Determination of 400 pesticide residues in green tea leaves by UPLC-MS/MS and GC-MS/MS combined with QuEChERS extraction and mixed-mode SPE clean-up method.

Maximum residue limits (MRLs) for pesticides have been established in teas for quality control and protection of consumer health in many countries and regions, including Europe. It is, however, challenging to quantify multi-pesticide residues at low concentrations in complex matrices, such as tea. In this study, highly sensitive, efficient, and rugged analytical methods were adapted for simultaneous determination of 400 pesticide residues in green tea products using ultra performance liquid and gas chromatography coupled to tandem mass spectroscopy (UPLC-MS/MS and GC-MS/MS). Matrix effects were minimized by combining QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction and mixed-mode SPE clean-up with different sorbents in sample preparation. A C18 SPE cartridge paired with SPE GCB/PSA proved to be the most effective clean-up method and enabled 225 pesticide residues to be quantified, based on solvent calibration curves (154 residues using UPLC-MS/MS and 71 residues using GC-MS/MS). The analytical methods were validated fully in accordance with the SANTE/11945/2015. LOQs for most pesticides (386/400 or 96.5%) were below 10 µg/kg, i.e., less than the EU MRL (5-70 mg/kg). Thus, these approaches can be applied for routine analysis of multi-pesticide residues in green tea.