Europium as a label in time-resolved immunofluorometric assays

Anal Biochem. 1984 Mar;137(2):335-43. doi: 10.1016/0003-2697(84)90095-2.


A nonisotopic immunoassay has been developed based on a sensitive detection of europium (III) in water solution using time-resolved fluorometry. The europium label is bound to the antibody with EDTA derivatives, either diazophenyl-EDTA-Eu or isothiocyanatophenyl-EDTA-Eu. After the immunometric assay has been completed the europium is preferably dissociated from the antibody at low pH and measured by time-resolved fluorescence in a micellar solution containing Triton X-100, beta-diketone, and a Lewis base. The detergent solubilizes the chelating compounds in the solution and excludes water from the fluorescent ligand-europium complex. Europium concentrations as low as 5 X 10(-14)M were measured using a 1-s counting time. The sensitivity of the immunoassay of rabbit IgG used as a model system was 25 pg/ml (6 pg/assay).

MeSH terms

  • Animals
  • Antibody Affinity
  • Europium*
  • Fluorescent Antibody Technique*
  • Hydrogen-Ion Concentration
  • Immunoglobulin G / analysis
  • Isotope Labeling
  • Rabbits
  • Spectrometry, Fluorescence
  • Terbium


  • Immunoglobulin G
  • Terbium
  • Europium