Pressure-assisted CEC versus CEC using methacrylate-based monolithic columns: influence of the polymerization-mixture...

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Pressure-assisted capillary electrophoresis (pCEC) can be performed using either a CE instrument with pressure application or a capillary liquid chromatography (LC) system with voltage. This study explores the utility of pCEC on an LC instrument.
• The composition of polymerization mixtures for monolithic capillary columns significantly influences chromatographic performance.

Purpose of the Study:

• To investigate the added value of pressure in pCEC using an LC instrument.
• To evaluate the influence of polymerization-mixture composition on monolithic columns under pCEC conditions.
• To compare the performance of pCEC with conventional CEC for pharmaceutical analysis.

Main Methods:

• An experimental design approach was used to vary the pore-forming solvent/total monomer ratio and solvent composition in polymerization mixtures for monolithic columns.
• The chromatographic behavior of pharmaceutical compounds was evaluated based on retention time, retention factor, peak asymmetry, and theoretical plates.
• pCEC experiments were compared with previous CEC experiments using identical setups and similar retention conditions.

Main Results:

• The optimal stationary phase composition for best chromatographic behavior was determined and demonstrated superior properties compared to the center-point column.
• Analysis time and efficiency in pCEC were found to be highly dependent on column porosity.
• pCEC did not offer significant advantages over CEC in terms of speed or efficiency, primarily due to instrument limitations on pressure-driven flow.

Conclusions:

• pCEC on an LC instrument did not provide a significant performance enhancement over CEC for pharmaceutical analysis under the tested conditions.
• Column porosity is a critical factor influencing both analysis time and efficiency in pCEC.
• A notable advantage of the pCEC setup was its integrated loop injection system, which mitigated injection issues sometimes encountered in CEC.