(Micellar) electrokinetic chromatography: an interesting solution for the liquid phase separation dilemma

High-performance liquid chromatography (HPLC) is a well-established method in modern analysis. The method is simple, very robust and is applicable to the majority of components to be analyzed in contrast to gas chromatography. Low efficiency and small peak capacity are sore points of HPLC when complex mixtures have to be separated. The reason for this dilemma is the small diffusion coefficient of the analytes in the liquid mobile phase compared to a gaseous phase. This review, complemented by exemplary calculated data and some latest results of our own research, illustrates the dilemma of liquid phase chromatography to achieve high efficiencies under reasonable conditions. It is shown that (micellar) electrokinetic chromatography, offering fast and efficient separations, is a very promising solution for this dilemma. Additional features of this method are possibilities of on-line analyte concentration, coupling to mass spectrometry and the easy change of selectivities by applying various separation additives. The pros and cons of electrokinetic chromatography are pointed out and some application examples are given.