微孔越深和越小，传 质速率越慢，对峰扩展的影响越显著）. The smaller the grain of stationary phase and the bigger the aperture(孔径）， the shorter the distance of mass transfer, the faster the mass transfer rate and the higher the column efficiency(固定相粒度越小，微孔孔径越大，传质途径越小， 传质速率越高，柱效越高）