Abstract: Abstract：The residues depletion of Enrofloxacin(ENR) and Ciprofloxacin(CIP) in the pig tissues was studied by using HPLC method. Enrofloxacin microcapsules was mixed-fed on consecutive seven days. After the last fed，five pigs were slaughtered and collected tissue samples. Tissue samples were extracted by phosphate buffer solution, purified through C18SPE. Then the extract was dissolved with a mobile phase: 0.05 mol/L phosphoric acid/triethylamine-acetonitrile (82 +18).Finally, the samples were detected by HPLC after filtration. Results showed that, when the sample concentrations were 0.02 μg/g to 1 μg/g， the linear relationship was good. The detection limit was 20 μg/kg.The recovery was between 72% to 90%，and the coefficient of variation was under 10%.The depletion of enrofloxacin in muscle and fat was fast, and the sum of concentration of ENR and CIP was declined, lower than LOD on the 5th day. However, compared with fat and muscle, the depletion of drugs in liver and kidney were slower. The sum of concentration of these in kidney was 91.48 μg/kg at the 7th day. Integrated total residues in tissues, we can identify Enrofloxacin microcapsules withdrawal time is 7 days.

Key words: Key words：Enrofloxacin microcapsules; pig; residues