Solvent front velocity

The solvent front velocity U from Equation 4.2 is given by differentiation of Equation 4.1 ... 

Equation (7.5) Indicates that the velocity constant should increase linearly with the average particle size. The solvent front velocity should be larger for coarse-particle layers than for fine-particle layers which is. in good agreement with experimental observations [27]. Also, from equation (7.5) we see that the velocity constant depends linearly on the ratio of the surface tension of the solvent to its viscosity and that solvents which maximize this ratio (and not just optimize one of the parameters) are preferred for TLC [8,30]. The contact angle for... 

Tapered plates, prepared with a gradual increase in thiclcness of the layer from 0.3 nm to 1.7 am, can be used to improve resolution of the sample [215]. On the tapered layer the solvent front velocity decreases as the thickness of the layer increases. This results in the formation of a negative velocity gradient in the direction of solvent migration. As a result the lower portion of a zone moves faster than the top portion, keeping each component focused as a narrow band. Plates with concentrating zones are useful for optimizing sample application. 

The solvent front velocities were determined for case II diffusion as being 12.6 and 14.5 nm/s, respectively. These values are more than twice the magnitude of... 

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