C_(60) and C_(70) HPLC Retention Reversal Study Using Organic Modifiers

摘要

A novel equation (Guillaume Y. C. et al. Anal. Chem. 1998, 70, 608) modeling the weak polar solute retention in reversed-phase liquid chromatography (RPLC) was applied to fullerene molecules C_(60) and C_(70). In RPLC, with an organic modifier (OM) /water mobile phase, the fullerene cluster solvation energies were calculated for OM=methanol, etthanol, propanol, butanol, and pentanol. An enthalpy-entropy compensation revealed that the type of interactions between fullerenes and the stationary phase was independent of both the fullerene and organic modifier structures. The energetics of OM and OM-water cluster exchange processes in the mobile phase were investigated in relation to the carbon atom number of the hydrophobic chain of the OM. Two linear correlations were found between the Gibbs free energy changes in the solvent exchange processes which confirmed that (i) a reversal elution order existed for C_(60) and C_(70) when methanol was changed into ethanol, propanol, butanol, pentanol and that (ii) the mobile phase was dominant in governing selectivity changes in nonpolar solutes.