Chiral Monolithic Columns for Enantioselective Capillary Electrochromatography Prepared by Copolymerization of a Monomer with Quinidine Functionality. 1. Optimization of Polymerization Conditions, Porous Properties, and Chemistry of the Stationary Phase

Abstract

Monolithic columns for chiral capillary electrochromatography have been prepared within the confines of untreated fused-silica capillaries in a single step by a simple copolymerization of mixtures of O-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydroquinidine , ethylene dimethacrylate, and glycidyl methacrylate or 2-hydroxyethyl methacrylate in the presence of mixture of cyclohexanol and 1-dodecanol as a porogenic solvent. The porous properties of the monolithic columns can easily be controlled through changes in the composition of the binary porogenic solvent. Although both thermal- and UV light-initiated polymerizations afford useful capillary columns, monoliths prepared using the former approach exhibit better chromatographic properties. The ability to control pore size independently of the polymerization mixture composition enables the preparation of monoliths with varying percentages of the chiral monomer and cross-linker, as well as the optimization of their separation properties. Very good separations of model racemate (R,S)-N-3,5-dinitrobenzoylleucine were achieved using an optimized monolithic CEC column, with high efficiencies of up to 74000 plates/m for the retained peaks.

Sensitive chiral analysis by capillary electrophoresis

“…Many of the chiral selectors employed to prepare packed capillary columns have also been used in order to prepare chiral monolithic capillary columns for CEC (see Table 1) [35,36,[44][45][46][47][48][49].…”

Fases estacionárias monolíticas para separações cromatográficas

“…11,25,31,37,38 no modo de fase reversa, seletividade quiral 34,[46][47][48] , troca iônica 35,39 , impressão molecular ("MIP -molecularly imprinted polymer") 49,50 , etc. Em ECC, as fases monolíticas preparadas com grupos carregados, para garantir o fluxo eletroosmótico, são consideradas de modo misto, uma vez que, freqüentemente, se realizam separações no modo de fase normal (ou reversa) e como trocadoras de íons 35,39 .…”

“…A simples adição de um monômero com função seletora quiral à mistura de polimerização produz excelentes colunas monolíticas quirais para ECC enantiosseletiva. Lämmerhofer et al 48 prepararam colunas monolíticas quirais à base de polimetacrilatos pela adição de um derivado da quinidina à mistura de polimerização. Esta coluna foi aplicada para separação de enantiômeros R,S de dinitrobenzoil-leucina (DNB-leucina), obtendo-se boa enantiosseparação e eficiências de até 75 000 pratos m -1 .…”

Polar stationary phases for capillary electrochromatography

“…Lämmerhofer et al [75,76] examined the effect on enantiomeric separations when polar monomers were incorporated in the methacrylate-based chiral monolith. The substitution of glycidyl methacrylate (GMA) for butyl methacrylate, and the subsequent hydrolysis of the epoxide groups into vicinal diol moieties, considerably improved the column efficiency.…”