Quantitative determination of Eu(III) complex speciation in aqueous complexes of Eu(III) with oxydiacetic acid using D-5(0)->F-7(0) excitation spectroscopy

In this work we report on the use of F-7(0)-->D-5(0) excitation spectroscopy in determination of the concentration of the mono-, bis-, and tris-complexes of Eu(III) with the terdendate ligand oxydiacetic acid (ODA) for various metal/ligand ratios. For each of these complexes a separate resolvable excitation peak is observed. Each of the peaks can be fit to a normalized Lorentzian lineshape function, and a multiplicative factor may be determined that is proportional to the concentration. Comparison is made with results from conventional potentiometric measurements, and the potential for the use of this procedure in other systems is discussed.