Dispersion in Chromatography Columns - Experimental Validation of the Van Deemter Equation > Page 93

Figure 26 shows the predicted linear relationship between the resistance to mass transfer term and the square of the particle diameter. The linear correlation is extremely good and it is seen that there is, indeed an intercept on the (C) term axis, at zero particle diameter, which confirms the existence of a small, but significant, contribution from the resistance to mass transfer in the stationary phase.



Figure 26. Graph of the (C) Term against the Square of the Particle Diameter

The Effect of the Function of (k') on Peak Dispersion

Reiterating the Van Deemter equation,


If it is assumed that the column is operated at relatively high velocities, such that the contribution from longitudinal diffusion is no longer significant, then,


Again, assuming that the diffusivity of the solute in the stationary phase (DS) is simply related to the diffusivity in the mobile phase (Dm),