This paper discusses a rapid and sensitive method developed to determine trace levels of mercury in natural water samples by cold vapor atomic absorption spectrometry using a preconcentration system composed by mini-column packed with 100 mg of 2-aminothiazol modified silica gel (SiAT) coupled on-line with the spectrometer's cold vapor generator system. The optimum preconcentration conditions are also described here. The preconcentrated Hg(II) ions were eluted directly from the column to the spectrometer's cold vapor generator system using 100 µL of 2 mol L-1 hydrochloric acid and the retention efficiency achieved exceeded 95%. The enrichment factors determined were 29, 38 and 46 using 3, 4 and 5 mL of preconcentrated aqueous solutions containing 400 ng L-1 of Hg. The detection limit calculated was 5 ng L-1. The preconcentration procedure was applied to determine trace level mercury in spiked river water samples.

Electroassisted separation methods based on the use of electrically conducting supported liquid membranes and of liquid/liquid extraction under control of the interfacial Galvani potential are described. The control of interfacial potentials and the use of metal ion specific ligands have been employed to achieve specificity in metal ion separations and for the stripping and concentration of metal ion from dilute streams. It is shown that a supported liquid membrane can be used as an ion. selective membrane for the electrolysis of specific metal ions. The interfacial potential for electroassisted solvent extraction is determined by the two-phase Nernst equation, which relates the distribution of ionic species to the Galvani potential and to the standard Gibbs energies of ionic transfer between an aqueous and an organic phase immiscible with water. It is shown that specificity in separations can be achieved in solvent extraction by controlling the Galvani potential.