Europium as a label in time-resolved immunofluorometric assays.
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).
D000818:Animals; D000915:Antibody Affinity; D005063:Europium; D005455:Fluorescent Antibody Technique; D006863:Hydrogen-Ion Concentration; D007074:Immunoglobulin G / Q000032:analysis; D007553:Isotope Labeling; D011817:Rabbits; D013050:Spectrometry, Fluorescence; D013725:Terbium
D007074:Immunoglobulin G; D013725:Terbium; D005063:Europium