Influence of buffer zone concentrations on efficiency in partial filling micellar electrokinetic chromatography

The potential of counter pressure-moderated partial filling micellar electr okinetic chromatography (PF-MEKC) was investigated in this work. Plate numb ers of homologous omega -phenylalcohols were measured in a two-plug PF-MEKC system varying the concentrations and hence the ionic strengths of the bac kground buffer compared to the sodium dodecyl sulfate-containing separation buffer and the counter pressure on the cathodic buffer reservoir. it was o bserved that plate numbers are strongly influenced by both the buffer conce ntrations and the counter pressure. Highest plate numbers were obtained wit h a buffer system when the concentrations are adjusted such that the electr oosmotic flow velocities in both zones are equal. Differences in the local electroosmotic flow velocities of the zones caused by different buffer conc entrations are responsible for tremendously reduced plate numbers. The effi ciency drop is explained in several models by the formation of an intersegm ental pressure which produces a parabolically shaped laminar flow component in both zones. Thus, the electroosmotic plug-like flow profile is distorte d and the efficiency is reduced. The effect of counter pressure on efficien cy turned out to be very complex in dependence on the buffer system applied . Lm 2001 Elsevier Science B.V. All rights reserved.