Capillary electrochromatographic separation of ionizable compounds with a molecular imprinted monolithic cationic exchange column

A polymer‐based monolithic capillary column imprinted with 4‐aminopyridine (4‐AP) was prepared by a thermally‐initiated polymerization process; and its performance as a capillary electrochromatographic medium was evaluated in separating 4‐AP and 2‐AP isomers. The effects of experimental parameters, such as pH value and ionic strength of the buffer, the acetonitrile content in the mobile phase, and the applied voltage, on the resolution of these isomers had been carefully investigated. It was found that in the retention process there were interplays of multiple mechanisms of ion‐exchange, molecular imprinting, and electrophoresis. These mechanisms allowed more sophisticated control of experimental parameters in the separation of ionizable compounds.