Retention and column efficiency in reversed phase liquid chromatography asa function of pH for optimization purposes

The effects of pH on both the solute retention and the peak shape of ionoge nic compounds are studied in order to propose accurate models for pH optimi zation purposes. Several mathematical models (theoretical and empirical) fo r describing the variation of the retention factor versus pH are compared w ithin different pH ranges Limits of such models used for optimizing the pH by requiring only 3 preliminary experimental runs, are discussed in terms o f deviations (less than or equal to +/- 5%) of predicted retention times fr om experimental retention times An original procedure is developed for sele cting the most convenient retention model, from a given set of three retent ion data. This set is also applied to modeling the variation of both peak w idth and peak asymmetry with mobile phase pH conditions. Such a procedure i s demonstrated as helpful for the separation of ionogenic solutes by consid ering mobile phase pH as an additional variable that can be useful during o ptimization procedures.