Abstract: A rapid method was developed for the simultaneous determination of flupyradifurone and its metabolites 6-chloronicotinic acid and difluoroacetic acid in milk using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). A simple and efficient dispersive solid phase extraction method was used to purify milk samples, and the purification strategy was evaluated. After improved quick, easy, cheap, effective, rugged and safe (QuEChERS) treatment, 0.1% formic acid in acetonitrile was used as the mobile phase for chromatographic separation on a Shim-pack-GIST C18 column, and the detection was performed in the multiple reaction monitoring (MRM) mode. The external standard method with matrix standard curves was used for quantification. The results showed that under the optimal conditions, good linearity (determination coefficient greater than 0.996) was observed for flurofuranone, 6-chloronicotinic acid and difluoroacetic acid in the concentration ranges of 0.005–0.5, 0.005–0.5 and 0.025–2.5 mg/L, respectively. The average recoveries of flupyradifurone and its metabolites at three spiked concentrations varied from 70.2% to 97.6%, with relative standard deviations (RSDs) between 3.6% and 5.3%, and the limits of detection (LODs) ranged from 0.01 to 0.05 mg/kg, much lower than the national maximum residue limits. This method was characterized by high accuracy, high sensitivity, and good reproducibility. Therefore, it is suitable for large batches of milk samples, and can provide reliable technical support for the management of the pesticide flupyradifurone.

Key words: ultra-high performance liquid chromatography-tandem mass spectrometry; quick, easy, cheap, effective, rugged and safe; flupyradifurone; metabolites; milk