A novel positively charged achiral co-monomer for β-cyclodextrin monolithic stationary phase: Improved chiral separation of acidic compounds using capillary electrochromatography coupled to mass spectrometry

Abstract

The work presented here demonstrates the incorporation of vinylbenzyl trimethylammonium (VBTA) as a novel positively charged achiral co-monomer to a glycidyl methacrylate-beta cyclodextrin (GMA/β-CD) based monolith, providing anion exchange sites with reversed electroosmotic flow (EOF) for capillary electrochromatography (CEC). The monolithic phases, GMA/β-CD-VBTA and GMA/β-CD (without co-monomer) were characterized by scanning electron microscopy, optical microscopy, pressure drop/flow-rate curves and nitrogen adsorption analysis. After optimizing the stationary phase and mobile phase parameters, chiral separations of 41 pairs of structurally diverse anionic chiral analytes were compared individually using the GMA/β-CD-VBTA and GMA/β-CD monolithic columns. The GMA/β-CD-VBTA monolith chiral stationary phase separated significantly more acidic compounds compared to the GMA/β-CD column. To-date there has been limited work in the development of chiral monolithic column for CEC-mass spectrometry (MS). Because of good electrodriven flow characteristics, which allow the column to maintain a stable current in the absence of outlet vial, GMA/β-CD-VBTA column was successfully coupled to single quadrupole mass spectrometer for CEC-MS of several chiral test compounds. In addition, the same monolithic CEC column when coupled to a triple quadrupole MS instrument, two orders of magnitude higher sensitivity was observed compared to a single quadrupole MS instrument.