Electrochemical investigation of complexation and speciation of zinc with 1,10-Phenanthroline (phen) in aqueous solution have been performed by an electrochemical technique, DPASV, using Mercury Film Coated Glassy Carbon Electrode (MFGCE). The work was carried out at constant pH and ionic strength.The overall formation constants of different complexes of zinc with phen were measured by applying Leden, DeFord and Hume model.It was found that three (1:1, 1:2 & 1:3; metal:ligand) complexes were formed with phen under the experimental conditions used in this work.The overall formation constant of complexes, Zn(phen)n which can be defined as Zn(Phen)n = [Zn(Phen)n]/[Zn2+][Phen]n [where, ‘Phen’ is the complexing ligand and ‘n’ is an integer]. The values of the formation constants were found to be 106.66, 1012.30 and 1017.44 for Zn(Phen), Zn(Phen)2 and Zn(Phen)3, respectively (for simplicity charges of the complexes were omitted).Finally it is concluded that electrochemical technique, specially DPASV is a simple and powerful tool to investigate the metal organic interaction in aqueous solution. Thin mercury film coated glassy carbon electrode acts as an ultra-microelectrode which is more sensitive than any other hanging mercury or dropping mercury electrode.

Keywords : DPASV, Complexation, Speciation, Mercury Film Coated Glassy Carbon Electrode.