Residual Analysis Of Pymetrozine And Its Metabolites On Chinese Kale And Its Safety Evaluation During The Processing Of Chinese Kale

A simple analytical method was developed using liquid chromatography with tandem mass spectrometry for determination of pymetrozine and its metabolites including CGA128632,GS23199 and CGA266591 in Chinese Kale.Plant was extracted with methanol,purified by combination of octadecylsilane(C₁₈)and formic acid,and detected by LC-MS/MS.The recoveries concentration range of pymetrozine,CGA128632,GS23199 and CGA266591 in Chinese Kale were 0.8-200,6-600,80-8000 and 40-4000?g/kg,respectively.The method had good linearity?R²>0.99?,accuracy?recoveries of 73.2%–94.1%?and precision?relative standard deviation of2.5%–9.8%?.The LODs of pymetrozine,CGA128632,GS23199 and CGA266591 in Chinese Kale were 0.14,0.35,20.31 and 8.52?g/kg,respectively,and LOQs were 0.46,1.17,67.7 and 28.4?g/kg.The accuracy,sensitivity and precision of this method were consistent with the acceptable range.The field experiments of pymetrozine?50%WG?in Chinese Kale were performed at six different locations?Guangxi,Heilongjiang,Anhui,Hunan,Zhejiang and Beijing?during the agricultural season in 2017.Field results showed that half-lives of pymetrozine were 3.0–4.1 d in Chinese Kale,and terminal residue concentrations were all below the United States Environmental Protection Agency's maximum residue limit?250?g/kg?at harvest.In terms of risk assessment,residues of pymetrozine and its metabolites were involved,therefore,combining with the dietary exposure risk of individual body,the RQ_a and RQ_c of pymetrozine were calculated.The results showed that the RQ_a and RQ_c were both far below 100%,indicated that pymetrozine is unlikely to express vital health concerns to human following the recommended application guidelines.Moreover,effects of typical home processing on pymetrozine residues in Chinese kale were monitored.The processing factor values of four processes were between 0.19and 0.60,which indicated that the used processes could remove pymetrozine residues from Chinese kale in various degrees,especially pickling after washing process.The data could provide guidance to safe and reasonable use of pymetrozine and help Chinese governments establish maximum residue limit for pymetrozine in Chinese kale.Moreover,study of home processing could provide data for effective removal method of pymetrozine in other vegetables.