Abstract
The isotopic exchange reaction of lutetium between the uncomplexed lutetium ion and its EDTA complex has been kinetically studied in a pH region from 6.5 to 5.5 by using lutetium-177 as a tracer. The rate is proportional to the first order of the concentration of both uncomplexed lutetium and its EDTA complex. The dependence of hydrogen ion concentration on the rate is very complicated. In the pH region from 6.5 to 6.0, the rate is independent on the concentration of hydrogen ion, and in the pH region below 6.0, clearly dependent on the hydrogen ion concentration. It may be supposed, therefore, that a possible mechanism for the exchange reaction in neutral solution is a simple displacement of the lutetium from the chelate compound by a collision with an uncomplexed lutetium.
The rate of exchange is given by the expression:
R=2.2×10-2 [Lu-EDTAOH-2] [Lu3+] mole l-1⋅min-1.
In acid solution, the acid catalized reaction may compete with the bimolecular reaction.
