Cetylpyridinium Chloride Micelle-mediated Mutual Separation of Zinc, Cadmium, and Mercury Ions by Thin-layer Chromatography

Cationic surfactant-mediated systems containing different concentrations of cetylpyridinium chloride have been used as mobile phases in thin-layer chromatographic separation of metal cations on silica layers. The effect of surfactant concentrations below and above the critical micelle concentration (CMC) on the retention behaviour of metal ions was examined. The best TLC system for rapid mutual separation of Zn, Cd, and Hg was unmodified silica as stationary phase and 5% aqueous cetylpyridinium chloride as mobile phase. The effects of pH (acidity or basicity), inorganic electrolytes (the acetate, formate, chloride, bromide, and carbonate of sodium and the chloride and nitrate of calcium), and organic compounds (urea) in the cetylpyridinium chloride solution on the mobility and separation efficiency of Zn, Cd, and Hg were assessed. The limits of detection for these metal cations were also determined. The method is well suited to identification and separation of Hg, Zn, and Cd from synthetically prepared ores, for example cinnabar (HgS), zinc blende (ZnS), and greenoekite (CdS), and from hydroxide sludge.