Effect of copper, nickel, zinc, and phosphorus on reactions of FeEDDHA and FeEDDHMA isomers under variable pH

The complexes of iron and o-EDDHA or EDDHMA decompose at low pH values although they are quickly recovered when pH increases. However this later reaction is affected by the occurrence in solution of cations different from iron or anions different from the chelating ligand. The influence of these ions depends on the chelate and on the isomeric form. In general, the isomer with lowest stability constant is the most affected. Copper and phosphate are the ions that impede to the greatest degree the recovery of FeEDDHA and FeEDDHMA. This study demonstrates that FeEDDHA is more stable than FeEDDHMA with respect to Cu2+, however, in regard to phosphate, FeEDDHMA shows higher per centages of recovery.