A new approach for developing a cloud-point extraction-flame atomic absorption spectrometric method has been described and used for the determination of cobalt. In this approach, water was removed from the final diluted surfactant rich phase obtained in cloud-point extraction procedure. The results indicated that removing water from this phase increased the enhancement factor by 4-fold. 1-(2-Pyridylazo)-2-naphthol (PAN) and octylphenoxypolyethoxyethanol (Triton X-114) were used as a hydrophobic ligand and a nonionic surfactant, respectively. The chemical variables affecting the preconcentration step were optimized. The effect of the water concentration in the final diluted methanolic surfactant solution on the analytical signal was investigated. The results showed that the analytical signal decreased by 30% and 52% in 15% and 25% water concentrations in methanol, respectively. An enhancement factor of 115 was obtained for cobalt extracted from only 10 ml of a sample. The detection limit obtained under the optimal condition was 0.38 µg l -1 . The proposed procedure was applied to the determination of cobalt in urine samples.

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Mercury(II ) and methylmercury cations at the sub-ppb level dithizone-anchored poly(vinylpyridine) as a chelating resin has also been described for this purpose,20,21 but the synthesis and were adsorbed quantitatively from aqueous solution onto a column packed with dithizone immobilized on sodium dodecyl preparation of this sorbent is tedious and requires three steps. Surfactant molecules are known to form self-aggregates sulfate coated alumina. The trapped mercury was then backextracted into the aqueous phase with 1 M hydrobromic acid called 'hemi-micelles' or 'ad-micelles' on solids. The hydrocarbon cores of the micelles give them the unique ability to and determined by cold vapour atomic absorption spectrometry by utilizing the reaction with sodium trap non-ionic compounds in acidic solutions. These micelles can also solubilize hydrophobic compounds which are other-tetrahydroborate. Mercury(II ) and methylmercury cations were completely recovered from water with a preconcentration wise sparsely soluble in water. For example, chromium() and chromium() in strong acidic solutions (0.24  HCl) were factor of 100. The analytical procedure was applied to the determination of mercury(II ) and methylmercury in river and separated by using a microcolumn of sodium dodecyl sulfate coated alumina.22 Under these conditions, chromium(), tap water.which is in the non-ionic state presumably in the form of Keywords: Mercury; dithizone; sodium dodecyl sulfate; cold H 2 CrO 4 or HCrO 3 Cl, is retained quantitatively on the column, vapour atomic absorption spectrometry while chromium(), which is cationic, remains unadsorbed. Surfactant-coated hydrated iron() oxide23 or alumina24 were Mercury compounds are known to be highly toxic. Sources of also used for the removal of toluene, p-xylene, trichloroethylene mercury are either man-made such as industrial wastes, pesticand pentachlorophenol from aqueous samples.

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