Simultaneous Determination of Ractopamine and Clenbuterol Residues in Animal Urine with Gas Chromatography-Mass Spectrometry

A new solid phase extractiongas chromatographymass spectrometry （SPE-GC/MS） method for simultaneous determination of ractopamine and clenbuterol in animal urine was reported. The drugs were extracted with ethyl acetate from sample. The extraction was evaporated at 40 ℃. After the residue was dissolved in ethyl acetate, it was purified by passing through SLH solid-phase extraction （SPE） cartridges. The eluate was evaporated by nitrogen blow and derivatizated with BSTFA, and then assayed by GC/MS. The limits of detection (LOD) were 0.3 μg/L, and the limits of quantitation (LOQ) were 1.0 μg/L. The calibration curves were linear between 0.02 μg/mL and 1.0 μg／mL for ractopamine and clenbuterol. Recoveries of ractopamine and clenbuterol were 78.6％-101.2％and 92.3％-112.2％, and the intrarelative standard deviation (n=5) less than 7.0% and 6.9%, respectively, at spiked levels of 4.0～20 μg/L.