Validation and uncertainty analysis of a multiresidue method for 42 pesticides in made tea, tea infusion and spent leaves using ethyl acetate extraction and liquid chromatography–tandem mass spectrometry

A rapid, specific and sensitive multiresidue method to determine 42 pesticides in made tea, tea infusion and spent leaves has been developed and validated for the routine analysis by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The method was reproducible (Horwitz ratio (HorRat) <0.5 at 50 ng/g) and validated by the analysis of sample spiked at 50 and 100 ng/g in made tea, tea infusion and spent leaves. The samples were extracted with ethyl acetate + cyclohexane (9:1; v/v), and the extracts were cleaned up by dispersive solid phase extraction with primary secondary amine sorbent + graphitized carbon black + Florisil. The recoveries of all the pesticides were between 70% and 120% with a relative standard deviation of less than 15% and correlation coefficient for each pesticide was R2 ≥0.99. The matrix effect on signal of respective compounds was measured by comparing matrix-matched calibration standards with those in solvent-only. The limits of quantitation (LOQ) met the requirements of the maximum residue limits (MRLs) for pesticides in tea as recommended by the European Union.