Ionophoretic studies on mixed metal--nitrilotriacetate--penicillamine complexes

Paper ionophoresis is described for the study of equilibria in a mixed ligand complex system in solution. This method is based on the movement of a spot of metal ion in an electric field with the complexants added in the background electrolyte at pH 8.5. The concentration of the primary ligand (nitrilotriacetate) was kept constant, while that of the secondary ligand (penicillamine) was varied. The stability constants of the metal-nitrilotriacetate-penicillamine complexes have been found to be 6.26 +/- 0.09 and 6.68 +/- 0.13 (log K values) for Al3+ and Th4+ complexes, respectively, at 35 degrees C and ionic strength 0.1 M.