Peak shapes in open tubular ion-exchange capillary electrochromatography of inorganic anions

Abstract

An experimental study of parameters influencing peak shapes in ion-exchange open tubular (OT) capillary electrochromatography (CEC) was conducted using adsorbed quaternary aminated latex particles as the stationary phase. The combination of separation mechanisms from both capillary electrophoresis and ion-exchange chromatography results in peak broadening in OT-CEC arising from both these techniques. The sources of peak broadening that were considered included the relative electrophoretic mobilities of the eluent co-ion and analyte, and resistance to mass transfer in both the mobile and stationary phases. The parameters investigated were the mobility of the eluent co-ion, column diameter, separation temperature and secondary interactions between the analyte and the stationary phase. The electromigration dispersion was found to influence peak shapes to a minor extent, indicating that chromatographic retention was the dominant source of dispersion. Improving the resistance to mass transfer in the mobile phase by decreasing the capillary diameter improved peak shapes, with symmetrical peaks being obtained in a 25 μm I.D. column. However, an increase in temperature from 25°C to 55°C failed to show any significant improvement. The addition of p-cyanophenol to the mobile phase to suppress secondary interactions with the stationary phase did not result in the expected improvement in efficiency.