Competitive Heterogeneous Enzyme Immunoassay for Theophylline by Flow-Injection Analysis with Electrochemical Detection of p-Aminophenol

A competitive enzyme-linked immunoabsorbent assay based on the flow-injection amperometnc detection of p-amino-phenol has been investigated with use of the materials and general procedure of a commercial kit for the determination of theophylline in human serum. The antibody is immobilized on glass beads, and the enzyme label is alkaline phospha-tase (EC 3.1.3.1). The high currents generated during the electrochemical detection allowed a rapid (35 mm) and simple determination of theophylline throughout its therapeu-tic range (10-20 mg/L) and also in the subtherapeutic range (detection limit of about 80 Lg/L). AdditIonalKeyphrases:alkaline phosphatase. electrochernical immunoassay. p-aminophenyl phosphate Enzymes, when used as labels in iinmunoassay methods, allow the development of diverse assay protocols, wit