Liposome-Based

We developed a method for quantitatively determining theophylline in serum, using a heterogeneous immunoas-say called flow-injection immunoanalysis. The reaction involves competition between serum theophylline and theophylline-labeled liposomes. Separation occurs on a solid-phase reactor column containing immobilized anti-body to theophylline incorporated in a flow-injection sys-tem. Subsequent lysis of the bound liposomes provides sensitivedetectionoftheanalyte.Effective regeneration of the immobilized antibody activity allows the reactor to be reused for hundreds of sequential samples. Compan-son of the results of the flow-injection immunoassay method with results obtained with a commercially avail-able fluorescence polarization method showed an excel-lent correlation