Europium(III) ion probe spectrofluorometric determination of diclofenac sodium

A new method has been devised for the determination of diclofenac sodium in bulk and in pharmaceutical preparations using Eu3+ ions as the Fluorescent probe. The technique was built around the hypersensitive property of the transitions of the fluorescent probe ion, Eu3+, at 616 nm. This is normally a forbidden transition, but the interaction with diclofenac sodium, which contains a carboxylic group, makes the transition allowed and enhances the intensity of its fluorescence emission. The Eu3+ fluorescence emission at 592 nm comes from a non-hypersensitive transition and is not affected by ligation. The intensity ratio, R, defined as I592/I616, was used as a measure of the percentage of bound probe ions. Diclofenac and Eu(III) forms a (1:1) molar complex. The relative stability constant of the complex was found to be 10(5). A linear relationship between bound Eu3+ and the concentration of diclofenac sodium was found for concentrations from 10 to 200 micrograms ml-1, with a recovery percentage of 100.22 +/- 2.27. The method shows a good agreement with a spectrophotometric method.