Determination of 19 Pesticides Residues in Strawberries by High Performance Liquid Chromatography-Tandem Mass Spectrometry

KeyWord:ultra high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)  solid-phase extraction(SPE)  pesticides  residue  strawberryÉèÊ©²ÝÝ®(Fragaria ananassa Duchesne)

Abstract:

      A solid phase exaction coupled with ultra high performance liquid chromatography-tandem mass spectrometric(UPLC-MS/MS) method was developed for the simultaneous determination of 19 pesticides in strawberry.After extraction with acetonitrile,purification with NH2 SPE cartridges and dissolution with methanol,the analytes were analyzed by UPLC-MS/MS on an Agilent Proshell120 EC-C18 column with a mixture of 0.1% formic acid-acetonitrile as mobile phase by gradient elution.The mass spectrometer was operated in multiple reactions monitoring(MRM) mode in positive mode.The purifying effects of 6 pretreatment methods were optimized by UPLC-Q-TOF.Matrix effects of real strawberries were studied.The limits of quantitation(LOQs),which were determined by adding standard solution to pesticide free strawberry samples,were 0.001 mg/kg for mandipropamid,bifenazate,picoxystrobin and pyraclostrobin and 0.01 mg/kg for the others.Good linearities were obtained for 19 pesticides in the concentration range of 0.000 5-1.0 mg/L with correlation coefficients more than 0.999.The fortified recoveries at low,intermediate and high concentration levels were in the range of 77.3%-100.3%,with relative standard deviations(RSDs) not more than 12.3%.False positive results were avoided effectively due to the method¬ðs good ablity of resistence matrix interference.All the above observations indicated that the established method was simple,efficient and sensitive,and was suitable for the determination of 19 pesticides in strawberry.