The Thermodynamics of Chromatography - Thermodynamics Basics > Page 6

  

 

There are two basic forms that the van't Hoff curve can take. These two types of curve relate to the two basic types of chromatography. The first interactive chromatography where the major retentive mechanism results from solute phase interactions and the second exclusion chromatography where the major retention mechanism depends on the amount of stationary phase available to each solute. As stated in book 7, neither form of chromatography can be exclusive, but one can be predominant. An example of the type of linear curve that is produced by interactive chromatography is shown in figure 1  

It is seen the van't Hoff curve indicates a very large enthalpy value (the slope of the curve is steep) but conversely a very low

entropy contribution (the intercept is relatively small).

Figure 1. Interactive Chromatography Using Energy Driven Distribution