| Pesticide residue in tea arouses continuous focus of the whole world in recent years.Many countries and international organizations have set the maximum residue limits(MRLs)for pesticide residues in tea.With more and more attentions paid to the food security,tea pesticide detection projects continue to increase and the limits are increasingly stringent;new requirement and challenges are put forward to the pesticide multi-residue detection technology of our country.In order to ensure quality safety of tea,the establishment of a perfect system which can effective monitor and control the pesticide residues in tea is an important issue.At present,the detection methods of multi-residues in tea are generally based on chromatography and low resolution mass spectrometry.It is a pity that the method is a waste of time and money due to the preparing of standard materials,as well as the workload of data analysis.Therefore,it is an urgent need to develop a fast,high-throughput,sensitive pesticide residue rapid screening and detection technology.For multi-residues pesticide analysis,the pretreatment technology and detection methods are the research hotspots and difficulties.As a high resolution mass spectrometry,Ultra Performance Liquid Chromatography coupled with Quadrupole-Time Of Flight Mass Spectrometry(UPLC-Q-TOF-MS)technology has the characteristics of wide mass range,high mass accuracy and fast analysis speed,which can provide a powerful tool for the quantification and confirmation of multi-residues detection.Meanwhile,solid phase extraction method has been widely utilized in tea research,which has the characteristics of simple operation,good purification effect and high repeatability.Therefore,this study focuses on the technology and method,by means of combining SPE with UPLC-Q-TOF-MS,the rapid determination method of 204 pesticide residues for tea are established.This method can provide technical support for routine monitoring of pesticide residues in tea.The main research contents and results are summarized as follows:1.An analytical method was established for the simultaneous determination of 204 pesticide residues in tea by UPLC-Q-TOF/MS.The samples were extracted with acetonitrile,and cleaned up by solid phase extraction(SPE)with a Carb-PSA cartridge,eluted with acetonitrile-toluene(3:1,v/v),determined by UPLC-Q-TOF/MS and quantified by the external standard method.A data base of the accurate mass number and library which contains 204 pesticides are established according to the testing results.Theautomatic retrieval of detection results was carried on according to the characteristics of the compound,such as accurate mass,retention time,isotopic ratio,and so on.Based on the above results,the qualitative identifications of 204 pesticides were accomplished under the condition of none standard substances.The results indicated that this method can be used to determine 204 pesticides in tea.At the three spike levels of 10?20?50 ?g/kg,mean recoveries for the 204 pesticides in tea were between 68.1% and 117.2%,with the relative standard deviations(RSDs)ranging from 3.1% to 18.9%.The limits of quantitation for 204 pesticides were lower than 10.0 ?g/kg.The method has been applied to four positive samples,and the results were generally in accord with the detection results by the method of GB/T 23205-2008.This method has the characteristics of high efficiency,as well as high sensitivity and accuracy,which can meet the requirements of the determination of the204 pesticides in tea.2.Determination of 204 pesticide residues in tea by UPLC-Q-TOF-MS with high resolution and LC-QQQ/MS with low resolution are carried on;in addition,the qualitative and quantitative capabilities of these two methods are compared.The results showthat the two methods can complete the screening and confirmation of 204 pesticides in tea,and the quantitative limit of 204 pesticides are all less than 10 ?g/kg,which can meet the requirements of pesticide residue limits in all countries.LC-QQQ/MS is proved to be the first choice for quantification of known compounds in complex background due to its superior sensitivity and wider linear range.UPLC-Q-TOF-MS is fast and accurate,and has high-throughput analysis,which shows a higher advantage in the rapid screening and confirmation of a large number of pesticides and non-target compounds. |
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