Hydrophobic salt-induced phase-separation and extraction for sample preparation in chromatographic determination of heavy metal ions as dibenzyldithiocarbamates

The dibenzyldithiocarbamate complexes with cadmium(II), nickel(II), mercury(II), copper(II) and cobalt(II) were extracted into an acetonitrile phase from aqueous media by adding tetrabutylammonium perchlorate as a phase-separation agent. The salt-induced phase-separation was used for the reversed-phase liquid chromatographic (LC) determination of these metal ions following direct injections of the acetonitrile extract onto a C18 column. The mobile phase was a mixture of 4 :1 (v/v) acetonitrile-0.02M acetate buffer (pH 4.4). Detection limits for the metal ions were in the range of the ng/ml concentration levels of the original aqueous solution. Analysis of standard biological samples (tea and citrus leaves) could be made to evaluate the present LC method.