Three for the price of one! Immunodetection of three amphenicols in foodstuffs using a universal standard curve
Antibiotics from the amphenicol family are widely used to treat farm animals; however, the regulation of their residues in livestock production varies significantly and depends on the type of animal and the type of particular amphenicol. In this regard, different requirements are imposed on immunoanalytical systems for their identification. In the present study, direct and indirect ELISA formats were developed for simultaneous determination of florfenicol (FF), its main metabolite florfenicol amine (FFA), and thiamphenicol (TAP) using antibodies against FFA conjugated to succinylated BSA. Among a panel of heterologous conjugates, a glutaraldehyde linked FFA-coating antigen and tracer were the only ones which provided equal recognition of FFA, FF, and TAP. Owing to equal 100% cross-reactivity, these analytes could be quantified in chicken muscle at their MRL level using a single universal standard curve. Recovery of amphenicols was in the range 77.2–98.8% with variation no more than 9.6%. The prohibited drug chloramphenicol was undetectable (<0.1%) and had no influence on the assay developed for quantification of approved amphenicols.