Enantioselective Optode Membranes with Enantiomer Selectivity for ( R )‐ and ( S )‐l‐Phenylethylammonium Ions

The recently developed general principle of ion‐selective optode membranes, based on conventional ionophores, was employed to design a new approach to the determination of enantiomeric excess. Highly lipophilic chiral crown derivatives, exhibiting a high selectivity for a chiral ammonium guest cation, are combined with a H + ‐selective chromoionophore in a plasticized PVC membrane. The enantiomer recognition process is translated by this sensor with an optical transduction into a signal easily measured by a conventional spectrophotometer, and enantiomeric excess can be determined without the need for polarized light. Characteristics and a theoretical description of these new optode membranes are given.