An quantificational method for 51 pesticide residues determination in Pu'er tea by LC-MS/MS

Pesticide residues in tea is a major issue due to their widely used in tea cultivation. Thus, to protect consumers, an appropriate method for determination of their residues in tea should be done. In this study, a method for the simultaneous determination of 51 pesticides in tea was developed and validated. The tea sample was extracted by acetonitrile and purified SPE clearnet TPT column followed by liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) with multi-reaction monitoring (MRM) mode. The method was validated according to the linearity, limit of detention, precision, the percentage of recovery at three different spike levels. The linear concentration range used was 10-100ng/ mL, the square of Correlation coefficient r2 was more than >0.995. Recoveries were adequate being in the acceptable range of 72-89% and RSD of <19 % for all the analytes at three level of 0.01,0.05 and 0.11mg/kg, the LOD of all chemicals from 0.001 mg/kg to 0.01 mg/kg .The method was applied for the determination for 400 tea samples collected from Pu'er which contain green tea and black tea. Among the analyzed samples , 36 % samples had Imidacloprid and 25% sample contain Acetamiprid, which were at a level below the European Union maximum residue levels (EU-MRLs). The information would be beneficial for Pu'er tea exporters.