Modified van Deemter equation

Since electromatography uses a stationary phase just like in conventional LC, the principles of band broadening in CEC and LC are similar. The plate height can be expressed using a modified Van Deemter equation ... 

The term H/u can be expressed in terms of the modified van Deemter equation ... 

For convenience the Van Deemter equation for the LC column will be generally used in the following argument. However, when GC columns are considered the equations will be appropriately modified, where... 

The Van Deemter equation can be applied to gas chromatography with a different emphasis on the relative importance of its terms. In fact, the interactions between an analyte and a stationary phase are much simpler in gas chromatography than those in liquid chromatography since the mobile phase does not modify the stationary phase in any way. The theoretical considerations are different for packed GC columns vs open tubular capillary columns. 

As in conventional liquid chromatography the plate height can be expressed using a modified Van Deemter plate height equation. 

Equation (11) accurately describes longitudinal diffusion in a capillary column where there is no impediment to the flow from particles of packing. In a packed column, however, the mobile phase swirls around the particles. This tends to increase the effective diffusivity of the solute. Van Deemter introduced a constant (y) to account for this effect. Thus, equation (11) must be modified, for a packed column, to the following form ... 

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