ALKYLENE BISITHIOCARBAMATES AS COMPLEXING AGENTS FOR THE PRECONCENTRATION OF TRACE-METALS IN AQUATIC SAMPLES

A series of alkylene bisdithiocarbamates (BDTCs) were synthesized and shown to be excellent chelating agents for heavy metal ions such as Cu(II), Fe(III), Zn(II), Ni(II), Cd(II), Pb(II), Co(II). Mn(II) and Cr(VI) in aqueous solution. The pH dependence of extraction with these chelating agents was extensively studied from pH 2.5 to 10.0. Except for Cr(VI) and Mn(II), most of the cations were recovered with near 100% efficiency within the working pH range of 4-8. If the pH was fixed at 5.0-5.5, even Cr(VI) could be successfully extracted with hexamethylene BDTC (HMBDTC) (95%). The efficiency of HMBDTC for the extraction of most ions was comparable to that of ammonium tetramethylenedithiocarbamate and sodium diethyldithiocarbamate and was better for extracting Cr(VI). Stock solutions of these bisdithiocarbamates were stable for at least 3 weeks after preparation. The detection limits were found to be in the range 3-90 ng l-1. Therefore, these alkylene BDTCs, particularly HMBDTC, can be applied to the preconcentration of trace heavy metals in environmental aquatic samples.