Development of a Direct Competitive Enzyme-Linked Immunosorbent Assay for the Detection of Fluoroquinolone Residues in Shrimp

Rabbit polyclonal antibodies were generated against norfloxacin, purified, and used as the basis of a direct competitive enzyme-linked immunosorbent assay for the screening of fluoroquinolones in shrimp. The developed method used a simple ethanol/acetic acid solvent extraction, which resulted in a 1.0-ng-norfloxacin/g limit of detection (based on the analysis of known negative and fortified shrimp samples). Norfloxacin extraction efficiencies were evaluated at two fortification concentrations and were greater than 70%, with an intra-assay variation less than 30%. The assay displayed greater than 10% cross reactivity against enro-, cipro-, sara-, and difloxacin. Incurred and known negative shrimp samples were analyzed and compared to the results obtained from an independent liquid chromatography tandem mass spectrometric method. All three instances in which fluoroquinolones were present at concentrations near or above the assay limit of detection (1.0 to 17 ng/g) were identified as positive by the newly developed assay, demonstrating the usefulness of this assay as a screening tool.