Determination of neonicotinoid pesticides residues in agricultural samples by solid-phase extraction combined with liquid chromatography–tandem mass spectrometry

This work reports a new sensitive multi-residue liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for detection, confirmation and quantification of six neonicotinoid pesticides (dinotefuran, thiamethoxam, clothiandin, imidacloprid, acetamiprid and thiacloprid) in agricultural samples (chestnut, shallot, ginger and tea). Activated carbon and HLB solid-phase extraction cartridges were used for cleaning up the extracts. Analysis is performed by LC–MS/MS operated in the multiple reaction monitoring (MRM) mode, acquiring two specific precursor-product ion transitions per target compound. Quantification was carried by the internal standard method with D4-labeled imidacloprid. The method showed excellent linearity (R2 ≥ 0.9991) and precision (relative standard deviation, RSD ≤ 8.6%) for all compounds. Limits of quantification (LOQs) were 0.01 mg kg−1 for chestnut, shallot, ginger sample and 0.02 mg kg−1 for tea sample. The average recoveries, measured at three concentrations levels (0.01 mg kg−1, 0.02 mg kg−1 and 0.1 mg kg−1 for chestnut, shallot, ginger sample, 0.02 mg kg−1, 0.04 mg kg−1 and 0.2 mg kg−1 for tea sample), were in the range 82.1–108.5%. The method was satisfactorily validated for the analysis of 150 agricultural samples (chestnut, shallot, ginger and tea). Imidacloprid and acetamiprid were detected at concentration levels ranging from 0.05 to 3.6 mg kg−1.