Trace Analysis of Heavy Metals with Two 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 μg L^?1 to 6.0 mg L^?1 for reagent 1, and from 0.2 mg L^?1 to 6.0mg 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 × 10⁹ M^?l. 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.