A qualitative and quantitative method was established based on modified QuEChERS for the simultaneous determination of 95 herbicide residues in tea using ultra-high performance liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS). The effects of multi-walled carbon nanotubes (MWCNTs), graphitized carbon black (GCB), primary secondary amine (PSA) and toluene on the precondition step were evaluated in terms of matrix-spiked recovery and pigment clean-up effect. Finally, the modified QuEChERS method was applied, which involved sample extraction with an acetonitrile-toluene (9:1, v/v) mixture containing 1% (v/v) acetic acid, followed by cleaning with 12.5 mg GCB, 12.5 mg MWCNTs and 150 mg PSA. The sample extract was separated on a Hypersil Gold C18 column and analyzed in full scan/data-dependent MS2(Full MS/dd-MS2) mode. The target herbicides were quantified by using the matrix-matched standard calibration. The three-level spiked recoveries were between 63.3% and 129.1% with the precision of 0.7%-15.2%. This method is easy, sensitive and rapid and can be applicable to the determination of trace herbicide residues in tea and other plant-derived complex matrix samples.
Keywords: herbicides; modified QuEChERS; multi-walled carbon nanotubes (MWCNTs); quadrupole/electrostatic field orbitrap high resolution mass spectrometry (Q-Orbitrap HRMS); tea; ultra-high performance liquid chromatography (UHPLC).