Determination Of Pesticide Multiresidue In Tea And Celery By GC-QqQ-MS/MS

With the social and economic development and people’s living standard continues to improve, there is growing emphasis on the inherent quality of the food, nutrition, health and safety. Pesticide residue has drawn increasing attention. The system of pesticide residue detemination is an important part of pesticide residue management. Therefore it is particularly important to establish a detection method which is accurate, fast, convenient and feasible.Tea and celery were selected as samples for the study of a variety of pesticide residues detected. Gas chromatography-triple quadrupole mass spectrometry was selected to establish accurate methods to detect pesticide multi-residues in tea and celery, which is sensitive, fast, efficient and comply with the need of pesticide residues analysis.In the second chapter, an analytical method was developed for determination of multi-pesticide residues, including organophosphorus, organohalogen, pyrethroid and organonitrogen in tea at trace levels by gas chromatography coupled with triple quadrupole mass spectrometry (GC-QqQ-MS/MS). Scan time was selected in order to get optimization of triple quadrupole MS/MS conditions. The key parameters for controlling clean-up performance were optimized, including SPE cartridge type and eluted solvent volume. Acetonitrile was the extraction solvent and a novel multilayer solid phase extraction (SPE) cartridge-Cleanet TPT was used in clean-up step. The LODs by gas chromatography-triple quadrupole mass spectrometry and gas chromatography-quadrupole-ion-trap mass spectrometry were0.002μ.g/kg-1.0μg/kg and0.05μg/kg-2.5μg/kg, and the LOQs were0.0066μg/kg-3.3μg/kg and0.15μg/kg-7.5μg/kg, which met the maximum residue limits (MRLs) for pesticides in tea recommended by the European Union or Japan.. The recoveries of the pesticides at5.0,10, and25μg/kg under studied were in the range of78%-104%with a relative standard deviation of less than14%. The optimized method was applied to analyze real tea samples obtained from local market. In the third chapter, a rapid and effective multiresidue method has been developed for the determination of15organophosphorus pesticides in celery by gas chromatography coupled with triple quadrupole mass spectrometry (GC-QqQ-MS/MS). Celery samples were extracted with acetonitrile, and purified by PC/NH2SPE cartridge. The comparison of recoveries of the analytes on acetonitrile-toluene (3:1, v/v), acetonitrile-acetone-toluene (4:2:1, v/v/v) and ethyl acetate-acetone (1:1, v/v) demonstrates that acetonitrile-acetone-toluene (4:2:1, v/v/v) used in sample pretreatment elute efficiently. The LODs by gas chromatography-triple quadrupole mass spectrometry and gas chromatography-quadrupole-ion-trap mass spectrometry were0.18μg/kg-2.5μg/kg and0.68μg/kg-5.0μg/kg, and the LOQs were0.59μg/kg-8.3ug/kg and2.0μg/kg-15μg/kg. The recoveries of the pesticides under study were in the range of84%-115%with a relative standard deviation of less than9.0%. Matrix-matched standard calibration curve was used to reduce errors related with matrix-induced enhancement or suppression effects.GC-QqQ-MS/MS is superior to GC-QIT-MS/MS in the detection limit and sensitivity. GC-QqQ-MS/MS has a higher accuracy in the quantitative of pesticide residues, and GC-QIT-MS/MS is more suitable for qualitative work.