Abstract: Objective: To establish a method for the simultaneous determination of avermectin and ivermectin residues in pork liver using high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). Methods: Avermectin and ivermectin residues were extracted with acetonitrile, cleaned up on a solid phase extraction (SPE) column containing alkaline aluminum oxide, separated on a C8 column, detected by tandem mass spectrometry with electrospray ionization and multiple reaction monitoring interface and quantitatively determined by high performance liquid chromatography in an external standard manner. Results: The limits of detection (LOD) for avermectin and ivermectin were 2μg/kg and limits of quantitation were 5μg/L. Both the linear ranges of avermectin and ivermectin were 5－100μg/L with correlation coefficients of both 0.9999. The recovery rate range of this method was 77.0%－83.3% for avermectin and 76.9%－79.8% for ivermectin with relative standard deviations (RSD) of 8.6%－12.1% and 9.9%－13.0% at spike levels of 2, 10μg/kg and 20μg/kg, respectively. Conclusion: This method is simple, sensitive and accurate, which can meet the domestic and international requirements for the detection of both veterinary drugs.

Key words: pork liver, avermectin, ivermectin, high performance liquid chromatography-tandem mass spectrometry