Simultaneous Determination of 13 Fluoroquinolone and 22 Sulfonamide Residues in Milk by a Dual-Colorimetric Enzyme-Linked Immunosorbent Assay

Enzyme-linked immunosorbent assays (ELISAs) usually focus on the detection of a single analyte or a single group of analytes, e.g., fluoroquinolones or sulfonamides. However, it is often necessary to simultaneously monitor two classes of antimicrobial residues in different food matrixes. In this paper, we describe a dual-colorimetric ELISA for the simultaneous detection of 13 fluoroquinolone and 22 sulfonamide residues. The limit of detection for fluoroquinolones and sulfonamides was 2.4 and 5.8 ng/mL, respectively. The developed immunoassay is suitable for high-throughput screening of these low-molecular weight contaminants. This is the first report where two different enzymes (alkaline phosphatase and horseradish peroxidase) were used in one immunoassay and together in a single well for simultaneous detection of multiple low-molecular weight chemical residues.