Improved QuEChERS Method with Carbon Nanomaterials Combined with GC-MS/MS for the Detection of 31 Pesticide Residues in Tea Leaves

Objective A detection method based on modified dispersive solid-phase extraction with carbon nanomaterials (QuEChERS) to improve the cleanup effect and combined with gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS) for the simultaneous determination of 31 pesticide residues in tea was developed.

Method The tea samples were pulverized uniformly and purified by the modified QuEChERS method using carbon nanotubes as adsorption and purification fillers, and the pesticide residues in tea were extracted using a fully automated QuEChERS sample pretreatment system and quantified by GC-MS/MS external standard method. The purification effects of three types of single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) and aminated multi-walled carbon nanotubes (MWCNTs-NH₂) were compared with each other and in different amounts.

Result In this study, aminated multi-walled carbon nanotubes (MWCNTs-NH₂) were finally selected to improve the traditional QuEChERS filler, and the limits of detection (LODs) of this research method were 0.02~1.68 μg·kg⁻¹, and the limits of quantification (LOQs) were 0.05~5.61 μg·kg⁻¹; The average recoveries of the target compounds at the three levels of spiked recoveries, low, medium and high, were 81.0%~119.7% with the relative standard deviation (RSD) ranging from 1.1% to 10.0%. The target pesticides showed different degrees of matrix effects in tea, and four target pesticides, such as chloroanisole, showed matrix inhibitory effects, while 27 target pesticides, such as lecithromycin, showed matrix-enhancing effects.

Conclusion The method is automatic and efficient, with high sensitivity, the whole process consumes less time, can effectively save labor costs, and is suitable for the detection of larger batches of tea samples.