Research On Rapid Screening Method Of Mixed Contaminants In Tea By Gas Chromatography-Mass Spectrometry

Because of its unique taste,elegant appearance and nutritious health,tea has been deeply loved by people,and has become one of the highest-selling drinks in the world.In recent years,the quality and safety of tea has been greatly received in the world.Because tea have rich types of contaminants,its diversified matrix will also affect the detection of contaminants.Therefore,how to avoid such influencing conditions and the detection of more and more accurate contaminants remains to be resolved.A high-throughput rapid detection method for 76 mixed contaminants in tea was established by gas chromatography tandem mass spectrometry(GC-MS/MS).A gas chromatography-based triple quadrupole mass spectrometry(GC-Q/TOF)was established.The high-resolution rapid screening method for 169 mixed contaminants in tea was analyzed simultaneously in a 20-minute full scan mode.Finally,the actual blank samples were tested to determine the practicability of the method.The main results are as follows:(1)A multi-reactive ion detection mode(MRM)instrument method was established on a gas chromatography tandem mass spectrometer(GC-MS/MS)within 20 minutes,in which a "retention time locked" mode was established using a methyl chlorpyrifos mono-label to ensure best data;add 8 PCBs contaminants based on 852 compounds in the Gas Chromatography Triple Quadrupole Mass Spectrometry(GC-Q/TOF)Pesticide Personal Compound Database and Library(PCDL)used to create a new personal PCDL database to provide a baseline of contaminants information for screening experiments.(2)The QuEChERS pretreatment method in this research is based on the common pesticides method published on AOAC to detect fruits and vegetables.The new scheme is determined through optimization experiments:A 2(±0.05)g portion of tea sample was weighed into a 50-mL polypropylene centrifuge tube followed by 10 mL of water and shaken for 30 seconds.Samples were allowed to stand for 30 minutes.Then,10 mL of 1%acetic acid acetonitrile were added to the centrifuge tube and scrolled for 30 seconds.After that,6 g MgSO4 and 1.5 g CH3COONa·3H2O were added to the centrifuge tube,and the tube was sealed and shaken vigorously for 1 minute.The tube was centrifuged for 5 minutes at 5000 r/min at 4 ?.2.5 mL of the upper supernatant solution was transferred into a 10-mL polypropylene centrifuge tube,and correct purification filler were added to it and vortexed for 30 seconds.Two millilitres of the solution was added to a clean centrifuge tube and dried under nitrogen in a 40? water bath.Finally,the residue was redissolved in 1 mL acetonitrile and filtered through a 0.22-?m PTFE filter prior to test on the machine analysis.(3)The GC-MS/MS method uses the new purification filler EMR-lipid.The results show that each contaminant to be tested has a good linear relationship and the correlation coefficient is greater than 0.99.The sample recovery rates are stable in the range of 70.2%-121.44%and the relative standard deviation(RSDs)are in the range of 0.09%-29.38%.The detection limit(LOD)of 76 mixed contaminants are 0.1-5?g/kg,and the limit of quantitation(LOQ)are 0.1-10 ?g/kg.(4)The GC-Q/TOF method uses zirconium dioxide(ZrO2)and N-propyl ethylene diamine(PSA)to purify the filler combination.The results showed that the recovery rates are mostly between 80%and 120%,and the relative standard deviation(RSDs)are mostly less than 20%.Make full use of the MassHunter Qualitative Software to validate 169 target contaminants using the Find by Fragments(FBF)workflow and the Pesticide Personal Compound Database and Library(PCDL)in electron ionization mode;Unknowns Analysis(UA)used in conjunction with the NIST library for target screening;datasets were integrated for non-target screening used Mass Profiler Professional(MPP)software.(5)The method is effectively applied to actual samples detection.Four kinds of contaminants were detected on GC-MS/MS:three polycyclic aromatic hydrocarbons(PAHs)and pesticide triazophos;polycyclic aromatic hydrocarbons(PAHs)and hexachlorocyclohexane and their metabolites were detected on GC-Q/TOF.Compared with traditional analytical methods,the developed method is more effective,faster,more sensitive,and more practical in monitoring pesticides and environmental contaminants residues in the tea.