Detection and Quantification of Sulfonamide Antibiotic Residues in Milk Using Scanning Electrochemical Microscopy

The use of scanning electrochemical microscopy (SECM) for the qualitative and quantitative determination of sulfapyridine (SPY) in milk is described. A direct competitive immunoassay was performed involving an antibiotic horseradish peroxidase (HRP)-labeled analog and using selective capture antibodies immobilized on the surface of Protein G-modified glassy carbon plates. SECM detection was accomplished by means of the sample generator/tip collector (GC) mode involving the reduction of benzoquinone (BQ) generated upon the HRP-catalyzed oxidation of hydroquinone (HQ) at the modified substrate surface in the presence of H2O2. The detection limit for SPY in milk samples was as low as 0.13ngmL(-1).