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The analytical potential of poly(ethylene glycol) p-isooctyl-phenyl ether (Triton X-100), a nonionic surfactant, is used as a mobile phase in the thin-layer chromatographic separation of heavy-metal cations. The surfactant concentration below its critical micellar concentration (CMC) as well as above the CMC value is used to investigate the migrational behavior of some heavy-metal ions on silica gel layers. The mobility of the metal ions is found to change marginally with the increase of surfactant concentration from 0.001M (below CMC) to 0.1M (above CMC). The influence of the pH of the medium, nonelectrolyte organic (urea and alkanols), and inorganic electrolyte (NaCI) additives in the surfactant containing mobile phase on the mobility of heavy metals on the silica gel layer is examined. For separating metal ions, surfactant must be used in the presence of buffers. Triton X-100 (0.02M) at pH 2.3 is found to be the best mobile phase for the separation of heavy-metal cations. In general, the presence of alcohol in aqueous surfactant solutions results in a decrease in the mobility of metal ions. Besides Cu2+ and Fe3+, all of the metal ions show a trend of increasing the retardation factor beyond a minima at 0.1 or 0.3M of added urea or NaCl. The proposed method is successfully applied for the simultaneous detection of Zn2+ and Cd2+ from a spiked human blood sample.

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...

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The migration behavior of heavy metal cations on cellulose layers using aqueous micellar, hydro-organic, and water-organic-surfactant mobile phases was investigated. Anionic, cationic, and nonionic surfactant systems were examined over a 0.001-5% concentration range. Brij-35, a nonionic surfactant capable of forming charged complexes with some metal ions, was identified as the best surfactant. The effect of the presence of organic additives, such as dimethylsulfoxide, dimethylformamide, methanol and acetone, on the mobility of metal ions was also studied. Acetone was found to be the most effective additive at 10% concentration with 3% Brij. Quantitative determination of UO 2 2+ by spectrophotometry after preliminary thin-layer chromatographic (TLC) separation from Fe 3+ and Hg 2+ was also performed. A maximal recovery of 93% was obtained. This TLC method is rapid, with development times averaging 2 min.Paper no. S1098 in JSD 2, 523-529 (October 1999). KEY WORDS:Acetone, Brij-35, DMSO, heavy metal cations, micelles, TLC, uranium.Micellar liquid chromatography (MLC) has increased in popularity because of its unique advantages, such as the capability to simultaneously separate ionic and nonionic compounds and to provide faster analysis, higher detection sensitivity, and selectivity (1-5). The most fascinating feature of micellar systems is their dual hydrophobic and hydrophilic character, which provide electrostatic and hydrophobic sites of interaction within the aqueous mobile phase, resulting in unique separation capabilities of both ionic and nonionic solutes. As a result, micellar mobile phases have been extensively used in reversed-phase chromatographic separation of various organic compounds. In comparison, the use of micellar mobile phases in inorganic chromatography has been limited. Efficiency of mobile phases in the separation of cations (6,7) and anions (8,9) has been reported and reviewed by Okada (10). Mullins and Kirkbright (11) used MLC as an alternative to ion chromatography for the separation of several inorganic anions using a cationic micellar eluent. Kirkman et al. (12) used a variety of micellar eluants to examine the chromatographic behavior of ionic, nonionic, chelated, and organometallic metal species. Although micellar mobile phases offer enhanced selectivity, they suffer from a serious loss of efficiency when compared to traditional hydro-organic mobile phases. Dorsey et al. (13) reported that addition of low concentrations of different organic solvents to micellar mobile phases improves efficiency by reducing the adsorbed amount of emulsifier (surfactant). This unique phenomenon in MLC was attributed to the existence of a competing equilibrium in MLC and an influence of micelles on the role of organic modifiers. Khaledi et al. (14) observed simultaneous enhancement of separation selectivity and solvent strength in MLC using hybrid eluants comprising cationic or anionic micellar-organic solvents for different groups of ionic and nonionic compounds.A few studies reported the use of surfac...