EN
The factors which efficiently reduce nonradiative energy degradation of the lanthanide ion fluorescence are described. The most sensitive systems in spectrofluorimetric determination of trace amounts of lanthanide ions based on the complex formation, intramolecular energy transfer and mixed complexes with synergic agents in a liquid phase, are presented. Detection limits of highly sensitive systems obtained with the use of conventional and laser-excited spectrofluorimetry for Sm(III), Eu(III), Tb(III) and Dy(III) are compared.