CONJOINT PREDICTION OF THE RETENTION OF NEUTRAL AND IONIC COMPOUNDS (PHENOLS) IN REVERSED-PHASE LIQUID-CHROMATOGRAPHY USING THE SOLVATION PARAMETER MODEL

The solvation parameter model can be modified to predict the retention of ionized compounds (phenols) under reversed-phase liquid chromatogr aphic conditions by the addition of a further solute descriptor derive d from the acid dissociation constant. Two solute descriptors are eval uated for this purpose. The degree of dissociation, D solute descripto r, is defined by Eq. (3), and the scaled effective acid dissociation c onstant, the P solute descriptor, by (14-pK)/10. The P solute descrip tor provided better predictive accuracy than the D solute descriptor a nd enabled the retention factor of phenols (log k) to be estimated to 0.1 to 0.2 log units depending on the pH of the mobile phase. The P s olute descriptor is also suitable for use in the conjoint analysis of neutral and ionized compounds with similar predictive accuracy. A sign ificant fraction of the error in retention prediction is due to change s in the solute dipolarity/polarizability pi(2)(H) and effective hydro gen-bond acidity Sigma alpha(2)(H) accompanying ionization that are no t allowed for in the current model. (C) 1998 Elsevier Science B.V.