Selectivity tuning in pressurized-flow electrochromatography

Pressurized-flow electrochromatography (PEC) is a developing separation technique in which both a pressure gradient and an electric field are applied across a packed capillary. In this work we present new results illustrating the principles and the potential of PEC. Home-made capillary columns with silica-based reversed phase packings were operated under PEC conditions separating low molecular weight analytes. Compared to the purely pressure-driven system enhanced selectivity for the charged analytes was observed. It is shown that the retention time of a retained cationic analyte in PEC can be calculated using the chromatographic capacity factor and the electrophoretic mobility of the compound. An example is given for a selectivity shift due to the application of an electric field before a chromatographic run.