New particle-loaded monoliths for chiral capillary electrochromatographic separation

Fritless particle-loaded monoliths for chiral capillary electrochromatographic (CEC) separation were prepared. Silica particles containing a chiral selector are suspended in a monomer solution, which is drawn into the capillary followed by in situ polymerization. Thereby the silica-based particles containing the chiral selector are embedded in a nonchiral continuous bed. This kind of chiral stationary phase is inexpensive, easy, and reproducible to prepare and circumvents the preparation of frits. As a model, teicoplanin aglycone as chiral selector bonded to 3 microm silica particles was used. The applicability of this approach is demonstrated by means of the chiral separation of aliphatic and aromatic amino acids and dipeptides. As a further application, the chiral selector ristocetin A bonded to 3 microm silica particles was used for the enantiomeric separation of chiral alpha-hydroxy acids. Since alpha-hydroxy acids migrate toward the anode, a cationic charge-providing agent was copolymerized with the matrix. This served to reverse the direction of the electroosmatic flow (EOF).