Dispersion in Chromatography Columns - Effect of Mobile Phase Compressibility On the HETP Equation for a Packed GC Column > Page 38

Thus,                          and 


Substituting for       and   in the HETP equation,




It is now seen that if the mobile phase velocity is taken as that at the column outlet, only the resistance to the mass transfer term for the stationary phase is position dependent. All the other terms can be used as developed by Van Deemter, providing the diffusivities are also measured at the outlet pressure (atmospheric).