Disposable and integrated amperometric immunosensor for direct determination of sulfonamide antibiotics in milk

The preparation and performance of a disposable amperometric immunosensor, based on the use of a selective capture antibody and screen-printed carbon electrodes (SPCEs), for the specific detection and quantification of sulfonamide residues in milk is reported. The antibody was covalently immobilized onto a 4-aminobenzoic acid (4-ABA) film grafted on the disposable electrode, and a direct competitive immunoassay using a tracer with horseradish peroxidase (HRP) for the enzymatic labeling was performed. The amperometric response measured at −0.2 V vs the silver pseudo-reference electrode of the SPCE upon the addition of H2O2 in the presence of hydroquinone (HQ) as mediator was used as transduction signal. The developed methodology showed very low limits of detection (in the low ppb level) for 6 sulfonamide antibiotics tested in untreated milk samples, and a good selectivity against other families of antibiotics residues frequently detected in milk and dairy products. These features, together with the short analysis time (30 min), the simplicity, and easy automation and miniaturization of the required instrumentation make the developed methodology a promising alternative in the development of devices for on-site analysis.

► First integrated amperometric immunosensor for detection of sulfonamide residues.
► Immunosensor with great sensitivity and specificity for sulfonamides detection.
► Detection in milk samples after just simple dilution treatment.
► LODs achieved two orders of magnitude lower than the MRLs established.
► Useful and affordable alternative to classical assays for sulfonamides detection.