Improved QuEchERS Method Based on Multi-Walled Carbon Nanotubes Loaded with Attapulgite Combined with Liquid Chromatography-Tandem Mass Spectrometry for the Determination of Pesticide Residues in Tea Leaves

An attapulgite-multi-walled carbon nanotube (ATP-CNTs) composite material was synthesized to enhance the QuEChERS method. When coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), an accurate, rapid, and reliable analytical method was established for the determination of multiple pesticide residues in tea. The ATP-CNTs purification agent was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Pesticides in tea were extracted under ultrasonication using water and acetonitrile, followed by purification with ATP-CNTs. Key experimental parameters—including extraction solvent, extraction time, soaking time, soaking water temperature, adsorbent combination ratio, and adsorbent amount—were systematically optimized. Under optimal conditions, the method’s limits of detection (LOD) and quantification (LOQ) were 1.05–4.11 μg/kg and 3.49–13.69 μg/kg, respectively. Recovery experiments at three spiked concentration levels yielded average recoveries ranging from 75.2% to 114.3%, with relative standard deviations (RSDs) between 2.3% and 13.8%. The results demonstrate that this method is simple, accurate, rapid, and suitable for the detection of relevant pesticide residues in tea.