Graphene as dispersive solidphase extraction materials for pesticides LC-MS/MS multi-residue analysis in leek, onion and garlic

Abstract

A multi-residue analytical method was validated for 24 representative pesticides residues in onion, garlic and leek. The method is based on modified QuEChERS sample preparation with a mixture of graphene, primary secondary amine (PSA), and graphitised carbon black (GCB) as reversed-dispersive solid-phase extraction (r-DSPE) material and LC-MS/MS. Graphene was first used as an r-DSPE clean-up sorbent in onion, garlic and leek. The results first show that the mixed sorbent of graphene, PSA and GCB has a remarkable ability to clean-up interfering substances in the r-DSPE procedure when compared with the mixture of PSA and GCB. Use of matrix-matched standards provided acceptable results for tested pesticides with overall average recoveries between 70.1% and 109.7% and consistent RSDs <15.6%. In any case, this method still meets the 1–10 μg kg–1 detection limit needed for pesticide testing and may be used for qualitative screening applications in which any identified pesticides can be quantified and confirmed by a more intensive method that achieves >70% recovery.