SPECTROFLUOROMETRIC DETERMINATION OF TRACE AMOUNTS OF TERBIUM(III) BASED ON A HIGHLY SELECTIVE FLUORESCENCE LIGAND

A simple, selective and sensitive spectrofluorimetric method has been developed for the determination of terbium(III). This method is based on the reaction of terbium(III) with excess benzene-1,2,4,5-tetracarbo xylic acid (PMA) in slightly acidic aqueous solution. The terbium ion can form a stable 1:1 chelate with PMA. The best excitation and maximu m emission wavelengths are observed at 270 nm and 546 nm, respectively The fluorescence intensity of terbium chelate reaches a maximum value within 10 min and remains stable up to 3 h. The fluorescence intensit y is a linear function of the terbium(III) concentration in the range of 0.198 similar to 6.356 mu g/ml with a detection limit of 0.198 mu g /ml under the optimum experimental conditions. The fluorescence system has good selectivity and stability. It has been applied to the direct fluorimetric determination of trace terbium(III) in rare earth ores a nd oxides.