Monolithic columns enantioselective separation

This technology was extended to the preparation of chiral capillary columns [ 138 -141 ]. For example, enantioselective columns were prepared using a simple copolymerization of mixtures of O-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydro quinidine, ethylene dimethacrylate, and 2-hydroxyethyl methacrylate in the presence of mixture of cyclohexanol and 1-dodecanol as porogenic solvents. The porous properties of the monolithic columns can easily be controlled through changes in the composition of this binary solvent. Very high column efficiencies of 250,000 plates/m and good selectivities were achieved for the separations of numerous enantiomers [140]. 

Obviously, the monolithic material may serve its purpose only if provided with a suitable surface chemistry, which depends on the desired application. For example, hydrophobic moieties are required for reversed phase chromatography, ionizable groups must be present for separation in the ion-exchange mode, and chiral functionalities are the prerequisite for enantioselective separations. Several methods can be used to prepare monolithic columns with a wide variety of surface chemistries. 

One-step method for the preparation of highly enantioselective monolithic columns for CEC has been developed by Frechet et al. The chiral polymer bed of defined pore distribution and chiral ligand concentration has been synthesized within the confines of untreated fused silica capillaries using a mixture of O-[2-(methacryloyloxy)ethylcarbamoyl]-10,ll-dihydroquinidine 76, ethylene dimethacrylate (EDMA), and glycidyl methacrylate or 2-hydroxyethyl methacrylate (HEMA) in the mixture of cyclohexanol and 1-dodecanol as porogenic solvents. Under optimized synthetic and chromatographic conditions, these materials with the desired characteristics were demonstrated to efficiently separate a model racemic DNZ-Leu, Figure 13.24 [146],... 

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