It is believed that over the last three decades the art of separating enantiomer has changed to routine. It is a convincing story associated with boundless success of separation technologies driven by the needs of life sciences and pharmaceutical sciences in particular. However, there are still challenges to be mastered depending on the analyte's (selectands, SAs) chemical structures, molecule sizes and polarity. Generalizations are therefore inappropriate. To date there exists on the market a large set of diverse so-called �chiral columns� as a result of hundreds of research projects in academia and industry driven by the dream to develop most broadly applicable, robust and affordable chiral selectors (SOs) and chiral stationary phases (CSPs) to master the tasks, analytically and preparatively. But this remains a dream possibly for good reasons.More than 30 years I am working on selectivity aspects in liquid chromatography (LC) and on enantiomer separations in particular observing the field thus getting a feeling what the status currently is. In this context we draw already early our attention to the development of chiral cationic, anionic and zwitterionic SOs and using them for chiral ion exchanger type CSPs. Following the complementarity principle this concept deals primarily with electrostatic intermolecular interactions of the SO and the SAs in combination with additional interactions like hydrogen bonding, ?-? and other van der Waal forces to support chiral discrimination mechanism being adapted to LC. Generally speaking our successful stereoselective SO-SA interaction concepts are based on charged (positively and/or negatively) sites of the chiral scaffolds of the SOs which interact with the charged antipodes of the SAs. The related chromatographic process follows a stoichiometric displacement model.On the one side one may argue this is a restriction towards the type of analytes to be tackled, it is true, but on the other side it opens up new possibilities as for instance the chiral separation of very polar acids, bases or ampholytes as e.g. of free alpha-, beta- or gama-amino acids and peptides.The development of the knowledge along that line reflects our effort to contribute to the �power of selectivity� in HPLC and SFC whether it is chiral or non-chiral.In this lecture emphasis will be given on variants of the above raised aspects and focus on our chiral ion exchangers supported by illustrative applications.

Award Address  (ACS Award in Chromatography sponsored by SUPELCO, Inc.). About the genesis and potential of chiral ion exchangers for the chromatographic resolution of stereoisomers

244th National Meeting (2012)

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