Pass Through Purification-UPLC-MS/MS For The Determination Of Phenylurea,Benzoylurea And Sulfonylurea Pesticide Residues In Plant Food

Phenylurea plant growth regulators,benzoylurea insecticides and sulfonylurea herbicides are commonly used pesticides.Advanced countries have set strict maximum residue limits for three species pesticide.The limit of quantitation for existing national standards of benzoylurea insecticides is higher than the maximum residue limits.There are only the national standards of sulfonylurea herbicides for soil and soybean matrix,and no detection standards for vegetables and vegetable oils.There are none national standards for forchlorfenuron.Pass-through purification process has the advantage of simple and rapid.This dissertation focuses on pass through purification technology combined with ultra performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS).A novel method of Sin-QuEChERS pretreatment method was proposed for determination of 15 pesticides in vegetables including plant growth regulator,benzoylurea and sulfonylurea by UPLC-MS/MS.Samples were extracted with acetonitrile,purified on a Sin-QuEChERS column.The pass through volume was optimized.The linear correlation coefficient(R~2)of 15 pesticides ranged from 0.996 6to 0.999 9.At spiked concentrations of 5,10,100?g/kg,the recoveries of plant growth regulator,benzoylurea and sulfonylurea pesticides were 72.6%~91.5%,71.9%~106.1%and 78.2%~105.2%,respectively,and the relative standard deviations(RSDs)were0.3%~6.0%,0.8%~8.4%,0.4%~6.5%,the method detection limit(S/N=3)was 0.3~1.5?g/kg,the limit of quantification(S/N=10)was 1.0~5.0?g/kg.The effects of three kinds of purification methods on the extraction effects of 15 pesticides were investigated.With SPSS 19.0 statistical analysis,the best pretreatment method was determined.It revealed that this method has the advantages of quick and simple pretreatment method,high recovery,and can be used multi-residue trace detection of pesticides in vegetables.A novel method of pass through efficient purification method was proposed for determination of 15 pesticides residues in vegetable oils coupled with UPLC-MS/MS.The samples were extracted with n-hexane saturated with acetonitrile and acetonitrile saturated with n-hexane,and purified with PRiME HLB solid phase extraction column.The extraction solvent and volume,purification method,eluent ratio were optimized.The linear correlation coefficient(R~2)of 15 pesticides ranged from 0.992 to 0.999.At the spiked concentrations of 5,10,50?g/kg,the recoveries of the three kinds of pesticides were 68.4%~77.7%,65.1%~95.8%and 73.9%~102.2%,respectively,and the relative standard deviations(RSDs)were 1.1%~6.2%,1.1%~9.3%,0.8%~14.2%.The limit of detection(S/N=3)was 0.3~1.5?g/kg,the limit of quantitation(S/N=10)was1.0~5.0?g/kg.A preliminary investigation of possible mass spectrometry fragmentation pathways for 15 pesticides under electrospray ionization(ESI)was performed.Finally,the sulfonylurea fragmentation patterns as follows:(1)The C-N bond between amides tends to break during fragmentation,(2)The N-S bond between sulfonyl groups is easily broken in fragmentation,(3)Retro-diels-Alder(RDA)ring-cracking fragmentation is prone to occur in MS~3.The fragmentation patterns of benzoylurea and phenylurea as follows:(1)it is easy to remove HF,HCl neutral molecules and form the corresponding cyclic compounds,(2)The C-N bond between amides tends to break during fragmentation.