Interaction forces and partition coefficient:

There are subsequent four interaction forces that can aid in the GC separation:

a) Orientation or Keesom forces: Forces resulting .from the interaction among two permanent dipoles. The "hydrogen-bond" is particularly significant categories of orientation force encountered in gas chromatography.

b) Induced dipole or Debye forces: Forces resulting from the interaction among a permanent dipole in one molecule and an induced dipole in a neighbouring molecule. These forces are commonly extremely small.

c) Dispersion, London or non-polar forces: Forces arising from synchronized variations within the instantaneous dipoles of the two interacting species. These forces are present in all cases and are the just source of attraction energy among two non-polar substances. They are weak compared to (a) and (b).

d) Specific interaction forces: Forces resulting from chemical bonding, complex formation among solute and solvents. Those forces of interaction determine the solubility and thus, the separation is achieved. Their joint effects are expressed through the distribution constant K_c, where

K_c = Amount of solute per unit volume of liquid phase/Amount of solute per unit volume of gas phase

The value of K_c is high while most of a solute is retained within the liquid phase. This means in which the solute moves slowly down the column since only a small fraction will be in the carrier gas at any provided time. Transport is negligible in the liquid phase and just that fraction within the gas phase is carried by the column. Therefore, separation among two solutes is probable if their distribution constants are dissimilar. The greater the dissimilarity in their K_c values, the fewer the plates or the shorter the column length which is required to achieve a separation.