The Thermodynamics of Chromatography - The Thermodynamic Analysis of the Dispersive Interactions that Can Take Place between Different Solutes and High Molecular Weigh > Page 24

This means that the intermolecular forces are stronger and, thus, the stationary phase molecules hold the solute molecules more tightly. In turn, this indicates that the freedom of movement and the random nature of the solute molecule are also more restricted, which results in a larger change in standard entropy. It follows that, unless other significant retentive factors are present, any increase in standard enthalpy would be expected to be accompanied by a corresponding increase in standard entropy. The simple relationship has been under some criticism but there does appear to be some relationship between the accuracy and precision of the original data that was collected and the correlation shown in figure 11. In addition, the nature of the interactions need to be taken into account and if there are mixed interactions (e.g., dispersive interactions together with polar interactions) then the two types of interaction need to be treated separately and exclusively to obtain the simple linear relationship shown in figure 11. These points are illustrated in the following analysis of the dispersive interactions of atoms as opposed to groups.