Capillary Electrokinetic Chromatography (CEC): An Introduction to a High-Efficiency Microanalytical Technique

Capillary electrokinetic chromatography (CEC, also called “capillary electrochromatography”) is a relatively new separation technique based on a combination of liquid chromatographic and electrophoretic separation methods. CEC offers both the efficiency of capillary electrophoresis (CE) and the selectivity and sample capacity of packed capillary high performance liquid chromatography (HPLC). These advantages are provided in part because of the favorable flow characteristics of electroosmosis, a method of pumping a liquid by applying a high potential axially to a thin, fluid-filled tube. The speed at which analytes move through the separation conduit under the influence of electroosmosis is quite uniform, regardless of the position of the analyte with respect to adjacent surfaces (within certain limits). This results in very little spreading of zones of analyte; narrow, compact bands of analytes are therefore maintained, which results in high efficiency. Because the capillaries used in CEC are packed with HPLC packing materials, the wealth of selectivities available in HPLC are also available in CEC. The high surface area of these packing materials enables CEC capillaries to accommodate relatively large amounts of sample, making detection a simpler task than it is in capillary electrophoresis (CE). This paper will briefly visit the theory and practice of CEC, and will provide examples of how CEC can be applied in sample analysis.