A study of dendrimer-solute interactions via electrokinetic chromatography

Polyacid cascade dendrimers (generations 1-4) are used as a pseudostationary phase for electrokinetic capillary chromatography to separate mixtures of neutral species. Separation of a homologous series of molecules allow the capacity factors and distribution coefficients to be calculated, which in turn allow the standard enthalpy, entropy, and Gibbs free energy for solubilization to be evaluated by van't Hoff analysis. Comparison of these values to analogous values measured for sodium dodecyl sulfate (SDS) micelles suggests fundamental differences in the thermodynamic quantities associated with solubilization. As the size of the polyacid dendrimer increases, entropy becomes the driving force for solubilization, and enthalpy is disfavored. Gibb's free energy values are negative for: all of the dendrimer/analyte interactions investigated. The capacity factor is found to increase linearly with increasing concentrations of dendrimer. Thermodynamic parameters are evaluated for several small molecules to show that the technique is not limited to molecules that are part of a homologous series.