A multi-residue method for the determination of pesticides in tea using multi-walled carbon nanotubes as a dispersive solid phase extraction absorbent

A modified QuEChERS (quick, easy, cheap, effective, rugged and safe) method using multi-walled carbon nanotubes (MWCNTs) as a dispersive solid phase extraction (d-SPE) absorbent was established for analysis of 78 pesticide residues in tea. A 6 mg MWCNT sample was selected as the optimised amount based on the distribution of pesticide recoveries and clean-up efficiency from 6 mL acetonitrile extracts. The matrix effects of the method were evaluated and matrix-matched calibration was recommended. The method was validated employing gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) at the spiked concentration levels of 0.05, 0.1 and 0.15 mg kg−1. For most of the targeted pesticides, the percent recoveries range from 70% to 120%, with relative standard deviations (RSDs) <20%. The linear correlation coefficients (r2) were higher than 0.99 at concentration levels of 0.025-0.500 mg kg−1. In this study, MWCNTs were proved to be a promising d-SPE absorbent with excellent cleanup efficiency, which could be widely applied for the analysis of pesticide residues.