Simultaneous Determination of 86 Pesticide Residues in Glycyrrhiza Uralensis by Improved QuEChERS-UPLC-MS/MS

Dried Glycyrrhiza uralensis is popular as a dietary supplement in China, and it is used as an ingredient in spice and herbal medicine in China. To ensure its yields and quality, pesticides have been abused to control insects and diseases. However, the use of pesticides readily leads to pesticide residues, which may pose a potential threat to human health. To ensure that these residues are kept below tolerated levels, the China Pharmacopeia has stipulated maximum residue levels (MRLs) for some pesticides, yet only a few methods are available for evaluation of the broadly contaminated multiclass pesticides in dried Glycyrrhiza uralensis. The quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, a combination of extraction and purification, has been widely accepted by the international community by virtue of providing high recovery, super efficiency, and good reproducibility. However, because of the complexity of Chinese herbal medicine matrix, QuEChERS method is not suitable for the analysis of multiclass pesticide residues. Therefore, it is urgent to establish an improved QuEChERS method for the analysis of multiple pesticide residues in Chinese herbal medicine. The method of ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established for simultaneous determination of 86 pesticides residue in Glycyrrhiza uralensis. 9 kinds of QuEChERS were compared in terms of purification efficiency and recovery, the best results were achieved with no graphitized carbon black(NGCB). The pesticides were quantified on a UPLC-MS/MS system in scheduled multiple reaction monitoring mode, and identified on the basis of product ion abundance ratios as well as characteristic fragments in enhanced product ion spectra UPLC-MS/MS system. The correlation coefficients of 86 analytes were better than 0.991 3. Detection limits ranged from 0.2 μg/kg to 9 μg/kg. The average recoveries of 86 pesticides at the spiked levels of 10, 50, 100 μg/kg were range of 65.0%-129.4% with RSDs of 1.0%-20.0%. The proposed method was applied to Glycyrrhiza uralensis samples from the Chinese market. 17 pesticides were detected, including carbofuran and thiamethoxam, which exceeded the recommended maximum residue limits in some samples. The established method has advantages of good recovery, economical and a rapid clean-up procedure, showing enhanced product ion scanassisted confirmation to be a useful tool for obtaining reliable results.