Determination of trace europium based on new fluorimetric system of europium(III) with thenoyltrifluoroacetone and N,N'-dinaphthyl-N,N'-diphenyl-3,6-dioxaoctanediamide.
In the present paper, N,N'-dinaphthyl-N,N'-diphenyl-3,6-dioxaoctanediamide acts as a specific reagent for enhancing the fluorescence intensity of Eu(III) complex with thenoyl trifluoroacetone (TTA), the spectrofluorimetric determination of trace amounts of Eu(III) based on the above system was carried out and its luminescence mechanism was studied. The excitation and emission wavelengths are 343.6 and 613.3 nm, respectively. The fluorescence intensities vary linearly with the concentration of europium(III) in the range 3.647x10(-3)-3.039 mug ml(-1) for the original fluorescence with a detection limit down to 2.279x10(-4) mug ml(-1) and the standard deviation is 0.063 mug ml(-1) for 10 times measurements, and in the range 7.598x10(-4)-0.0243 mug ml(-1) (SD=0.035 for 15 times measurements), 0.06078-0.6100 mug ml(-1) (SD=0.52 for 10 times measurements) for the first derivative fluorescence signal with a detection limit down to 8.566x10(-5) mug ml(-1). The interferences of other rare earths and some of inorganic ions are described. This method is a direct, rapid, selective and sensitive analytical method for the determination of trivalent europium in rare earth ore samples and high purity of rare earth oxides.
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 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 (TbIII : 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 TbIII. The method has been applied successfully to a number of synthetic mixtures of various composition and artificially mixed rare earth ore samples.
EXTREME VARIATIONS OF THE EMISSION SPECTRA OF DYSPROSIUM CHELATES
The luminescence spectra of Dy/sup 3+/ and Tb/sup 3+/ ions in chelates with ligands derived from benzoylacetonate, dibenzoylimethide, and tribenzoylmethide were investigated. The data indicate that the triplet states of all the chelates which emit lines characteristic of the ion lie above the resonance level of that respective ion. (C.J.G.)