Organic monolithic capillary columns coated with cellulose tris(3,5-dimethylphenyl carbamate) for enantioseparations by capillary HPLC

Abstract

A new chiral monolithic column for enantiomer separation in capillary LC was successfully prepared by coating the chiral selector cellulose tris(3,5-dimethylphenyl carbamate) onto an organic polymer. This polymer, with optimized porous properties, has been prepared in situ in pretreated fused-silica capillaries by thermal polymerization of 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate in the presence of a binary porogenic mixture (1-dodecanol and cyclohexanol). The chiral selector was deposited onto the monolithic support to obtain a stable and reproducible chiral stationary phase. The column was used under normal phase mode with different compositions of n-hexane and 2-propanol. The effect of acidic or basic additives on the enantioresolution was studied. Nine chiral acid, neutral, and basic compounds (profens, β-blockers, pesticides, among others) were partially or completely resolved in short analysis times. Enantioselectivity values up to 7.1 and enantioresolutions up to 2.4 were obtained. The monolithic chiral column exhibited good stability, with RSD% for intra- and inter-day reproducibility values of the retention factor as low as 1.5% and 4.3%, respectively. Also, column fabrication is robust since RSD% was as low as 12.7%. This is the first report in which the chiral selector cellulose tris(3,5-dimethylphenyl carbamate) was successfully coated onto an organic polymeric monolith prepared in capillary columns for enantiomeric separations by capillary LC.