Comparison between a bioassay and liquid chromatography-fluorescence-mass spectrometry(n) for the determination of incurred enrofloxacin in whole eggs.

The objective of this study was to compare a bioassay with a liquid chromatography-fluorescence-mass spectrometry(n) method for detection of enrofloxacin (ENRO) in incurred eggs. The bioassay developed by our laboratories involves an agar diffusion microbiological method using Klebsiella pneumoniae as an indicator organism. Results demonstrate that both methods are capable of detecting incurred fluoroquinolone residues in eggs. During the 3-day dosing period of hens (Days 1-3) and following drug withdrawal (Days 5, 7, and 9), both of these methods were able to detect incurred ENRO in eggs above the zero tolerance established by the U.S. Food and Drug Administration. The LC-fluorescence-MS(n) method has the benefit of providing confirmation for fluoroquinolones, while the bioassay may be used as an effective, rapid screening method for detection of fluoroquinolone residues in eggs.