An-Najah Staff

Published methods based on the use of water-soluble binary and ternary complexes for the spectrofluorimetric determination of terbium(III) are compared. The complexes formed by terbium(III) with (1) ethylenediamine-N,N′-bis-o-hydroxyphenylacetic acid, (2) o-hydroxyphenyliminodiacetic acid, (3) EDTA and sulphosalicylic acid, (4) EDTA and Tiron, and (5) iminodiacetic acid and Tiron were examined. In each system, the characteristic sharp-line emission from terbium(III) at around 545 nm is measured. On the basis of emission spectra from 400 to 600 nm, fluorescence intensity in relation to variation in terbium/reagent mole ratios, sensitivity and some interference tests involving other lanthanides, yttrium, thorium and dioxouranium(VI) ions, it is concluded that the system represented by (4) is best, followed by (1), (5) and (3) in that order; (2) is least satisfactory on account of the strong dependence of fluorescence intensity on the terbium(III)/reagent mole ratio.