Mechanistic implications of the equality of compensation temperatures in chromatography

A common interpretation of the observation that two processes exhibit similar compensation temperatures in an enthalpy-entropy plot is that the two processes occur via the same mechanism. We show that this interpretation is not rigorously allowed. In fact, the only thing that can be concluded from the observation of identical compensation temperatures is that the relative contributions of enthalpy and entropy to the overall free energy are the same in the two processes. Since it is possible that two processes occur via different mechanisms that, by chance, result in the same relative blends of enthalpy and entropy, the observation of identical compensation temperatures cannot be used as evidence for mechanistic identity. If two processes exhibit different compensation temperatures, however, it can logically be concluded that the two processes are mechanistically distinct. (C) 2002 Elsevier Science B.V. All rights reserved.