Water-in-oil (w/o) microemulsions consisting of surfactant [sodium dodecyl sulfate (SDS) or N-Cetyl-N,N,Ntrimethyl ammonium bromide], water, heptane or hexane, and a cosurfactant (1-pentanol or butanol) have been used as a mobile phase in combination with alumina, microcrystalline cellulose, silica gel G, silica gel H, and Kieselguhr thin layers to study the retention efficiency of amines. The separation of amines from their ternary and binary mixtures is achieved. Thin layers of alumina as the stationary phase and SDS/water/heptane/1-pentanol microemulsion as mobile phase is identified as the best chromatographic system for amine analysis. The limits of identification and dilution are reported for amines. Effects of heavy metals, anions, and phenols on the separation efficacy of diphenylamine-p-chloroaniline-p-nitroaniline have also been examined. The effect of electrolyte in the microemulsion on amine mobility is investigated. The o-and p-isomers move faster compared to the m-isomer of aniline.Paper no. S1093 in JSD 2, 85-90 (January 1999).Microemulsions are thermodynamically stable microstructured mixtures containing oil (nonpolar solvent), water, surfactant, and often an amphiphilic molecule called a cosurfactant (1). Unlike macroemulsions, however, microemulsions appear to be absolutely stable toward phase separation (2). The microemulsion systems are optically clear because of a much smaller droplet size (0.01-0.1 mm) compared to the droplet size of macroemulsions (0.4-10 mm). A microemulsion is formed when a cosurfactant (medium short-chain alcohols or amines) are added to a coarse-emulsion, water-surfactant oil (3-5) up to clarity. These microemulsions are also called swollen micellar solutions due to having structures similar to micellar solutions, except that they have a core either of water or of hydrophobic fluids (normally hydrocarbons). Microemulsions are generally found in two forms: (i) an oil-in-water (o/w) and (ii) a water-in-oil (w/o). In the former case, oil microdroplets enclosed in the surfactant-cosurfactant film are dispersed in the continuous water phase, whereas in the latter case the water phase is dispersed as globules in the continuous oil phase. Micellar systems have been extensively studied by physical chemists and biochemists for many years (6). Recently many analytical chemists have realized that micellar systems can often be advantageously applied to chemical analysis. These systems offer the unique capability of simultaneous separation of ionic and nonionic compounds, solubilization of hydrophobic compounds in aqueous solutions, organization of reactants on a molecular level to increase the proximity of reagents and analytes, and enhanced luminescence detection (7,8). One of the areas of great interest has been in the use of micellar systems as mobile phases in reversed-phase liquid chromatography (9-14) because of their unique separation selectivities. Micellar mobile phases provide a combination of remarkable advantages in chemical analysis not offered by any single high-pres...
