An Equilibrium Model for the Nta Complexation of Metal Ions in Natural Waters

Abstract
The equilibrium distribution of NTA among several naturally occurring metal ions has been calculated from previously reported complex ion formation constants. Competition among chelators for the same metals is deduced by introducing the additional model ligands cysteine and citrate to the system. The fraction of NTA, and in the mixed system the fractions of each ligand, bound to each metal at 25°C and pH 7.4 are reported. It is concluded that the most important NTA complexes are those of copper and zinc, and because of their predominance and known biological properties there should be no new toxicological problems arising because of chelation of metal ions already present in the environment as a result of the substitution of NTA for phosphates in detergents.