FLUORESCENCE SENSITIZATION OF AQUEOUS TERBIUM AND EUROPIUM IONS WITHOUT AROMATIC DONORS OR SYNERGISTIC AGENTS

EDTA and DTPA complexes of terbium and europium are excited at wavelen gths below 250 nm, producing the typical lanthanide emission through e nergy transfer from the complex to the coordinated metal. This allows determination of these rare earth ions in water without solvent extrac tion, the use of synergistic agents, or aromatic sensitizers. Terbium- EDTA has the most efficient energy transfer, 31%, giving a 165-fold em ission enhancement and a limit of detection of 6 x 10(-7) M. Calibrati on curves are linear over a concentration range spanning three orders of magnitude. The characteristic lanthanide ion emission is obtained i n all cases, but the excitation of the complexes is pH dependent, show ing intensity increases up to pH 12. Mild interference by alkali and a lkaline earth metals was overcome by increasing the ligand concentrati on, but transition metal interference was more severe. Only minor enha ncement was observed at higher ligand/metal ratios.