Terminal‐vinyl liquid crystal crown ether‐modified,vinyl‐functionalized hybrid silica monolith for capillary electrochromatography

A novel terminal‐vinyl liquid crystal crown ether (2‐4‐(3‐undeceny‐1‐yloxy)‐phenyl]‐2‐4′‐(4′‐carboxybenzo‐15‐crown‐5)‐phenyl] propane) (LCCE) was synthesized and used to modify hybrid silica‐based monolithic column possessing vinyl ligands for CEC. The monolithic silica matrix containing vinyl functionalities was prepared by in situ co‐condensation of tetramethoxysilane and vinyl‐trimethoxysilane via sol–gel process and chemically modified with LCCE by free radical polymerization procedure using α,α'‐azobisisobutyronitrile as an initiator. Morphology of the monolithic column was examined by SEM and mercury porosimetry and the successful incorporation of terminal‐vinyl LCCE to the vinyl‐hybrid monolith was characterized by infrared spectra. Polycyclic aromatic hydrocarbons, benzenediols, carbamate pesticides and steroids, were successfully separated on the column. The separations were dominated hydrogen bonding supplied by crown ether and hydrophobic interaction offered by the liquid crystal. The effect of ACN concentration on separation performance was studied and the result indicated that RP retention mechanism played an important role. Reproducibilities of migration times for the six selected polycyclic aromatic hydrocarbons were reasonable, with relative standard deviation less than 3.50% for five consecutive within‐column runs and were 8.38–9.11% for column‐to‐column measurements of three columns.