A Novel Complexing Reagent Containing Bisdithiocarbamate Applicable to Determination of Trace Heavy Metal Ions

Triethylenetetramine(TETA) was reacted with carbon bisulfide in an alkaline medium in order to prepare a bisdithiocarbamate chelator, namely sodion triethylenetetramine- bisdithiocarbamate(DTC-TETA). The chelator was characterized and examined by FTIR, UV spectroscopy and elemental analysis. Its complexes with heavy metal ions were also checked by UV spectroscopy. Comparison of heavy metal ions' stability for DTC- TETA with that for sodium diethyldithiocarbamate (DDTC) was accomplished using flame atomic absorption spectrometry (FAAS) coupled with flow-injection. By introducing NCS groups onto the TETA terminals, the FTIR spectrum shows strong absorption peaks at 1461~1388 cm -1 and 1174 ~ 996 cm -1 which were attributed to partly double bonds of C - .... N and C - .... S, respectively, representing the formation of DTC-TETA. The UV spectrum of DTC-TETA has two absorption peaks at 265 nm and 290 nm, assigned to pi-pi* transition of NhellipChellipS radical and nonbonding electron n-pi* transition of ShellipChellipS radical to conjugated system, respectively. The elemental analysis results demonstrate that the mol ratio of C, H, N and S in DTC-TETA was about 2:4:1:1. As for UV spectra of its Complexes with Cu (II) , Cd (II) , Zn (II) and Ni (II) , there are new four absorption peaks at 321 nm, 310 nm, 311 nm and 325 nm, respectively, confirming the formation of metal complexes. Coupled with flow- injection, FAAS determination shows that the complexation properties ofCu 2+ , Cd 2+ , Ni 2+ and Zn 2+ complexes of DTC-TETA are all better than those of DDTC at the same concentration.