Time-resolved fluorometric determination of terbium in aqueous solution

The fluorescent properties of water-soluble binary and ternary complexes of terbium(III) were studied and their applications in time-resolved fluorometric analysis were tested. Solutions composed of different β-diketones, tri-n-octylphosphine oxide as the synergistic agent, and Triton X-100 as the detergent were optimized to maximize fluorescence emission in Tb measurement. The results were then compared with seven published methods which included the use of the following respective solutions, ethylenediamine-N,N'-bis[(o-hydroxy-phenyl)acetic acid], dipicolinic acid, iminodiacetic acid with Tiron, EDTA with Tiron, EDTA with 2,3-dihydroxynaphthalene, EDTA with sulfosalicylic acid, and EDTA with salicylate. Fluorinated aliphatic β-diketones showed the most promising properties in acidic solution. They were especially suitable for use in time-resolved fluorometric analyses where Tb was used as the label after being conjugated to the analyte via bifunctional complexones. An acidic pH is required for Tb release before conversion into a fluorescent chelate. The applicability of the developed measurement solutions to the measurement of Eu was also tested. 22 references, 3 figures, 7 tables