Effects and nature on buffer ion enrichment in electric field assisted liquid chromatography

Sammanfattning: The aim of this study has been to investigate the properties and limitations of the separation technique electric field assisted capillary liquid chromatography (EF-LC). The electric current in the EF-LC has shown to be a limiting factor and has been the focus of the study. The results show an enhanced current due to the combination of pressurized flow and electric field in EF-LC. The high current was found to origin from an overall increase in mobile phase ion concentration that results from the electrophoretic velocities of the mobile phase ions.

In the combination of electric field and pressurized flow the concentration of the ions having electrophoretic and flow velocities in the same directions will be decreased and the concentration of the ions having electrophoretic and flow velocities in opposite directions will be increased. We have found that this increase in ion concentration is larger than corresponding decrease in ion concentration in the cases when the electrophoretic and flow velocities are of the same range in magnitude. This condition leads to the observed overall increase in ion concentration. Further, we have shown that the current is depending on the distribution of the ions in the column due to the different flow profile of the pressurized flow and the electrophoretic mobility. The current is therefore believed to be, to a large extent, transported in a section close to the wall where the ion concentration is large.