Residue dynamics of spirotetramat and its metabolites & chlorantraniliprole in longan (Dimocarpus longan Lour.)

A sensitive method for determination of spirotetramat and its metabolites and chlorantraniliprole in longan (Dimocarpus longan Lour.) were developed based on high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) technique. The terminal residues of spirotetramat and chlorantraniliprole in longan under field conditions were studied in 6 experimental sites in 2018. The samples were extracted with acetonitrile, cleaned up with PSA, detected by HPLC-MS/MS, and quantified by external standard method. The mean recoveries of spirotetramat and its four metabolites and chlorantraniliprole in longan whole fruit and longan pulp were 83%-103%, and 87%-92%, respectively, at the three spiking levels from 0.01 to 1 mg/kg with relative standard deviations (RSDs) of 2.3%-8.7%, and 3.3%-6.3%. The limits of quantitation (LOQs) of spirotetramat and its four metabolites and chlorantraniliprole was 0.01 mg/kg. In the field trials, 22.4% spirotetramat SC and 5% chlorantraniliprole SC were applied at the dosage of 60 and 50 mg/kg for two times with the interval 7-10 d, respectively. The results showed that terminal residues of spirotetramat and chlorantraniliprole in longan whole fruit were 0.30-1.14 and 0.06-0.29 mg/kg, respectively, at 14 d after application, and were <0.05 and < 0.01 mg/kg, respectively in longan pulp. This study would be helpful to guide scientific and efficient utilization of these pesticides. Because of the absence of maximum residue limits (MRLs) value of spirotetramat and chlorantraniliprole in longan, these results could provide data to facilitate the setting of longan MRL.