Abstract: The present invention is directed to a method of measuring the dissociation rate of the binding of an antibody to an antigen. The method has two phases: a first phase of binding and a second phase of dissociation. The first phase of the assay has a probe coated with an antigen, or protein G, or an anti-human IgG Fc antibody. The probe is immersed in a sample solution containing an antibody, followed by a wash sequence, then the probe is transferred to a reagent with a biotinylated antigen. After an incubation, the antibody bound on the probe binds to the biotinylated antigen to form an immune complex. Fluorescent signal is produced by immersing the probe in a reagent having a fluorescent tagged streptavidin. The last step of the first phase is a measurement of fluorescent on the probe tip.