Application of the Retention Index Concept in Micellar Electrokinetic Capillary Chromatography. [Erratum to document cited in CA120:123851]

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Capillary zone electrophoresis of proteins with a dynamic surfactant coating: influence of a voltage gradient on the separation efficiency

In capillary zone electrophoresis of proteins, the adsorption of the proteins on the capillary wall is a considerable problem that seriously impairs the sepn. efficiency. The use of a dynamic surfactant coating is a possible way to diminish this adsorption. Highly efficient sepns. were achieved with a cationic fluorinated buffer additive as a dynamic surfactant coating in untreated fused-silica capillaries at neutral pH. The influence of a voltage gradient on the sepn. efficiency is discussed and a simple relationship is presented to calc. effective mobilities under voltage gradient condition

Application of the Retention Index Concept in Micellar Electrokinetic Capillary Chromatography

The application of the retention index concept in micellar electrokinetic capillary chromatog. (MECC) was evaluated for the identification of neutral species. Homologous series of alkylbenzenes and alkylaryl ketones were applied as retention index stds. and also for the calcn. of the micelle migration time by an iteration procedure. The relation between retention indexes, I, and octanol-H2O partition coeffs. is discussed, and DI values were calcd. from retention indexes, obtained with both anionic and cationic surfactant systems, to study the sepn. mechanism for solutes with different functionalities in MECC. The influence of the phase ratio is treated theor., and the capacity factor is linearly related to the surfactant concn., whereas the retention index is independent of the surfactant concn. The temp. dependence of the retention index was studied and the std. enthalpy, entropy, and Gibbs free energy for micellar solubilization of the sample compds. were detd., showing that the hydrophobic interaction plays a significant role in MECC ana

Unsteady-state flux behaviour in relation to the presence of a gel layer

The unsteady-state flux behavior for silica and dextran in a stirred ultrafiltration cell was studied. The 2 compds. show clearly different flux behaviors. During the filtration of dextran, only a polarization layer is built up. For silica, a gel layer formation also occurs. As a result, the time to reach steady-state flux is 1 h. The osmotic pressure model provides a good description of the flux for the expts. with dextran. If mass-transfer coeffs. are used that are higher than those electrochem. measured, the transient flux for silica can be rather well predicted by the gel-polarization model. The use of flux measurements under unsteady-state conditions as an indication for the presence of a gel layer is discussed. [on SciFinder (R)

Retention indices in micellar electrokinetic chromatography

The use of retention indices in micellar electrokinetic chromatography (MEKC) is evaluated both from a theoretical and a practical point of view. Fundamental equations for the determination of retention indices in MEKC are described, showing that retention indices are independent of the surfactant concentration. Possibilities as well as limitations of different homologous series as reference standards are described. In addition, the practical application of retention indices for identification, investigation of solute-micelle interactions, characterization and classification of pseudo-stationary phases and determination of solute lipophilicity are discussed

Solute retention and resolution in parallel-current open tubular liquid chromatography

A polemic is given to show that the solute retention equation for micellar electrokinetic capillary chromatog. can be used to derive the capacity factor in parallel-current open tubular liq. chromatog. as developed by K. Slais et al. (J. Chromatog. 1992, 605, 167; J. Microcol. Sep. 1993, 5, 63). Differences in flow ratio caused by inhomogeneity of the retentive film will not affect the calcd. capacity factor in contrast to the dependence on flow ratio of the reduced capacity factor derived by Slais et a

Optimization of the elution range in micellar electrokinetic capillary chromatography

The resolution of neutra! solutes in micellar electrokinetic capillary chromatagrophy is influenced by the migration time of the electroosmotie flow, tEoF' the migration time of the micelles, tMe, and the capacity factors of the solutes, k. The resolution of a separation can be improved by increasing the elution window and by optimizing the capacity factors of the solutes. The influence of the buffer pH, surfactant concentration and organic modifier content of the electrolyte system on both the elution window and the capacity factors was investigated