Abstract: A method for simultaneous determination of gibberellin and β-cypermethrin residues in vegetables and fruits by liquid chromatography tandem mass spectrometry was established. The samples were extracted by acetonitrile shake and separated by salting out principle, and the clarified acetonitrile layer was dissolved in 50% methanol 1∶1（V/V）, and the acetonitrile was separated by acetonitrile and 5 mmol/L ammonium acetate solution. The data were collected by electrospray ionization mode （ESI⁺, ESI^-） Multi-reaction monitoring （MRM）, and the external standard method was used to quantify the ionic ratio. The results showed that the average recoveries of the two pesticides at three levels （0.040, 0.100 and 0.400 mg/kg） ranged from 80.0% to 112.1%, and the relative standard deviation （RSD） was less than 15%. The standard curves of gibberellin and β-cypermethrin standard solutions were obtained by LC-MS/MS. The linear relationship was good in the range of mass concentration 0.010~0.400 mg/L, and the correlation coefficient R² was greater than 0.999. The limits of detection （LODs） were 0.001 mg/kg and the limits of quantification （LQDs） were 0.004 mg/kg, which met the requirements of conventional detection methods. The method is convenient for pre-processing and is suitable for screening large quantities of samples. It has good sensitivity, accuracy and precision. It is a low-consumable, efficient and reliable qualitative and quantitative detection method for improving the quality and safety of vegetables and fruits.

Key words: LC-MS/MS, vegetables and fruits, gibberellin, β-cypermethrin, detection method