STABILIZATION INDUCED BY GELATIN IN THE SPECTROFLUOROMETRIC ASSAY OF TERBIUM(III) IONS USING TRIMESIC ACID

The reaction conditions for the fluorescence system of terbium with tr imesic acid [benzene-1,3,5-tricarboxylic acid (TMA)] in the presence o f gelatin in aqueous solution have been investigated. The fluorescent chelate, having the maximum excitation wavelength at 263.8 nm and maxi mum emission wavelength at 547 nm, shows a constant fluorescence inten sity in the pH range of 5-6. The reaction is instantaneous and the res ulting product causes an adsorption equilibrium on the surface of the gelatin molecule in 30 min and the relative fluorescence intensity rem ains stable for 12 h. The stoichiometric composition of the chelate is 1:1 (Tb-III:TMA). Under the optimal experimental conditions, fluoresc ence intensity is a linear function of concentration in the range 0.02 48-6.356 mu g ml(-1) for Tb-III. The method has been applied successfu lly to a number,of synthetic mixtures of various composition and artif icially mixed rare earth ore samples.