To establish a method for determination of cyhalofop-butyl and its main metabolite cyhalofop acid residues in a variety of plant-derived foods by QuEChERS-liquid chromatography-tandem mass spectrometry.

The acetonitrile contain 1% formic acid was used as the extraction solution, and the QuEChERS dispersion solid phase extraction method was used for purification. Electrospray ion source was used for mass spectrometry. Data were collected simultaneously under multiple reaction monitoring mode with positive and negative ion switching.

Under optimized conditions, the limit of quantitation of cyhalofop acid could reach 0.01 mg/kg, while that of cyhalofop-butyl could reach 0.02 mg/kg. The linear relationship between the 2 kinds of target substances and their mass concentrations ranges from 0.05 to 2.00 mg/L, with correlation coefficients (r²) all greater than 0.99. In 3 kinds of spiked levels of 10 kinds of plant-derived matrices including brown rice, wheat, soybeans, peanuts, apples, peaches, tomatoes, cucumbers, spinach and tea, the average recovery rate ranged from 68.7% to 106.7%, with relative standard deviations ranging from 0.6% to 14.3%.

This method features simple sample pretreatment. Its accuracy and precision meet the requirements for residue analysis. It can effectively eliminate interferences from complex matrices, satisfy the simultaneous confirmation and quantification of cyhalofop-butyl and its metabolite cyhalofop acid in plant-derived foods, and is suitable for routine monitoring and risk assessment of cyhalofop-butyl and its metabolite in large batches of plant-derived foods.