Abstract: An analytical method using QuEChERS (quick, easy, cheap, effective, rugged and safe) pretreatment combined with high performance liquid chromatography-quadrupole-time of flight mass spectrometry (HPLC-Q-TOF-MS) was developed for the rapid non-targeted screening of unknown pesticide residues in litchi flower, hive and honey. The samples were extracted with acetonitrile-water, cleaned up with a mixture of anhydrous magnesium sulfate, N-propyl ethylene diamine (PSA) and octadecyl (C18) sorbent, separated on an Xbridge BEH C18 column by gradient elution using a mobile phase consisting of formic acid in water and acetonitrile, and detected using both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) under the positive and negative ion modes. Screening for unknown compounds suspected of being pesticides were carried out through database matching with the exact mass, isotopic distribution, secondary fragmentation information and retention time of the characteristic ions of the target compounds, and in the targeted MS/MS mode, the selected compounds were confirmed based on the ion fragment information at each collision energy. The analytes were quantified by using matrix-matched standard solutions. The results showed that eight pesticides (including azoxystrobin, pyraclostrobin and its metabolite BF 500-3, difenoconazole, carbendazim, chlorpyrifos, diflubenzuron and chlorbenzuron) were screened out. The calibration curves for these analyes had good linearity in the range of 1–1 000 μg/L with correlation coefficients (r2) above 0.99. The limits of detection were 0.03–0.50 μg/kg and the limits of quantification were 0.4–0.8 μg/kg. The average spiked recoveries of the pesticides in litchi flower, hive and honey samples were 80%–96% with relative standard deviations (RSDs) of 1.2%–6.1%. The developed method is quick, easy, sensitive and suitable for the rapid screening and identification of pesticide residues in litchi flower, hive and honey.

Key words: litchi flower, hive and honey; high performance liquid chromatography-quadrupole-time of flight mass spectrometry; screening; pesticide