Principles and Practice of Chromatography - Factors Controlling Retention > The Thermodynamic Explanation of Retention > Page 15

Prior to discussing the parameters that determine the magnitude of (K) and (Vs) and how they can be changed, it is useful to develop the thermodynamic approach to the problem of solute retention in chromatographic separations.

The Thermodynamic Explanation of Retention

Classical thermodynamics provides an expression that describes the change in free energy of a solute when transferring from one phase to the other as a function of the equilibrium constant (distribution coefficient). The expression is as follows,

RT ln K = -DGo

where (R) is the gas constant,

(T) is the absolute temperature,

and (DGo) is the Standard Free Energy Change.

In addition, classical thermodynamics provides an expression for (DGo),