The behaviour of functional groups having widely different physicochemical character has been examined in reversed phase ion-pair high performance liquid chromatography using surface active pairing-ions of both positive and negative charges. The effects of organic modifier type and concentration, stationary phase carbon loading and chain length, ionic strength, pH, pairing-ion structure and concentration and solute charge on the extrathermodynamic functional group values, have been determined. Analysis of group behaviour within the framework provided by solvophobic theory is often found to be possible using linear free energy approaches, and it is shown that retention in such systems can be described in terms of ion-pair formation in the mobile phase followed by distribution to the stationary phase. In addition the substituents were found to exhibit linear enthalpy-entropy compensation behaviour, suggesting further that a common retention mechanism can be described for all ionised solutes using these pairing-ions. These theoretical considerations permitted the optimisation of the separation conditions for the analysis of solutes of pharmaceutical and biomedical interest in environments such as drug formulations and biological fluids. It is shown that chromatographically derived group contribution values may be used to predict bulk phase hydrophobicity properties and may be used directly in drug design models. Conversely, liquid-liquid distribution hydrophobicity parameters can be used for the rationalisation of retention behaviour in reversed phase high performance liquid chromatography using surface active pairing-ions.
|Date of Award||1980|