A potentiometric study of guanidinoacetic acid complexation with the ions Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II)

The guanidinoacetic acid (GAA) complexation with some ions of biological interest, such as Mn(II), co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) has been investigated. GAA was prepared and analysed. The dissociation constants of its complexes and hydroxy complexes with the above ions have been potentiometrically determined. Most of the ions formed complexes of the type MGAA, M(GAA)(2) and M(GAA)(3). Zn(II) and Cu(II) did not form M(GAA)(3) and M(GAA)(OH)(3). The hydrolysis of CuGAA and ZnGAA begins near pH 6-7; for the other MGAA complexes it begins near pH 8. Above these pH values, polymerized, hydrolysed species predominated.