Role of the water as a surface tension modifier for the retention of a series of dansylaminoacids on a β-CD stationary phase

In reversed phase liquid chromatography (RPLC), using a surface tension treatment, the retention and separation of a series of d,l-dansylaminoacids were investigated with native β-cyclodextrin as a chiral stationary phase. The enantioselectivity thermodynamic parameters were determined from linear vanʹt Hoff plots. An analysis of the experimental variations in the retention factor with different fractions of water in the mobile phase was performed. The number of water molecules, n, excluded from the solute β-cyclodextrin cavity interface when the analyte transfer occurred, was determined. Using these n values, the relative degrees of compound inclusion were calculated and correlated to both the steric bulkiness of the solute and the thermodynamic data.