Simultaneous and sequential enzyme immunoassays on gold bands with flow electrochemical detection

The feasibility of carrying out enzyme (AP) immumoassays on thin gold bands is demonstrated here for the determination of an analyte (IgG) model, following two different formats: simultaneous and sequential. The detection, that also employs a gold band as the working electrode of the potentionstatic system, is amperometrically performed in a flow system. After the reaction between IgG and IgG-AP for binding anti-IgG places, the enzymatic hydrolysis of naphthylphosphate occurs. The naphtol generated in the immunoreactor is conducted to the detector where it is oxidised to naphtoquinone providing highly reproducible analytical signals. Comparison of both formats of immunoassays was made in terms of analysis time and sensitivity. Since the gold bands where the immunoreactions took place have to be inserted in the,flow system for the detection, a novel single flow cell that enabled their rapid insertion was specially designed. (C) 2002 Elsevier Science B.V. All rights reserved.