TRACE ANALYSIS OF HEAVY-METALS WITH 2 NEW DISODIUM BISDITHIOCARBAMATES

Two chelating reagents, disodium N,N'-dibenzylethylenebisdithiocarbamate 1 and disodium piperazinebisdithiocarbamate 2, were synthesized and used to preconcentrate trace metals in aqueous samples. For analysis of Cu(II) using a UV-vis spectrometer, Beer's law was obeyed from 5.0 mu g L(-1) to 6.0 mg L(-1) for reagent 1, and from 0.2 mg L(-1) to 6.0 mg L(-1) for reagent 2. The chelation ratio for reagent 1 to Cu(II) was determined to be 1:1, with a formation constant 1.0 x 10(9) M(-1). The dependence of extraction and extraction efficiency of reagent 1 on pH was also studied with an atomic absorption spectrometer for nine heavy-metal ions-Cu(II), Fe(III), Pb(II), Co(II), Cr(VI), Ni(II), Zn(II), Mn(II) and Cd(II). Except Cr(VI) and Mn(II), the recovery yields of the other seven metal ions were almost quantitative at pH = 4 - 6. The recovery was 82% for Cr(VI) at pH = 4 - 5, and 52% for Mn(II) at pH = 6 - 7.