HPLC residues of enrofloxacin and ciprofloxacin in eggs of laying hens.

Eggs of 12 laying hens with 5 mg/kg/day oral administration of 5% enrofloxacin (EFX) or ciprofloxacin (CFX) solution during 5 days contained residues from 0.02 to 1.98 microg/g (EFX) or 0.14 to 0.28 microg/g (CFX). At identical dosage regime High Performance Liquid Chromatograhy (HPLC) residues of EFX were 6-fold greater than CFX ones. Maximun concentrations were detected at the second day after the administration withdrawal. The limits of detection were 0.019 microg/g for EFX and 0.156 microg/g for CFX. The recovery was 36-50% for CFX and 49-85% for EFX. The withdrawal treatment periods in hens are six days for EFX and five days for CFX in order to avoid violative levels of egg residues.