Screening of pesticide residues in Traditional Chinese Medicines using modified QuEChERS sample preparation procedure and LC-MS/MS analysis

A robust and high-throughput method was developed for the determination of 108 pesticide residues in Traditional Chinese Medicines (TCMs) simultaneously using a combination of UHPLC-MS/MS analysis and the modified QuEChERS method. Extraction was carried out in acetonitrile containing 0.75% (v/v) acetic acid with ultrasonication for 15 min; MgSO4 and C18 were used as the dispersive-solid phase extraction sorbents. The method exhibited good linearity (r2 > 0.9901), in addition to good selectivity, precision and repeatability. More than 92% of pesticides exhibited high rates or recovery in the 70–120% range. This method showed high sensitivity, with Limits of Quantitation in the 0.01–20 ng/mL range in Cortex Moutan, and 0.01–50 ng/mL in the other TCMs. The method was employed for the analysis of 39 real samples from different habitats, and pesticides were detected in 92.3% of the samples, with 26 pesticides being detected in these three TCMs. More than four pesticides were detected in a third of the samples. Among them, tebuconazole was detected in all the three TCMs with 0.22–22.02 μg/kg concentration, which was lower than the provisions in GB 2763-2019 (50 μg/kg). In addition, the paclobutrazol detection rate in Ophiopogon japonicus was 100%, and the detected concentrations of 9 samples exceeded the Maximum Residue Levels defined for vegetables (50 μg/kg). Considering there are no regulations that govern the limits of pesticide residues in the three TCMs in China, we recommend the acceleration of efforts to introduce appropriate regulations.