Kinetic performance evaluation and perspectives of contemporary packed column capillary electrochromatography

Abstract

Capillary electrochromatography (CEC) is in essence a highly efficient and fast separation technique but practical constraints limit the current performance, robustness and routine implementation of the technique. In this work the kinetic performance limit (KPL) curve was used to evaluate commercial packed column CEC; this firstly in order to assess the broader applicability of the kinetic plot approach in electrodriven chromatographic techniques, and secondly to allow a more general unbiased comparison with HPLC performance. Evaluations were performed with a mixture of well retained and electrophoretically neutral phenones, to allow the observation of only chromatographic processes. Initial CEC retention time irreproducibility issues were solved by applying high acetonitrile content (80%) in the mobile phase, and solute retention was increased by increasing the phenone chain length. Comparison was performed with HPLC, with a column packed with an identical stationary phase to allow measurement of the performance under optimal conditions, and not with μ-LC on the CEC column as extra column peak broadening phenomena would thereby negatively affect the μ-LC performance. This comparison demonstrated that current HPLC performance largely outcompetes what is achievable with contemporary packed column CEC. Interestingly, significantly improved CEC performance could be obtained at lower temperatures (10°C) indicating a persistent degree of joule heating phenomena taking place in the contemporary packed column (100μm) CEC approach. Effective suppression of the latter opens possibilities for increasing the applicable voltage and outperforming HPLC and UHPLC.