Water-in-oil microemulsion as mobile phase in thin-layer chromatographic retention studies of anions

A water-in-oil (W/O) microemulsion, consisting of sodium dodecyl sulphate (SDS)/1-pentanol/water/heptane, has been used as mobile phase for the separation of inorganic anions from their binary mixtures, for example, IO ₄ ⁻ -NO ₂ ⁻ , IO ₄ ⁻ -BrO ₃ ⁻ , IO ₄ ⁻ -I⁻, MnO ₄ ⁻ -BrO ₃ ⁻ , MnO ₄ ⁻ -NO ₂ ⁻ , and MnO ₄ ⁻ -Br⁻. The weight ratio, SDS/n-pentanol was kept constant at 1/2.46 for all compositions. The retention efficiency of anions on layers of silica gel G, alumina, microcrystalline cellulose, kieselguhr G, and mixtures of kieselguhr and cellulose in 4:1 and 3:2 ratios has been examined with the W/O microemulsion system as a mobile phase. Thin layers of kieselguhr were most useful for differential migration of anions. Quantitative separation of IO ₄ ⁻ from accompanying ions, limits of identification, and dilution of few anions are reported. The effects of amines, phenols, and heavy metals on the separation efficacy of IO ₄ ⁻ also have been investigated.