Preparation and electrochromatographic characterization of methacrylate-based weak cation exchange columns for capillary electrochromatography

Abstract

Polymethacrylate based monolithic columns with weak cation exchange (WCX) properties were synthesized in fused silica capillary columns by capillary electrochromatography. Monolithic columns were prepared by in situ copolymerization of butyl methacrylate, ethylene dimethacrylate and N-methacryloyl-L-glutamic acid (MAGA) in a binary porogenic solvent composed of N,N-dimethyl formamide and phosphate buffer. The carboxyl groups provided by the monomer MAGA on the surface of the stationary phases generated the EOF from anode to cathode, and served as the WCX stationary phase at the same time. One of the originalities of this study was to make it clear the effect of MAGA as a novel weak cation exchange monomer in capillary columns. In this respect, in addition, the weak cation exchange character of MAGA, the effect of MAGA percentage on the electroosmotic mobility and column efficiency were investigated. The prepared columns were evaluated by SEM microphotographs and characterized with regard to the separation of alkyl benzenes. The monoliths prepared under optimized polymerization conditions were successfully characterized by using alkyl benzenes. The applied voltage was changed between 5 kV and 30 kV for separation of alkyl benzenes. The total analysis time of alkyl benzenes was shortened approximately tenfold (i.e. from 60 to 6 min). The synthesised monoliths contained ionizable carboxylic acid groups, which exhibited cation-exchange capability, that are useful for weak cation exchange chromatography. The applications of the optimized column were demonstrated using phenolic compounds and underivatized amino acids. The separation of phenolic compounds was achieved using a mobile phase consisting of 40/60% ACN/PB (10.0 mM, pH 7.0). The theoretical plate number up to 190 000 plates per m was achieved in the separation of phenols. The stability of the column was tested by conducting repeated analyses.