Amine modified graphene as reversed-dispersive solid phase extraction materials combined with liquid chromatography-tandem mass spectrometry for pesticide multi-residue analysis in oil crops.

Amine modified graphene is successfully synthesized via a one-pot solvothermal reaction between graphene oxide and ammonia water, methylamine or n-butyl amine. The presence of amine groups in graphene is identified by Fourier-transform infrared spectrometry, X-ray photoelectron spectroscopy and an X-ray diffractometer. The ability of amine modified graphene to cleanup fatty acids and other interfering substances from acetonitrile extracts of oil crops has been evaluated. It is found that the resulting CH3NH-G exhibits the best performance in interfering substances removal. Meanwhile, a multi-residue method is validated on 28 representative pesticide residues in four oil crops (rapeseed, peanut, sesame seeds and soybean). This method is based on modified QuEChERS sample preparation with CH3NH-G as reversed-dispersive solid phase extraction material and liquid chromatography-tandem mass spectrometry. Use of matrix-matched standards provides acceptable results for most pesticides with overall average recoveries between 70.5 and 100% and consistent RSDs<13%, except for pymetrozine, thidiazuron and diuron. In any case, this method still meets the 0.1-8.3 μg/kg detection limit needs for most pesticides 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.