Homogeneous electrochemical immunoassay using a perfluorosulfonated ionomer-modified electrode as detector for a cationic-labeled hapten

A Nafion film-modified electrode has been used as an electroanalytical sensor to detect a drug containing a cationic redox label by square wave voltammetry. A tracer, composed of the model drug amphetamine covalently attached to a cobaltocenium redox label, was synthesized and used in a competitive immunoassay technique. In this assay, only the positively charged tracer not vound to the antibody preconcentrated in the anionic film. Consequently, it was not necessary to separate free from antibody-bound labeled amphetamine, thereby allowing the assay to be carried out in homogeneous media at the electrode surface