Principles and Practice of Chromatography - Factors Controlling Retention > The Thermodynamic Explanation of Retention > Page 17

Noting, V' = KVs

 

Thus, a curve relating log(V') to 1/T will give a straight line the slope of which will be proportional to the standard enthalpy and the intercept will be related to the standard entropy and, two, the dominant effects that control the distribution system can be identified from such curves. Such curves are called Vant Hoff curves and an example of two Vant Hoff for two different types of distribution systems are shown in figure 5.

It is seen that distribution system (A) has a large enthalpy value and a low entropy contribution . The large

value of means that the distribution is predominantly controlled by molecular forces. The solute is preferentially distributed