Determinationof15pesticidesresiduesinricebyultraperformanceliquidchromatography-tandemmassspectrometry

A method was established for the residue detection of 15 pesticides in rice by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The influences of the matrix effects, the types of extraction solvent, extraction methods and different purification methods were all investigated. After homogenized mixing, samples were extracted by V (acetonitrile): V (acetone): V (water) = 16 : 2 : 2 and cleaned up by disperse solid phase extraction. The samples were then detected by MS/MS with positive electrospray ionization (ESI⁺) in multiple reaction monitoring (MRM) mode and quantified by external standard method. The results showed that the correlation coefficient (r) of 15 pesticides including emamectin benzoate were higher than 0.99 in the concentration ranged from 0.005 mg/L to 1 mg/L. The mean spiked recoveries of 15 pesticides at 0.01, 0.1, 1 and 4 mg/kg spiked levels ranged from 82% to 116% with the relative standard deviations (RSD, n = 5) between 1.2% and 12%. The limits of detection were 0.000 5-0.005 mg/kg, and the limits of quantitation for the method were 0.01 mg/kg. Twenty batches of rice from the outskirts of Shanghai municipality were determined by the established method. Excessive pesticide residues were not detected in all the rice samples. This new method is practical, fast and accurate, which meets the requirements for the determination of 15 pesticides including emamectin benzoate in rice at the same time.