Homogeneous enzymatic fluorescence immunoassay of serum IgG by continuous flow-injection analysis

A new technique for automated homogeneous immunoassay has been developed and applied to the determination of serum IgG. An enzyme label, horseradish peroxidase (HRP), conjugated to the antibody (anti-human IgG) was inhibited on immunochemical association. The inhibition of activity was monitored as a decrease in the laser-induced fluorescence of dichlorofluorescein, produced by the HRP-catalysed oxidation of leuco-diacetyldichlorofluorescein by hydrogen peroxide. The entire procedure was performed by flow-injection analysis at a rate of 60 samples per hour. Serum IgG concentrations from 1.4 to 25 mg/ml could be determined after a 1:700 dilution, with a within-run precision of +/-9.8%.