Complexation Studies of N, N'-ethylenedi-L-cysteine with Some Metal Ions

As part of a search for environmentally friendly metal chelating ligands, the stability constants of N, N'-ethylenedi-L-cysteine (EC) complexes with Ca(II), Cu(II), Mg(II) and Mn(II) were determined by potentiometry with a glass electrode in aqueous solutions containing 0.1 mola <...L-1 KCl at 25 A degrees C. Final models are proposed. For the Ca(II)-EC system, the overall stability constants are log (10) beta (CaHL)=14.53 +/- 0.03, log (10) beta (CaL)=4.79 +/- 0.01 and log (10) beta (CaL2)=8.38 +/- 0.04. For the M(II)-EC systems, where M=Cu(II) or Mg(II), the overall stability constants are log(10) beta (CuHL)=31.19 +/- 0.02 and log (10) beta (CuL)=27.02 +/- 0.06 for Cu(II), and are log (10) beta (MgHL)=14.84 +/- 0.02 and log (10) beta (MgL)=6.164 +/- 0.008 for Mg(II). For the Mn(II)-EC system, the overall stability constant is log (10) beta (MnL)=10.12 +/- 0.01. Metal-chelate speciations simulations showed that EC is an efficient chelating agent for Cd(II), Co(II), Cu(II), Ni(II), Pb(II) and Zn(II) for pHa parts per thousand yen7.