Preparation of an O-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine-silica hybrid monolithic column for the enantioseparation of amino acids by nano-liquid chromatography.

An O-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine (MQD)-silica hybrid monolithic column was prepared by a facile "one-step" strategy within a 100 μm I.D. capillary. The influence of the methanol, ethylene glycol and water volume ratio, reaction temperature and time, cetyltrimethylammonium bromide and MQD monomers content and volume ratio of tetramethoxysilane and vinyltrimethoxysilane was investigated to obtain a satisfactory morphology of monolithic columns. The optimized MQD-silica hybrid monolithic column was evaluated in terms of permeability, stability, efficiency, reproducibility, and was characterized by scanning electron microscopy and nano-liquid chromatography. Among the 52 N-derivatized protein and non-protein amino acids, a total of 44 analytes could be baseline enantioseparated using the optimized conditions in either reversed phase mode (RPM) or polar organic phase mode (POM). The results showed that POM (ACN/MeOH/HAc/TEA (60/40/0.055/0.005, v/v/v/v)) offered better performance than RPM (10 mM ammonium acetate/ACN (30/70, v/v) (apparent pH=5.3)) in terms of enantioresolution and efficiency with shorter analysis times.