Stabilization induced by gelatin in the spectrofluorometric assay of terbium(III) ions using trimesic acid

Abstract

The reaction conditions for the fluorescence system of terbium with trimesic acid [benzene-1,3,5-tricarboxylic acid (TMA)] in the presence of gelatin in aqueous solution have been investigated. The fluorescent chelate, having the maximum excitation wavelength at 263.8 nm and maximum emission wavelength at 547 nm, shows a constant fluorescence intensity in the pH range of 5–6. The reaction is instantaneous and the resulting product causes an adsorption equilibrium on the surface of the gelatin molecule in 30 min and the relative fluorescence intensity remains stable for 12 h. The stoichiometric composition of the chelate is 1:1 (Tb^III : TMA). Under the optimal experimental conditions, fluorescence intensity is a linear function of concentration in the range 0.0248–6.356 µg ml^–1 for Tb^III. The method has been applied successfully to a number of synthetic mixtures of various composition and artificially mixed rare earth ore samples.