Principles of Chiral Separation Using Achiral Counterions

The achiral counterion itself does not provide stereochemical interactions and thus it is expected to only influence the retention and not the separation of an enantiomeric pair. Different counterions have been added to the aqueous mobile phase in a liquid-liquid chromatographic system with a nonpolar chiral stationary phase (a tartaric acid ester). The enantioselectivity was about the same for all counter-ions studied and, as expected, the type of ion and its concentration could be used to control the retention (Table 1).

Several of the chiral selectors used are, however, complex biomolecules, e.g., proteins which cannot be treated as simple organic phases. The addition of charged (and uncharged) compounds to the mobile phase, when a protein is used as the stationary phase, may change both the retention and the enantioselec-tivity. The changes in enantioselectivity may be dramatic; the two enantiomers in a pair may even elute in an opposite order.

Solar Panel Basics

Solar Panel Basics

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