(Po) is the pressure at the column exit,
and (uo) is the linear velocity of the mobile phase at the column
exit.
Now from the kinetic theory of gases, it can be shown that the diffusivity of a solute in a gas is inversely proportional to the pressure.
Thus, DxPx
= DoPo or
where (Do) is the solute diffusivity at the end of the column at (Po)
and (Dx) is the solute diffusivity at point (x) and pressure (Px)
