BINDING FORCES CONTRIBUTING TO REVERSED-PHASE LIQUID-CHROMATOGRAPHIC RETENTION ON A BETA-CYCLODEXTRIN-BONDED PHASE

Reversed-phase liquid chromatographic (RPLC) capacity factors for a nu mber of organic solutes on a beta-cyclodextrin (beta-CD) bonded phase column in pure water mobile phase (k(w)') were compared with formation constants of inclusion complexes (K-f) between beta-CD and the solute s based on the linear solvation energy relationship (LSER) in order to understand the types and relative strengths of various intermolecular forces between CD and the guest solute affecting the stability of inc lusion complexes and hence retention in RPLC. A close fit of capacity factors (k(w)') with complexation constants indicated that inclusion c omplexation is the major driving force in retention on the beta-CD-bon ded phase in RPLC. Comparison of LSERs for K-f and k(w)' showed that a n increasing guest molecular size stabilizes the complex by virtue of increasing dispersive interactions between the hydrophobic interior of CD cavity and the guest and hence increases the RPLC retention, and t hat increasing guest dipolarity and hydrogen bond (HE) acceptor basici ty lead to a decrease in the stability of the complex due to the stron ger dipolar and HE interactions with water, and hence decrease the ret ention.