Analytical applications of triethylenetetraminehexa-acetic acid: Part 4. amperometric titrations of metal ions

The behaviour of metal ions during titration with triethylenetetraminehexaacetic acid (TTHA) in several supporting electrolytes was investigated by d.c. and square-wave polarography. The composition of the complexes (M₂L or ML) formed during titration is reported as well as the M] : L] ratio corresponding to the end-point of amperometric titration. The optimal conditions (by d.c. and s.w. detection) are given for titrations of Cu(II), Ni(II), Cd(II), Pb(II) and Zn(II) based on the reduction current of metal ions, as well as for titrations of Cu(II), Cd(II), Pb(II), Zn(II), Al(III), Ca(II) and Mg(II) based on the anodic current of TTHA. Application of the anodic current of TTHA permits determinations of polarographically inactive metals and is valuable in analysis of mixtures.