Properties of aqueous solutions for two binary mixed systems between two kinds of bile salts and nonionic surfactants

Study of Structure of Water Droplets of Nonionic Polyoxyethylene (4) Lauryl Ether Reverse Micelles in the Presence of Sodium Cholate

The microenvironment of water droplets of nonionic polyoxyethylene (4) lauryl ether reverse micelles was investigated with infrared and ultraviolet-visible spectroscopy, also by viscosity and dynamic light scattering measurements in the presence of biological surfactant sodium cholate as additive. Influence of concentrations of polyoxyethylene (4) lauryl ether and sodium cholate on the microstructure of mixed reverse micelles was studied. Influence of sodium cholate as additive on the ratio of free, bound and trapped water fractions was studied via deconvolution of the O-H stretching vibrational absorption spectra in the region of 3 000–3 800 cm−1 into three subpeaks with a Monte Carlo method. Several characteristic parameters of reverse microemulsions were calculated on the basis of measurements of their kinematic viscosity. A different influence of concentration of sodium cholate on the binding constant and association degree of optical probes (o-nitroaniline and methyl orange respectively) to ethylene oxide groups of nonionic surfactant was observed. It was found that the bound water fraction, the binding constants and association degrees, the relative density of water pockets, etc. change their values passing through an extremum under the influence of sodium cholate.

Separation of chiral compounds by capillary electrophoresis

This review presents the different chiral selectors used in capillary electrophoresis (CE) for the separation of enantiomers. The use of charged cyclodextrins, crown ethers, polysaccharides, proteins, natural and synthetic micelles, macrocyclic antibiotics and ergot alkaloids is discussed in detail. Neutral native and derivatized cyclodextrins are not treated because several review articles have already been published on this topic. Recent developments like the application of two chiral selectors in the same background electrolyte are highlighted.

Effects of bile salt structure on chiral separations with mixed micelles of bile salts and polyoxyethylene ethers using micellar electrokinetic capillary chromatography

The chiral resolving abilities of micellar solutions of four different bile salts alone and in mixtures with polyoxyethylene-4-dodecyl ether (C12E4) and methanol were investigated using MECC. The four bile salts investigated were the unconjugated sodium salts of cholic, deoxycholic, chenodeoxycholic and ursodeoxycholic acids. The test solutes included verapamil, norverapamil, gallopamil, bi-2-naphthol, atenolol and BAYK8644. The relative hydrophobicities of the micellar aggregates formed in solutions of binary mixtures of each bile salt with C12E4 were investigated by fluorescence spectroscopy using pyrene as a probe molecule. The observed enantiomeric resolution for the test compounds using these binary mixtures as MECC pseudo-stationary phases was determined. Correlations between micellar hydrophobicity for these solutions and chiral resolution of these test solutes are presented. The addition of C12E4 with or without methanol to solutions of sodium cholate and sodium deoxycholate enhanced the chiral resolution observed for compounds containing a longer hydrocarbon chain separating some of the major functional groups from the chiral center. The pure bile salt solutions generally provided better chiral resolution for the compounds where the major functional groups, such as aromatic rings, were closer to the chiral center.