Study On The Chromatography And Mass Spectrum Method Of Three Types Of Pesticide Residues In Tea

Tea is one of the most important economical crops in China,and it is also a critical component of export trade because its rich organic nutrients and inorganic minerals.With the increasing living standards and the spread of health concepts,the issues of the quality and safety in tea have been concerned widely.Our country has enacted strict limit standards for pesticide residues,in the case of the increasingly fierce competition in international trade and the increasing serious food safety issues.So it is significant to explore a multi-residues and high sensitivity detection method for improving quality and increasing export in tea.As methods of detecting multi-class pesticide residues,the solid phase extraction and QuEChERS(Quick,Easy,Cheap,Effective,Rugged and Safe)have easy,rapid and efficient merits.The main job in this research is to improve the pretreatment conditions and the critical factors of dispersive solid phase extraction and QuChERS methods.The methods has been applied to detect pyrethroid?nicotion and carbamate pesticide residues in tea coupling with gas chromatography-mass spectrometry with negative chemical ionization(GC-NCI-MS)and high performance liquid chromatography tandem mass spectrometry(HPLC-MS/MS).The main contents and results are as follows:1.The GC-MS methods were developed to detect 10 pyrethroid pesticides in tea by using the dispersive solid phase extraction method(dSPE).The experimental paremeters of the dSPE were optimized,such as the extraction solvent?the ratio of eluent and the volume of eluent.At the same time,the optimum conditions of gas chromatography and mass spectrometry were determined.In addition,the use of matrix matching standard curve method can reduce matrix effect in tea.The average recoveries of the method were 83.5-118.3%,with the intra-day and inter-day precision less than 11.1%.The limit of quantification(LOQ)for cyhalothrin?fenpropathrin were 0.01 mg/kg;the others were 0.05 mg/kg,respectively.The developed method were applied to analysis 9 samples and the bifenthrin was confirmed positive.2.The QuChERS method by using multi-walled carbon nanotubes as sorbent material was modified for the detection of 5 nicotion pesticides in tea coupling with HPLC-MS/MS.In the experiment,the extraction method was optimized.The effect on matrix effect in tea was explored by MWCNTs according to the special adsorption properties.The amount of MWCNTs were optimized as well.Compare to the original sorbent,MWCNTs have better ability of adsorption,which can adsorb the pigments?tea polyphenol?theophyline and other interference impurities in tea.As a result,the effect of purification was obvious and it significantly reduced matrix effect.The average recoveries of the method were 72-110%,with the intra-day and inter day less than 13%.The LOQ for five nicotion pesticides were 0.01 mg/kg.The proposed method was applied to analysis 10 samples,and the positive samples were detected.3.The QuChERS method by using a new nano-material-graphene as sorbent material was modified for the quantification of 15 carbamate pesticide residues in tea coupling with HPLC-MS/MS.The matrix effect was explored and the amount of graphene was optimized.It showed the advantages of reducing the total extraction of impurities and reducing the matrix effect.The average recoveries of the method were 61-106%,with the intra-day and inter day less than 15%.The LOQ for fifteen carbamate pesticides were 0.01 mg/kg.The developed QuEChERS-HPLC-MS/MS method was applied to analysis 8 samples,and the positive samples were detected.