Chromatographic study of terpene-β-cyclodextrin complexes on porous graphitic carbon stationary phase

The effect of temperature on the retention of terpene derivatives on a porous graphitic carbon stationary phase has been investigated with methanol-water mobile phases containing β-cyclodextrin. Changes in Van't Hoff plots were evaluated in relation to the β-cyclodextrin concentration. Thermodynamic data were determined for both (i) solute transfer from the mobile phase to the PGC stationary phase and (ii) complexation of the solute with the β-CD. Enthalpyentropy compensation studies were performed for these two processes. Solute transfer was shown to be enthalpically driven and independent of terpene structure, β-cyclodextrin concentration, and mobile phase methanol content. The complexation reaction was shown to be entropically controlled and independent of terpene structure and mobile-phase composition. Comparison of the compensation temperatures of these two physicochemical processes led to the conclusion that each process had an similar influence on the global retention process.