Stokes shift lanthanide chelates

Heterogeneous fluorescent immunoassays for T4 based on lanthanide rare earth ions and time-resolved fluorescence were also developed. The use of europium chelates as fluorescent probes is particularly attractive because of their extraordinarily long Stokes shifts and long fluorescence decay times. Thus the sharp emission peak of europium (613 nm) can be easily separated fr om scattering caused by excitation light (340 nm) or by interfering substances in... 

Secondly, the Stokes shift is very large, almost 300 nm. This difference between excitation and emission peaks means that the fluorescence measurement is made at a wavelength where the influence of non-specific signals is minimal. In addition, the emission peak is very sharp which means that the detector can be set to very fine limits and that the emission signals from different lanthanide chelates can be easily distinguished from each other (Figure 1). 

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