Validation of an ultra-performance liquid chromatography-tandem mass spectrometry method for determination of ractopamine: Application to residue depletion study in swine

► Rapid UPLC-MS/MS analysis of ractopamine was performed in 4min. ► The highest residual concentration of ractopamine was found in lung tissue. ► The estimated withdrawal time was 5days. A sensitive and reliable method was developed and validated for the analysis of ractopamine in swine tissues. The sample preparation procedure was based on hydrolysis overnight, extraction with ethyl acetate, and solid-phase extraction cleanup. The target compound was determined by ultra-performance liquid chromatography coupled with tandem mass spectrometry. The average recoveries ranged between 93.3% and 106.5%, with relative standard deviations of 7.2–12.8%. The detection and quantification limits were 0.2 and 0.5μg/kg, respectively. The depletion profile of ractopamine was studied in healthy pigs after oral administration of feed containing 20mg/kg ractopamine for 30 consecutive days. Ractopamine residues were still detected 11days post-medication in all tissues examined with the exception of muscle. The highest ractopamine level was found in lung tissue. The developed method has been successfully applied to the depletion study of ractopamine in swine tissues.