Abstract: In this study, a simple and practical QuEChERS-liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was established to detect the residues of imidacloprid and fenpyroximate in the roots, stems, leaves of celery. The samples were extracted and purified by QuEChERS method, and analyzed by LC-MS/MS. Results showed that the average recoveries of imidacloprid in roots, stems, leaves of celery were 77.15%-103.48% at three spiking levels from 0.05 mg·kg^-1 to 1.00 mg·kg^-1 with relative standard deviations (RSDs) of 1.40%-9.97%. The average recoveries of fenpyroximate in roots, stems, leaves of celery were 77.35%-100.42% at three spiking levels from 0.05 mg·kg^-1 to 1.00 mg·kg^-1 with relative standard deviations (RSDs) of 2.01%-6.95%. Limit of detections (LODs) were estimated to be 0.120 μg·kg^-1 for imidacloprid, and 0.015 μg·kg^-1 for fenpyroximate, respectively. Limit of quantitations (LOQs) for imidacloprid in the roots, stems, leaves of celery were 1.65, 0.87 and 1.08 μg·kg^-1, respectively. LOQs for fenpyroximate were 1.24 μg·kg^-1 (roots), 0.75 μg·kg^-1 (stems) and 0.78 μg·kg^-1 (leaves). The celery samples were detected using this established method, the recovery and the precision were in accordance with the requirements of pesticide residue analysis. The method was suitable for the detection of a large number of samples in the laboratory.

Key words: celery, imidacloprid, fenpyroximate, QuEChERS, liquid chromatography-tandem mass spectrometry