Study of Indoxacarb Residue Degradation in Tea and Tea Infusion by Ultra High Performance Liquid Chromatography Coupled with Tandem Mass Spectrometry after Dispersive Solid Phase Extraction Cleanup
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KeyWord:indoxacarb  tea  tea infusion  (dispersive) solid phase extraction  ultra high performance liquid chromatography coupled with tandem mass spectrometry(UPLC-MS/MS)  residue and degradation
张新忠,罗逢健,陈宗懋,刘光明,楼正云 1.中国农业科学院茶叶研究所农产品质量安全研究中心;2.农业部茶及饮料植物产品加工与质量控制重点开放实验室;3.农业部茶叶产品质量安全风险评估实验室
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      A convenient and sensitive method for the residue analysis of indoxacarb in tea and tea infusion was developed and validated by using ultra high performance liquid chromatography coupled with tandem mass spectrometry followed by(dispersive) solid phase extraction cleanup.The calibration curve was linear over the concentration range of 0.01-20.0 mg/L for indoxacarb,with a correlation coefficient(r) of 0.993 7,and the limit of detection(LOD) of 0.025 ng.The average recoveries of indoxacarb at three spiked concentration levels in different sample matrixes(made tea,tea infusion and fresh tea leave) ranged from 96% to 107% with relative standard deviations(RSDs,n=6) of 1.3%-7.8%.The limits of quantitation(LOQs) of indoxacarb were 5 μg/kg in tea and 0.10 μg/L in tea infusion,respectively.The proposed method was successfully applied in the degradation and final residue study of 150 g/L indoxacarb emulsifiable concentrates(EC) in the field treatment experiment,and the dissolution dynamic of indoxacarb from made tea to tea infusion was investigated for the risk assessment.The degradation half-life time of indoxacarb in fresh tea leaves was from 1.42 days to 2.47 days.And the total leaching rate of indoxacarb for the brewing processes from made tea to tea infusion for three times was lower than 10%.For the risk assessment,the MRL proposed at 3.0 mg/kg was safety for tea drinking with the pre-harvest intervals(PHI) of ten days.The estimated intake of indoxacarb was shown to be 0.619% of acceptable daily intake(ADI).