Study On GC-MS And UPLC-MS/MS Analytical Techniques Of Pesticides Multi-Residues In Tea

Analytical techniques such as gas chromatography (GC), GC-mass Spectrometry (GC-MS), high performance liquid chromatography (HPLC) and HPLC-mass spectrometry allow for the determination of pesticides residues in tea samples. However, many of the published methods for pesticide determination in tea require time-consumed procedure for sample preparation before analyzing so as to eliminate the effects from matrices. In this thesis, we concentrated ourselves on development of simple, rapid ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and GC-MS method for analysis of pesticides residues in tea.This dissertation consists of two parts.1. This second and third chapter described a method for the determination of 74 pesticides residues in tea by Gas Chromatography/Mass Spectrometry. Pesticides were extracted from tea with acetonitrile in an ultrasonic bath and cleaned up on a graphitised carbon black column, then were determined by gas chromatography with electron ionization mass spectrometric detection in the selected ion monitoring mode. When the spike level were 0.01-0.8 mg/kg, the recoveries ranged from 60.9% to 121.9% with the relative standard deviation less than 18.3% for the different pesticides. The detection limit of the method was from 0.3 to 20μg/kg. The developed method was linear over the range assayed, 0.004-20 mg/kg, with determination coefficients R²>0.992.2. This fourth chapter described a method for the determination of 16 carbamate pesticides residues in tea by UPLC-MS/MS. The pesticides residues were extracted from tea samples by acetonitrile under ultrasonic and cleaned up on a Carbon-NH₂ column. The extractive was determined by liquid chromatography using acetonitrile-water(10mmol ammonia acetate+0.1% fomic acid) as mobile phase. The carbamate pesticides were detected using electrospay ionization (ESI) on a tandem mass spectrometer in multiple reaction monitoring (MRM) mode. 16 carbamate pesticides residues could be detected quantitatively within 9 min. The Linear calibration curves were obtained in the whole range (5ng/mL-480ng/mL) proved to be linearity for all the above pesticides. The resulted linear correlation coefficients was higher than 0.998. The average recoveries in tea obtained for each pesticide were ranged from 49.6% to 96.0% with the relative standard deviation less than 27% for the different pesticides. The detection limit of the method was from 0.014 to 0.5ng/kg.