Fluorimetric determination of thyroxine hormone with Eu(III)-(pyridine-2,6-dicarboxylate) tris complex

Gok E., Ates S.

JOURNAL OF FLUORESCENCE, vol.13, no.3, pp.221-225, 2003 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 13 Issue: 3
  • Publication Date: 2003
  • Doi Number: 10.1023/a:1025085715447
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.221-225
  • Hacettepe University Affiliated: No


We describe a method for the determination of thyroxine ( Thy) using its quenching effect on Eu(PDA)(3)(3-) tris complex fluorescence. The relative fluorescence intensities are measured at fixed lambda(exc) = 282 nm, lambda(em) = 615 nm by titrating the metal complex with Thy in piperazine buffer solution at pH 6.5. Data indicated an associative type of reaction of two molecules valid between 0.0 < R < 1.0, R being the mole ratio of Eu(PDA)(3)(3-) to Thy. Over this ratio and up to (R >> 1.0) collisional quenching of Eu(PDA)(3)(3-) complex ion emission is seen as a result of heavy atom effect, intermolecular energy transfer playing the main role. This is also confirmed by the Stern-Volmer equation. In optimized experimental conditions, the L- form of Thy is determined in a range of 15.5 - 551.6 mug/ml (2.0 x 10(-5) - 7.1 x 10(-4) M) with relative error of +/- 1.17%.