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A novel, comprehensive two-dimensional asymmetric field-flow fractionation-liquid chromatographic system is described (AsF1FFF-RPLC). The interface is based on a switching valve, and the whole sample is analyzed in both dimensions. The system proved to be repeatable and quantitative in the characterization of egg white proteins. Four peaks at 4, 5.5-6.0, 7.5-8.0, and 10.0-11.0 nm, and corresponding to lysozyme, ovalbumin, transferrin, and a dimer of transferrin, were obtained in the AsFIFFF first-dimension system. Lysozyme also produced an additional peak, which overlapped with ovalbumin. Twelve compounds were separated in the LC second-dimension system. Identifications were made with the help of standards (ovalbumin, ovotransferrin, lysozyme) and by comparison of the peak areas, particle sizes, and retention data with values given in the literature. The effect of heat on egg white denaturation was studied, and the unfolding of peptide bonds of the protein was found to be pronounced when the sample was heated in phosphate solution.

Low-density lipoprotein (LDL) particles were immobilized on the inner wall of a fused-silica capillary and used in a study of the interactions between LDL and neutral drugs in electrochromatography. The effect of coating parameters (pH, ionic strength of the coating solution, duration of the coating procedure) on the properties and stability of the coating was examined. The stability of the coating was highest when the pH of the coating solution was under the pI value of the LDL particles. Interactions of unmodified LDL coatings with drugs were compared with those of acetylated LDL coatings. Acetylation of LDL neutralizes the positive charge on the lysine residues of the protein component of LDL particles, and acetylated LDL was used as a reference to examine the effect of the positively charged amino acids in the unmodified coating. Under similar coating conditions, acetylated LDL coating yielded stronger EOF evidently due to the decreased number of positive charges on LDL particles. The interactions of the unmodified and acetylated LDL coatings with steroids aldosterone, testosterone, and progesterone were comparable, which indicates that the density of immobilized LDL particles is not appreciably altered by acetylation. As expected, the strength of the interactions between steroids and the LDL coating increased with hydrophobicity of the drug.

Physicochemical properties of a mixed micellar system of sodium dodecyl sulfate (SDS) and sodium cholate (SC) were investigated. The micelle-micelle and micellebuffer interactions in an SDS/SC/[(1,1-dimethyl-2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid buffer system for separations by micellar electrokinetic capillary chromatography (MEKC) were studied by capillary electrophoresis (CE) and nuclear magnetic resonance (NMR) techniques. A mixed micellar system of SDS and SC can effectively be used for the separation by MEKC of highly hydrophobic compounds like corticosteroids. Marked differences in distribution coefficients of the corticosteroids were observed when the micellar phase was changed from the highly hydrophobic SDS to the less hydrophobic SC. Measurements of critical micelle concentration were made by CE and conductometric titration. The mixed micellar system was further characterized by NMR methods. NMR-based serf-diffusion measurements and NMR relaxation measurements showed that SC affects the micellization of SDS primarily by decreasing the amount of nonmicellized (monomeric) SDS in the mixed system.