Development of a modified QuEChERS-UPLC-MS/MS method based on multi-walled carbon nanotubes for 27 pesticide residues followed by determination of the residue levels and dietary intake risk assessment in Chrysanthemum morifolium Ramat.

A modified QuEChERS purification liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was designed to identify 27 pesticide residues in Chrysanthemum morifolium Ramat (C. morifolium). The preparation process was optimized, using carboxylated multi-walled carbon nanotubes (MWCNTs) as the single-category sorbents. Matrix-matched calibration curves were adopted for identifying the limit of quantification (LOQ) of 1.62-4.68 μg·kg-1. This method showed high pesticide recoveries at three spiked levels, from 71.6 % to 116.7 %, with the relative standard deviations less than 10 %. By analyzing 40C. morifolium samples, omethoate and epoxiconazole exceeded the maximum residue levels, and their transfer rates to the infusion were estimated to range from 9.4 % to 25.4 %. The two detected pesticides pose a negligible risk to consumer health, with the hazard quotients less than 0.85 %. Moreover, this study establishes an optimized QuEChERS-UPLC-MS/MS method to identify multiclass residues, enhancing the understanding of the potential exposure risk of omethoate and epoxiconazole in C. morifolium.