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 ofCu²⁺, Cd²⁺, Ni²⁺ and Zn²⁺ complexes of DTC-TETA are all better than those of DDTC at the same concentration.