General method for the determination of stability constansts of lanthanide ion chelates by ligand-ligand competition laser excited Eu{sup 3+} luminescence excitation spectroscopy
- Pennsylvania State Univ., University Park, PA (United States)
A highly sensitive, convenient, direct spectroscopic method for the measurement of stability constants of Eu{sup 3+} ion complexes of multidentate ligands is described. The method involves the competition against one another, of two ligands, one (L`) of known and one (L) of unknown stability constant for its Eu{sup 3+} complex. Using ethylenediaminetetraacetic acid (edta) as the reference ligand, formation constants for the 1:1 complexes of Eu{sup 3+} with N-(2-hydroxyethyl)ethylenediaminetriacetic acid (hedta), diethylenetriaminepentaacetic acid (dtpa), and 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (do3a) were determined, all in good to excellent agreement with their literature values. The method was also applied to the Eu{sup 3+}-dtpa-dien [1,4,7- tris(carboxymethyl)-9,17-dioxo-1,4,7,10,13,16- hexaazacyclooctadecane] system, where the species EuH(dtpa-dien){sup +}, Eu(dtpa-dien), and Eu(OH)(dtpa-dien){sup -} exist in different pH regions. The respective formation constants are given. Advantages of the present method include high sensitivity (1-10 {mu}M concentrations of Eu{sup 3+} and ligand), small sample volumes (1 mL or less), and the ability to detect directly and characterize the spices present in solution under particular PH conditions using excitation spectroscopy and lifetime measurements. 44 refs., 9 figs., 3 tabs.
- OSTI ID:
- 199409
- Journal Information:
- Analytical Chemistry (Washington), Journal Name: Analytical Chemistry (Washington) Journal Issue: 2 Vol. 68; ISSN ANCHAM; ISSN 0003-2700
- Country of Publication:
- United States
- Language:
- English
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