COMPETITION OF IRON(III) an‎d LEAD(II) FOR COMPLEXATION WITH DTPA (A MULTIDENTATE-NON SPECIFIC LIGAND)

Diethylenetriaminepentaacetic acid (DTPA), a polyaminocarboxylic acid is widely used as chelating agent for the detoxification of lead. The ligand is non-specific to all metals forming stable complex in 1 : 1 molar ratio. Lead competes with the action and metabolism of essential metals specially Fe (III). Since the 4.0, 7.0 and 9.0 are the important pH representing acidic environment as found in stomach, neutral environment as in blood and alkaline medium as found in intestine. These pH are therefore selected for the present spectrophotometric study. Pb (II) successfully replaces Fe (III), from its DTPA complex at neutral and alkaline pH, but fails to do so at pH 4.0. Increase in concentration of added metal and ligand has also considerable effect. Thermodynamic stability was also studied. Increase in temperature from 30 to 60°C has negligible effect on the trend.