Employing Luminescence to Determine Eu-DTPA Complex Formation Rate Constants in Lactate and Citrate Media: Experiment and Aggregate-Species Kinetic Modelling

ABSTRACT

The formation kinetics for DTPA binding to europium ions in aqueous media were determined using the change in photoluminescence. The influence of lactic acid and citric acid on these kinetics were also investigated. The total formation rate constant of DTPA complexation with europium ions was strongly dependent upon the pH and DTPA speciation, with values ranging from 5 × 10³ M^–1s^–1 to >1 × 10⁶ M^–1s^–1 over the pH range 1.5 to 2.3. The ligand-metal binding in the presence of lactate and citrate ions showed an inverse kinetic behavior, with strongly decreasing reaction rates at higher buffer concentrations and pH.

KEYWORDS:

• Europium complexation
• DTPA
• kinetics
• lactate; citrate

Acknowledgments

This research was funded under the Nuclear Energy Universities Program, under DOE-NEUP program DE-NE0008410.