An analytical method was established for the determination of thiacloprid

spirotetramat and its four metabolites residues in litchi and longan by high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS) with QuEChERS cleanup.The residues in samples were extracted with acetonitrile

dehydrated with anhydrous magnesium sulfate and sodium chloride

then purified with C18 and GCB.The extract was separated on a Poroshell-120 EC-C18 column with 0.1% formic acid-acetonitrile as mobile phase by isocratic elution

detected by HPLC-MS/MS with positive electrospray ion source in multi reaction monitoring(MRM) mode

and quantified by external standard method.Results showed that there existed good linearities for six analytes in the range of 1-500 μg/L with their correlation coefficients(r2) more than 0.990.The limits of detection(LODs) and limits of quantitation(LOQs) were 0.03-0.3 μg/kg and 0.1-1.5 μg/kg

respectively.The average recoveries for the analytes at spiked levels of 1

10

100 μg/kg were in the range of 80.4%-99.5% with relative standard deviations of 1.4%-6.4%.The developed method was simple

sensitive

accurate and reliable

and could meet the requirements for rapid screening and monitoring of thiacloprid，spirotetramat and its metabolites in fruits such as litchi and longan.