Capillary electrokinetic separations: Influence of mobile phase composition on performance

Abstract

SummatvThecomposition of the mobile phaseemployed in capillary zone electrophoresis and the related technique, micellar electrokinetic capillary chromatography, is an important factor in determining separation performance. The influences of ionic salt, surfactant, and organic solvent mobile phase additives on separation efficiency, retention, and elution range are discussed and demonstrated.

Separation of anabolic steroids by micellar electrokinetic capillary chromatography

“…The migration time and resolution obviously increased as the electrolyte concentration increased. The phenomenon is in accord with previous studies [11][12][13]. This effect was explained by the fact that the zeta potential decreased as electrolyte concentration increased, which caused the EOF to decrease, thereby leading to a slower migration of the micelles.…”

Enantioselectivity of alcohol‐modified polymeric surfactants in micellar electrokinetic chromatography

“…Throughout this study, d, n, and t had respective values of 4.0, 250.0, and 0.20 ms. For each of the fifteen spectra in the resulting data set, the resonances in the region from 0.85 to 1.50 ppm were integrated and plots were prepared of the natural log of the peak integral versus the quantity (gGd) 2 (n-d/3-t/2). A linear regression analysis of the resulting graph provided the diffusion coefficient, D. The diffusion coefficients obtained from linear regression analysis of the data were then used to calculate the hydrodynamic radius, R h , of each polymer via the Stokes-Einstein equation given by:…”

“…Over the past decade, there has been considerable interest in the use of short-chain organic modifiers like methanol, ethanol, propanol, and acetonitrile in micellar electrokinetic chromatography (MEKC) [1][2][3]. These modifiers alter physicochemical properties of pseudostationary phases thus affecting the resolution of solutes [4].…”

“…Consequently, pronounced effects on migration time window, selectivity, peak symmetry, and separation efficiency in MEKC are observed [8,[10][11][12][13][14][15][16]. Micellar parameters such as critical micelle concentration (cmc), aggregation number, and the viscosity of the buffer solution are altered by the presence of alcohols in the surfactant solution [1,2,14,16]. In addition, alcohol modifiers in the MEKC buffer improve the wetting of the capillary wall silica surface, resulting in changes in zeta-potential and hence the electroosmotic flow (EOF) [17,18].…”

Separation of drug enantiomers by capillary electrophoresis in the presence of neutral cyclodextrins

“…The cavity of b-cyclodextrin is just sufficiently large to accommodate a whole benzene ring, but the substituents in ortho-position may sterically restrict the degree of inclusion. Although tricyclic structures have been suggested to fit especially well into g-cyclodextrin [33,34], the cavity is presumably far too narrow for a complete inclusion of the tricyclic system. Despite the increased cavity diameter, side-on-binding of the benzene ring is still the most likely possibility, although this may be paralleled by pi-pi stacking of two drug molecules in a 2:1 complex.…”