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

摘要

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 ～ 1388cm~(-1) and 1174～996cm~(-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 265nm and 290nm, assigned to π-π~* transition of N...C...S radical and nonbonding electron n-π~* transition of S...C...S 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 321nm, 310nm, 311nm and 325nm, respectively, confirming the formation of metal complexes. Coupled with flow-injection, FAAS determination shows that the complexation properties of Cu~(2+), Cd~(2+), Ni~(2+) and Zn~(2+) complexes of DTC-TETA are all better than those of DDTC at the same concentration.