The electrophoretic behaviors of five bases and corresponding nucleosides in the oil in water (o/w) microemulsion capillary electrophoresis, microemulsion electrokinetic chromatography (MEEKC), were examined in comparison with those in normal capillary zone electrophoresis (CZE). The microemulsion systems were composed of heptane, sodium dodecyl sulfate (SDS), 1-butanol and 10 mM phosphate buffer (pH 7.0) or toluene, SDS, 1-butanol and 5 mM carbonate buffer (pH 10.0). CZE was carried out in the range of pH 9.7-10.9, and the dissociation constants, pKa, of the bases and nucleosides and the electrophoretic mobilities of the anionic forms were determined. The electrophoretic behaviors of the solutes in the microemulsion systems were analyzed from their pKa, the electrophoretic mobilities of the anions determined by CZE, and the distribution constants, K(D), of the neutral forms between the microemulsion droplets and the outer aqueous phase. The importance of adsorption mechanism in MEEKC system was suggested from the correlation between log K(D) and log P.

A reverse osmosis experiment was performed to separate and concentrate lactate from cassava fermentation broth.Pure lactic acid and ammonium lactate solutions were also used as model solutions. The influence of operating conditions, including feed velocity, transmembrane pressure and feed concentration, on the filtration properties (permeate flux, rejection and osmotic pressure) were studied. The concentration factor of lactic acid during batch operation of reverse osmosis was also evaluated. In the laminar flow regime, permeate flux increased with increasing of feed velocity due to concentration polarization of the solute on the membrane surface. However, the permeate flux was not affected by feed velocity in the turbulent regime. Permeate flux and rejection increased with transmembrane pressure and decreased with feed concentration due to higher osmotic pressure. At a transmembrane pressure of 5.5MPa and an initial feed velocity of 0.7 m/s, lactic acid in the model solutions could be concentrated from three to six times; however, the concentration factor in fermentation broth only reached two. The degree of concentration increase of lactic acid was affected by the presence of medium and residual sugar in the fermentation broth, as both may contribute to the increase of osmotic pressure and also polarize the concentration effect that occurs on the membrane surface.